serial: 8250: fix null-ptr-deref in serial8250_start_tx()

[linux/fpc-iii.git] / drivers / tty / serial / 8250 / 8250_omap.c

// SPDX-License-Identifier: GPL-2.0
/*
 * 8250-core based driver for the OMAP internal UART
 *
 * based on omap-serial.c, Copyright (C) 2010 Texas Instruments.
 *
 * Copyright (C) 2014 Sebastian Andrzej Siewior
 *
 */

#include <linux/clk.h>
#include <linux/device.h>
#include <linux/io.h>
#include <linux/module.h>
#include <linux/serial_8250.h>
#include <linux/serial_reg.h>
#include <linux/tty_flip.h>
#include <linux/platform_device.h>
#include <linux/slab.h>
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/of_gpio.h>
#include <linux/of_irq.h>
#include <linux/delay.h>
#include <linux/pm_runtime.h>
#include <linux/console.h>
#include <linux/pm_qos.h>
#include <linux/pm_wakeirq.h>
#include <linux/dma-mapping.h>

#include "8250.h"

#define DEFAULT_CLK_SPEED       48000000

#define UART_ERRATA_i202_MDR1_ACCESS    (1 << 0)
#define OMAP_UART_WER_HAS_TX_WAKEUP     (1 << 1)
#define OMAP_DMA_TX_KICK                (1 << 2)
/*
 * See Advisory 21 in AM437x errata SPRZ408B, updated April 2015.
 * The same errata is applicable to AM335x and DRA7x processors too.
 */
#define UART_ERRATA_CLOCK_DISABLE       (1 << 3)
#define UART_HAS_EFR2                   BIT(4)

#define OMAP_UART_FCR_RX_TRIG           6
#define OMAP_UART_FCR_TX_TRIG           4

/* SCR register bitmasks */
#define OMAP_UART_SCR_RX_TRIG_GRANU1_MASK       (1 << 7)
#define OMAP_UART_SCR_TX_TRIG_GRANU1_MASK       (1 << 6)
#define OMAP_UART_SCR_TX_EMPTY                  (1 << 3)
#define OMAP_UART_SCR_DMAMODE_MASK              (3 << 1)
#define OMAP_UART_SCR_DMAMODE_1                 (1 << 1)
#define OMAP_UART_SCR_DMAMODE_CTL               (1 << 0)

/* MVR register bitmasks */
#define OMAP_UART_MVR_SCHEME_SHIFT      30
#define OMAP_UART_LEGACY_MVR_MAJ_MASK   0xf0
#define OMAP_UART_LEGACY_MVR_MAJ_SHIFT  4
#define OMAP_UART_LEGACY_MVR_MIN_MASK   0x0f
#define OMAP_UART_MVR_MAJ_MASK          0x700
#define OMAP_UART_MVR_MAJ_SHIFT         8
#define OMAP_UART_MVR_MIN_MASK          0x3f

/* SYSC register bitmasks */
#define OMAP_UART_SYSC_SOFTRESET        (1 << 1)

/* SYSS register bitmasks */
#define OMAP_UART_SYSS_RESETDONE        (1 << 0)

#define UART_TI752_TLR_TX       0
#define UART_TI752_TLR_RX       4

#define TRIGGER_TLR_MASK(x)     ((x & 0x3c) >> 2)
#define TRIGGER_FCR_MASK(x)     (x & 3)

/* Enable XON/XOFF flow control on output */
#define OMAP_UART_SW_TX         0x08
/* Enable XON/XOFF flow control on input */
#define OMAP_UART_SW_RX         0x02

#define OMAP_UART_WER_MOD_WKUP  0x7f
#define OMAP_UART_TX_WAKEUP_EN  (1 << 7)

#define TX_TRIGGER      1
#define RX_TRIGGER      48

#define OMAP_UART_TCR_RESTORE(x)        ((x / 4) << 4)
#define OMAP_UART_TCR_HALT(x)           ((x / 4) << 0)

#define UART_BUILD_REVISION(x, y)       (((x) << 8) | (y))

#define OMAP_UART_REV_46 0x0406
#define OMAP_UART_REV_52 0x0502
#define OMAP_UART_REV_63 0x0603

/* Enhanced features register 2 */
#define UART_OMAP_EFR2                  0x23
#define UART_OMAP_EFR2_TIMEOUT_BEHAVE   BIT(6)

struct omap8250_priv {
        int line;
        u8 habit;
        u8 mdr1;
        u8 efr;
        u8 scr;
        u8 wer;
        u8 xon;
        u8 xoff;
        u8 delayed_restore;
        u16 quot;

        u8 tx_trigger;
        u8 rx_trigger;
        bool is_suspending;
        int wakeirq;
        int wakeups_enabled;
        u32 latency;
        u32 calc_latency;
        struct pm_qos_request pm_qos_request;
        struct work_struct qos_work;
        struct uart_8250_dma omap8250_dma;
        spinlock_t rx_dma_lock;
        bool rx_dma_broken;
        bool throttled;
};

struct omap8250_dma_params {
        u32 rx_size;
        u8 rx_trigger;
        u8 tx_trigger;
};

struct omap8250_platdata {
        struct omap8250_dma_params *dma_params;
        u8 habit;
};

