Merge branch 'work.regset' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

[linux/fpc-iii.git] / drivers / i2c / busses / i2c-npcm7xx.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Nuvoton NPCM7xx I2C Controller driver
 *
 * Copyright (C) 2020 Nuvoton Technologies tali.perry@nuvoton.com
 */
#include <linux/bitfield.h>
#include <linux/clk.h>
#include <linux/debugfs.h>
#include <linux/errno.h>
#include <linux/i2c.h>
#include <linux/interrupt.h>
#include <linux/iopoll.h>
#include <linux/irq.h>
#include <linux/jiffies.h>
#include <linux/kernel.h>
#include <linux/mfd/syscon.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/regmap.h>

enum i2c_mode {
        I2C_MASTER,
        I2C_SLAVE,
};

/*
 * External I2C Interface driver xfer indication values, which indicate status
 * of the bus.
 */
enum i2c_state_ind {
        I2C_NO_STATUS_IND = 0,
        I2C_SLAVE_RCV_IND,
        I2C_SLAVE_XMIT_IND,
        I2C_SLAVE_XMIT_MISSING_DATA_IND,
        I2C_SLAVE_RESTART_IND,
        I2C_SLAVE_DONE_IND,
        I2C_MASTER_DONE_IND,
        I2C_NACK_IND,
        I2C_BUS_ERR_IND,
        I2C_WAKE_UP_IND,
        I2C_BLOCK_BYTES_ERR_IND,
        I2C_SLAVE_RCV_MISSING_DATA_IND,
};

/*
 * Operation type values (used to define the operation currently running)
 * module is interrupt driven, on each interrupt the current operation is
 * checked to see if the module is currently reading or writing.
 */
enum i2c_oper {
        I2C_NO_OPER = 0,
        I2C_WRITE_OPER,
        I2C_READ_OPER,
};

/* I2C Bank (module had 2 banks of registers) */
enum i2c_bank {
        I2C_BANK_0 = 0,
        I2C_BANK_1,
};

/* Internal I2C states values (for the I2C module state machine). */
enum i2c_state {
        I2C_DISABLE = 0,
        I2C_IDLE,
        I2C_MASTER_START,
        I2C_SLAVE_MATCH,
        I2C_OPER_STARTED,
        I2C_STOP_PENDING,
};

#if IS_ENABLED(CONFIG_I2C_SLAVE)
/* Module supports setting multiple own slave addresses */
enum i2c_addr {
        I2C_SLAVE_ADDR1 = 0,
        I2C_SLAVE_ADDR2,
        I2C_SLAVE_ADDR3,
        I2C_SLAVE_ADDR4,
        I2C_SLAVE_ADDR5,
        I2C_SLAVE_ADDR6,
        I2C_SLAVE_ADDR7,
        I2C_SLAVE_ADDR8,
        I2C_SLAVE_ADDR9,
        I2C_SLAVE_ADDR10,
        I2C_GC_ADDR,
        I2C_ARP_ADDR,
};
#endif

/* init register and default value required to enable module */
#define NPCM_I2CSEGCTL                  0xE4
#define NPCM_I2CSEGCTL_INIT_VAL         0x0333F000

/* Common regs */
#define NPCM_I2CSDA                     0x00
#define NPCM_I2CST                      0x02
#define NPCM_I2CCST                     0x04
#define NPCM_I2CCTL1                    0x06
#define NPCM_I2CADDR1                   0x08
#define NPCM_I2CCTL2                    0x0A
#define NPCM_I2CADDR2                   0x0C
#define NPCM_I2CCTL3                    0x0E
#define NPCM_I2CCST2                    0x18
#define NPCM_I2CCST3                    0x19
#define I2C_VER                         0x1F

/*BANK0 regs*/
#define NPCM_I2CADDR3                   0x10
#define NPCM_I2CADDR7                   0x11
#define NPCM_I2CADDR4                   0x12
#define NPCM_I2CADDR8                   0x13
#define NPCM_I2CADDR5                   0x14
#define NPCM_I2CADDR9                   0x15
#define NPCM_I2CADDR6                   0x16
#define NPCM_I2CADDR10                  0x17

#if IS_ENABLED(CONFIG_I2C_SLAVE)
/*
 * npcm_i2caddr array:
 * The module supports having multiple own slave addresses.
 * Since the addr regs are sprinkled all over the address space,
 * use this array to get the address or each register.
 */
#define I2C_NUM_OWN_ADDR 10
static const int npcm_i2caddr[I2C_NUM_OWN_ADDR] = {
        NPCM_I2CADDR1, NPCM_I2CADDR2, NPCM_I2CADDR3, NPCM_I2CADDR4,
        NPCM_I2CADDR5, NPCM_I2CADDR6, NPCM_I2CADDR7, NPCM_I2CADDR8,
        NPCM_I2CADDR9, NPCM_I2CADDR10,
};
#endif

#define NPCM_I2CCTL4                    0x1A
#define NPCM_I2CCTL5                    0x1B
#define NPCM_I2CSCLLT                   0x1C /* SCL Low Time */
#define NPCM_I2CFIF_CTL                 0x1D /* FIFO Control */
#define NPCM_I2CSCLHT                   0x1E /* SCL High Time */

/* BANK 1 regs */
#define NPCM_I2CFIF_CTS                 0x10 /* Both FIFOs Control and Status */
#define NPCM_I2CTXF_CTL                 0x12 /* Tx-FIFO Control */
#define NPCM_I2CT_OUT                   0x14 /* Bus T.O. */
#define NPCM_I2CPEC                     0x16 /* PEC Data */
#define NPCM_I2CTXF_STS                 0x1A /* Tx-FIFO Status */
#define NPCM_I2CRXF_STS                 0x1C /* Rx-FIFO Status */
#define NPCM_I2CRXF_CTL                 0x1E /* Rx-FIFO Control */

/* NPCM_I2CST reg fields */
#define NPCM_I2CST_XMIT                 BIT(0)
#define NPCM_I2CST_MASTER               BIT(1)
#define NPCM_I2CST_NMATCH               BIT(2)
#define NPCM_I2CST_STASTR               BIT(3)
#define NPCM_I2CST_NEGACK               BIT(4)
#define NPCM_I2CST_BER                  BIT(5)
#define NPCM_I2CST_SDAST                BIT(6)
#define NPCM_I2CST_SLVSTP               BIT(7)

/* NPCM_I2CCST reg fields */
#define NPCM_I2CCST_BUSY                BIT(0)
#define NPCM_I2CCST_BB                  BIT(1)
#define NPCM_I2CCST_MATCH               BIT(2)
#define NPCM_I2CCST_GCMATCH             BIT(3)
#define NPCM_I2CCST_TSDA                BIT(4)
#define NPCM_I2CCST_TGSCL               BIT(5)
#define NPCM_I2CCST_MATCHAF             BIT(6)
#define NPCM_I2CCST_ARPMATCH            BIT(7)

/* NPCM_I2CCTL1 reg fields */
#define NPCM_I2CCTL1_START              BIT(0)
#define NPCM_I2CCTL1_STOP               BIT(1)
#define NPCM_I2CCTL1_INTEN              BIT(2)
#define NPCM_I2CCTL1_EOBINTE            BIT(3)
#define NPCM_I2CCTL1_ACK                BIT(4)
#define NPCM_I2CCTL1_GCMEN              BIT(5)
#define NPCM_I2CCTL1_NMINTE             BIT(6)
#define NPCM_I2CCTL1_STASTRE            BIT(7)

/* RW1S fields (inside a RW reg): */
#define NPCM_I2CCTL1_RWS   \
        (NPCM_I2CCTL1_START | NPCM_I2CCTL1_STOP | NPCM_I2CCTL1_ACK)

/* npcm_i2caddr reg fields */
#define NPCM_I2CADDR_A                  GENMASK(6, 0)
#define NPCM_I2CADDR_SAEN               BIT(7)

/* NPCM_I2CCTL2 reg fields */
#define I2CCTL2_ENABLE                  BIT(0)
#define I2CCTL2_SCLFRQ6_0               GENMASK(7, 1)

/* NPCM_I2CCTL3 reg fields */
#define I2CCTL3_SCLFRQ8_7               GENMASK(1, 0)
#define I2CCTL3_ARPMEN                  BIT(2)
#define I2CCTL3_IDL_START               BIT(3)
#define I2CCTL3_400K_MODE               BIT(4)
#define I2CCTL3_BNK_SEL                 BIT(5)
#define I2CCTL3_SDA_LVL                 BIT(6)
#define I2CCTL3_SCL_LVL                 BIT(7)

/* NPCM_I2CCST2 reg fields */
#define NPCM_I2CCST2_MATCHA1F           BIT(0)
#define NPCM_I2CCST2_MATCHA2F           BIT(1)
#define NPCM_I2CCST2_MATCHA3F           BIT(2)
#define NPCM_I2CCST2_MATCHA4F           BIT(3)
#define NPCM_I2CCST2_MATCHA5F           BIT(4)
#define NPCM_I2CCST2_MATCHA6F           BIT(5)
#define NPCM_I2CCST2_MATCHA7F           BIT(5)
#define NPCM_I2CCST2_INTSTS             BIT(7)

/* NPCM_I2CCST3 reg fields */
#define NPCM_I2CCST3_MATCHA8F           BIT(0)
#define NPCM_I2CCST3_MATCHA9F           BIT(1)
#define NPCM_I2CCST3_MATCHA10F          BIT(2)
#define NPCM_I2CCST3_EO_BUSY            BIT(7)

/* NPCM_I2CCTL4 reg fields */
#define I2CCTL4_HLDT                    GENMASK(5, 0)
#define I2CCTL4_LVL_WE                  BIT(7)

/* NPCM_I2CCTL5 reg fields */
#define I2CCTL5_DBNCT                   GENMASK(3, 0)

/* NPCM_I2CFIF_CTS reg fields */
#define NPCM_I2CFIF_CTS_RXF_TXE         BIT(1)
#define NPCM_I2CFIF_CTS_RFTE_IE         BIT(3)
#define NPCM_I2CFIF_CTS_CLR_FIFO        BIT(6)
#define NPCM_I2CFIF_CTS_SLVRSTR         BIT(7)

/* NPCM_I2CTXF_CTL reg fields */
#define NPCM_I2CTXF_CTL_TX_THR          GENMASK(4, 0)
#define NPCM_I2CTXF_CTL_THR_TXIE        BIT(6)

/* NPCM_I2CT_OUT reg fields */
#define NPCM_I2CT_OUT_TO_CKDIV          GENMASK(5, 0)
#define NPCM_I2CT_OUT_T_OUTIE           BIT(6)
#define NPCM_I2CT_OUT_T_OUTST           BIT(7)

/* NPCM_I2CTXF_STS reg fields */
#define NPCM_I2CTXF_STS_TX_BYTES        GENMASK(4, 0)
#define NPCM_I2CTXF_STS_TX_THST         BIT(6)

/* NPCM_I2CRXF_STS reg fields */
#define NPCM_I2CRXF_STS_RX_BYTES        GENMASK(4, 0)
#define NPCM_I2CRXF_STS_RX_THST         BIT(6)

/* NPCM_I2CFIF_CTL reg fields */
#define NPCM_I2CFIF_CTL_FIFO_EN         BIT(4)

/* NPCM_I2CRXF_CTL reg fields */
#define NPCM_I2CRXF_CTL_RX_THR          GENMASK(4, 0)
#define NPCM_I2CRXF_CTL_LAST_PEC        BIT(5)
#define NPCM_I2CRXF_CTL_THR_RXIE        BIT(6)

