WIP FPC-III support

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

// SPDX-License-Identifier: GPL-2.0-only
/*
 * I2C adapter for the IMG Serial Control Bus (SCB) IP block.
 *
 * Copyright (C) 2009, 2010, 2012, 2014 Imagination Technologies Ltd.
 *
 * There are three ways that this I2C controller can be driven:
 *
 * - Raw control of the SDA and SCK signals.
 *
 *   This corresponds to MODE_RAW, which takes control of the signals
 *   directly for a certain number of clock cycles (the INT_TIMING
 *   interrupt can be used for timing).
 *
 * - Atomic commands. A low level I2C symbol (such as generate
 *   start/stop/ack/nack bit, generate byte, receive byte, and receive
 *   ACK) is given to the hardware, with detection of completion by bits
 *   in the LINESTAT register.
 *
 *   This mode of operation is used by MODE_ATOMIC, which uses an I2C
 *   state machine in the interrupt handler to compose/react to I2C
 *   transactions using atomic mode commands, and also by MODE_SEQUENCE,
 *   which emits a simple fixed sequence of atomic mode commands.
 *
 *   Due to software control, the use of atomic commands usually results
 *   in suboptimal use of the bus, with gaps between the I2C symbols while
 *   the driver decides what to do next.
 *
 * - Automatic mode. A bus address, and whether to read/write is
 *   specified, and the hardware takes care of the I2C state machine,
 *   using a FIFO to send/receive bytes of data to an I2C slave. The
 *   driver just has to keep the FIFO drained or filled in response to the
 *   appropriate FIFO interrupts.
 *
 *   This corresponds to MODE_AUTOMATIC, which manages the FIFOs and deals
 *   with control of repeated start bits between I2C messages.
 *
 *   Use of automatic mode and the FIFO can make much more efficient use
 *   of the bus compared to individual atomic commands, with potentially
 *   no wasted time between I2C symbols or I2C messages.
 *
 * In most cases MODE_AUTOMATIC is used, however if any of the messages in
 * a transaction are zero byte writes (e.g. used by i2cdetect for probing
 * the bus), MODE_ATOMIC must be used since automatic mode is normally
 * started by the writing of data into the FIFO.
 *
 * The other modes are used in specific circumstances where MODE_ATOMIC and
 * MODE_AUTOMATIC aren't appropriate. MODE_RAW is used to implement a bus
 * recovery routine. MODE_SEQUENCE is used to reset the bus and make sure
 * it is in a sane state.
 *
 * Notice that the driver implements a timer-based timeout mechanism.
 * The reason for this mechanism is to reduce the number of interrupts
 * received in automatic mode.
 *
 * The driver would get a slave event and transaction done interrupts for
 * each atomic mode command that gets completed. However, these events are
 * not needed in automatic mode, becase those atomic mode commands are
 * managed automatically by the hardware.
 *
 * In practice, normal I2C transactions will be complete well before you
 * get the timer interrupt, as the timer is re-scheduled during FIFO
 * maintenance and disabled after the transaction is complete.
 *
 * In this way normal automatic mode operation isn't impacted by
 * unnecessary interrupts, but the exceptional abort condition can still be
 * detected (with a slight delay).
 */

#include <linux/bitops.h>
#include <linux/clk.h>
#include <linux/completion.h>
#include <linux/err.h>
#include <linux/i2c.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/of_platform.h>
#include <linux/platform_device.h>
#include <linux/pm_runtime.h>
#include <linux/slab.h>
#include <linux/timer.h>

/* Register offsets */

#define SCB_STATUS_REG                  0x00
#define SCB_OVERRIDE_REG                0x04
#define SCB_READ_ADDR_REG               0x08
#define SCB_READ_COUNT_REG              0x0c
#define SCB_WRITE_ADDR_REG              0x10
#define SCB_READ_DATA_REG               0x14
#define SCB_WRITE_DATA_REG              0x18
#define SCB_FIFO_STATUS_REG             0x1c
#define SCB_CONTROL_SOFT_RESET          0x1f
#define SCB_CLK_SET_REG                 0x3c
#define SCB_INT_STATUS_REG              0x40
#define SCB_INT_CLEAR_REG               0x44
#define SCB_INT_MASK_REG                0x48
#define SCB_CONTROL_REG                 0x4c
#define SCB_TIME_TPL_REG                0x50
#define SCB_TIME_TPH_REG                0x54
#define SCB_TIME_TP2S_REG               0x58
#define SCB_TIME_TBI_REG                0x60
#define SCB_TIME_TSL_REG                0x64
#define SCB_TIME_TDL_REG                0x68
#define SCB_TIME_TSDL_REG               0x6c
#define SCB_TIME_TSDH_REG               0x70
#define SCB_READ_XADDR_REG              0x74
#define SCB_WRITE_XADDR_REG             0x78
#define SCB_WRITE_COUNT_REG             0x7c
#define SCB_CORE_REV_REG                0x80
#define SCB_TIME_TCKH_REG               0x84
#define SCB_TIME_TCKL_REG               0x88
#define SCB_FIFO_FLUSH_REG              0x8c
#define SCB_READ_FIFO_REG               0x94
#define SCB_CLEAR_REG                   0x98

/* SCB_CONTROL_REG bits */

#define SCB_CONTROL_CLK_ENABLE          0x1e0
#define SCB_CONTROL_TRANSACTION_HALT    0x200

#define FIFO_READ_FULL                  BIT(0)
#define FIFO_READ_EMPTY                 BIT(1)
#define FIFO_WRITE_FULL                 BIT(2)
#define FIFO_WRITE_EMPTY                BIT(3)

/* SCB_CLK_SET_REG bits */
#define SCB_FILT_DISABLE                BIT(31)
#define SCB_FILT_BYPASS                 BIT(30)
#define SCB_FILT_INC_MASK               0x7f
#define SCB_FILT_INC_SHIFT              16
#define SCB_INC_MASK                    0x7f
#define SCB_INC_SHIFT                   8

/* SCB_INT_*_REG bits */

#define INT_BUS_INACTIVE                BIT(0)
#define INT_UNEXPECTED_START            BIT(1)
#define INT_SCLK_LOW_TIMEOUT            BIT(2)
#define INT_SDAT_LOW_TIMEOUT            BIT(3)
#define INT_WRITE_ACK_ERR               BIT(4)
#define INT_ADDR_ACK_ERR                BIT(5)
#define INT_FIFO_FULL                   BIT(9)
#define INT_FIFO_FILLING                BIT(10)
#define INT_FIFO_EMPTY                  BIT(11)
#define INT_FIFO_EMPTYING               BIT(12)
#define INT_TRANSACTION_DONE            BIT(15)
#define INT_SLAVE_EVENT                 BIT(16)
#define INT_MASTER_HALTED               BIT(17)
#define INT_TIMING                      BIT(18)
#define INT_STOP_DETECTED               BIT(19)

#define INT_FIFO_FULL_FILLING   (INT_FIFO_FULL  | INT_FIFO_FILLING)

/* Level interrupts need clearing after handling instead of before */
#define INT_LEVEL                       0x01e00

/* Don't allow any interrupts while the clock may be off */
#define INT_ENABLE_MASK_INACTIVE        0x00000