#ifdef CONFIG_SERIAL_8250_DMA
static void omap_8250_rx_dma_flush(struct uart_8250_port *p);
#else
static inline void omap_8250_rx_dma_flush(struct uart_8250_port *p) { }
#endif

static u32 uart_read(struct uart_8250_port *up, u32 reg)
{
        return readl(up->port.membase + (reg << up->port.regshift));
}

static void omap8250_set_mctrl(struct uart_port *port, unsigned int mctrl)
{
        struct uart_8250_port *up = up_to_u8250p(port);
        struct omap8250_priv *priv = up->port.private_data;
        u8 lcr;

        serial8250_do_set_mctrl(port, mctrl);

        if (!mctrl_gpio_to_gpiod(up->gpios, UART_GPIO_RTS)) {
                /*
                 * Turn off autoRTS if RTS is lowered and restore autoRTS
                 * setting if RTS is raised
                 */
                lcr = serial_in(up, UART_LCR);
                serial_out(up, UART_LCR, UART_LCR_CONF_MODE_B);
                if ((mctrl & TIOCM_RTS) && (port->status & UPSTAT_AUTORTS))
                        priv->efr |= UART_EFR_RTS;
                else
                        priv->efr &= ~UART_EFR_RTS;
                serial_out(up, UART_EFR, priv->efr);
                serial_out(up, UART_LCR, lcr);
        }
}

/*
 * Work Around for Errata i202 (2430, 3430, 3630, 4430 and 4460)
 * The access to uart register after MDR1 Access
 * causes UART to corrupt data.
 *
 * Need a delay =
 * 5 L4 clock cycles + 5 UART functional clock cycle (@48MHz = ~0.2uS)
 * give 10 times as much
 */
static void omap_8250_mdr1_errataset(struct uart_8250_port *up,
                                     struct omap8250_priv *priv)
{
        u8 timeout = 255;
        u8 old_mdr1;

        old_mdr1 = serial_in(up, UART_OMAP_MDR1);
        if (old_mdr1 == priv->mdr1)
                return;

        serial_out(up, UART_OMAP_MDR1, priv->mdr1);
        udelay(2);
        serial_out(up, UART_FCR, up->fcr | UART_FCR_CLEAR_XMIT |
                        UART_FCR_CLEAR_RCVR);
        /*
         * Wait for FIFO to empty: when empty, RX_FIFO_E bit is 0 and
         * TX_FIFO_E bit is 1.
         */
        while (UART_LSR_THRE != (serial_in(up, UART_LSR) &
                                (UART_LSR_THRE | UART_LSR_DR))) {
                timeout--;
                if (!timeout) {
                        /* Should *never* happen. we warn and carry on */
                        dev_crit(up->port.dev, "Errata i202: timedout %x\n",
                                 serial_in(up, UART_LSR));
                        break;
                }
                udelay(1);
        }
}

static void omap_8250_get_divisor(struct uart_port *port, unsigned int baud,
                                  struct omap8250_priv *priv)
{
        unsigned int uartclk = port->uartclk;
        unsigned int div_13, div_16;
        unsigned int abs_d13, abs_d16;

        /*
         * Old custom speed handling.
         */
        if (baud == 38400 && (port->flags & UPF_SPD_MASK) == UPF_SPD_CUST) {
                priv->quot = port->custom_divisor & UART_DIV_MAX;
                /*
                 * I assume that nobody is using this. But hey, if somebody
                 * would like to specify the divisor _and_ the mode then the
                 * driver is ready and waiting for it.
                 */
                if (port->custom_divisor & (1 << 16))
                        priv->mdr1 = UART_OMAP_MDR1_13X_MODE;
                else
                        priv->mdr1 = UART_OMAP_MDR1_16X_MODE;
                return;
        }
        div_13 = DIV_ROUND_CLOSEST(uartclk, 13 * baud);
        div_16 = DIV_ROUND_CLOSEST(uartclk, 16 * baud);

        if (!div_13)
                div_13 = 1;
        if (!div_16)
                div_16 = 1;

        abs_d13 = abs(baud - uartclk / 13 / div_13);
        abs_d16 = abs(baud - uartclk / 16 / div_16);

        if (abs_d13 >= abs_d16) {
                priv->mdr1 = UART_OMAP_MDR1_16X_MODE;
                priv->quot = div_16;
        } else {
                priv->mdr1 = UART_OMAP_MDR1_13X_MODE;
                priv->quot = div_13;
        }
}

static void omap8250_update_scr(struct uart_8250_port *up,
                                struct omap8250_priv *priv)
{
        u8 old_scr;

        old_scr = serial_in(up, UART_OMAP_SCR);
        if (old_scr == priv->scr)
                return;

        /*
         * The manual recommends not to enable the DMA mode selector in the SCR
         * (instead of the FCR) register _and_ selecting the DMA mode as one
         * register write because this may lead to malfunction.
         */
        if (priv->scr & OMAP_UART_SCR_DMAMODE_MASK)
                serial_out(up, UART_OMAP_SCR,
                           priv->scr & ~OMAP_UART_SCR_DMAMODE_MASK);
        serial_out(up, UART_OMAP_SCR, priv->scr);
}

static void omap8250_update_mdr1(struct uart_8250_port *up,
                                 struct omap8250_priv *priv)
{
        if (priv->habit & UART_ERRATA_i202_MDR1_ACCESS)
                omap_8250_mdr1_errataset(up, priv);
        else
                serial_out(up, UART_OMAP_MDR1, priv->mdr1);
}

static void omap8250_restore_regs(struct uart_8250_port *up)
{
        struct omap8250_priv *priv = up->port.private_data;
        struct uart_8250_dma    *dma = up->dma;

        if (dma && dma->tx_running) {
                /*
                 * TCSANOW requests the change to occur immediately however if
                 * we have a TX-DMA operation in progress then it has been
                 * observed that it might stall and never complete. Therefore we
                 * delay DMA completes to prevent this hang from happen.
                 */
                priv->delayed_restore = 1;
                return;
        }

        serial_out(up, UART_LCR, UART_LCR_CONF_MODE_B);
        serial_out(up, UART_EFR, UART_EFR_ECB);

        serial_out(up, UART_LCR, UART_LCR_CONF_MODE_A);
        serial8250_out_MCR(up, UART_MCR_TCRTLR);
        serial_out(up, UART_FCR, up->fcr);

        omap8250_update_scr(up, priv);

        serial_out(up, UART_LCR, UART_LCR_CONF_MODE_B);

        serial_out(up, UART_TI752_TCR, OMAP_UART_TCR_RESTORE(16) |
                        OMAP_UART_TCR_HALT(52));
        serial_out(up, UART_TI752_TLR,
                   TRIGGER_TLR_MASK(priv->tx_trigger) << UART_TI752_TLR_TX |
                   TRIGGER_TLR_MASK(priv->rx_trigger) << UART_TI752_TLR_RX);

        serial_out(up, UART_LCR, 0);