#define I2C_HW_FIFO_SIZE                16

/* I2C_VER reg fields */
#define I2C_VER_VERSION                 GENMASK(6, 0)
#define I2C_VER_FIFO_EN                 BIT(7)

/* stall/stuck timeout in us */
#define DEFAULT_STALL_COUNT             25

/* SCLFRQ field position */
#define SCLFRQ_0_TO_6                   GENMASK(6, 0)
#define SCLFRQ_7_TO_8                   GENMASK(8, 7)

/* supported clk settings. values in Hz. */
#define I2C_FREQ_MIN_HZ                 10000
#define I2C_FREQ_MAX_HZ                 I2C_MAX_FAST_MODE_PLUS_FREQ

/* Status of one I2C module */
struct npcm_i2c {
        struct i2c_adapter adap;
        struct device *dev;
        unsigned char __iomem *reg;
        spinlock_t lock;   /* IRQ synchronization */
        struct completion cmd_complete;
        int cmd_err;
        struct i2c_msg *msgs;
        int msgs_num;
        int num;
        u32 apb_clk;
        struct i2c_bus_recovery_info rinfo;
        enum i2c_state state;
        enum i2c_oper operation;
        enum i2c_mode master_or_slave;
        enum i2c_state_ind stop_ind;
        u8 dest_addr;
        u8 *rd_buf;
        u16 rd_size;
        u16 rd_ind;
        u8 *wr_buf;
        u16 wr_size;
        u16 wr_ind;
        bool fifo_use;
        u16 PEC_mask; /* PEC bit mask per slave address */
        bool PEC_use;
        bool read_block_use;
        unsigned long int_time_stamp;
        unsigned long bus_freq; /* in Hz */
#if IS_ENABLED(CONFIG_I2C_SLAVE)
        u8 own_slave_addr;
        struct i2c_client *slave;
        int slv_rd_size;
        int slv_rd_ind;
        int slv_wr_size;
        int slv_wr_ind;
        u8 slv_rd_buf[I2C_HW_FIFO_SIZE];
        u8 slv_wr_buf[I2C_HW_FIFO_SIZE];
#endif
        struct dentry *debugfs; /* debugfs device directory */
        u64 ber_cnt;
        u64 rec_succ_cnt;
        u64 rec_fail_cnt;
        u64 nack_cnt;
        u64 timeout_cnt;
};

static inline void npcm_i2c_select_bank(struct npcm_i2c *bus,
                                        enum i2c_bank bank)
{
        u8 i2cctl3 = ioread8(bus->reg + NPCM_I2CCTL3);

        if (bank == I2C_BANK_0)
                i2cctl3 = i2cctl3 & ~I2CCTL3_BNK_SEL;
        else
                i2cctl3 = i2cctl3 | I2CCTL3_BNK_SEL;
        iowrite8(i2cctl3, bus->reg + NPCM_I2CCTL3);
}

static void npcm_i2c_init_params(struct npcm_i2c *bus)
{
        bus->stop_ind = I2C_NO_STATUS_IND;
        bus->rd_size = 0;
        bus->wr_size = 0;
        bus->rd_ind = 0;
        bus->wr_ind = 0;
        bus->read_block_use = false;
        bus->int_time_stamp = 0;
        bus->PEC_use = false;
        bus->PEC_mask = 0;
#if IS_ENABLED(CONFIG_I2C_SLAVE)
        if (bus->slave)
                bus->master_or_slave = I2C_SLAVE;
#endif
}

static inline void npcm_i2c_wr_byte(struct npcm_i2c *bus, u8 data)
{
        iowrite8(data, bus->reg + NPCM_I2CSDA);
}

static inline u8 npcm_i2c_rd_byte(struct npcm_i2c *bus)
{
        return ioread8(bus->reg + NPCM_I2CSDA);
}

static int npcm_i2c_get_SCL(struct i2c_adapter *_adap)
{
        struct npcm_i2c *bus = container_of(_adap, struct npcm_i2c, adap);

        return !!(I2CCTL3_SCL_LVL & ioread32(bus->reg + NPCM_I2CCTL3));
}

static int npcm_i2c_get_SDA(struct i2c_adapter *_adap)
{
        struct npcm_i2c *bus = container_of(_adap, struct npcm_i2c, adap);

        return !!(I2CCTL3_SDA_LVL & ioread32(bus->reg + NPCM_I2CCTL3));
}

static inline u16 npcm_i2c_get_index(struct npcm_i2c *bus)
{
        if (bus->operation == I2C_READ_OPER)
                return bus->rd_ind;
        if (bus->operation == I2C_WRITE_OPER)
                return bus->wr_ind;
        return 0;
}

/* quick protocol (just address) */
static inline bool npcm_i2c_is_quick(struct npcm_i2c *bus)
{
        return bus->wr_size == 0 && bus->rd_size == 0;
}

static void npcm_i2c_disable(struct npcm_i2c *bus)
{
        u8 i2cctl2;

#if IS_ENABLED(CONFIG_I2C_SLAVE)
        int i;

        /* select bank 0 for I2C addresses */
        npcm_i2c_select_bank(bus, I2C_BANK_0);

        /* Slave addresses removal */
        for (i = I2C_SLAVE_ADDR1; i < I2C_NUM_OWN_ADDR; i++)
                iowrite8(0, bus->reg + npcm_i2caddr[i]);

        npcm_i2c_select_bank(bus, I2C_BANK_1);
#endif
        /* Disable module */
        i2cctl2 = ioread8(bus->reg + NPCM_I2CCTL2);
        i2cctl2 = i2cctl2 & ~I2CCTL2_ENABLE;
        iowrite8(i2cctl2, bus->reg + NPCM_I2CCTL2);

        bus->state = I2C_DISABLE;
}

static void npcm_i2c_enable(struct npcm_i2c *bus)
{
        u8 i2cctl2 = ioread8(bus->reg + NPCM_I2CCTL2);

        i2cctl2 = i2cctl2 | I2CCTL2_ENABLE;
        iowrite8(i2cctl2, bus->reg + NPCM_I2CCTL2);
        bus->state = I2C_IDLE;
}

/* enable\disable end of busy (EOB) interrupts */
static inline void npcm_i2c_eob_int(struct npcm_i2c *bus, bool enable)
{
        u8 val;

        /* Clear EO_BUSY pending bit: */
        val = ioread8(bus->reg + NPCM_I2CCST3);
        val = val | NPCM_I2CCST3_EO_BUSY;
        iowrite8(val, bus->reg + NPCM_I2CCST3);

        val = ioread8(bus->reg + NPCM_I2CCTL1);
        val &= ~NPCM_I2CCTL1_RWS;
        if (enable)
                val |= NPCM_I2CCTL1_EOBINTE;
        else
                val &= ~NPCM_I2CCTL1_EOBINTE;
        iowrite8(val, bus->reg + NPCM_I2CCTL1);
}

static inline bool npcm_i2c_tx_fifo_empty(struct npcm_i2c *bus)
{
        u8 tx_fifo_sts;

        tx_fifo_sts = ioread8(bus->reg + NPCM_I2CTXF_STS);
        /* check if TX FIFO is not empty */
        if ((tx_fifo_sts & NPCM_I2CTXF_STS_TX_BYTES) == 0)
                return false;

        /* check if TX FIFO status bit is set: */
        return !!FIELD_GET(NPCM_I2CTXF_STS_TX_THST, tx_fifo_sts);
}

static inline bool npcm_i2c_rx_fifo_full(struct npcm_i2c *bus)
{
        u8 rx_fifo_sts;

        rx_fifo_sts = ioread8(bus->reg + NPCM_I2CRXF_STS);
        /* check if RX FIFO is not empty: */
        if ((rx_fifo_sts & NPCM_I2CRXF_STS_RX_BYTES) == 0)
                return false;

        /* check if rx fifo full status is set: */
        return !!FIELD_GET(NPCM_I2CRXF_STS_RX_THST, rx_fifo_sts);
}

static inline void npcm_i2c_clear_fifo_int(struct npcm_i2c *bus)
{
        u8 val;

        val = ioread8(bus->reg + NPCM_I2CFIF_CTS);
        val = (val & NPCM_I2CFIF_CTS_SLVRSTR) | NPCM_I2CFIF_CTS_RXF_TXE;
        iowrite8(val, bus->reg + NPCM_I2CFIF_CTS);
}

static inline void npcm_i2c_clear_tx_fifo(struct npcm_i2c *bus)
{
        u8 val;

        val = ioread8(bus->reg + NPCM_I2CTXF_STS);
        val = val | NPCM_I2CTXF_STS_TX_THST;
        iowrite8(val, bus->reg + NPCM_I2CTXF_STS);
}

static inline void npcm_i2c_clear_rx_fifo(struct npcm_i2c *bus)
{
        u8 val;

        val = ioread8(bus->reg + NPCM_I2CRXF_STS);
        val = val | NPCM_I2CRXF_STS_RX_THST;
        iowrite8(val, bus->reg + NPCM_I2CRXF_STS);
}

static void npcm_i2c_int_enable(struct npcm_i2c *bus, bool enable)
{
        u8 val;

        val = ioread8(bus->reg + NPCM_I2CCTL1);
        val &= ~NPCM_I2CCTL1_RWS;
        if (enable)
                val |= NPCM_I2CCTL1_INTEN;
        else
                val &= ~NPCM_I2CCTL1_INTEN;
        iowrite8(val, bus->reg + NPCM_I2CCTL1);
}

static inline void npcm_i2c_master_start(struct npcm_i2c *bus)
{
        u8 val;

        val = ioread8(bus->reg + NPCM_I2CCTL1);
        val &= ~(NPCM_I2CCTL1_STOP | NPCM_I2CCTL1_ACK);
        val |= NPCM_I2CCTL1_START;
        iowrite8(val, bus->reg + NPCM_I2CCTL1);
}

static inline void npcm_i2c_master_stop(struct npcm_i2c *bus)
{
        u8 val;

        /*
         * override HW issue: I2C may fail to supply stop condition in Master
         * Write operation.
         * Need to delay at least 5 us from the last int, before issueing a stop
         */
        udelay(10); /* function called from interrupt, can't sleep */
        val = ioread8(bus->reg + NPCM_I2CCTL1);
        val &= ~(NPCM_I2CCTL1_START | NPCM_I2CCTL1_ACK);
        val |= NPCM_I2CCTL1_STOP;
        iowrite8(val, bus->reg + NPCM_I2CCTL1);

        if (!bus->fifo_use)
                return;

        npcm_i2c_select_bank(bus, I2C_BANK_1);

        if (bus->operation == I2C_READ_OPER)
                npcm_i2c_clear_rx_fifo(bus);
        else
                npcm_i2c_clear_tx_fifo(bus);
        npcm_i2c_clear_fifo_int(bus);
        iowrite8(0, bus->reg + NPCM_I2CTXF_CTL);
}

static inline void npcm_i2c_stall_after_start(struct npcm_i2c *bus, bool stall)
{
        u8 val;

        val = ioread8(bus->reg + NPCM_I2CCTL1);
        val &= ~NPCM_I2CCTL1_RWS;
        if (stall)
                val |= NPCM_I2CCTL1_STASTRE;
        else
                val &= ~NPCM_I2CCTL1_STASTRE;
        iowrite8(val, bus->reg + NPCM_I2CCTL1);
}

static inline void npcm_i2c_nack(struct npcm_i2c *bus)
{
        u8 val;

        val = ioread8(bus->reg + NPCM_I2CCTL1);
        val &= ~(NPCM_I2CCTL1_STOP | NPCM_I2CCTL1_START);
        val |= NPCM_I2CCTL1_ACK;
        iowrite8(val, bus->reg + NPCM_I2CCTL1);
}