/* Interrupt masks for the different driver modes */

#define INT_ENABLE_MASK_RAW             INT_TIMING

#define INT_ENABLE_MASK_ATOMIC          (INT_TRANSACTION_DONE | \
                                         INT_SLAVE_EVENT      | \
                                         INT_ADDR_ACK_ERR     | \
                                         INT_WRITE_ACK_ERR)

#define INT_ENABLE_MASK_AUTOMATIC       (INT_SCLK_LOW_TIMEOUT | \
                                         INT_ADDR_ACK_ERR     | \
                                         INT_WRITE_ACK_ERR    | \
                                         INT_FIFO_FULL        | \
                                         INT_FIFO_FILLING     | \
                                         INT_FIFO_EMPTY       | \
                                         INT_MASTER_HALTED    | \
                                         INT_STOP_DETECTED)

#define INT_ENABLE_MASK_WAITSTOP        (INT_SLAVE_EVENT      | \
                                         INT_ADDR_ACK_ERR     | \
                                         INT_WRITE_ACK_ERR)

/* SCB_STATUS_REG fields */

#define LINESTAT_SCLK_LINE_STATUS       BIT(0)
#define LINESTAT_SCLK_EN                BIT(1)
#define LINESTAT_SDAT_LINE_STATUS       BIT(2)
#define LINESTAT_SDAT_EN                BIT(3)
#define LINESTAT_DET_START_STATUS       BIT(4)
#define LINESTAT_DET_STOP_STATUS        BIT(5)
#define LINESTAT_DET_ACK_STATUS         BIT(6)
#define LINESTAT_DET_NACK_STATUS        BIT(7)
#define LINESTAT_BUS_IDLE               BIT(8)
#define LINESTAT_T_DONE_STATUS          BIT(9)
#define LINESTAT_SCLK_OUT_STATUS        BIT(10)
#define LINESTAT_SDAT_OUT_STATUS        BIT(11)
#define LINESTAT_GEN_LINE_MASK_STATUS   BIT(12)
#define LINESTAT_START_BIT_DET          BIT(13)
#define LINESTAT_STOP_BIT_DET           BIT(14)
#define LINESTAT_ACK_DET                BIT(15)
#define LINESTAT_NACK_DET               BIT(16)
#define LINESTAT_INPUT_HELD_V           BIT(17)
#define LINESTAT_ABORT_DET              BIT(18)
#define LINESTAT_ACK_OR_NACK_DET        (LINESTAT_ACK_DET | LINESTAT_NACK_DET)
#define LINESTAT_INPUT_DATA             0xff000000
#define LINESTAT_INPUT_DATA_SHIFT       24

#define LINESTAT_CLEAR_SHIFT            13
#define LINESTAT_LATCHED                (0x3f << LINESTAT_CLEAR_SHIFT)

/* SCB_OVERRIDE_REG fields */

#define OVERRIDE_SCLK_OVR               BIT(0)
#define OVERRIDE_SCLKEN_OVR             BIT(1)
#define OVERRIDE_SDAT_OVR               BIT(2)
#define OVERRIDE_SDATEN_OVR             BIT(3)
#define OVERRIDE_MASTER                 BIT(9)
#define OVERRIDE_LINE_OVR_EN            BIT(10)
#define OVERRIDE_DIRECT                 BIT(11)
#define OVERRIDE_CMD_SHIFT              4
#define OVERRIDE_CMD_MASK               0x1f
#define OVERRIDE_DATA_SHIFT             24

#define OVERRIDE_SCLK_DOWN              (OVERRIDE_LINE_OVR_EN | \
                                         OVERRIDE_SCLKEN_OVR)
#define OVERRIDE_SCLK_UP                (OVERRIDE_LINE_OVR_EN | \
                                         OVERRIDE_SCLKEN_OVR | \
                                         OVERRIDE_SCLK_OVR)
#define OVERRIDE_SDAT_DOWN              (OVERRIDE_LINE_OVR_EN | \
                                         OVERRIDE_SDATEN_OVR)
#define OVERRIDE_SDAT_UP                (OVERRIDE_LINE_OVR_EN | \
                                         OVERRIDE_SDATEN_OVR | \
                                         OVERRIDE_SDAT_OVR)

/* OVERRIDE_CMD values */

#define CMD_PAUSE                       0x00
#define CMD_GEN_DATA                    0x01
#define CMD_GEN_START                   0x02
#define CMD_GEN_STOP                    0x03
#define CMD_GEN_ACK                     0x04
#define CMD_GEN_NACK                    0x05
#define CMD_RET_DATA                    0x08
#define CMD_RET_ACK                     0x09

/* Fixed timing values */

#define TIMEOUT_TBI                     0x0
#define TIMEOUT_TSL                     0xffff
#define TIMEOUT_TDL                     0x0

/* Transaction timeout */

#define IMG_I2C_TIMEOUT                 (msecs_to_jiffies(1000))

/*
 * Worst incs are 1 (innacurate) and 16*256 (irregular).
 * So a sensible inc is the logarithmic mean: 64 (2^6), which is
 * in the middle of the valid range (0-127).
 */
#define SCB_OPT_INC             64

/* Setup the clock enable filtering for 25 ns */
#define SCB_FILT_GLITCH         25

/*
 * Bits to return from interrupt handler functions for different modes.
 * This delays completion until we've finished with the registers, so that the
 * function waiting for completion can safely disable the clock to save power.
 */
#define ISR_COMPLETE_M          BIT(31)
#define ISR_FATAL_M             BIT(30)
#define ISR_WAITSTOP            BIT(29)
#define ISR_STATUS_M            0x0000ffff      /* contains +ve errno */
#define ISR_COMPLETE(err)       (ISR_COMPLETE_M | (ISR_STATUS_M & (err)))
#define ISR_FATAL(err)          (ISR_COMPLETE(err) | ISR_FATAL_M)

#define IMG_I2C_PM_TIMEOUT      1000 /* ms */

enum img_i2c_mode {
        MODE_INACTIVE,
        MODE_RAW,
        MODE_ATOMIC,
        MODE_AUTOMATIC,
        MODE_SEQUENCE,
        MODE_FATAL,
        MODE_WAITSTOP,
        MODE_SUSPEND,
};

/* Timing parameters for i2c modes (in ns) */
struct img_i2c_timings {
        const char *name;
        unsigned int max_bitrate;
        unsigned int tckh, tckl, tsdh, tsdl;
        unsigned int tp2s, tpl, tph;
};

/* The timings array must be ordered from slower to faster */
static struct img_i2c_timings timings[] = {
        /* Standard mode */
        {
                .name = "standard",
                .max_bitrate = I2C_MAX_STANDARD_MODE_FREQ,
                .tckh = 4000,
                .tckl = 4700,
                .tsdh = 4700,
                .tsdl = 8700,
                .tp2s = 4700,
                .tpl = 4700,
                .tph = 4000,
        },
        /* Fast mode */
        {
                .name = "fast",
                .max_bitrate = I2C_MAX_FAST_MODE_FREQ,
                .tckh = 600,
                .tckl = 1300,
                .tsdh = 600,
                .tsdl = 1200,
                .tp2s = 1300,
                .tpl = 600,
                .tph = 600,
        },
};