        /* drop TCR + TLR access, we setup XON/XOFF later */
        serial8250_out_MCR(up, up->mcr);
        serial_out(up, UART_IER, up->ier);

        serial_out(up, UART_LCR, UART_LCR_CONF_MODE_B);
        serial_dl_write(up, priv->quot);

        serial_out(up, UART_EFR, priv->efr);

        /* Configure flow control */
        serial_out(up, UART_LCR, UART_LCR_CONF_MODE_B);
        serial_out(up, UART_XON1, priv->xon);
        serial_out(up, UART_XOFF1, priv->xoff);

        serial_out(up, UART_LCR, up->lcr);

        omap8250_update_mdr1(up, priv);

        up->port.ops->set_mctrl(&up->port, up->port.mctrl);
}

/*
 * OMAP can use "CLK / (16 or 13) / div" for baud rate. And then we have have
 * some differences in how we want to handle flow control.
 */
static void omap_8250_set_termios(struct uart_port *port,
                                  struct ktermios *termios,
                                  struct ktermios *old)
{
        struct uart_8250_port *up = up_to_u8250p(port);
        struct omap8250_priv *priv = up->port.private_data;
        unsigned char cval = 0;
        unsigned int baud;

        switch (termios->c_cflag & CSIZE) {
        case CS5:
                cval = UART_LCR_WLEN5;
                break;
        case CS6:
                cval = UART_LCR_WLEN6;
                break;
        case CS7:
                cval = UART_LCR_WLEN7;
                break;
        default:
        case CS8:
                cval = UART_LCR_WLEN8;
                break;
        }

        if (termios->c_cflag & CSTOPB)
                cval |= UART_LCR_STOP;
        if (termios->c_cflag & PARENB)
                cval |= UART_LCR_PARITY;
        if (!(termios->c_cflag & PARODD))
                cval |= UART_LCR_EPAR;
        if (termios->c_cflag & CMSPAR)
                cval |= UART_LCR_SPAR;

        /*
         * Ask the core to calculate the divisor for us.
         */
        baud = uart_get_baud_rate(port, termios, old,
                                  port->uartclk / 16 / UART_DIV_MAX,
                                  port->uartclk / 13);
        omap_8250_get_divisor(port, baud, priv);

        /*
         * Ok, we're now changing the port state. Do it with
         * interrupts disabled.
         */
        pm_runtime_get_sync(port->dev);
        spin_lock_irq(&port->lock);

        /*
         * Update the per-port timeout.
         */
        uart_update_timeout(port, termios->c_cflag, baud);

        up->port.read_status_mask = UART_LSR_OE | UART_LSR_THRE | UART_LSR_DR;
        if (termios->c_iflag & INPCK)
                up->port.read_status_mask |= UART_LSR_FE | UART_LSR_PE;
        if (termios->c_iflag & (IGNBRK | PARMRK))
                up->port.read_status_mask |= UART_LSR_BI;

        /*
         * Characters to ignore
         */
        up->port.ignore_status_mask = 0;
        if (termios->c_iflag & IGNPAR)
                up->port.ignore_status_mask |= UART_LSR_PE | UART_LSR_FE;
        if (termios->c_iflag & IGNBRK) {
                up->port.ignore_status_mask |= UART_LSR_BI;
                /*
                 * If we're ignoring parity and break indicators,
                 * ignore overruns too (for real raw support).
                 */
                if (termios->c_iflag & IGNPAR)
                        up->port.ignore_status_mask |= UART_LSR_OE;
        }

        /*
         * ignore all characters if CREAD is not set
         */
        if ((termios->c_cflag & CREAD) == 0)
                up->port.ignore_status_mask |= UART_LSR_DR;

        /*
         * Modem status interrupts
         */
        up->ier &= ~UART_IER_MSI;
        if (UART_ENABLE_MS(&up->port, termios->c_cflag))
                up->ier |= UART_IER_MSI;

        up->lcr = cval;
        /* Up to here it was mostly serial8250_do_set_termios() */

        /*
         * We enable TRIG_GRANU for RX and TX and additionally we set
         * SCR_TX_EMPTY bit. The result is the following:
         * - RX_TRIGGER amount of bytes in the FIFO will cause an interrupt.
         * - less than RX_TRIGGER number of bytes will also cause an interrupt
         *   once the UART decides that there no new bytes arriving.
         * - Once THRE is enabled, the interrupt will be fired once the FIFO is
         *   empty - the trigger level is ignored here.
         *
         * Once DMA is enabled:
         * - UART will assert the TX DMA line once there is room for TX_TRIGGER
         *   bytes in the TX FIFO. On each assert the DMA engine will move
         *   TX_TRIGGER bytes into the FIFO.
         * - UART will assert the RX DMA line once there are RX_TRIGGER bytes in
         *   the FIFO and move RX_TRIGGER bytes.
         * This is because threshold and trigger values are the same.
         */
        up->fcr = UART_FCR_ENABLE_FIFO;
        up->fcr |= TRIGGER_FCR_MASK(priv->tx_trigger) << OMAP_UART_FCR_TX_TRIG;
        up->fcr |= TRIGGER_FCR_MASK(priv->rx_trigger) << OMAP_UART_FCR_RX_TRIG;