#if IS_ENABLED(CONFIG_I2C_SLAVE)
static void npcm_i2c_slave_int_enable(struct npcm_i2c *bus, bool enable)
{
        u8 i2cctl1;

        /* enable interrupt on slave match: */
        i2cctl1 = ioread8(bus->reg + NPCM_I2CCTL1);
        i2cctl1 &= ~NPCM_I2CCTL1_RWS;
        if (enable)
                i2cctl1 |= NPCM_I2CCTL1_NMINTE;
        else
                i2cctl1 &= ~NPCM_I2CCTL1_NMINTE;
        iowrite8(i2cctl1, bus->reg + NPCM_I2CCTL1);
}

static int npcm_i2c_slave_enable(struct npcm_i2c *bus, enum i2c_addr addr_type,
                                 u8 addr, bool enable)
{
        u8 i2cctl1;
        u8 i2cctl3;
        u8 sa_reg;

        sa_reg = (addr & 0x7F) | FIELD_PREP(NPCM_I2CADDR_SAEN, enable);
        if (addr_type == I2C_GC_ADDR) {
                i2cctl1 = ioread8(bus->reg + NPCM_I2CCTL1);
                if (enable)
                        i2cctl1 |= NPCM_I2CCTL1_GCMEN;
                else
                        i2cctl1 &= ~NPCM_I2CCTL1_GCMEN;
                iowrite8(i2cctl1, bus->reg + NPCM_I2CCTL1);
                return 0;
        }
        if (addr_type == I2C_ARP_ADDR) {
                i2cctl3 = ioread8(bus->reg + NPCM_I2CCTL3);
                if (enable)
                        i2cctl3 |= I2CCTL3_ARPMEN;
                else
                        i2cctl3 &= ~I2CCTL3_ARPMEN;
                iowrite8(i2cctl3, bus->reg + NPCM_I2CCTL3);
                return 0;
        }
        if (addr_type >= I2C_ARP_ADDR)
                return -EFAULT;
        /* select bank 0 for address 3 to 10 */
        if (addr_type > I2C_SLAVE_ADDR2)
                npcm_i2c_select_bank(bus, I2C_BANK_0);
        /* Set and enable the address */
        iowrite8(sa_reg, bus->reg + npcm_i2caddr[addr_type]);
        npcm_i2c_slave_int_enable(bus, enable);
        if (addr_type > I2C_SLAVE_ADDR2)
                npcm_i2c_select_bank(bus, I2C_BANK_1);
        return 0;
}
#endif

static void npcm_i2c_reset(struct npcm_i2c *bus)
{
        /*
         * Save I2CCTL1 relevant bits. It is being cleared when the module
         *  is disabled.
         */
        u8 i2cctl1;
#if IS_ENABLED(CONFIG_I2C_SLAVE)
        u8 addr;
#endif

        i2cctl1 = ioread8(bus->reg + NPCM_I2CCTL1);

        npcm_i2c_disable(bus);
        npcm_i2c_enable(bus);

        /* Restore NPCM_I2CCTL1 Status */
        i2cctl1 &= ~NPCM_I2CCTL1_RWS;
        iowrite8(i2cctl1, bus->reg + NPCM_I2CCTL1);

        /* Clear BB (BUS BUSY) bit */
        iowrite8(NPCM_I2CCST_BB, bus->reg + NPCM_I2CCST);
        iowrite8(0xFF, bus->reg + NPCM_I2CST);

        /* Clear EOB bit */
        iowrite8(NPCM_I2CCST3_EO_BUSY, bus->reg + NPCM_I2CCST3);

        /* Clear all fifo bits: */
        iowrite8(NPCM_I2CFIF_CTS_CLR_FIFO, bus->reg + NPCM_I2CFIF_CTS);

#if IS_ENABLED(CONFIG_I2C_SLAVE)
        if (bus->slave) {
                addr = bus->slave->addr;
                npcm_i2c_slave_enable(bus, I2C_SLAVE_ADDR1, addr, true);
        }
#endif

        bus->state = I2C_IDLE;
}

static inline bool npcm_i2c_is_master(struct npcm_i2c *bus)
{
        return !!FIELD_GET(NPCM_I2CST_MASTER, ioread8(bus->reg + NPCM_I2CST));
}

static void npcm_i2c_callback(struct npcm_i2c *bus,
                              enum i2c_state_ind op_status, u16 info)
{
        struct i2c_msg *msgs;
        int msgs_num;

        msgs = bus->msgs;
        msgs_num = bus->msgs_num;
        /*
         * check that transaction was not timed-out, and msgs still
         * holds a valid value.
         */
        if (!msgs)
                return;

        if (completion_done(&bus->cmd_complete))
                return;

        switch (op_status) {
        case I2C_MASTER_DONE_IND:
                bus->cmd_err = bus->msgs_num;
                fallthrough;
        case I2C_BLOCK_BYTES_ERR_IND:
                /* Master tx finished and all transmit bytes were sent */
                if (bus->msgs) {
                        if (msgs[0].flags & I2C_M_RD)
                                msgs[0].len = info;
                        else if (msgs_num == 2 &&
                                 msgs[1].flags & I2C_M_RD)
                                msgs[1].len = info;
                }
                if (completion_done(&bus->cmd_complete) == false)
                        complete(&bus->cmd_complete);
        break;

        case I2C_NACK_IND:
                /* MASTER transmit got a NACK before tx all bytes */
                bus->cmd_err = -ENXIO;
                if (bus->master_or_slave == I2C_MASTER)
                        complete(&bus->cmd_complete);

                break;
        case I2C_BUS_ERR_IND:
                /* Bus error */
                bus->cmd_err = -EAGAIN;
                if (bus->master_or_slave == I2C_MASTER)
                        complete(&bus->cmd_complete);

                break;
        case I2C_WAKE_UP_IND:
                /* I2C wake up */
                break;
        default:
                break;
        }

        bus->operation = I2C_NO_OPER;
#if IS_ENABLED(CONFIG_I2C_SLAVE)
        if (bus->slave)
                bus->master_or_slave = I2C_SLAVE;
#endif
}

static u8 npcm_i2c_fifo_usage(struct npcm_i2c *bus)
{
        if (bus->operation == I2C_WRITE_OPER)
                return FIELD_GET(NPCM_I2CTXF_STS_TX_BYTES,
                                 ioread8(bus->reg + NPCM_I2CTXF_STS));
        if (bus->operation == I2C_READ_OPER)
                return FIELD_GET(NPCM_I2CRXF_STS_RX_BYTES,
                                 ioread8(bus->reg + NPCM_I2CRXF_STS));
        return 0;
}

static void npcm_i2c_write_to_fifo_master(struct npcm_i2c *bus, u16 max_bytes)
{
        u8 size_free_fifo;

        /*
         * Fill the FIFO, while the FIFO is not full and there are more bytes
         * to write
         */
        size_free_fifo = I2C_HW_FIFO_SIZE - npcm_i2c_fifo_usage(bus);
        while (max_bytes-- && size_free_fifo) {
                if (bus->wr_ind < bus->wr_size)
                        npcm_i2c_wr_byte(bus, bus->wr_buf[bus->wr_ind++]);
                else
                        npcm_i2c_wr_byte(bus, 0xFF);
                size_free_fifo = I2C_HW_FIFO_SIZE - npcm_i2c_fifo_usage(bus);
        }
}

/*
 * npcm_i2c_set_fifo:
 * configure the FIFO before using it. If nread is -1 RX FIFO will not be
 * configured. same for nwrite
 */
static void npcm_i2c_set_fifo(struct npcm_i2c *bus, int nread, int nwrite)
{
        u8 rxf_ctl = 0;

        if (!bus->fifo_use)
                return;
        npcm_i2c_select_bank(bus, I2C_BANK_1);
        npcm_i2c_clear_tx_fifo(bus);
        npcm_i2c_clear_rx_fifo(bus);

        /* configure RX FIFO */
        if (nread > 0) {
                rxf_ctl = min_t(int, nread, I2C_HW_FIFO_SIZE);

                /* set LAST bit. if LAST is set next FIFO packet is nacked */
                if (nread <= I2C_HW_FIFO_SIZE)
                        rxf_ctl |= NPCM_I2CRXF_CTL_LAST_PEC;

                /*
                 * if we are about to read the first byte in blk rd mode,
                 * don't NACK it. If slave returns zero size HW can't NACK
                 * it immidiattly, it will read extra byte and then NACK.
                 */
                if (bus->rd_ind == 0 && bus->read_block_use) {
                        /* set fifo to read one byte, no last: */
                        rxf_ctl = 1;
                }

                /* set fifo size: */
                iowrite8(rxf_ctl, bus->reg + NPCM_I2CRXF_CTL);
        }

        /* configure TX FIFO */
        if (nwrite > 0) {
                if (nwrite > I2C_HW_FIFO_SIZE)
                        /* data to send is more then FIFO size. */
                        iowrite8(I2C_HW_FIFO_SIZE, bus->reg + NPCM_I2CTXF_CTL);
                else
                        iowrite8(nwrite, bus->reg + NPCM_I2CTXF_CTL);

                npcm_i2c_clear_tx_fifo(bus);
        }
}

static void npcm_i2c_read_fifo(struct npcm_i2c *bus, u8 bytes_in_fifo)
{
        u8 data;

        while (bytes_in_fifo--) {
                data = npcm_i2c_rd_byte(bus);
                if (bus->rd_ind < bus->rd_size)
                        bus->rd_buf[bus->rd_ind++] = data;
        }
}

static inline void npcm_i2c_clear_master_status(struct npcm_i2c *bus)
{
        u8 val;

        /* Clear NEGACK, STASTR and BER bits */
        val = NPCM_I2CST_BER | NPCM_I2CST_NEGACK | NPCM_I2CST_STASTR;
        iowrite8(val, bus->reg + NPCM_I2CST);
}

static void npcm_i2c_master_abort(struct npcm_i2c *bus)
{
        /* Only current master is allowed to issue a stop condition */
        if (!npcm_i2c_is_master(bus))
                return;

        npcm_i2c_eob_int(bus, true);
        npcm_i2c_master_stop(bus);
        npcm_i2c_clear_master_status(bus);
}

#if IS_ENABLED(CONFIG_I2C_SLAVE)
static u8 npcm_i2c_get_slave_addr(struct npcm_i2c *bus, enum i2c_addr addr_type)
{
        u8 slave_add;

        /* select bank 0 for address 3 to 10 */
        if (addr_type > I2C_SLAVE_ADDR2)
                npcm_i2c_select_bank(bus, I2C_BANK_0);

        slave_add = ioread8(bus->reg + npcm_i2caddr[(int)addr_type]);

        if (addr_type > I2C_SLAVE_ADDR2)
                npcm_i2c_select_bank(bus, I2C_BANK_1);

        return slave_add;
}

static int npcm_i2c_remove_slave_addr(struct npcm_i2c *bus, u8 slave_add)
{
        int i;