/* Reset dance */
static u8 img_i2c_reset_seq[] = { CMD_GEN_START,
                                  CMD_GEN_DATA, 0xff,
                                  CMD_RET_ACK,
                                  CMD_GEN_START,
                                  CMD_GEN_STOP,
                                  0 };
/* Just issue a stop (after an abort condition) */
static u8 img_i2c_stop_seq[] = {  CMD_GEN_STOP,
                                  0 };

/* We're interested in different interrupts depending on the mode */
static unsigned int img_i2c_int_enable_by_mode[] = {
        [MODE_INACTIVE]  = INT_ENABLE_MASK_INACTIVE,
        [MODE_RAW]       = INT_ENABLE_MASK_RAW,
        [MODE_ATOMIC]    = INT_ENABLE_MASK_ATOMIC,
        [MODE_AUTOMATIC] = INT_ENABLE_MASK_AUTOMATIC,
        [MODE_SEQUENCE]  = INT_ENABLE_MASK_ATOMIC,
        [MODE_FATAL]     = 0,
        [MODE_WAITSTOP]  = INT_ENABLE_MASK_WAITSTOP,
        [MODE_SUSPEND]   = 0,
};

/* Atomic command names */
static const char * const img_i2c_atomic_cmd_names[] = {
        [CMD_PAUSE]     = "PAUSE",
        [CMD_GEN_DATA]  = "GEN_DATA",
        [CMD_GEN_START] = "GEN_START",
        [CMD_GEN_STOP]  = "GEN_STOP",
        [CMD_GEN_ACK]   = "GEN_ACK",
        [CMD_GEN_NACK]  = "GEN_NACK",
        [CMD_RET_DATA]  = "RET_DATA",
        [CMD_RET_ACK]   = "RET_ACK",
};

struct img_i2c {
        struct i2c_adapter adap;

        void __iomem *base;

        /*
         * The scb core clock is used to get the input frequency, and to disable
         * it after every set of transactions to save some power.
         */
        struct clk *scb_clk, *sys_clk;
        unsigned int bitrate;
        bool need_wr_rd_fence;

        /* state */
        struct completion msg_complete;
        spinlock_t lock;        /* lock before doing anything with the state */
        struct i2c_msg msg;

        /* After the last transaction, wait for a stop bit */
        bool last_msg;
        int msg_status;

        enum img_i2c_mode mode;
        u32 int_enable;         /* depends on mode */
        u32 line_status;        /* line status over command */

        /*
         * To avoid slave event interrupts in automatic mode, use a timer to
         * poll the abort condition if we don't get an interrupt for too long.
         */
        struct timer_list check_timer;
        bool t_halt;

        /* atomic mode state */
        bool at_t_done;
        bool at_slave_event;
        int at_cur_cmd;
        u8 at_cur_data;

        /* Sequence: either reset or stop. See img_i2c_sequence. */
        u8 *seq;

        /* raw mode */
        unsigned int raw_timeout;
};

static int img_i2c_runtime_suspend(struct device *dev);
static int img_i2c_runtime_resume(struct device *dev);

static void img_i2c_writel(struct img_i2c *i2c, u32 offset, u32 value)
{
        writel(value, i2c->base + offset);
}

static u32 img_i2c_readl(struct img_i2c *i2c, u32 offset)
{
        return readl(i2c->base + offset);
}

/*
 * The code to read from the master read fifo, and write to the master
 * write fifo, checks a bit in an SCB register before every byte to
 * ensure that the fifo is not full (write fifo) or empty (read fifo).
 * Due to clock domain crossing inside the SCB block the updated value
 * of this bit is only visible after 2 cycles.
 *
 * The scb_wr_rd_fence() function does 2 dummy writes (to the read-only
 * revision register), and it's called after reading from or writing to the
 * fifos to ensure that subsequent reads of the fifo status bits do not read
 * stale values.
 */
static void img_i2c_wr_rd_fence(struct img_i2c *i2c)
{
        if (i2c->need_wr_rd_fence) {
                img_i2c_writel(i2c, SCB_CORE_REV_REG, 0);
                img_i2c_writel(i2c, SCB_CORE_REV_REG, 0);
        }
}

static void img_i2c_switch_mode(struct img_i2c *i2c, enum img_i2c_mode mode)
{
        i2c->mode = mode;
        i2c->int_enable = img_i2c_int_enable_by_mode[mode];
        i2c->line_status = 0;
}

static void img_i2c_raw_op(struct img_i2c *i2c)
{
        i2c->raw_timeout = 0;
        img_i2c_writel(i2c, SCB_OVERRIDE_REG,
                OVERRIDE_SCLKEN_OVR |
                OVERRIDE_SDATEN_OVR |
                OVERRIDE_MASTER |
                OVERRIDE_LINE_OVR_EN |
                OVERRIDE_DIRECT |
                ((i2c->at_cur_cmd & OVERRIDE_CMD_MASK) << OVERRIDE_CMD_SHIFT) |
                (i2c->at_cur_data << OVERRIDE_DATA_SHIFT));
}

static const char *img_i2c_atomic_op_name(unsigned int cmd)
{
        if (unlikely(cmd >= ARRAY_SIZE(img_i2c_atomic_cmd_names)))
                return "UNKNOWN";
        return img_i2c_atomic_cmd_names[cmd];
}

/* Send a single atomic mode command to the hardware */
static void img_i2c_atomic_op(struct img_i2c *i2c, int cmd, u8 data)
{
        i2c->at_cur_cmd = cmd;
        i2c->at_cur_data = data;

        /* work around lack of data setup time when generating data */
        if (cmd == CMD_GEN_DATA && i2c->mode == MODE_ATOMIC) {
                u32 line_status = img_i2c_readl(i2c, SCB_STATUS_REG);

                if (line_status & LINESTAT_SDAT_LINE_STATUS && !(data & 0x80)) {
                        /* hold the data line down for a moment */
                        img_i2c_switch_mode(i2c, MODE_RAW);
                        img_i2c_raw_op(i2c);
                        return;
                }
        }

        dev_dbg(i2c->adap.dev.parent,
                "atomic cmd=%s (%d) data=%#x\n",
                img_i2c_atomic_op_name(cmd), cmd, data);
        i2c->at_t_done = (cmd == CMD_RET_DATA || cmd == CMD_RET_ACK);
        i2c->at_slave_event = false;
        i2c->line_status = 0;

        img_i2c_writel(i2c, SCB_OVERRIDE_REG,
                ((cmd & OVERRIDE_CMD_MASK) << OVERRIDE_CMD_SHIFT) |
                OVERRIDE_MASTER |
                OVERRIDE_DIRECT |
                (data << OVERRIDE_DATA_SHIFT));
}

/* Start a transaction in atomic mode */
static void img_i2c_atomic_start(struct img_i2c *i2c)
{
        img_i2c_switch_mode(i2c, MODE_ATOMIC);
        img_i2c_writel(i2c, SCB_INT_MASK_REG, i2c->int_enable);
        img_i2c_atomic_op(i2c, CMD_GEN_START, 0x00);
}

static void img_i2c_soft_reset(struct img_i2c *i2c)
{
        i2c->t_halt = false;
        img_i2c_writel(i2c, SCB_CONTROL_REG, 0);
        img_i2c_writel(i2c, SCB_CONTROL_REG,
                       SCB_CONTROL_CLK_ENABLE | SCB_CONTROL_SOFT_RESET);
}