        priv->scr = OMAP_UART_SCR_RX_TRIG_GRANU1_MASK | OMAP_UART_SCR_TX_EMPTY |
                OMAP_UART_SCR_TX_TRIG_GRANU1_MASK;

        if (up->dma)
                priv->scr |= OMAP_UART_SCR_DMAMODE_1 |
                        OMAP_UART_SCR_DMAMODE_CTL;

        priv->xon = termios->c_cc[VSTART];
        priv->xoff = termios->c_cc[VSTOP];

        priv->efr = 0;
        up->port.status &= ~(UPSTAT_AUTOCTS | UPSTAT_AUTORTS | UPSTAT_AUTOXOFF);

        if (termios->c_cflag & CRTSCTS && up->port.flags & UPF_HARD_FLOW &&
            !mctrl_gpio_to_gpiod(up->gpios, UART_GPIO_RTS) &&
            !mctrl_gpio_to_gpiod(up->gpios, UART_GPIO_CTS)) {
                /* Enable AUTOCTS (autoRTS is enabled when RTS is raised) */
                up->port.status |= UPSTAT_AUTOCTS | UPSTAT_AUTORTS;
                priv->efr |= UART_EFR_CTS;
        } else  if (up->port.flags & UPF_SOFT_FLOW) {
                /*
                 * OMAP rx s/w flow control is borked; the transmitter remains
                 * stuck off even if rx flow control is subsequently disabled
                 */

                /*
                 * IXOFF Flag:
                 * Enable XON/XOFF flow control on output.
                 * Transmit XON1, XOFF1
                 */
                if (termios->c_iflag & IXOFF) {
                        up->port.status |= UPSTAT_AUTOXOFF;
                        priv->efr |= OMAP_UART_SW_TX;
                }
        }
        omap8250_restore_regs(up);

        spin_unlock_irq(&up->port.lock);
        pm_runtime_mark_last_busy(port->dev);
        pm_runtime_put_autosuspend(port->dev);

        /* calculate wakeup latency constraint */
        priv->calc_latency = USEC_PER_SEC * 64 * 8 / baud;
        priv->latency = priv->calc_latency;

        schedule_work(&priv->qos_work);

        /* Don't rewrite B0 */
        if (tty_termios_baud_rate(termios))
                tty_termios_encode_baud_rate(termios, baud, baud);
}

/* same as 8250 except that we may have extra flow bits set in EFR */
static void omap_8250_pm(struct uart_port *port, unsigned int state,
                         unsigned int oldstate)
{
        struct uart_8250_port *up = up_to_u8250p(port);
        u8 efr;

        pm_runtime_get_sync(port->dev);
        serial_out(up, UART_LCR, UART_LCR_CONF_MODE_B);
        efr = serial_in(up, UART_EFR);
        serial_out(up, UART_EFR, efr | UART_EFR_ECB);
        serial_out(up, UART_LCR, 0);

        serial_out(up, UART_IER, (state != 0) ? UART_IERX_SLEEP : 0);
        serial_out(up, UART_LCR, UART_LCR_CONF_MODE_B);
        serial_out(up, UART_EFR, efr);
        serial_out(up, UART_LCR, 0);

        pm_runtime_mark_last_busy(port->dev);
        pm_runtime_put_autosuspend(port->dev);
}

static void omap_serial_fill_features_erratas(struct uart_8250_port *up,
                                              struct omap8250_priv *priv)
{
        u32 mvr, scheme;
        u16 revision, major, minor;

        mvr = uart_read(up, UART_OMAP_MVER);

        /* Check revision register scheme */
        scheme = mvr >> OMAP_UART_MVR_SCHEME_SHIFT;

        switch (scheme) {
        case 0: /* Legacy Scheme: OMAP2/3 */
                /* MINOR_REV[0:4], MAJOR_REV[4:7] */
                major = (mvr & OMAP_UART_LEGACY_MVR_MAJ_MASK) >>
                        OMAP_UART_LEGACY_MVR_MAJ_SHIFT;
                minor = (mvr & OMAP_UART_LEGACY_MVR_MIN_MASK);
                break;
        case 1:
                /* New Scheme: OMAP4+ */
                /* MINOR_REV[0:5], MAJOR_REV[8:10] */
                major = (mvr & OMAP_UART_MVR_MAJ_MASK) >>
                        OMAP_UART_MVR_MAJ_SHIFT;
                minor = (mvr & OMAP_UART_MVR_MIN_MASK);
                break;
        default:
                dev_warn(up->port.dev,
                         "Unknown revision, defaulting to highest\n");
                /* highest possible revision */
                major = 0xff;
                minor = 0xff;
        }
        /* normalize revision for the driver */
        revision = UART_BUILD_REVISION(major, minor);

        switch (revision) {
        case OMAP_UART_REV_46:
                priv->habit |= UART_ERRATA_i202_MDR1_ACCESS;
                break;
        case OMAP_UART_REV_52:
                priv->habit |= UART_ERRATA_i202_MDR1_ACCESS |
                                OMAP_UART_WER_HAS_TX_WAKEUP;
                break;
        case OMAP_UART_REV_63:
                priv->habit |= UART_ERRATA_i202_MDR1_ACCESS |
                        OMAP_UART_WER_HAS_TX_WAKEUP;
                break;
        default:
                break;
        }
}

static void omap8250_uart_qos_work(struct work_struct *work)
{
        struct omap8250_priv *priv;

        priv = container_of(work, struct omap8250_priv, qos_work);
        cpu_latency_qos_update_request(&priv->pm_qos_request, priv->latency);
}