        /* Set the enable bit */
        slave_add |= 0x80;
        npcm_i2c_select_bank(bus, I2C_BANK_0);
        for (i = I2C_SLAVE_ADDR1; i < I2C_NUM_OWN_ADDR; i++) {
                if (ioread8(bus->reg + npcm_i2caddr[i]) == slave_add)
                        iowrite8(0, bus->reg + npcm_i2caddr[i]);
        }
        npcm_i2c_select_bank(bus, I2C_BANK_1);
        return 0;
}

static void npcm_i2c_write_fifo_slave(struct npcm_i2c *bus, u16 max_bytes)
{
        /*
         * Fill the FIFO, while the FIFO is not full and there are more bytes
         * to write
         */
        npcm_i2c_clear_fifo_int(bus);
        npcm_i2c_clear_tx_fifo(bus);
        iowrite8(0, bus->reg + NPCM_I2CTXF_CTL);
        while (max_bytes-- && I2C_HW_FIFO_SIZE != npcm_i2c_fifo_usage(bus)) {
                if (bus->slv_wr_size <= 0)
                        break;
                bus->slv_wr_ind = bus->slv_wr_ind % I2C_HW_FIFO_SIZE;
                npcm_i2c_wr_byte(bus, bus->slv_wr_buf[bus->slv_wr_ind]);
                bus->slv_wr_ind++;
                bus->slv_wr_ind = bus->slv_wr_ind % I2C_HW_FIFO_SIZE;
                bus->slv_wr_size--;
        }
}

static void npcm_i2c_read_fifo_slave(struct npcm_i2c *bus, u8 bytes_in_fifo)
{
        u8 data;

        if (!bus->slave)
                return;

        while (bytes_in_fifo--) {
                data = npcm_i2c_rd_byte(bus);

                bus->slv_rd_ind = bus->slv_rd_ind % I2C_HW_FIFO_SIZE;
                bus->slv_rd_buf[bus->slv_rd_ind] = data;
                bus->slv_rd_ind++;

                /* 1st byte is length in block protocol: */
                if (bus->slv_rd_ind == 1 && bus->read_block_use)
                        bus->slv_rd_size = data + bus->PEC_use + 1;
        }
}

static int npcm_i2c_slave_get_wr_buf(struct npcm_i2c *bus)
{
        int i;
        u8 value;
        int ind;
        int ret = bus->slv_wr_ind;

        /* fill a cyclic buffer */
        for (i = 0; i < I2C_HW_FIFO_SIZE; i++) {
                if (bus->slv_wr_size >= I2C_HW_FIFO_SIZE)
                        break;
                i2c_slave_event(bus->slave, I2C_SLAVE_READ_REQUESTED, &value);
                ind = (bus->slv_wr_ind + bus->slv_wr_size) % I2C_HW_FIFO_SIZE;
                bus->slv_wr_buf[ind] = value;
                bus->slv_wr_size++;
                i2c_slave_event(bus->slave, I2C_SLAVE_READ_PROCESSED, &value);
        }
        return I2C_HW_FIFO_SIZE - ret;
}

static void npcm_i2c_slave_send_rd_buf(struct npcm_i2c *bus)
{
        int i;

        for (i = 0; i < bus->slv_rd_ind; i++)
                i2c_slave_event(bus->slave, I2C_SLAVE_WRITE_RECEIVED,
                                &bus->slv_rd_buf[i]);
        /*
         * once we send bytes up, need to reset the counter of the wr buf
         * got data from master (new offset in device), ignore wr fifo:
         */
        if (bus->slv_rd_ind) {
                bus->slv_wr_size = 0;
                bus->slv_wr_ind = 0;
        }

        bus->slv_rd_ind = 0;
        bus->slv_rd_size = bus->adap.quirks->max_read_len;

        npcm_i2c_clear_fifo_int(bus);
        npcm_i2c_clear_rx_fifo(bus);
}

static void npcm_i2c_slave_receive(struct npcm_i2c *bus, u16 nread,
                                   u8 *read_data)
{
        bus->state = I2C_OPER_STARTED;
        bus->operation = I2C_READ_OPER;
        bus->slv_rd_size = nread;
        bus->slv_rd_ind = 0;

        iowrite8(0, bus->reg + NPCM_I2CTXF_CTL);
        iowrite8(I2C_HW_FIFO_SIZE, bus->reg + NPCM_I2CRXF_CTL);
        npcm_i2c_clear_tx_fifo(bus);
        npcm_i2c_clear_rx_fifo(bus);
}

static void npcm_i2c_slave_xmit(struct npcm_i2c *bus, u16 nwrite,
                                u8 *write_data)
{
        if (nwrite == 0)
                return;

        bus->state = I2C_OPER_STARTED;
        bus->operation = I2C_WRITE_OPER;

        /* get the next buffer */
        npcm_i2c_slave_get_wr_buf(bus);
        npcm_i2c_write_fifo_slave(bus, nwrite);
}

/*
 * npcm_i2c_slave_wr_buf_sync:
 * currently slave IF only supports single byte operations.
 * in order to utilyze the npcm HW FIFO, the driver will ask for 16 bytes
 * at a time, pack them in buffer, and then transmit them all together
 * to the FIFO and onward to the bus.
 * NACK on read will be once reached to bus->adap->quirks->max_read_len.
 * sending a NACK wherever the backend requests for it is not supported.
 * the next two functions allow reading to local buffer before writing it all
 * to the HW FIFO.
 */
static void npcm_i2c_slave_wr_buf_sync(struct npcm_i2c *bus)
{
        int left_in_fifo;

        left_in_fifo = FIELD_GET(NPCM_I2CTXF_STS_TX_BYTES,
                                 ioread8(bus->reg + NPCM_I2CTXF_STS));

        /* fifo already full: */
        if (left_in_fifo >= I2C_HW_FIFO_SIZE ||
            bus->slv_wr_size >= I2C_HW_FIFO_SIZE)
                return;

        /* update the wr fifo index back to the untransmitted bytes: */
        bus->slv_wr_ind = bus->slv_wr_ind - left_in_fifo;
        bus->slv_wr_size = bus->slv_wr_size + left_in_fifo;

        if (bus->slv_wr_ind < 0)
                bus->slv_wr_ind += I2C_HW_FIFO_SIZE;
}

static void npcm_i2c_slave_rd_wr(struct npcm_i2c *bus)
{
        if (NPCM_I2CST_XMIT & ioread8(bus->reg + NPCM_I2CST)) {
                /*
                 * Slave got an address match with direction bit 1 so it should
                 * transmit data. Write till the master will NACK
                 */
                bus->operation = I2C_WRITE_OPER;
                npcm_i2c_slave_xmit(bus, bus->adap.quirks->max_write_len,
                                    bus->slv_wr_buf);
        } else {
                /*
                 * Slave got an address match with direction bit 0 so it should
                 * receive data.
                 * this module does not support saying no to bytes.
                 * it will always ACK.
                 */
                bus->operation = I2C_READ_OPER;
                npcm_i2c_read_fifo_slave(bus, npcm_i2c_fifo_usage(bus));
                bus->stop_ind = I2C_SLAVE_RCV_IND;
                npcm_i2c_slave_send_rd_buf(bus);
                npcm_i2c_slave_receive(bus, bus->adap.quirks->max_read_len,
                                       bus->slv_rd_buf);
        }
}

static irqreturn_t npcm_i2c_int_slave_handler(struct npcm_i2c *bus)
{
        u8 val;
        irqreturn_t ret = IRQ_NONE;
        u8 i2cst = ioread8(bus->reg + NPCM_I2CST);

        /* Slave: A NACK has occurred */
        if (NPCM_I2CST_NEGACK & i2cst) {
                bus->stop_ind = I2C_NACK_IND;
                npcm_i2c_slave_wr_buf_sync(bus);
                if (bus->fifo_use)
                        /* clear the FIFO */
                        iowrite8(NPCM_I2CFIF_CTS_CLR_FIFO,
                                 bus->reg + NPCM_I2CFIF_CTS);

                /* In slave write, NACK is OK, otherwise it is a problem */
                bus->stop_ind = I2C_NO_STATUS_IND;
                bus->operation = I2C_NO_OPER;
                bus->own_slave_addr = 0xFF;

                /*
                 * Slave has to wait for STOP to decide this is the end
                 * of the transaction. tx is not yet considered as done
                 */
                iowrite8(NPCM_I2CST_NEGACK, bus->reg + NPCM_I2CST);

                ret = IRQ_HANDLED;
        }

        /* Slave mode: a Bus Error (BER) has been identified */
        if (NPCM_I2CST_BER & i2cst) {
                /*
                 * Check whether bus arbitration or Start or Stop during data
                 * xfer bus arbitration problem should not result in recovery
                 */
                bus->stop_ind = I2C_BUS_ERR_IND;

                /* wait for bus busy before clear fifo */
                iowrite8(NPCM_I2CFIF_CTS_CLR_FIFO, bus->reg + NPCM_I2CFIF_CTS);

                bus->state = I2C_IDLE;

                /*
                 * in BER case we might get 2 interrupts: one for slave one for
                 * master ( for a channel which is master\slave switching)
                 */
                if (completion_done(&bus->cmd_complete) == false) {
                        bus->cmd_err = -EIO;
                        complete(&bus->cmd_complete);
                }
                bus->own_slave_addr = 0xFF;
                iowrite8(NPCM_I2CST_BER, bus->reg + NPCM_I2CST);
                ret = IRQ_HANDLED;
        }

        /* A Slave Stop Condition has been identified */
        if (NPCM_I2CST_SLVSTP & i2cst) {
                u8 bytes_in_fifo = npcm_i2c_fifo_usage(bus);

                bus->stop_ind = I2C_SLAVE_DONE_IND;

                if (bus->operation == I2C_READ_OPER)
                        npcm_i2c_read_fifo_slave(bus, bytes_in_fifo);

                /* if the buffer is empty nothing will be sent */
                npcm_i2c_slave_send_rd_buf(bus);

                /* Slave done transmitting or receiving */
                bus->stop_ind = I2C_NO_STATUS_IND;

                /*
                 * Note, just because we got here, it doesn't mean we through
                 * away the wr buffer.
                 * we keep it until the next received offset.
                 */
                bus->operation = I2C_NO_OPER;
                bus->own_slave_addr = 0xFF;
                i2c_slave_event(bus->slave, I2C_SLAVE_STOP, 0);
                iowrite8(NPCM_I2CST_SLVSTP, bus->reg + NPCM_I2CST);
                if (bus->fifo_use) {
                        npcm_i2c_clear_fifo_int(bus);
                        npcm_i2c_clear_rx_fifo(bus);
                        npcm_i2c_clear_tx_fifo(bus);

                        iowrite8(NPCM_I2CFIF_CTS_CLR_FIFO,
                                 bus->reg + NPCM_I2CFIF_CTS);
                }
                bus->state = I2C_IDLE;
                ret = IRQ_HANDLED;
        }

        /* restart condition occurred and Rx-FIFO was not empty */
        if (bus->fifo_use && FIELD_GET(NPCM_I2CFIF_CTS_SLVRSTR,
                                       ioread8(bus->reg + NPCM_I2CFIF_CTS))) {
                bus->stop_ind = I2C_SLAVE_RESTART_IND;
                bus->master_or_slave = I2C_SLAVE;
                if (bus->operation == I2C_READ_OPER)
                        npcm_i2c_read_fifo_slave(bus, npcm_i2c_fifo_usage(bus));
                bus->operation = I2C_WRITE_OPER;
                iowrite8(0, bus->reg + NPCM_I2CRXF_CTL);
                val = NPCM_I2CFIF_CTS_CLR_FIFO | NPCM_I2CFIF_CTS_SLVRSTR |
                      NPCM_I2CFIF_CTS_RXF_TXE;
                iowrite8(val, bus->reg + NPCM_I2CFIF_CTS);
                npcm_i2c_slave_rd_wr(bus);
                ret = IRQ_HANDLED;
        }

        /* A Slave Address Match has been identified */
        if (NPCM_I2CST_NMATCH & i2cst) {
                u8 info = 0;