/*
 * Enable or release transaction halt for control of repeated starts.
 * In version 3.3 of the IP when transaction halt is set, an interrupt
 * will be generated after each byte of a transfer instead of after
 * every transfer but before the stop bit.
 * Due to this behaviour we have to be careful that every time we
 * release the transaction halt we have to re-enable it straight away
 * so that we only process a single byte, not doing so will result in
 * all remaining bytes been processed and a stop bit being issued,
 * which will prevent us having a repeated start.
 */
static void img_i2c_transaction_halt(struct img_i2c *i2c, bool t_halt)
{
        u32 val;

        if (i2c->t_halt == t_halt)
                return;
        i2c->t_halt = t_halt;
        val = img_i2c_readl(i2c, SCB_CONTROL_REG);
        if (t_halt)
                val |= SCB_CONTROL_TRANSACTION_HALT;
        else
                val &= ~SCB_CONTROL_TRANSACTION_HALT;
        img_i2c_writel(i2c, SCB_CONTROL_REG, val);
}

/* Drain data from the FIFO into the buffer (automatic mode) */
static void img_i2c_read_fifo(struct img_i2c *i2c)
{
        while (i2c->msg.len) {
                u32 fifo_status;
                u8 data;

                img_i2c_wr_rd_fence(i2c);
                fifo_status = img_i2c_readl(i2c, SCB_FIFO_STATUS_REG);
                if (fifo_status & FIFO_READ_EMPTY)
                        break;

                data = img_i2c_readl(i2c, SCB_READ_DATA_REG);
                *i2c->msg.buf = data;

                img_i2c_writel(i2c, SCB_READ_FIFO_REG, 0xff);
                i2c->msg.len--;
                i2c->msg.buf++;
        }
}

/* Fill the FIFO with data from the buffer (automatic mode) */
static void img_i2c_write_fifo(struct img_i2c *i2c)
{
        while (i2c->msg.len) {
                u32 fifo_status;

                img_i2c_wr_rd_fence(i2c);
                fifo_status = img_i2c_readl(i2c, SCB_FIFO_STATUS_REG);
                if (fifo_status & FIFO_WRITE_FULL)
                        break;

                img_i2c_writel(i2c, SCB_WRITE_DATA_REG, *i2c->msg.buf);
                i2c->msg.len--;
                i2c->msg.buf++;
        }

        /* Disable fifo emptying interrupt if nothing more to write */
        if (!i2c->msg.len)
                i2c->int_enable &= ~INT_FIFO_EMPTYING;
}

/* Start a read transaction in automatic mode */
static void img_i2c_read(struct img_i2c *i2c)
{
        img_i2c_switch_mode(i2c, MODE_AUTOMATIC);
        if (!i2c->last_msg)
                i2c->int_enable |= INT_SLAVE_EVENT;

        img_i2c_writel(i2c, SCB_INT_MASK_REG, i2c->int_enable);
        img_i2c_writel(i2c, SCB_READ_ADDR_REG, i2c->msg.addr);
        img_i2c_writel(i2c, SCB_READ_COUNT_REG, i2c->msg.len);

        mod_timer(&i2c->check_timer, jiffies + msecs_to_jiffies(1));
}

/* Start a write transaction in automatic mode */
static void img_i2c_write(struct img_i2c *i2c)
{
        img_i2c_switch_mode(i2c, MODE_AUTOMATIC);
        if (!i2c->last_msg)
                i2c->int_enable |= INT_SLAVE_EVENT;

        img_i2c_writel(i2c, SCB_WRITE_ADDR_REG, i2c->msg.addr);
        img_i2c_writel(i2c, SCB_WRITE_COUNT_REG, i2c->msg.len);

        mod_timer(&i2c->check_timer, jiffies + msecs_to_jiffies(1));
        img_i2c_write_fifo(i2c);

        /* img_i2c_write_fifo() may modify int_enable */
        img_i2c_writel(i2c, SCB_INT_MASK_REG, i2c->int_enable);
}

/*
 * Indicate that the transaction is complete. This is called from the
 * ISR to wake up the waiting thread, after which the ISR must not
 * access any more SCB registers.
 */
static void img_i2c_complete_transaction(struct img_i2c *i2c, int status)
{
        img_i2c_switch_mode(i2c, MODE_INACTIVE);
        if (status) {
                i2c->msg_status = status;
                img_i2c_transaction_halt(i2c, false);
        }
        complete(&i2c->msg_complete);
}

static unsigned int img_i2c_raw_atomic_delay_handler(struct img_i2c *i2c,
                                        u32 int_status, u32 line_status)
{
        /* Stay in raw mode for this, so we don't just loop infinitely */
        img_i2c_atomic_op(i2c, i2c->at_cur_cmd, i2c->at_cur_data);
        img_i2c_switch_mode(i2c, MODE_ATOMIC);
        return 0;
}

static unsigned int img_i2c_raw(struct img_i2c *i2c, u32 int_status,
                                u32 line_status)
{
        if (int_status & INT_TIMING) {
                if (i2c->raw_timeout == 0)
                        return img_i2c_raw_atomic_delay_handler(i2c,
                                int_status, line_status);
                --i2c->raw_timeout;
        }
        return 0;
}

static unsigned int img_i2c_sequence(struct img_i2c *i2c, u32 int_status)
{
        static const unsigned int continue_bits[] = {
                [CMD_GEN_START] = LINESTAT_START_BIT_DET,
                [CMD_GEN_DATA]  = LINESTAT_INPUT_HELD_V,
                [CMD_RET_ACK]   = LINESTAT_ACK_DET | LINESTAT_NACK_DET,
                [CMD_RET_DATA]  = LINESTAT_INPUT_HELD_V,
                [CMD_GEN_STOP]  = LINESTAT_STOP_BIT_DET,
        };
        int next_cmd = -1;
        u8 next_data = 0x00;

        if (int_status & INT_SLAVE_EVENT)
                i2c->at_slave_event = true;
        if (int_status & INT_TRANSACTION_DONE)
                i2c->at_t_done = true;

        if (!i2c->at_slave_event || !i2c->at_t_done)
                return 0;

        /* wait if no continue bits are set */
        if (i2c->at_cur_cmd >= 0 &&
            i2c->at_cur_cmd < ARRAY_SIZE(continue_bits)) {
                unsigned int cont_bits = continue_bits[i2c->at_cur_cmd];

                if (cont_bits) {
                        cont_bits |= LINESTAT_ABORT_DET;
                        if (!(i2c->line_status & cont_bits))
                                return 0;
                }
        }

        /* follow the sequence of commands in i2c->seq */
        next_cmd = *i2c->seq;
        /* stop on a nil */
        if (!next_cmd) {
                img_i2c_writel(i2c, SCB_OVERRIDE_REG, 0);
                return ISR_COMPLETE(0);
        }
        /* when generating data, the next byte is the data */
        if (next_cmd == CMD_GEN_DATA) {
                ++i2c->seq;
                next_data = *i2c->seq;
        }
        ++i2c->seq;
        img_i2c_atomic_op(i2c, next_cmd, next_data);

        return 0;
}

static void img_i2c_reset_start(struct img_i2c *i2c)
{
        /* Initiate the magic dance */
        img_i2c_switch_mode(i2c, MODE_SEQUENCE);
        img_i2c_writel(i2c, SCB_INT_MASK_REG, i2c->int_enable);
        i2c->seq = img_i2c_reset_seq;
        i2c->at_slave_event = true;
        i2c->at_t_done = true;
        i2c->at_cur_cmd = -1;