#ifdef CONFIG_SERIAL_8250_DMA
static int omap_8250_dma_handle_irq(struct uart_port *port);
#endif

static irqreturn_t omap8250_irq(int irq, void *dev_id)
{
        struct uart_port *port = dev_id;
        struct uart_8250_port *up = up_to_u8250p(port);
        unsigned int iir;
        int ret;

#ifdef CONFIG_SERIAL_8250_DMA
        if (up->dma) {
                ret = omap_8250_dma_handle_irq(port);
                return IRQ_RETVAL(ret);
        }
#endif

        serial8250_rpm_get(up);
        iir = serial_port_in(port, UART_IIR);
        ret = serial8250_handle_irq(port, iir);
        serial8250_rpm_put(up);

        return IRQ_RETVAL(ret);
}

static int omap_8250_startup(struct uart_port *port)
{
        struct uart_8250_port *up = up_to_u8250p(port);
        struct omap8250_priv *priv = port->private_data;
        int ret;

        if (priv->wakeirq) {
                ret = dev_pm_set_dedicated_wake_irq(port->dev, priv->wakeirq);
                if (ret)
                        return ret;
        }

        pm_runtime_get_sync(port->dev);

        up->mcr = 0;
        serial_out(up, UART_FCR, UART_FCR_CLEAR_RCVR | UART_FCR_CLEAR_XMIT);

        serial_out(up, UART_LCR, UART_LCR_WLEN8);

        up->lsr_saved_flags = 0;
        up->msr_saved_flags = 0;

        /* Disable DMA for console UART */
        if (uart_console(port))
                up->dma = NULL;

        if (up->dma) {
                ret = serial8250_request_dma(up);
                if (ret) {
                        dev_warn_ratelimited(port->dev,
                                             "failed to request DMA\n");
                        up->dma = NULL;
                }
        }

        ret = request_irq(port->irq, omap8250_irq, IRQF_SHARED,
                          dev_name(port->dev), port);
        if (ret < 0)
                goto err;

        up->ier = UART_IER_RLSI | UART_IER_RDI;
        serial_out(up, UART_IER, up->ier);

#ifdef CONFIG_PM
        up->capabilities |= UART_CAP_RPM;
#endif

        /* Enable module level wake up */
        priv->wer = OMAP_UART_WER_MOD_WKUP;
        if (priv->habit & OMAP_UART_WER_HAS_TX_WAKEUP)
                priv->wer |= OMAP_UART_TX_WAKEUP_EN;
        serial_out(up, UART_OMAP_WER, priv->wer);

        if (up->dma && !(priv->habit & UART_HAS_EFR2))
                up->dma->rx_dma(up);

        pm_runtime_mark_last_busy(port->dev);
        pm_runtime_put_autosuspend(port->dev);
        return 0;
err:
        pm_runtime_mark_last_busy(port->dev);
        pm_runtime_put_autosuspend(port->dev);
        dev_pm_clear_wake_irq(port->dev);
        return ret;
}

static void omap_8250_shutdown(struct uart_port *port)
{
        struct uart_8250_port *up = up_to_u8250p(port);
        struct omap8250_priv *priv = port->private_data;

        flush_work(&priv->qos_work);
        if (up->dma)
                omap_8250_rx_dma_flush(up);

        pm_runtime_get_sync(port->dev);

        serial_out(up, UART_OMAP_WER, 0);
        if (priv->habit & UART_HAS_EFR2)
                serial_out(up, UART_OMAP_EFR2, 0x0);

        up->ier = 0;
        serial_out(up, UART_IER, 0);

        if (up->dma)
                serial8250_release_dma(up);

        /*
         * Disable break condition and FIFOs
         */
        if (up->lcr & UART_LCR_SBC)
                serial_out(up, UART_LCR, up->lcr & ~UART_LCR_SBC);
        serial_out(up, UART_FCR, UART_FCR_CLEAR_RCVR | UART_FCR_CLEAR_XMIT);

        pm_runtime_mark_last_busy(port->dev);
        pm_runtime_put_autosuspend(port->dev);
        free_irq(port->irq, port);
        dev_pm_clear_wake_irq(port->dev);
}

static void omap_8250_throttle(struct uart_port *port)
{
        struct omap8250_priv *priv = port->private_data;
        unsigned long flags;

        pm_runtime_get_sync(port->dev);

        spin_lock_irqsave(&port->lock, flags);
        port->ops->stop_rx(port);
        priv->throttled = true;
        spin_unlock_irqrestore(&port->lock, flags);

        pm_runtime_mark_last_busy(port->dev);
        pm_runtime_put_autosuspend(port->dev);
}

static void omap_8250_unthrottle(struct uart_port *port)
{
        struct omap8250_priv *priv = port->private_data;
        struct uart_8250_port *up = up_to_u8250p(port);
        unsigned long flags;

        pm_runtime_get_sync(port->dev);

        spin_lock_irqsave(&port->lock, flags);
        priv->throttled = false;
        if (up->dma)
                up->dma->rx_dma(up);
        up->ier |= UART_IER_RLSI | UART_IER_RDI;
        port->read_status_mask |= UART_LSR_DR;
        serial_out(up, UART_IER, up->ier);
        spin_unlock_irqrestore(&port->lock, flags);

        pm_runtime_mark_last_busy(port->dev);
        pm_runtime_put_autosuspend(port->dev);
}

#ifdef CONFIG_SERIAL_8250_DMA
static int omap_8250_rx_dma(struct uart_8250_port *p);