                /* Address match automatically implies slave mode */
                bus->master_or_slave = I2C_SLAVE;
                npcm_i2c_clear_fifo_int(bus);
                npcm_i2c_clear_rx_fifo(bus);
                npcm_i2c_clear_tx_fifo(bus);
                iowrite8(0, bus->reg + NPCM_I2CTXF_CTL);
                iowrite8(I2C_HW_FIFO_SIZE, bus->reg + NPCM_I2CRXF_CTL);
                if (NPCM_I2CST_XMIT & i2cst) {
                        bus->operation = I2C_WRITE_OPER;
                } else {
                        i2c_slave_event(bus->slave, I2C_SLAVE_WRITE_REQUESTED,
                                        &info);
                        bus->operation = I2C_READ_OPER;
                }
                if (bus->own_slave_addr == 0xFF) {
                        /* Check which type of address match */
                        val = ioread8(bus->reg + NPCM_I2CCST);
                        if (NPCM_I2CCST_MATCH & val) {
                                u16 addr;
                                enum i2c_addr eaddr;
                                u8 i2ccst2;
                                u8 i2ccst3;

                                i2ccst3 = ioread8(bus->reg + NPCM_I2CCST3);
                                i2ccst2 = ioread8(bus->reg + NPCM_I2CCST2);

                                /*
                                 * the i2c module can response to 10 own SA.
                                 * check which one was addressed by the master.
                                 * repond to the first one.
                                 */
                                addr = ((i2ccst3 & 0x07) << 7) |
                                        (i2ccst2 & 0x7F);
                                info = ffs(addr);
                                eaddr = (enum i2c_addr)info;
                                addr = npcm_i2c_get_slave_addr(bus, eaddr);
                                addr &= 0x7F;
                                bus->own_slave_addr = addr;
                                if (bus->PEC_mask & BIT(info))
                                        bus->PEC_use = true;
                                else
                                        bus->PEC_use = false;
                        } else {
                                if (NPCM_I2CCST_GCMATCH & val)
                                        bus->own_slave_addr = 0;
                                if (NPCM_I2CCST_ARPMATCH & val)
                                        bus->own_slave_addr = 0x61;
                        }
                } else {
                        /*
                         *  Slave match can happen in two options:
                         *  1. Start, SA, read (slave read without further ado)
                         *  2. Start, SA, read, data, restart, SA, read,  ...
                         *     (slave read in fragmented mode)
                         *  3. Start, SA, write, data, restart, SA, read, ..
                         *     (regular write-read mode)
                         */
                        if ((bus->state == I2C_OPER_STARTED &&
                             bus->operation == I2C_READ_OPER &&
                             bus->stop_ind == I2C_SLAVE_XMIT_IND) ||
                             bus->stop_ind == I2C_SLAVE_RCV_IND) {
                                /* slave tx after slave rx w/o STOP */
                                bus->stop_ind = I2C_SLAVE_RESTART_IND;
                        }
                }

                if (NPCM_I2CST_XMIT & i2cst)
                        bus->stop_ind = I2C_SLAVE_XMIT_IND;
                else
                        bus->stop_ind = I2C_SLAVE_RCV_IND;
                bus->state = I2C_SLAVE_MATCH;
                npcm_i2c_slave_rd_wr(bus);
                iowrite8(NPCM_I2CST_NMATCH, bus->reg + NPCM_I2CST);
                ret = IRQ_HANDLED;
        }

        /* Slave SDA status is set - tx or rx */
        if ((NPCM_I2CST_SDAST & i2cst) ||
            (bus->fifo_use &&
            (npcm_i2c_tx_fifo_empty(bus) || npcm_i2c_rx_fifo_full(bus)))) {
                npcm_i2c_slave_rd_wr(bus);
                iowrite8(NPCM_I2CST_SDAST, bus->reg + NPCM_I2CST);
                ret = IRQ_HANDLED;
        } /* SDAST */

        return ret;
}

static int npcm_i2c_reg_slave(struct i2c_client *client)
{
        unsigned long lock_flags;
        struct npcm_i2c *bus = i2c_get_adapdata(client->adapter);

        bus->slave = client;

        if (!bus->slave)
                return -EINVAL;

        if (client->flags & I2C_CLIENT_TEN)
                return -EAFNOSUPPORT;

        spin_lock_irqsave(&bus->lock, lock_flags);

        npcm_i2c_init_params(bus);
        bus->slv_rd_size = 0;
        bus->slv_wr_size = 0;
        bus->slv_rd_ind = 0;
        bus->slv_wr_ind = 0;
        if (client->flags & I2C_CLIENT_PEC)
                bus->PEC_use = true;

        dev_info(bus->dev, "i2c%d register slave SA=0x%x, PEC=%d\n", bus->num,
                 client->addr, bus->PEC_use);

        npcm_i2c_slave_enable(bus, I2C_SLAVE_ADDR1, client->addr, true);
        npcm_i2c_clear_fifo_int(bus);
        npcm_i2c_clear_rx_fifo(bus);
        npcm_i2c_clear_tx_fifo(bus);
        npcm_i2c_slave_int_enable(bus, true);

        spin_unlock_irqrestore(&bus->lock, lock_flags);
        return 0;
}

static int npcm_i2c_unreg_slave(struct i2c_client *client)
{
        struct npcm_i2c *bus = client->adapter->algo_data;
        unsigned long lock_flags;

        spin_lock_irqsave(&bus->lock, lock_flags);
        if (!bus->slave) {
                spin_unlock_irqrestore(&bus->lock, lock_flags);
                return -EINVAL;
        }
        npcm_i2c_slave_int_enable(bus, false);
        npcm_i2c_remove_slave_addr(bus, client->addr);
        bus->slave = NULL;
        spin_unlock_irqrestore(&bus->lock, lock_flags);
        return 0;
}
#endif /* CONFIG_I2C_SLAVE */

static void npcm_i2c_master_fifo_read(struct npcm_i2c *bus)
{
        int rcount;
        int fifo_bytes;
        enum i2c_state_ind ind = I2C_MASTER_DONE_IND;

        fifo_bytes = npcm_i2c_fifo_usage(bus);
        rcount = bus->rd_size - bus->rd_ind;

        /*
         * In order not to change the RX_TRH during transaction (we found that
         * this might be problematic if it takes too much time to read the FIFO)
         * we read the data in the following way. If the number of bytes to
         * read == FIFO Size + C (where C < FIFO Size)then first read C bytes
         * and in the next int we read rest of the data.
         */
        if (rcount < (2 * I2C_HW_FIFO_SIZE) && rcount > I2C_HW_FIFO_SIZE)
                fifo_bytes = rcount - I2C_HW_FIFO_SIZE;

        if (rcount <= fifo_bytes) {
                /* last bytes are about to be read - end of tx */
                bus->state = I2C_STOP_PENDING;
                bus->stop_ind = ind;
                npcm_i2c_eob_int(bus, true);
                /* Stop should be set before reading last byte. */
                npcm_i2c_master_stop(bus);
                npcm_i2c_read_fifo(bus, fifo_bytes);
        } else {
                npcm_i2c_read_fifo(bus, fifo_bytes);
                rcount = bus->rd_size - bus->rd_ind;
                npcm_i2c_set_fifo(bus, rcount, -1);
        }
}

static void npcm_i2c_irq_master_handler_write(struct npcm_i2c *bus)
{
        u16 wcount;

        if (bus->fifo_use)
                npcm_i2c_clear_tx_fifo(bus); /* clear the TX fifo status bit */

        /* Master write operation - last byte handling */
        if (bus->wr_ind == bus->wr_size) {
                if (bus->fifo_use && npcm_i2c_fifo_usage(bus) > 0)
                        /*
                         * No more bytes to send (to add to the FIFO),
                         * however the FIFO is not empty yet. It is
                         * still in the middle of tx. Currently there's nothing
                         * to do except for waiting to the end of the tx
                         * We will get an int when the FIFO will get empty.
                         */
                        return;

                if (bus->rd_size == 0) {
                        /* all bytes have been written, in wr only operation */
                        npcm_i2c_eob_int(bus, true);
                        bus->state = I2C_STOP_PENDING;
                        bus->stop_ind = I2C_MASTER_DONE_IND;
                        npcm_i2c_master_stop(bus);
                        /* Clear SDA Status bit (by writing dummy byte) */
                        npcm_i2c_wr_byte(bus, 0xFF);

                } else {
                        /* last write-byte written on previous int - restart */
                        npcm_i2c_set_fifo(bus, bus->rd_size, -1);
                        /* Generate repeated start upon next write to SDA */
                        npcm_i2c_master_start(bus);

                        /*
                         * Receiving one byte only - stall after successful
                         * completion of send address byte. If we NACK here, and
                         * slave doesn't ACK the address, we might
                         * unintentionally NACK the next multi-byte read.
                         */
                        if (bus->rd_size == 1)
                                npcm_i2c_stall_after_start(bus, true);

                        /* Next int will occur on read */
                        bus->operation = I2C_READ_OPER;
                        /* send the slave address in read direction */
                        npcm_i2c_wr_byte(bus, bus->dest_addr | 0x1);
                }
        } else {
                /* write next byte not last byte and not slave address */
                if (!bus->fifo_use || bus->wr_size == 1) {
                        npcm_i2c_wr_byte(bus, bus->wr_buf[bus->wr_ind++]);
                } else {
                        wcount = bus->wr_size - bus->wr_ind;
                        npcm_i2c_set_fifo(bus, -1, wcount);
                        if (wcount)
                                npcm_i2c_write_to_fifo_master(bus, wcount);
                }
        }
}

static void npcm_i2c_irq_master_handler_read(struct npcm_i2c *bus)
{
        u16 block_extra_bytes_size;
        u8 data;

        /* added bytes to the packet: */
        block_extra_bytes_size = bus->read_block_use + bus->PEC_use;

        /*
         * Perform master read, distinguishing between last byte and the rest of
         * the bytes. The last byte should be read when the clock is stopped
         */
        if (bus->rd_ind == 0) { /* first byte handling: */
                if (bus->read_block_use) {
                        /* first byte in block protocol is the size: */
                        data = npcm_i2c_rd_byte(bus);
                        data = clamp_val(data, 1, I2C_SMBUS_BLOCK_MAX);
                        bus->rd_size = data + block_extra_bytes_size;
                        bus->rd_buf[bus->rd_ind++] = data;

                        /* clear RX FIFO interrupt status: */
                        if (bus->fifo_use) {
                                data = ioread8(bus->reg + NPCM_I2CFIF_CTS);
                                data = data | NPCM_I2CFIF_CTS_RXF_TXE;
                                iowrite8(data, bus->reg + NPCM_I2CFIF_CTS);
                        }

                        npcm_i2c_set_fifo(bus, bus->rd_size - 1, -1);
                        npcm_i2c_stall_after_start(bus, false);
                } else {
                        npcm_i2c_clear_tx_fifo(bus);
                        npcm_i2c_master_fifo_read(bus);
                }
        } else {
                if (bus->rd_size == block_extra_bytes_size &&
                    bus->read_block_use) {
                        bus->state = I2C_STOP_PENDING;
                        bus->stop_ind = I2C_BLOCK_BYTES_ERR_IND;
                        bus->cmd_err = -EIO;
                        npcm_i2c_eob_int(bus, true);
                        npcm_i2c_master_stop(bus);
                        npcm_i2c_read_fifo(bus, npcm_i2c_fifo_usage(bus));
                } else {
                        npcm_i2c_master_fifo_read(bus);
                }
        }
}

static void npcm_i2c_irq_handle_nmatch(struct npcm_i2c *bus)
{
        iowrite8(NPCM_I2CST_NMATCH, bus->reg + NPCM_I2CST);
        npcm_i2c_nack(bus);
        bus->stop_ind = I2C_BUS_ERR_IND;
        npcm_i2c_callback(bus, bus->stop_ind, npcm_i2c_get_index(bus));
}