        /* img_i2c_reset_seq isn't empty so the following won't fail */
        img_i2c_sequence(i2c, 0);
}

static void img_i2c_stop_start(struct img_i2c *i2c)
{
        /* Initiate a stop bit sequence */
        img_i2c_switch_mode(i2c, MODE_SEQUENCE);
        img_i2c_writel(i2c, SCB_INT_MASK_REG, i2c->int_enable);
        i2c->seq = img_i2c_stop_seq;
        i2c->at_slave_event = true;
        i2c->at_t_done = true;
        i2c->at_cur_cmd = -1;

        /* img_i2c_stop_seq isn't empty so the following won't fail */
        img_i2c_sequence(i2c, 0);
}

static unsigned int img_i2c_atomic(struct img_i2c *i2c,
                                   u32 int_status,
                                   u32 line_status)
{
        int next_cmd = -1;
        u8 next_data = 0x00;

        if (int_status & INT_SLAVE_EVENT)
                i2c->at_slave_event = true;
        if (int_status & INT_TRANSACTION_DONE)
                i2c->at_t_done = true;

        if (!i2c->at_slave_event || !i2c->at_t_done)
                goto next_atomic_cmd;
        if (i2c->line_status & LINESTAT_ABORT_DET) {
                dev_dbg(i2c->adap.dev.parent, "abort condition detected\n");
                next_cmd = CMD_GEN_STOP;
                i2c->msg_status = -EIO;
                goto next_atomic_cmd;
        }

        /* i2c->at_cur_cmd may have completed */
        switch (i2c->at_cur_cmd) {
        case CMD_GEN_START:
                next_cmd = CMD_GEN_DATA;
                next_data = i2c_8bit_addr_from_msg(&i2c->msg);
                break;
        case CMD_GEN_DATA:
                if (i2c->line_status & LINESTAT_INPUT_HELD_V)
                        next_cmd = CMD_RET_ACK;
                break;
        case CMD_RET_ACK:
                if (i2c->line_status & LINESTAT_ACK_DET ||
                    (i2c->line_status & LINESTAT_NACK_DET &&
                    i2c->msg.flags & I2C_M_IGNORE_NAK)) {
                        if (i2c->msg.len == 0) {
                                next_cmd = CMD_GEN_STOP;
                        } else if (i2c->msg.flags & I2C_M_RD) {
                                next_cmd = CMD_RET_DATA;
                        } else {
                                next_cmd = CMD_GEN_DATA;
                                next_data = *i2c->msg.buf;
                                --i2c->msg.len;
                                ++i2c->msg.buf;
                        }
                } else if (i2c->line_status & LINESTAT_NACK_DET) {
                        i2c->msg_status = -EIO;
                        next_cmd = CMD_GEN_STOP;
                }
                break;
        case CMD_RET_DATA:
                if (i2c->line_status & LINESTAT_INPUT_HELD_V) {
                        *i2c->msg.buf = (i2c->line_status &
                                                LINESTAT_INPUT_DATA)
                                        >> LINESTAT_INPUT_DATA_SHIFT;
                        --i2c->msg.len;
                        ++i2c->msg.buf;
                        if (i2c->msg.len)
                                next_cmd = CMD_GEN_ACK;
                        else
                                next_cmd = CMD_GEN_NACK;
                }
                break;
        case CMD_GEN_ACK:
                if (i2c->line_status & LINESTAT_ACK_DET) {
                        next_cmd = CMD_RET_DATA;
                } else {
                        i2c->msg_status = -EIO;
                        next_cmd = CMD_GEN_STOP;
                }
                break;
        case CMD_GEN_NACK:
                next_cmd = CMD_GEN_STOP;
                break;
        case CMD_GEN_STOP:
                img_i2c_writel(i2c, SCB_OVERRIDE_REG, 0);
                return ISR_COMPLETE(0);
        default:
                dev_err(i2c->adap.dev.parent, "bad atomic command %d\n",
                        i2c->at_cur_cmd);
                i2c->msg_status = -EIO;
                next_cmd = CMD_GEN_STOP;
                break;
        }

next_atomic_cmd:
        if (next_cmd != -1) {
                /* don't actually stop unless we're the last transaction */
                if (next_cmd == CMD_GEN_STOP && !i2c->msg_status &&
                                                !i2c->last_msg)
                        return ISR_COMPLETE(0);
                img_i2c_atomic_op(i2c, next_cmd, next_data);
        }
        return 0;
}

/*
 * Timer function to check if something has gone wrong in automatic mode (so we
 * don't have to handle so many interrupts just to catch an exception).
 */
static void img_i2c_check_timer(struct timer_list *t)
{
        struct img_i2c *i2c = from_timer(i2c, t, check_timer);
        unsigned long flags;
        unsigned int line_status;

        spin_lock_irqsave(&i2c->lock, flags);
        line_status = img_i2c_readl(i2c, SCB_STATUS_REG);

        /* check for an abort condition */
        if (line_status & LINESTAT_ABORT_DET) {
                dev_dbg(i2c->adap.dev.parent,
                        "abort condition detected by check timer\n");
                /* enable slave event interrupt mask to trigger irq */
                img_i2c_writel(i2c, SCB_INT_MASK_REG,
                               i2c->int_enable | INT_SLAVE_EVENT);
        }

        spin_unlock_irqrestore(&i2c->lock, flags);
}

static unsigned int img_i2c_auto(struct img_i2c *i2c,
                                 unsigned int int_status,
                                 unsigned int line_status)
{
        if (int_status & (INT_WRITE_ACK_ERR | INT_ADDR_ACK_ERR))
                return ISR_COMPLETE(EIO);

        if (line_status & LINESTAT_ABORT_DET) {
                dev_dbg(i2c->adap.dev.parent, "abort condition detected\n");
                /* empty the read fifo */
                if ((i2c->msg.flags & I2C_M_RD) &&
                    (int_status & INT_FIFO_FULL_FILLING))
                        img_i2c_read_fifo(i2c);
                /* use atomic mode and try to force a stop bit */
                i2c->msg_status = -EIO;
                img_i2c_stop_start(i2c);
                return 0;
        }