/* Must be called while priv->rx_dma_lock is held */
static void __dma_rx_do_complete(struct uart_8250_port *p)
{
        struct uart_8250_dma    *dma = p->dma;
        struct tty_port         *tty_port = &p->port.state->port;
        struct dma_chan         *rxchan = dma->rxchan;
        dma_cookie_t            cookie;
        struct dma_tx_state     state;
        int                     count;
        int                     ret;

        if (!dma->rx_running)
                goto out;

        cookie = dma->rx_cookie;
        dma->rx_running = 0;
        dmaengine_tx_status(rxchan, cookie, &state);

        count = dma->rx_size - state.residue + state.in_flight_bytes;
        if (count < dma->rx_size) {
                dmaengine_terminate_async(rxchan);

                /*
                 * Poll for teardown to complete which guarantees in
                 * flight data is drained.
                 */
                if (state.in_flight_bytes) {
                        int poll_count = 25;

                        while (dmaengine_tx_status(rxchan, cookie, NULL) &&
                               poll_count--)
                                cpu_relax();

                        if (!poll_count)
                                dev_err(p->port.dev, "teardown incomplete\n");
                }
        }
        if (!count)
                goto out;
        ret = tty_insert_flip_string(tty_port, dma->rx_buf, count);

        p->port.icount.rx += ret;
        p->port.icount.buf_overrun += count - ret;
out:

        tty_flip_buffer_push(tty_port);
}

static void __dma_rx_complete(void *param)
{
        struct uart_8250_port *p = param;
        struct omap8250_priv *priv = p->port.private_data;
        struct uart_8250_dma *dma = p->dma;
        struct dma_tx_state     state;
        unsigned long flags;

        spin_lock_irqsave(&p->port.lock, flags);

        /*
         * If the tx status is not DMA_COMPLETE, then this is a delayed
         * completion callback. A previous RX timeout flush would have
         * already pushed the data, so exit.
         */
        if (dmaengine_tx_status(dma->rxchan, dma->rx_cookie, &state) !=
                        DMA_COMPLETE) {
                spin_unlock_irqrestore(&p->port.lock, flags);
                return;
        }
        __dma_rx_do_complete(p);
        if (!priv->throttled) {
                p->ier |= UART_IER_RLSI | UART_IER_RDI;
                serial_out(p, UART_IER, p->ier);
                if (!(priv->habit & UART_HAS_EFR2))
                        omap_8250_rx_dma(p);
        }

        spin_unlock_irqrestore(&p->port.lock, flags);
}

static void omap_8250_rx_dma_flush(struct uart_8250_port *p)
{
        struct omap8250_priv    *priv = p->port.private_data;
        struct uart_8250_dma    *dma = p->dma;
        struct dma_tx_state     state;
        unsigned long           flags;
        int ret;

        spin_lock_irqsave(&priv->rx_dma_lock, flags);

        if (!dma->rx_running) {
                spin_unlock_irqrestore(&priv->rx_dma_lock, flags);
                return;
        }

        ret = dmaengine_tx_status(dma->rxchan, dma->rx_cookie, &state);
        if (ret == DMA_IN_PROGRESS) {
                ret = dmaengine_pause(dma->rxchan);
                if (WARN_ON_ONCE(ret))
                        priv->rx_dma_broken = true;
        }
        __dma_rx_do_complete(p);
        spin_unlock_irqrestore(&priv->rx_dma_lock, flags);
}

static int omap_8250_rx_dma(struct uart_8250_port *p)
{
        struct omap8250_priv            *priv = p->port.private_data;
        struct uart_8250_dma            *dma = p->dma;
        int                             err = 0;
        struct dma_async_tx_descriptor  *desc;
        unsigned long                   flags;

        if (priv->rx_dma_broken)
                return -EINVAL;

        spin_lock_irqsave(&priv->rx_dma_lock, flags);

        if (dma->rx_running) {
                enum dma_status state;

                state = dmaengine_tx_status(dma->rxchan, dma->rx_cookie, NULL);
                if (state == DMA_COMPLETE) {
                        /*
                         * Disable RX interrupts to allow RX DMA completion
                         * callback to run.
                         */
                        p->ier &= ~(UART_IER_RLSI | UART_IER_RDI);
                        serial_out(p, UART_IER, p->ier);
                }
                goto out;
        }

        desc = dmaengine_prep_slave_single(dma->rxchan, dma->rx_addr,
                                           dma->rx_size, DMA_DEV_TO_MEM,
                                           DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
        if (!desc) {
                err = -EBUSY;
                goto out;
        }

        dma->rx_running = 1;
        desc->callback = __dma_rx_complete;
        desc->callback_param = p;

        dma->rx_cookie = dmaengine_submit(desc);

        dma_async_issue_pending(dma->rxchan);
out:
        spin_unlock_irqrestore(&priv->rx_dma_lock, flags);
        return err;
}

static int omap_8250_tx_dma(struct uart_8250_port *p);

static void omap_8250_dma_tx_complete(void *param)
{
        struct uart_8250_port   *p = param;
        struct uart_8250_dma    *dma = p->dma;
        struct circ_buf         *xmit = &p->port.state->xmit;
        unsigned long           flags;
        bool                    en_thri = false;
        struct omap8250_priv    *priv = p->port.private_data;

        dma_sync_single_for_cpu(dma->txchan->device->dev, dma->tx_addr,
                                UART_XMIT_SIZE, DMA_TO_DEVICE);

        spin_lock_irqsave(&p->port.lock, flags);

        dma->tx_running = 0;

        xmit->tail += dma->tx_size;
        xmit->tail &= UART_XMIT_SIZE - 1;
        p->port.icount.tx += dma->tx_size;

        if (priv->delayed_restore) {
                priv->delayed_restore = 0;
                omap8250_restore_regs(p);
        }

        if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
                uart_write_wakeup(&p->port);

        if (!uart_circ_empty(xmit) && !uart_tx_stopped(&p->port)) {
                int ret;

                ret = omap_8250_tx_dma(p);
                if (ret)
                        en_thri = true;
        } else if (p->capabilities & UART_CAP_RPM) {
                en_thri = true;
        }

        if (en_thri) {
                dma->tx_err = 1;
                serial8250_set_THRI(p);
        }

        spin_unlock_irqrestore(&p->port.lock, flags);
}

static int omap_8250_tx_dma(struct uart_8250_port *p)
{
        struct uart_8250_dma            *dma = p->dma;
        struct omap8250_priv            *priv = p->port.private_data;
        struct circ_buf                 *xmit = &p->port.state->xmit;
        struct dma_async_tx_descriptor  *desc;
        unsigned int    skip_byte = 0;
        int ret;

        if (dma->tx_running)
                return 0;
        if (uart_tx_stopped(&p->port) || uart_circ_empty(xmit)) {