/* A NACK has occurred */
static void npcm_i2c_irq_handle_nack(struct npcm_i2c *bus)
{
        u8 val;

        if (bus->nack_cnt < ULLONG_MAX)
                bus->nack_cnt++;

        if (bus->fifo_use) {
                /*
                 * if there are still untransmitted bytes in TX FIFO
                 * reduce them from wr_ind
                 */
                if (bus->operation == I2C_WRITE_OPER)
                        bus->wr_ind -= npcm_i2c_fifo_usage(bus);

                /* clear the FIFO */
                iowrite8(NPCM_I2CFIF_CTS_CLR_FIFO, bus->reg + NPCM_I2CFIF_CTS);
        }

        /* In master write operation, got unexpected NACK */
        bus->stop_ind = I2C_NACK_IND;
        /* Only current master is allowed to issue Stop Condition */
        if (npcm_i2c_is_master(bus)) {
                /* stopping in the middle */
                npcm_i2c_eob_int(bus, false);
                npcm_i2c_master_stop(bus);

                /*
                 * The bus is released from stall only after the SW clears
                 * NEGACK bit. Then a Stop condition is sent.
                 */
                npcm_i2c_clear_master_status(bus);
                readx_poll_timeout_atomic(ioread8, bus->reg + NPCM_I2CCST, val,
                                          !(val & NPCM_I2CCST_BUSY), 10, 200);
        }
        bus->state = I2C_IDLE;

        /*
         * In Master mode, NACK should be cleared only after STOP.
         * In such case, the bus is released from stall only after the
         * software clears NACK bit. Then a Stop condition is sent.
         */
        npcm_i2c_callback(bus, bus->stop_ind, bus->wr_ind);
}

        /* Master mode: a Bus Error has been identified */
static void npcm_i2c_irq_handle_ber(struct npcm_i2c *bus)
{
        if (bus->ber_cnt < ULLONG_MAX)
                bus->ber_cnt++;
        bus->stop_ind = I2C_BUS_ERR_IND;
        if (npcm_i2c_is_master(bus)) {
                npcm_i2c_master_abort(bus);
        } else {
                npcm_i2c_clear_master_status(bus);

                /* Clear BB (BUS BUSY) bit */
                iowrite8(NPCM_I2CCST_BB, bus->reg + NPCM_I2CCST);

                bus->cmd_err = -EAGAIN;
                npcm_i2c_callback(bus, bus->stop_ind, npcm_i2c_get_index(bus));
        }
        bus->state = I2C_IDLE;
}

        /* EOB: a master End Of Busy (meaning STOP completed) */
static void npcm_i2c_irq_handle_eob(struct npcm_i2c *bus)
{
        npcm_i2c_eob_int(bus, false);
        bus->state = I2C_IDLE;
        npcm_i2c_callback(bus, bus->stop_ind, bus->rd_ind);
}

/* Address sent and requested stall occurred (Master mode) */
static void npcm_i2c_irq_handle_stall_after_start(struct npcm_i2c *bus)
{
        if (npcm_i2c_is_quick(bus)) {
                bus->state = I2C_STOP_PENDING;
                bus->stop_ind = I2C_MASTER_DONE_IND;
                npcm_i2c_eob_int(bus, true);
                npcm_i2c_master_stop(bus);
        } else if ((bus->rd_size == 1) && !bus->read_block_use) {
                /*
                 * Receiving one byte only - set NACK after ensuring
                 * slave ACKed the address byte.
                 */
                npcm_i2c_nack(bus);
        }

        /* Reset stall-after-address-byte */
        npcm_i2c_stall_after_start(bus, false);

        /* Clear stall only after setting STOP */
        iowrite8(NPCM_I2CST_STASTR, bus->reg + NPCM_I2CST);
}

/* SDA status is set - TX or RX, master */
static void npcm_i2c_irq_handle_sda(struct npcm_i2c *bus, u8 i2cst)
{
        u8 fif_cts;

        if (!npcm_i2c_is_master(bus))
                return;

        if (bus->state == I2C_IDLE) {
                bus->stop_ind = I2C_WAKE_UP_IND;

                if (npcm_i2c_is_quick(bus) || bus->read_block_use)
                        /*
                         * Need to stall after successful
                         * completion of sending address byte
                         */
                        npcm_i2c_stall_after_start(bus, true);
                else
                        npcm_i2c_stall_after_start(bus, false);

                /*
                 * Receiving one byte only - stall after successful completion
                 * of sending address byte If we NACK here, and slave doesn't
                 * ACK the address, we might unintentionally NACK the next
                 * multi-byte read
                 */
                if (bus->wr_size == 0 && bus->rd_size == 1)
                        npcm_i2c_stall_after_start(bus, true);

                /* Initiate I2C master tx */

                /* select bank 1 for FIFO regs */
                npcm_i2c_select_bank(bus, I2C_BANK_1);

                fif_cts = ioread8(bus->reg + NPCM_I2CFIF_CTS);
                fif_cts = fif_cts & ~NPCM_I2CFIF_CTS_SLVRSTR;

                /* clear FIFO and relevant status bits. */
                fif_cts = fif_cts | NPCM_I2CFIF_CTS_CLR_FIFO;
                iowrite8(fif_cts, bus->reg + NPCM_I2CFIF_CTS);

                /* re-enable */
                fif_cts = fif_cts | NPCM_I2CFIF_CTS_RXF_TXE;
                iowrite8(fif_cts, bus->reg + NPCM_I2CFIF_CTS);

                /*
                 * Configure the FIFO threshold:
                 * according to the needed # of bytes to read.
                 * Note: due to HW limitation can't config the rx fifo before it
                 * got and ACK on the restart. LAST bit will not be reset unless
                 * RX completed. It will stay set on the next tx.
                 */
                if (bus->wr_size)
                        npcm_i2c_set_fifo(bus, -1, bus->wr_size);
                else
                        npcm_i2c_set_fifo(bus, bus->rd_size, -1);

                bus->state = I2C_OPER_STARTED;

                if (npcm_i2c_is_quick(bus) || bus->wr_size)
                        npcm_i2c_wr_byte(bus, bus->dest_addr);
                else
                        npcm_i2c_wr_byte(bus, bus->dest_addr | BIT(0));
        /* SDA interrupt, after start\restart */
        } else {
                if (NPCM_I2CST_XMIT & i2cst) {
                        bus->operation = I2C_WRITE_OPER;
                        npcm_i2c_irq_master_handler_write(bus);
                } else {
                        bus->operation = I2C_READ_OPER;
                        npcm_i2c_irq_master_handler_read(bus);
                }
        }
}

static int npcm_i2c_int_master_handler(struct npcm_i2c *bus)
{
        u8 i2cst;
        int ret = -EIO;

        i2cst = ioread8(bus->reg + NPCM_I2CST);

        if (FIELD_GET(NPCM_I2CST_NMATCH, i2cst)) {
                npcm_i2c_irq_handle_nmatch(bus);
                return 0;
        }
        /* A NACK has occurred */
        if (FIELD_GET(NPCM_I2CST_NEGACK, i2cst)) {
                npcm_i2c_irq_handle_nack(bus);
                return 0;
        }

        /* Master mode: a Bus Error has been identified */
        if (FIELD_GET(NPCM_I2CST_BER, i2cst)) {
                npcm_i2c_irq_handle_ber(bus);
                return 0;
        }

        /* EOB: a master End Of Busy (meaning STOP completed) */
        if ((FIELD_GET(NPCM_I2CCTL1_EOBINTE,
                       ioread8(bus->reg + NPCM_I2CCTL1)) == 1) &&
            (FIELD_GET(NPCM_I2CCST3_EO_BUSY,
                       ioread8(bus->reg + NPCM_I2CCST3)))) {
                npcm_i2c_irq_handle_eob(bus);
                return 0;
        }

        /* Address sent and requested stall occurred (Master mode) */
        if (FIELD_GET(NPCM_I2CST_STASTR, i2cst)) {
                npcm_i2c_irq_handle_stall_after_start(bus);
                ret = 0;
        }

        /* SDA status is set - TX or RX, master */
        if (FIELD_GET(NPCM_I2CST_SDAST, i2cst) ||
            (bus->fifo_use &&
            (npcm_i2c_tx_fifo_empty(bus) || npcm_i2c_rx_fifo_full(bus)))) {
                npcm_i2c_irq_handle_sda(bus, i2cst);
                ret = 0;
        }

        return ret;
}

/* recovery using TGCLK functionality of the module */
static int npcm_i2c_recovery_tgclk(struct i2c_adapter *_adap)
{
        u8               val;
        u8               fif_cts;
        bool             done = false;
        int              status = -ENOTRECOVERABLE;
        struct npcm_i2c *bus = container_of(_adap, struct npcm_i2c, adap);
        /* Allow 3 bytes (27 toggles) to be read from the slave: */
        int              iter = 27;

        if ((npcm_i2c_get_SDA(_adap) == 1) && (npcm_i2c_get_SCL(_adap) == 1)) {
                dev_dbg(bus->dev, "bus%d recovery skipped, bus not stuck",
                        bus->num);
                npcm_i2c_reset(bus);
                return status;
        }

        npcm_i2c_int_enable(bus, false);
        npcm_i2c_disable(bus);
        npcm_i2c_enable(bus);
        iowrite8(NPCM_I2CCST_BB, bus->reg + NPCM_I2CCST);
        npcm_i2c_clear_tx_fifo(bus);
        npcm_i2c_clear_rx_fifo(bus);
        iowrite8(0, bus->reg + NPCM_I2CRXF_CTL);
        iowrite8(0, bus->reg + NPCM_I2CTXF_CTL);
        npcm_i2c_stall_after_start(bus, false);

        /* select bank 1 for FIFO regs */
        npcm_i2c_select_bank(bus, I2C_BANK_1);

        /* clear FIFO and relevant status bits. */
        fif_cts = ioread8(bus->reg + NPCM_I2CFIF_CTS);
        fif_cts &= ~NPCM_I2CFIF_CTS_SLVRSTR;
        fif_cts |= NPCM_I2CFIF_CTS_CLR_FIFO;
        iowrite8(fif_cts, bus->reg + NPCM_I2CFIF_CTS);
        npcm_i2c_set_fifo(bus, -1, 0);

        /* Repeat the following sequence until SDA is released */
        do {
                /* Issue a single SCL toggle */
                iowrite8(NPCM_I2CCST_TGSCL, bus->reg + NPCM_I2CCST);
                usleep_range(20, 30);
                /* If SDA line is inactive (high), stop */
                if (npcm_i2c_get_SDA(_adap)) {
                        done = true;
                        status = 0;
                }
        } while (!done && iter--);