        /* Enable transaction halt on start bit */
        if (!i2c->last_msg && line_status & LINESTAT_START_BIT_DET) {
                img_i2c_transaction_halt(i2c, !i2c->last_msg);
                /* we're no longer interested in the slave event */
                i2c->int_enable &= ~INT_SLAVE_EVENT;
        }

        mod_timer(&i2c->check_timer, jiffies + msecs_to_jiffies(1));

        if (int_status & INT_STOP_DETECTED) {
                /* Drain remaining data in FIFO and complete transaction */
                if (i2c->msg.flags & I2C_M_RD)
                        img_i2c_read_fifo(i2c);
                return ISR_COMPLETE(0);
        }

        if (i2c->msg.flags & I2C_M_RD) {
                if (int_status & (INT_FIFO_FULL_FILLING | INT_MASTER_HALTED)) {
                        img_i2c_read_fifo(i2c);
                        if (i2c->msg.len == 0)
                                return ISR_WAITSTOP;
                }
        } else {
                if (int_status & (INT_FIFO_EMPTY | INT_MASTER_HALTED)) {
                        if ((int_status & INT_FIFO_EMPTY) &&
                            i2c->msg.len == 0)
                                return ISR_WAITSTOP;
                        img_i2c_write_fifo(i2c);
                }
        }
        if (int_status & INT_MASTER_HALTED) {
                /*
                 * Release and then enable transaction halt, to
                 * allow only a single byte to proceed.
                 */
                img_i2c_transaction_halt(i2c, false);
                img_i2c_transaction_halt(i2c, !i2c->last_msg);
        }

        return 0;
}

static irqreturn_t img_i2c_isr(int irq, void *dev_id)
{
        struct img_i2c *i2c = (struct img_i2c *)dev_id;
        u32 int_status, line_status;
        /* We handle transaction completion AFTER accessing registers */
        unsigned int hret;

        /* Read interrupt status register. */
        int_status = img_i2c_readl(i2c, SCB_INT_STATUS_REG);
        /* Clear detected interrupts. */
        img_i2c_writel(i2c, SCB_INT_CLEAR_REG, int_status);

        /*
         * Read line status and clear it until it actually is clear.  We have
         * to be careful not to lose any line status bits that get latched.
         */
        line_status = img_i2c_readl(i2c, SCB_STATUS_REG);
        if (line_status & LINESTAT_LATCHED) {
                img_i2c_writel(i2c, SCB_CLEAR_REG,
                              (line_status & LINESTAT_LATCHED)
                                >> LINESTAT_CLEAR_SHIFT);
                img_i2c_wr_rd_fence(i2c);
        }

        spin_lock(&i2c->lock);

        /* Keep track of line status bits received */
        i2c->line_status &= ~LINESTAT_INPUT_DATA;
        i2c->line_status |= line_status;

        /*
         * Certain interrupts indicate that sclk low timeout is not
         * a problem. If any of these are set, just continue.
         */
        if ((int_status & INT_SCLK_LOW_TIMEOUT) &&
            !(int_status & (INT_SLAVE_EVENT |
                            INT_FIFO_EMPTY |
                            INT_FIFO_FULL))) {
                dev_crit(i2c->adap.dev.parent,
                         "fatal: clock low timeout occurred %s addr 0x%02x\n",
                         (i2c->msg.flags & I2C_M_RD) ? "reading" : "writing",
                         i2c->msg.addr);
                hret = ISR_FATAL(EIO);
                goto out;
        }

        if (i2c->mode == MODE_ATOMIC)
                hret = img_i2c_atomic(i2c, int_status, line_status);
        else if (i2c->mode == MODE_AUTOMATIC)
                hret = img_i2c_auto(i2c, int_status, line_status);
        else if (i2c->mode == MODE_SEQUENCE)
                hret = img_i2c_sequence(i2c, int_status);
        else if (i2c->mode == MODE_WAITSTOP && (int_status & INT_SLAVE_EVENT) &&
                         (line_status & LINESTAT_STOP_BIT_DET))
                hret = ISR_COMPLETE(0);
        else if (i2c->mode == MODE_RAW)
                hret = img_i2c_raw(i2c, int_status, line_status);
        else
                hret = 0;

        /* Clear detected level interrupts. */
        img_i2c_writel(i2c, SCB_INT_CLEAR_REG, int_status & INT_LEVEL);

out:
        if (hret & ISR_WAITSTOP) {
                /*
                 * Only wait for stop on last message.
                 * Also we may already have detected the stop bit.
                 */
                if (!i2c->last_msg || i2c->line_status & LINESTAT_STOP_BIT_DET)
                        hret = ISR_COMPLETE(0);
                else
                        img_i2c_switch_mode(i2c, MODE_WAITSTOP);
        }

        /* now we've finished using regs, handle transaction completion */
        if (hret & ISR_COMPLETE_M) {
                int status = -(hret & ISR_STATUS_M);

                img_i2c_complete_transaction(i2c, status);
                if (hret & ISR_FATAL_M)
                        img_i2c_switch_mode(i2c, MODE_FATAL);
        }

        /* Enable interrupts (int_enable may be altered by changing mode) */
        img_i2c_writel(i2c, SCB_INT_MASK_REG, i2c->int_enable);

        spin_unlock(&i2c->lock);

        return IRQ_HANDLED;
}

/* Force a bus reset sequence and wait for it to complete */
static int img_i2c_reset_bus(struct img_i2c *i2c)
{
        unsigned long flags;
        unsigned long time_left;

        spin_lock_irqsave(&i2c->lock, flags);
        reinit_completion(&i2c->msg_complete);
        img_i2c_reset_start(i2c);
        spin_unlock_irqrestore(&i2c->lock, flags);

        time_left = wait_for_completion_timeout(&i2c->msg_complete,
                                              IMG_I2C_TIMEOUT);
        if (time_left == 0)
                return -ETIMEDOUT;
        return 0;
}

static int img_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
                        int num)
{
        struct img_i2c *i2c = i2c_get_adapdata(adap);
        bool atomic = false;
        int i, ret;
        unsigned long time_left;

        if (i2c->mode == MODE_SUSPEND) {
                WARN(1, "refusing to service transaction in suspended state\n");
                return -EIO;
        }

        if (i2c->mode == MODE_FATAL)
                return -EIO;

        for (i = 0; i < num; i++) {
                /*
                 * 0 byte reads are not possible because the slave could try
                 * and pull the data line low, preventing a stop bit.
                 */
                if (!msgs[i].len && msgs[i].flags & I2C_M_RD)
                        return -EIO;
                /*
                 * 0 byte writes are possible and used for probing, but we
                 * cannot do them in automatic mode, so use atomic mode
                 * instead.
                 *
                 * Also, the I2C_M_IGNORE_NAK mode can only be implemented
                 * in atomic mode.
                 */
                if (!msgs[i].len ||
                    (msgs[i].flags & I2C_M_IGNORE_NAK))
                        atomic = true;
        }

        ret = pm_runtime_get_sync(adap->dev.parent);
        if (ret < 0)
                return ret;

        for (i = 0; i < num; i++) {
                struct i2c_msg *msg = &msgs[i];
                unsigned long flags;

                spin_lock_irqsave(&i2c->lock, flags);

                /*
                 * Make a copy of the message struct. We mustn't modify the
                 * original or we'll confuse drivers and i2c-dev.
                 */
                i2c->msg = *msg;
                i2c->msg_status = 0;

                /*
                 * After the last message we must have waited for a stop bit.
                 * Not waiting can cause problems when the clock is disabled
                 * before the stop bit is sent, and the linux I2C interface
                 * requires separate transfers not to joined with repeated
                 * start.
                 */
                i2c->last_msg = (i == num - 1);
                reinit_completion(&i2c->msg_complete);

                /*
                 * Clear line status and all interrupts before starting a
                 * transfer, as we may have unserviced interrupts from
                 * previous transfers that might be handled in the context
                 * of the new transfer.
                 */
                img_i2c_writel(i2c, SCB_INT_CLEAR_REG, ~0);
                img_i2c_writel(i2c, SCB_CLEAR_REG, ~0);

                if (atomic) {
                        img_i2c_atomic_start(i2c);
                } else {
                        /*
                         * Enable transaction halt if not the last message in
                         * the queue so that we can control repeated starts.
                         */
                        img_i2c_transaction_halt(i2c, !i2c->last_msg);