                /*
                 * Even if no data, we need to return an error for the two cases
                 * below so serial8250_tx_chars() is invoked and properly clears
                 * THRI and/or runtime suspend.
                 */
                if (dma->tx_err || p->capabilities & UART_CAP_RPM) {
                        ret = -EBUSY;
                        goto err;
                }
                serial8250_clear_THRI(p);
                return 0;
        }

        dma->tx_size = CIRC_CNT_TO_END(xmit->head, xmit->tail, UART_XMIT_SIZE);
        if (priv->habit & OMAP_DMA_TX_KICK) {
                u8 tx_lvl;

                /*
                 * We need to put the first byte into the FIFO in order to start
                 * the DMA transfer. For transfers smaller than four bytes we
                 * don't bother doing DMA at all. It seem not matter if there
                 * are still bytes in the FIFO from the last transfer (in case
                 * we got here directly from omap_8250_dma_tx_complete()). Bytes
                 * leaving the FIFO seem not to trigger the DMA transfer. It is
                 * really the byte that we put into the FIFO.
                 * If the FIFO is already full then we most likely got here from
                 * omap_8250_dma_tx_complete(). And this means the DMA engine
                 * just completed its work. We don't have to wait the complete
                 * 86us at 115200,8n1 but around 60us (not to mention lower
                 * baudrates). So in that case we take the interrupt and try
                 * again with an empty FIFO.
                 */
                tx_lvl = serial_in(p, UART_OMAP_TX_LVL);
                if (tx_lvl == p->tx_loadsz) {
                        ret = -EBUSY;
                        goto err;
                }
                if (dma->tx_size < 4) {
                        ret = -EINVAL;
                        goto err;
                }
                skip_byte = 1;
        }

        desc = dmaengine_prep_slave_single(dma->txchan,
                        dma->tx_addr + xmit->tail + skip_byte,
                        dma->tx_size - skip_byte, DMA_MEM_TO_DEV,
                        DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
        if (!desc) {
                ret = -EBUSY;
                goto err;
        }

        dma->tx_running = 1;

        desc->callback = omap_8250_dma_tx_complete;
        desc->callback_param = p;

        dma->tx_cookie = dmaengine_submit(desc);

        dma_sync_single_for_device(dma->txchan->device->dev, dma->tx_addr,
                                   UART_XMIT_SIZE, DMA_TO_DEVICE);

        dma_async_issue_pending(dma->txchan);
        if (dma->tx_err)
                dma->tx_err = 0;

        serial8250_clear_THRI(p);
        if (skip_byte)
                serial_out(p, UART_TX, xmit->buf[xmit->tail]);
        return 0;
err:
        dma->tx_err = 1;
        return ret;
}

static bool handle_rx_dma(struct uart_8250_port *up, unsigned int iir)
{
        switch (iir & 0x3f) {
        case UART_IIR_RLSI:
        case UART_IIR_RX_TIMEOUT:
        case UART_IIR_RDI:
                omap_8250_rx_dma_flush(up);
                return true;
        }
        return omap_8250_rx_dma(up);
}

static unsigned char omap_8250_handle_rx_dma(struct uart_8250_port *up,
                                             u8 iir, unsigned char status)
{
        if ((status & (UART_LSR_DR | UART_LSR_BI)) &&
            (iir & UART_IIR_RDI)) {
                if (handle_rx_dma(up, iir)) {
                        status = serial8250_rx_chars(up, status);
                        omap_8250_rx_dma(up);
                }
        }

        return status;
}

static void am654_8250_handle_rx_dma(struct uart_8250_port *up, u8 iir,
                                     unsigned char status)
{
        /*
         * Queue a new transfer if FIFO has data.
         */
        if ((status & (UART_LSR_DR | UART_LSR_BI)) &&
            (up->ier & UART_IER_RDI)) {
                omap_8250_rx_dma(up);
                serial_out(up, UART_OMAP_EFR2, UART_OMAP_EFR2_TIMEOUT_BEHAVE);
        } else if ((iir & 0x3f) == UART_IIR_RX_TIMEOUT) {
                /*
                 * Disable RX timeout, read IIR to clear
                 * current timeout condition, clear EFR2 to
                 * periodic timeouts, re-enable interrupts.
                 */
                up->ier &= ~(UART_IER_RLSI | UART_IER_RDI);
                serial_out(up, UART_IER, up->ier);
                omap_8250_rx_dma_flush(up);
                serial_in(up, UART_IIR);
                serial_out(up, UART_OMAP_EFR2, 0x0);
                up->ier |= UART_IER_RLSI | UART_IER_RDI;
                serial_out(up, UART_IER, up->ier);
        }
}