        /* If SDA line is released: send start-addr-stop, to re-sync. */
        if (npcm_i2c_get_SDA(_adap)) {
                /* Send an address byte in write direction: */
                npcm_i2c_wr_byte(bus, bus->dest_addr);
                npcm_i2c_master_start(bus);
                /* Wait until START condition is sent */
                status = readx_poll_timeout(npcm_i2c_get_SCL, _adap, val, !val,
                                            20, 200);
                /* If START condition was sent */
                if (npcm_i2c_is_master(bus) > 0) {
                        usleep_range(20, 30);
                        npcm_i2c_master_stop(bus);
                        usleep_range(200, 500);
                }
        }
        npcm_i2c_reset(bus);
        npcm_i2c_int_enable(bus, true);

        if ((npcm_i2c_get_SDA(_adap) == 1) && (npcm_i2c_get_SCL(_adap) == 1))
                status = 0;
        else
                status = -ENOTRECOVERABLE;
        if (status) {
                if (bus->rec_fail_cnt < ULLONG_MAX)
                        bus->rec_fail_cnt++;
        } else {
                if (bus->rec_succ_cnt < ULLONG_MAX)
                        bus->rec_succ_cnt++;
        }
        return status;
}

/* recovery using bit banging functionality of the module */
static void npcm_i2c_recovery_init(struct i2c_adapter *_adap)
{
        struct npcm_i2c *bus = container_of(_adap, struct npcm_i2c, adap);
        struct i2c_bus_recovery_info *rinfo = &bus->rinfo;

        rinfo->recover_bus = npcm_i2c_recovery_tgclk;

        /*
         * npcm i2c HW allows direct reading of SCL and SDA.
         * However, it does not support setting SCL and SDA directly.
         * The recovery function can togle SCL when SDA is low (but not set)
         * Getter functions used internally, and can be used externaly.
         */
        rinfo->get_scl = npcm_i2c_get_SCL;
        rinfo->get_sda = npcm_i2c_get_SDA;
        _adap->bus_recovery_info = rinfo;
}

/* SCLFRQ min/max field values */
#define SCLFRQ_MIN  10
#define SCLFRQ_MAX  511
#define clk_coef(freq, mul)     DIV_ROUND_UP((freq) * (mul), 1000000)

/*
 * npcm_i2c_init_clk: init HW timing parameters.
 * NPCM7XX i2c module timing parameters are depenent on module core clk (APB)
 * and bus frequency.
 * 100kHz bus requires tSCL = 4 * SCLFRQ * tCLK. LT and HT are simetric.
 * 400kHz bus requires assymetric HT and LT. A different equation is recomended
 * by the HW designer, given core clock range (equations in comments below).
 *
 */
static int npcm_i2c_init_clk(struct npcm_i2c *bus, u32 bus_freq_hz)
{
        u32  k1 = 0;
        u32  k2 = 0;
        u8   dbnct = 0;
        u32  sclfrq = 0;
        u8   hldt = 7;
        u8   fast_mode = 0;
        u32  src_clk_khz;
        u32  bus_freq_khz;

        src_clk_khz = bus->apb_clk / 1000;
        bus_freq_khz = bus_freq_hz / 1000;
        bus->bus_freq = bus_freq_hz;

        /* 100KHz and below: */
        if (bus_freq_hz <= I2C_MAX_STANDARD_MODE_FREQ) {
                sclfrq = src_clk_khz / (bus_freq_khz * 4);

                if (sclfrq < SCLFRQ_MIN || sclfrq > SCLFRQ_MAX)
                        return -EDOM;

                if (src_clk_khz >= 40000)
                        hldt = 17;
                else if (src_clk_khz >= 12500)
                        hldt = 15;
                else
                        hldt = 7;
        }

        /* 400KHz: */
        else if (bus_freq_hz <= I2C_MAX_FAST_MODE_FREQ) {
                sclfrq = 0;
                fast_mode = I2CCTL3_400K_MODE;

                if (src_clk_khz < 7500)
                        /* 400KHZ cannot be supported for core clock < 7.5MHz */
                        return -EDOM;

                else if (src_clk_khz >= 50000) {
                        k1 = 80;
                        k2 = 48;
                        hldt = 12;
                        dbnct = 7;
                }

                /* Master or Slave with frequency > 25MHz */
                else if (src_clk_khz > 25000) {
                        hldt = clk_coef(src_clk_khz, 300) + 7;
                        k1 = clk_coef(src_clk_khz, 1600);
                        k2 = clk_coef(src_clk_khz, 900);
                }
        }

        /* 1MHz: */
        else if (bus_freq_hz <= I2C_MAX_FAST_MODE_PLUS_FREQ) {
                sclfrq = 0;
                fast_mode = I2CCTL3_400K_MODE;

                /* 1MHZ cannot be supported for core clock < 24 MHz */
                if (src_clk_khz < 24000)
                        return -EDOM;

                k1 = clk_coef(src_clk_khz, 620);
                k2 = clk_coef(src_clk_khz, 380);

                /* Core clk > 40 MHz */
                if (src_clk_khz > 40000) {
                        /*
                         * Set HLDT:
                         * SDA hold time:  (HLDT-7) * T(CLK) >= 120
                         * HLDT = 120/T(CLK) + 7 = 120 * FREQ(CLK) + 7
                         */
                        hldt = clk_coef(src_clk_khz, 120) + 7;
                } else {
                        hldt = 7;
                        dbnct = 2;
                }
        }

        /* Frequency larger than 1 MHz is not supported */
        else
                return -EINVAL;

        if (bus_freq_hz >= I2C_MAX_FAST_MODE_FREQ) {
                k1 = round_up(k1, 2);
                k2 = round_up(k2 + 1, 2);
                if (k1 < SCLFRQ_MIN || k1 > SCLFRQ_MAX ||
                    k2 < SCLFRQ_MIN || k2 > SCLFRQ_MAX)
                        return -EDOM;
        }

        /* write sclfrq value. bits [6:0] are in I2CCTL2 reg */
        iowrite8(FIELD_PREP(I2CCTL2_SCLFRQ6_0, sclfrq & 0x7F),
                 bus->reg + NPCM_I2CCTL2);

        /* bits [8:7] are in I2CCTL3 reg */
        iowrite8(fast_mode | FIELD_PREP(I2CCTL3_SCLFRQ8_7, (sclfrq >> 7) & 0x3),
                 bus->reg + NPCM_I2CCTL3);

        /* Select Bank 0 to access NPCM_I2CCTL4/NPCM_I2CCTL5 */
        npcm_i2c_select_bank(bus, I2C_BANK_0);

        if (bus_freq_hz >= I2C_MAX_FAST_MODE_FREQ) {
                /*
                 * Set SCL Low/High Time:
                 * k1 = 2 * SCLLT7-0 -> Low Time  = k1 / 2
                 * k2 = 2 * SCLLT7-0 -> High Time = k2 / 2
                 */
                iowrite8(k1 / 2, bus->reg + NPCM_I2CSCLLT);
                iowrite8(k2 / 2, bus->reg + NPCM_I2CSCLHT);

                iowrite8(dbnct, bus->reg + NPCM_I2CCTL5);
        }

        iowrite8(hldt, bus->reg + NPCM_I2CCTL4);

        /* Return to Bank 1, and stay there by default: */
        npcm_i2c_select_bank(bus, I2C_BANK_1);

        return 0;
}

static int npcm_i2c_init_module(struct npcm_i2c *bus, enum i2c_mode mode,
                                u32 bus_freq_hz)
{
        u8 val;
        int ret;

        /* Check whether module already enabled or frequency is out of bounds */
        if ((bus->state != I2C_DISABLE && bus->state != I2C_IDLE) ||
            bus_freq_hz < I2C_FREQ_MIN_HZ || bus_freq_hz > I2C_FREQ_MAX_HZ)
                return -EINVAL;

        npcm_i2c_disable(bus);

        /* Configure FIFO mode : */
        if (FIELD_GET(I2C_VER_FIFO_EN, ioread8(bus->reg + I2C_VER))) {
                bus->fifo_use = true;
                npcm_i2c_select_bank(bus, I2C_BANK_0);
                val = ioread8(bus->reg + NPCM_I2CFIF_CTL);
                val |= NPCM_I2CFIF_CTL_FIFO_EN;
                iowrite8(val, bus->reg + NPCM_I2CFIF_CTL);
                npcm_i2c_select_bank(bus, I2C_BANK_1);
        } else {
                bus->fifo_use = false;
        }

        /* Configure I2C module clock frequency */
        ret = npcm_i2c_init_clk(bus, bus_freq_hz);
        if (ret) {
                dev_err(bus->dev, "npcm_i2c_init_clk failed\n");
                return ret;
        }

        /* Enable module (before configuring CTL1) */
        npcm_i2c_enable(bus);
        bus->state = I2C_IDLE;
        val = ioread8(bus->reg + NPCM_I2CCTL1);
        val = (val | NPCM_I2CCTL1_NMINTE) & ~NPCM_I2CCTL1_RWS;
        iowrite8(val, bus->reg + NPCM_I2CCTL1);

        npcm_i2c_int_enable(bus, true);

        npcm_i2c_reset(bus);

        return 0;
}

static int __npcm_i2c_init(struct npcm_i2c *bus, struct platform_device *pdev)
{
        u32 clk_freq_hz;
        int ret;

        /* Initialize the internal data structures */
        bus->state = I2C_DISABLE;
        bus->master_or_slave = I2C_SLAVE;
        bus->int_time_stamp = 0;
#if IS_ENABLED(CONFIG_I2C_SLAVE)
        bus->slave = NULL;
#endif

        ret = device_property_read_u32(&pdev->dev, "clock-frequency",
                                       &clk_freq_hz);
        if (ret) {
                dev_info(&pdev->dev, "Could not read clock-frequency property");
                clk_freq_hz = I2C_MAX_STANDARD_MODE_FREQ;
        }

        ret = npcm_i2c_init_module(bus, I2C_MASTER, clk_freq_hz);
        if (ret) {
                dev_err(&pdev->dev, "npcm_i2c_init_module failed\n");
                return ret;
        }

        return 0;
}

static irqreturn_t npcm_i2c_bus_irq(int irq, void *dev_id)
{
        struct npcm_i2c *bus = dev_id;

        if (npcm_i2c_is_master(bus))
                bus->master_or_slave = I2C_MASTER;

        if (bus->master_or_slave == I2C_MASTER) {
                bus->int_time_stamp = jiffies;
                if (!npcm_i2c_int_master_handler(bus))
                        return IRQ_HANDLED;
        }
#if IS_ENABLED(CONFIG_I2C_SLAVE)
        if (bus->slave) {
                bus->master_or_slave = I2C_SLAVE;
                return npcm_i2c_int_slave_handler(bus);
        }
#endif
        return IRQ_NONE;
}

static bool npcm_i2c_master_start_xmit(struct npcm_i2c *bus,
                                       u8 slave_addr, u16 nwrite, u16 nread,
                                       u8 *write_data, u8 *read_data,
                                       bool use_PEC, bool use_read_block)
{
        if (bus->state != I2C_IDLE) {
                bus->cmd_err = -EBUSY;
                return false;
        }
        bus->dest_addr = slave_addr << 1;
        bus->wr_buf = write_data;
        bus->wr_size = nwrite;
        bus->wr_ind = 0;
        bus->rd_buf = read_data;
        bus->rd_size = nread;
        bus->rd_ind = 0;
        bus->PEC_use = 0;