                        if (msg->flags & I2C_M_RD)
                                img_i2c_read(i2c);
                        else
                                img_i2c_write(i2c);

                        /*
                         * Release and then enable transaction halt, to
                         * allow only a single byte to proceed.
                         * This doesn't have an effect on the initial transfer
                         * but will allow the following transfers to start
                         * processing if the previous transfer was marked as
                         * complete while the i2c block was halted.
                         */
                        img_i2c_transaction_halt(i2c, false);
                        img_i2c_transaction_halt(i2c, !i2c->last_msg);
                }
                spin_unlock_irqrestore(&i2c->lock, flags);

                time_left = wait_for_completion_timeout(&i2c->msg_complete,
                                                      IMG_I2C_TIMEOUT);
                del_timer_sync(&i2c->check_timer);

                if (time_left == 0) {
                        dev_err(adap->dev.parent, "i2c transfer timed out\n");
                        i2c->msg_status = -ETIMEDOUT;
                        break;
                }

                if (i2c->msg_status)
                        break;
        }

        pm_runtime_mark_last_busy(adap->dev.parent);
        pm_runtime_put_autosuspend(adap->dev.parent);

        return i2c->msg_status ? i2c->msg_status : num;
}

static u32 img_i2c_func(struct i2c_adapter *adap)
{
        return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
}

static const struct i2c_algorithm img_i2c_algo = {
        .master_xfer = img_i2c_xfer,
        .functionality = img_i2c_func,
};

static int img_i2c_init(struct img_i2c *i2c)
{
        unsigned int clk_khz, bitrate_khz, clk_period, tckh, tckl, tsdh;
        unsigned int i, data, prescale, inc, int_bitrate, filt;
        struct img_i2c_timings timing;
        u32 rev;
        int ret;

        ret = pm_runtime_get_sync(i2c->adap.dev.parent);
        if (ret < 0)
                return ret;

        rev = img_i2c_readl(i2c, SCB_CORE_REV_REG);
        if ((rev & 0x00ffffff) < 0x00020200) {
                dev_info(i2c->adap.dev.parent,
                         "Unknown hardware revision (%d.%d.%d.%d)\n",
                         (rev >> 24) & 0xff, (rev >> 16) & 0xff,
                         (rev >> 8) & 0xff, rev & 0xff);
                pm_runtime_mark_last_busy(i2c->adap.dev.parent);
                pm_runtime_put_autosuspend(i2c->adap.dev.parent);
                return -EINVAL;
        }

        /* Fencing enabled by default. */
        i2c->need_wr_rd_fence = true;

        /* Determine what mode we're in from the bitrate */
        timing = timings[0];
        for (i = 0; i < ARRAY_SIZE(timings); i++) {
                if (i2c->bitrate <= timings[i].max_bitrate) {
                        timing = timings[i];
                        break;
                }
        }
        if (i2c->bitrate > timings[ARRAY_SIZE(timings) - 1].max_bitrate) {
                dev_warn(i2c->adap.dev.parent,
                         "requested bitrate (%u) is higher than the max bitrate supported (%u)\n",
                         i2c->bitrate,
                         timings[ARRAY_SIZE(timings) - 1].max_bitrate);
                timing = timings[ARRAY_SIZE(timings) - 1];
                i2c->bitrate = timing.max_bitrate;
        }

        bitrate_khz = i2c->bitrate / 1000;
        clk_khz = clk_get_rate(i2c->scb_clk) / 1000;

        /* Find the prescale that would give us that inc (approx delay = 0) */
        prescale = SCB_OPT_INC * clk_khz / (256 * 16 * bitrate_khz);
        prescale = clamp_t(unsigned int, prescale, 1, 8);
        clk_khz /= prescale;

        /* Setup the clock increment value */
        inc = (256 * 16 * bitrate_khz) / clk_khz;

        /*
         * The clock generation logic allows to filter glitches on the bus.
         * This filter is able to remove bus glitches shorter than 50ns.
         * If the clock enable rate is greater than 20 MHz, no filtering
         * is required, so we need to disable it.
         * If it's between the 20-40 MHz range, there's no need to divide
         * the clock to get a filter.
         */
        if (clk_khz < 20000) {
                filt = SCB_FILT_DISABLE;
        } else if (clk_khz < 40000) {
                filt = SCB_FILT_BYPASS;
        } else {
                /* Calculate filter clock */
                filt = (64000 / ((clk_khz / 1000) * SCB_FILT_GLITCH));

                /* Scale up if needed */
                if (64000 % ((clk_khz / 1000) * SCB_FILT_GLITCH))
                        inc++;

                if (filt > SCB_FILT_INC_MASK)
                        filt = SCB_FILT_INC_MASK;

                filt = (filt & SCB_FILT_INC_MASK) << SCB_FILT_INC_SHIFT;
        }
        data = filt | ((inc & SCB_INC_MASK) << SCB_INC_SHIFT) | (prescale - 1);
        img_i2c_writel(i2c, SCB_CLK_SET_REG, data);

        /* Obtain the clock period of the fx16 clock in ns */
        clk_period = (256 * 1000000) / (clk_khz * inc);

        /* Calculate the bitrate in terms of internal clock pulses */
        int_bitrate = 1000000 / (bitrate_khz * clk_period);
        if ((1000000 % (bitrate_khz * clk_period)) >=
            ((bitrate_khz * clk_period) / 2))
                int_bitrate++;

        /*
         * Setup clock duty cycle, start with 50% and adjust TCKH and TCKL
         * values from there if they don't meet minimum timing requirements
         */
        tckh = int_bitrate / 2;
        tckl = int_bitrate - tckh;

        /* Adjust TCKH and TCKL values */
        data = DIV_ROUND_UP(timing.tckl, clk_period);

        if (tckl < data) {
                tckl = data;
                tckh = int_bitrate - tckl;
        }

        if (tckh > 0)
                --tckh;

        if (tckl > 0)
                --tckl;

        img_i2c_writel(i2c, SCB_TIME_TCKH_REG, tckh);
        img_i2c_writel(i2c, SCB_TIME_TCKL_REG, tckl);

        /* Setup TSDH value */
        tsdh = DIV_ROUND_UP(timing.tsdh, clk_period);

        if (tsdh > 1)
                data = tsdh - 1;
        else
                data = 0x01;
        img_i2c_writel(i2c, SCB_TIME_TSDH_REG, data);

        /* This value is used later */
        tsdh = data;

        /* Setup TPL value */
        data = timing.tpl / clk_period;
        if (data > 0)
                --data;
        img_i2c_writel(i2c, SCB_TIME_TPL_REG, data);

        /* Setup TPH value */
        data = timing.tph / clk_period;
        if (data > 0)
                --data;
        img_i2c_writel(i2c, SCB_TIME_TPH_REG, data);

        /* Setup TSDL value to TPL + TSDH + 2 */
        img_i2c_writel(i2c, SCB_TIME_TSDL_REG, data + tsdh + 2);

        /* Setup TP2S value */
        data = timing.tp2s / clk_period;
        if (data > 0)
                --data;
        img_i2c_writel(i2c, SCB_TIME_TP2S_REG, data);

        img_i2c_writel(i2c, SCB_TIME_TBI_REG, TIMEOUT_TBI);
        img_i2c_writel(i2c, SCB_TIME_TSL_REG, TIMEOUT_TSL);
        img_i2c_writel(i2c, SCB_TIME_TDL_REG, TIMEOUT_TDL);

        /* Take module out of soft reset and enable clocks */
        img_i2c_soft_reset(i2c);

        /* Disable all interrupts */
        img_i2c_writel(i2c, SCB_INT_MASK_REG, 0);

        /* Clear all interrupts */
        img_i2c_writel(i2c, SCB_INT_CLEAR_REG, ~0);

        /* Clear the scb_line_status events */
        img_i2c_writel(i2c, SCB_CLEAR_REG, ~0);

        /* Enable interrupts */
        img_i2c_writel(i2c, SCB_INT_MASK_REG, i2c->int_enable);

        /* Perform a synchronous sequence to reset the bus */
        ret = img_i2c_reset_bus(i2c);

        pm_runtime_mark_last_busy(i2c->adap.dev.parent);
        pm_runtime_put_autosuspend(i2c->adap.dev.parent);

        return ret;
}

static int img_i2c_probe(struct platform_device *pdev)
{
        struct device_node *node = pdev->dev.of_node;
        struct img_i2c *i2c;
        int irq, ret;
        u32 val;

        i2c = devm_kzalloc(&pdev->dev, sizeof(struct img_i2c), GFP_KERNEL);
        if (!i2c)
                return -ENOMEM;

        i2c->base = devm_platform_ioremap_resource(pdev, 0);
        if (IS_ERR(i2c->base))
                return PTR_ERR(i2c->base);

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

        i2c->sys_clk = devm_clk_get(&pdev->dev, "sys");
        if (IS_ERR(i2c->sys_clk)) {
                dev_err(&pdev->dev, "can't get system clock\n");
                return PTR_ERR(i2c->sys_clk);
        }

        i2c->scb_clk = devm_clk_get(&pdev->dev, "scb");
        if (IS_ERR(i2c->scb_clk)) {
                dev_err(&pdev->dev, "can't get core clock\n");
                return PTR_ERR(i2c->scb_clk);
        }

        ret = devm_request_irq(&pdev->dev, irq, img_i2c_isr, 0,
                               pdev->name, i2c);
        if (ret) {
                dev_err(&pdev->dev, "can't request irq %d\n", irq);
                return ret;
        }

        /* Set up the exception check timer */
        timer_setup(&i2c->check_timer, img_i2c_check_timer, 0);

        i2c->bitrate = timings[0].max_bitrate;
        if (!of_property_read_u32(node, "clock-frequency", &val))
                i2c->bitrate = val;

        i2c_set_adapdata(&i2c->adap, i2c);
        i2c->adap.dev.parent = &pdev->dev;
        i2c->adap.dev.of_node = node;
        i2c->adap.owner = THIS_MODULE;
        i2c->adap.algo = &img_i2c_algo;
        i2c->adap.retries = 5;
        i2c->adap.nr = pdev->id;
        snprintf(i2c->adap.name, sizeof(i2c->adap.name), "IMG SCB I2C");

        img_i2c_switch_mode(i2c, MODE_INACTIVE);
        spin_lock_init(&i2c->lock);
        init_completion(&i2c->msg_complete);

        platform_set_drvdata(pdev, i2c);

        pm_runtime_set_autosuspend_delay(&pdev->dev, IMG_I2C_PM_TIMEOUT);
        pm_runtime_use_autosuspend(&pdev->dev);
        pm_runtime_enable(&pdev->dev);
        if (!pm_runtime_enabled(&pdev->dev)) {
                ret = img_i2c_runtime_resume(&pdev->dev);
                if (ret)
                        return ret;
        }

        ret = img_i2c_init(i2c);
        if (ret)
                goto rpm_disable;

        ret = i2c_add_numbered_adapter(&i2c->adap);
        if (ret < 0)
                goto rpm_disable;

        return 0;

rpm_disable:
        if (!pm_runtime_enabled(&pdev->dev))
                img_i2c_runtime_suspend(&pdev->dev);
        pm_runtime_disable(&pdev->dev);
        pm_runtime_dont_use_autosuspend(&pdev->dev);
        return ret;
}

static int img_i2c_remove(struct platform_device *dev)
{
        struct img_i2c *i2c = platform_get_drvdata(dev);

        i2c_del_adapter(&i2c->adap);
        pm_runtime_disable(&dev->dev);
        if (!pm_runtime_status_suspended(&dev->dev))
                img_i2c_runtime_suspend(&dev->dev);

        return 0;
}

static int img_i2c_runtime_suspend(struct device *dev)
{
        struct img_i2c *i2c = dev_get_drvdata(dev);

        clk_disable_unprepare(i2c->scb_clk);
        clk_disable_unprepare(i2c->sys_clk);

        return 0;
}

static int img_i2c_runtime_resume(struct device *dev)
{
        struct img_i2c *i2c = dev_get_drvdata(dev);
        int ret;

        ret = clk_prepare_enable(i2c->sys_clk);
        if (ret) {
                dev_err(dev, "Unable to enable sys clock\n");
                return ret;
        }

        ret = clk_prepare_enable(i2c->scb_clk);
        if (ret) {
                dev_err(dev, "Unable to enable scb clock\n");
                clk_disable_unprepare(i2c->sys_clk);
                return ret;
        }

        return 0;
}

#ifdef CONFIG_PM_SLEEP
static int img_i2c_suspend(struct device *dev)
{
        struct img_i2c *i2c = dev_get_drvdata(dev);
        int ret;

        ret = pm_runtime_force_suspend(dev);
        if (ret)
                return ret;

        img_i2c_switch_mode(i2c, MODE_SUSPEND);

        return 0;
}

static int img_i2c_resume(struct device *dev)
{
        struct img_i2c *i2c = dev_get_drvdata(dev);
        int ret;

        ret = pm_runtime_force_resume(dev);
        if (ret)
                return ret;

        img_i2c_init(i2c);

        return 0;
}
#endif /* CONFIG_PM_SLEEP */

static const struct dev_pm_ops img_i2c_pm = {
        SET_RUNTIME_PM_OPS(img_i2c_runtime_suspend,
                           img_i2c_runtime_resume,
                           NULL)
        SET_SYSTEM_SLEEP_PM_OPS(img_i2c_suspend, img_i2c_resume)
};

static const struct of_device_id img_scb_i2c_match[] = {
        { .compatible = "img,scb-i2c" },
        { }
};
MODULE_DEVICE_TABLE(of, img_scb_i2c_match);

static struct platform_driver img_scb_i2c_driver = {
        .driver = {
                .name           = "img-i2c-scb",
                .of_match_table = img_scb_i2c_match,
                .pm             = &img_i2c_pm,
        },
        .probe = img_i2c_probe,
        .remove = img_i2c_remove,
};
module_platform_driver(img_scb_i2c_driver);

MODULE_AUTHOR("James Hogan <jhogan@kernel.org>");
MODULE_DESCRIPTION("IMG host I2C driver");
MODULE_LICENSE("GPL v2");