        /* for tx PEC is appended to buffer from i2c IF. PEC flag is ignored */
        if (nread)
                bus->PEC_use = use_PEC;

        bus->read_block_use = use_read_block;
        if (nread && !nwrite)
                bus->operation = I2C_READ_OPER;
        else
                bus->operation = I2C_WRITE_OPER;
        if (bus->fifo_use) {
                u8 i2cfif_cts;

                npcm_i2c_select_bank(bus, I2C_BANK_1);
                /* clear FIFO and relevant status bits. */
                i2cfif_cts = ioread8(bus->reg + NPCM_I2CFIF_CTS);
                i2cfif_cts &= ~NPCM_I2CFIF_CTS_SLVRSTR;
                i2cfif_cts |= NPCM_I2CFIF_CTS_CLR_FIFO;
                iowrite8(i2cfif_cts, bus->reg + NPCM_I2CFIF_CTS);
        }

        bus->state = I2C_IDLE;
        npcm_i2c_stall_after_start(bus, true);
        npcm_i2c_master_start(bus);
        return true;
}

static int npcm_i2c_master_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
                                int num)
{
        struct npcm_i2c *bus = container_of(adap, struct npcm_i2c, adap);
        struct i2c_msg *msg0, *msg1;
        unsigned long time_left, flags;
        u16 nwrite, nread;
        u8 *write_data, *read_data;
        u8 slave_addr;
        int timeout;
        int ret = 0;
        bool read_block = false;
        bool read_PEC = false;
        u8 bus_busy;
        unsigned long timeout_usec;

        if (bus->state == I2C_DISABLE) {
                dev_err(bus->dev, "I2C%d module is disabled", bus->num);
                return -EINVAL;
        }

        msg0 = &msgs[0];
        slave_addr = msg0->addr;
        if (msg0->flags & I2C_M_RD) { /* read */
                nwrite = 0;
                write_data = NULL;
                read_data = msg0->buf;
                if (msg0->flags & I2C_M_RECV_LEN) {
                        nread = 1;
                        read_block = true;
                        if (msg0->flags & I2C_CLIENT_PEC)
                                read_PEC = true;
                } else {
                        nread = msg0->len;
                }
        } else { /* write */
                nwrite = msg0->len;
                write_data = msg0->buf;
                nread = 0;
                read_data = NULL;
                if (num == 2) {
                        msg1 = &msgs[1];
                        read_data = msg1->buf;
                        if (msg1->flags & I2C_M_RECV_LEN) {
                                nread = 1;
                                read_block = true;
                                if (msg1->flags & I2C_CLIENT_PEC)
                                        read_PEC = true;
                        } else {
                                nread = msg1->len;
                                read_block = false;
                        }
                }
        }

        /* Adaptive TimeOut: astimated time in usec + 100% margin */
        timeout_usec = (2 * 10000 / bus->bus_freq) * (2 + nread + nwrite);
        timeout = max(msecs_to_jiffies(35), usecs_to_jiffies(timeout_usec));
        if (nwrite >= 32 * 1024 || nread >= 32 * 1024) {
                dev_err(bus->dev, "i2c%d buffer too big\n", bus->num);
                return -EINVAL;
        }

        time_left = jiffies + msecs_to_jiffies(DEFAULT_STALL_COUNT) + 1;
        do {
                /*
                 * we must clear slave address immediately when the bus is not
                 * busy, so we spinlock it, but we don't keep the lock for the
                 * entire while since it is too long.
                 */
                spin_lock_irqsave(&bus->lock, flags);
                bus_busy = ioread8(bus->reg + NPCM_I2CCST) & NPCM_I2CCST_BB;
#if IS_ENABLED(CONFIG_I2C_SLAVE)
                if (!bus_busy && bus->slave)
                        iowrite8((bus->slave->addr & 0x7F),
                                 bus->reg + NPCM_I2CADDR1);
#endif
                spin_unlock_irqrestore(&bus->lock, flags);

        } while (time_is_after_jiffies(time_left) && bus_busy);

        if (bus_busy) {
                iowrite8(NPCM_I2CCST_BB, bus->reg + NPCM_I2CCST);
                npcm_i2c_reset(bus);
                i2c_recover_bus(adap);
                return -EAGAIN;
        }

        npcm_i2c_init_params(bus);
        bus->dest_addr = slave_addr;
        bus->msgs = msgs;
        bus->msgs_num = num;
        bus->cmd_err = 0;
        bus->read_block_use = read_block;

        reinit_completion(&bus->cmd_complete);
        if (!npcm_i2c_master_start_xmit(bus, slave_addr, nwrite, nread,
                                        write_data, read_data, read_PEC,
                                        read_block))
                ret = -EBUSY;

        if (ret != -EBUSY) {
                time_left = wait_for_completion_timeout(&bus->cmd_complete,
                                                        timeout);

                if (time_left == 0) {
                        if (bus->timeout_cnt < ULLONG_MAX)
                                bus->timeout_cnt++;
                        if (bus->master_or_slave == I2C_MASTER) {
                                i2c_recover_bus(adap);
                                bus->cmd_err = -EIO;
                                bus->state = I2C_IDLE;
                        }
                }
        }
        ret = bus->cmd_err;

        /* if there was BER, check if need to recover the bus: */
        if (bus->cmd_err == -EAGAIN)
                ret = i2c_recover_bus(adap);

#if IS_ENABLED(CONFIG_I2C_SLAVE)
        /* reenable slave if it was enabled */
        if (bus->slave)
                iowrite8((bus->slave->addr & 0x7F) | NPCM_I2CADDR_SAEN,
                         bus->reg + NPCM_I2CADDR1);
#endif
        return bus->cmd_err;
}

static u32 npcm_i2c_functionality(struct i2c_adapter *adap)
{
        return I2C_FUNC_I2C |
               I2C_FUNC_SMBUS_EMUL |
               I2C_FUNC_SMBUS_BLOCK_DATA |
               I2C_FUNC_SMBUS_PEC |
               I2C_FUNC_SLAVE;
}

static const struct i2c_adapter_quirks npcm_i2c_quirks = {
        .max_read_len = 32768,
        .max_write_len = 32768,
        .flags = I2C_AQ_COMB_WRITE_THEN_READ,
};

static const struct i2c_algorithm npcm_i2c_algo = {
        .master_xfer = npcm_i2c_master_xfer,
        .functionality = npcm_i2c_functionality,
#if IS_ENABLED(CONFIG_I2C_SLAVE)
        .reg_slave      = npcm_i2c_reg_slave,
        .unreg_slave    = npcm_i2c_unreg_slave,
#endif
};

/* i2c debugfs directory: used to keep health monitor of i2c devices */
static struct dentry *npcm_i2c_debugfs_dir;

static void npcm_i2c_init_debugfs(struct platform_device *pdev,
                                  struct npcm_i2c *bus)
{
        struct dentry *d;

        if (!npcm_i2c_debugfs_dir)
                return;
        d = debugfs_create_dir(dev_name(&pdev->dev), npcm_i2c_debugfs_dir);
        if (IS_ERR_OR_NULL(d))
                return;
        debugfs_create_u64("ber_cnt", 0444, d, &bus->ber_cnt);
        debugfs_create_u64("nack_cnt", 0444, d, &bus->nack_cnt);
        debugfs_create_u64("rec_succ_cnt", 0444, d, &bus->rec_succ_cnt);
        debugfs_create_u64("rec_fail_cnt", 0444, d, &bus->rec_fail_cnt);
        debugfs_create_u64("timeout_cnt", 0444, d, &bus->timeout_cnt);

        bus->debugfs = d;
}

static int npcm_i2c_probe_bus(struct platform_device *pdev)
{
        struct npcm_i2c *bus;
        struct i2c_adapter *adap;
        struct clk *i2c_clk;
        static struct regmap *gcr_regmap;
        static struct regmap *clk_regmap;
        int irq;
        int ret;

        bus = devm_kzalloc(&pdev->dev, sizeof(*bus), GFP_KERNEL);
        if (!bus)
                return -ENOMEM;

        bus->dev = &pdev->dev;

        bus->num = of_alias_get_id(pdev->dev.of_node, "i2c");
        /* core clk must be acquired to calculate module timing settings */
        i2c_clk = devm_clk_get(&pdev->dev, NULL);
        if (IS_ERR(i2c_clk))
                return PTR_ERR(i2c_clk);
        bus->apb_clk = clk_get_rate(i2c_clk);

        gcr_regmap = syscon_regmap_lookup_by_compatible("nuvoton,npcm750-gcr");
        if (IS_ERR(gcr_regmap))
                return PTR_ERR(gcr_regmap);
        regmap_write(gcr_regmap, NPCM_I2CSEGCTL, NPCM_I2CSEGCTL_INIT_VAL);

        clk_regmap = syscon_regmap_lookup_by_compatible("nuvoton,npcm750-clk");
        if (IS_ERR(clk_regmap))
                return PTR_ERR(clk_regmap);

        bus->reg = devm_platform_ioremap_resource(pdev, 0);
        if (IS_ERR(bus->reg))
                return PTR_ERR(bus->reg);

        spin_lock_init(&bus->lock);
        init_completion(&bus->cmd_complete);

        adap = &bus->adap;
        adap->owner = THIS_MODULE;
        adap->retries = 3;
        adap->timeout = HZ;
        adap->algo = &npcm_i2c_algo;
        adap->quirks = &npcm_i2c_quirks;
        adap->algo_data = bus;
        adap->dev.parent = &pdev->dev;
        adap->dev.of_node = pdev->dev.of_node;
        adap->nr = pdev->id;

        irq = platform_get_irq(pdev, 0);
        if (irq < 0)
                return irq;

        ret = devm_request_irq(bus->dev, irq, npcm_i2c_bus_irq, 0,
                               dev_name(bus->dev), bus);
        if (ret)
                return ret;

        ret = __npcm_i2c_init(bus, pdev);
        if (ret)
                return ret;

        npcm_i2c_recovery_init(adap);

        i2c_set_adapdata(adap, bus);

        snprintf(bus->adap.name, sizeof(bus->adap.name), "npcm_i2c_%d",
                 bus->num);
        ret = i2c_add_numbered_adapter(&bus->adap);
        if (ret)
                return ret;

        platform_set_drvdata(pdev, bus);
        npcm_i2c_init_debugfs(pdev, bus);
        return 0;
}

static int npcm_i2c_remove_bus(struct platform_device *pdev)
{
        unsigned long lock_flags;
        struct npcm_i2c *bus = platform_get_drvdata(pdev);

        debugfs_remove_recursive(bus->debugfs);
        spin_lock_irqsave(&bus->lock, lock_flags);
        npcm_i2c_disable(bus);
        spin_unlock_irqrestore(&bus->lock, lock_flags);
        i2c_del_adapter(&bus->adap);
        return 0;
}

static const struct of_device_id npcm_i2c_bus_of_table[] = {
        { .compatible = "nuvoton,npcm750-i2c", },
        {}
};
MODULE_DEVICE_TABLE(of, npcm_i2c_bus_of_table);

static struct platform_driver npcm_i2c_bus_driver = {
        .probe = npcm_i2c_probe_bus,
        .remove = npcm_i2c_remove_bus,
        .driver = {
                .name = "nuvoton-i2c",
                .of_match_table = npcm_i2c_bus_of_table,
        }
};

static int __init npcm_i2c_init(void)
{
        npcm_i2c_debugfs_dir = debugfs_create_dir("npcm_i2c", NULL);
        platform_driver_register(&npcm_i2c_bus_driver);
        return 0;
}
module_init(npcm_i2c_init);

static void __exit npcm_i2c_exit(void)
{
        platform_driver_unregister(&npcm_i2c_bus_driver);
        debugfs_remove_recursive(npcm_i2c_debugfs_dir);
}
module_exit(npcm_i2c_exit);

MODULE_AUTHOR("Avi Fishman <avi.fishman@gmail.com>");
MODULE_AUTHOR("Tali Perry <tali.perry@nuvoton.com>");
MODULE_AUTHOR("Tyrone Ting <kfting@nuvoton.com>");
MODULE_DESCRIPTION("Nuvoton I2C Bus Driver");
MODULE_LICENSE("GPL v2");