/*
 * This is mostly serial8250_handle_irq(). We have a slightly different DMA
 * hoook for RX/TX and need different logic for them in the ISR. Therefore we
 * use the default routine in the non-DMA case and this one for with DMA.
 */
static int omap_8250_dma_handle_irq(struct uart_port *port)
{
        struct uart_8250_port *up = up_to_u8250p(port);
        struct omap8250_priv *priv = up->port.private_data;
        unsigned char status;
        unsigned long flags;
        u8 iir;

        serial8250_rpm_get(up);

        iir = serial_port_in(port, UART_IIR);
        if (iir & UART_IIR_NO_INT) {
                serial8250_rpm_put(up);
                return IRQ_HANDLED;
        }

        spin_lock_irqsave(&port->lock, flags);

        status = serial_port_in(port, UART_LSR);

        if (priv->habit & UART_HAS_EFR2)
                am654_8250_handle_rx_dma(up, iir, status);
        else
                status = omap_8250_handle_rx_dma(up, iir, status);

        serial8250_modem_status(up);
        if (status & UART_LSR_THRE && up->dma->tx_err) {
                if (uart_tx_stopped(&up->port) ||
                    uart_circ_empty(&up->port.state->xmit)) {
                        up->dma->tx_err = 0;
                        serial8250_tx_chars(up);
                } else  {
                        /*
                         * try again due to an earlier failer which
                         * might have been resolved by now.
                         */
                        if (omap_8250_tx_dma(up))
                                serial8250_tx_chars(up);
                }
        }

        uart_unlock_and_check_sysrq(port, flags);
        serial8250_rpm_put(up);
        return 1;
}

static bool the_no_dma_filter_fn(struct dma_chan *chan, void *param)
{
        return false;
}

#else

static inline int omap_8250_rx_dma(struct uart_8250_port *p)
{
        return -EINVAL;
}
#endif

static int omap8250_no_handle_irq(struct uart_port *port)
{
        /* IRQ has not been requested but handling irq? */
        WARN_ONCE(1, "Unexpected irq handling before port startup\n");
        return 0;
}

static struct omap8250_dma_params am654_dma = {
        .rx_size = SZ_2K,
        .rx_trigger = 1,
        .tx_trigger = TX_TRIGGER,
};

static struct omap8250_dma_params am33xx_dma = {
        .rx_size = RX_TRIGGER,
        .rx_trigger = RX_TRIGGER,
        .tx_trigger = TX_TRIGGER,
};

static struct omap8250_platdata am654_platdata = {
        .dma_params     = &am654_dma,
        .habit          = UART_HAS_EFR2,
};

static struct omap8250_platdata am33xx_platdata = {
        .dma_params     = &am33xx_dma,
        .habit          = OMAP_DMA_TX_KICK | UART_ERRATA_CLOCK_DISABLE,
};

static struct omap8250_platdata omap4_platdata = {
        .dma_params     = &am33xx_dma,
        .habit          = UART_ERRATA_CLOCK_DISABLE,
};

static const struct of_device_id omap8250_dt_ids[] = {
        { .compatible = "ti,am654-uart", .data = &am654_platdata, },
        { .compatible = "ti,omap2-uart" },
        { .compatible = "ti,omap3-uart" },
        { .compatible = "ti,omap4-uart", .data = &omap4_platdata, },
        { .compatible = "ti,am3352-uart", .data = &am33xx_platdata, },
        { .compatible = "ti,am4372-uart", .data = &am33xx_platdata, },
        { .compatible = "ti,dra742-uart", .data = &omap4_platdata, },
        {},
};
MODULE_DEVICE_TABLE(of, omap8250_dt_ids);

static int omap8250_probe(struct platform_device *pdev)
{
        struct resource *regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        struct resource *irq = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
        struct device_node *np = pdev->dev.of_node;
        struct omap8250_priv *priv;
        const struct omap8250_platdata *pdata;
        struct uart_8250_port up;
        int ret;
        void __iomem *membase;

        if (!regs || !irq) {
                dev_err(&pdev->dev, "missing registers or irq\n");
                return -EINVAL;
        }

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

        membase = devm_ioremap(&pdev->dev, regs->start,
                                       resource_size(regs));
        if (!membase)
                return -ENODEV;

        memset(&up, 0, sizeof(up));
        up.port.dev = &pdev->dev;
        up.port.mapbase = regs->start;
        up.port.membase = membase;
        up.port.irq = irq->start;
        /*
         * It claims to be 16C750 compatible however it is a little different.
         * It has EFR and has no FCR7_64byte bit. The AFE (which it claims to
         * have) is enabled via EFR instead of MCR. The type is set here 8250
         * just to get things going. UNKNOWN does not work for a few reasons and
         * we don't need our own type since we don't use 8250's set_termios()
         * or pm callback.
         */
        up.port.type = PORT_8250;
        up.port.iotype = UPIO_MEM;
        up.port.flags = UPF_FIXED_PORT | UPF_FIXED_TYPE | UPF_SOFT_FLOW |
                UPF_HARD_FLOW;
        up.port.private_data = priv;

        up.port.regshift = 2;
        up.port.fifosize = 64;
        up.tx_loadsz = 64;
        up.capabilities = UART_CAP_FIFO;
#ifdef CONFIG_PM
        /*
         * Runtime PM is mostly transparent. However to do it right we need to a
         * TX empty interrupt before we can put the device to auto idle. So if
         * PM is not enabled we don't add that flag and can spare that one extra
         * interrupt in the TX path.
         */
        up.capabilities |= UART_CAP_RPM;
#endif
        up.port.set_termios = omap_8250_set_termios;
        up.port.set_mctrl = omap8250_set_mctrl;
        up.port.pm = omap_8250_pm;
        up.port.startup = omap_8250_startup;
        up.port.shutdown = omap_8250_shutdown;
        up.port.throttle = omap_8250_throttle;
        up.port.unthrottle = omap_8250_unthrottle;
        up.port.rs485_config = serial8250_em485_config;
        up.rs485_start_tx = serial8250_em485_start_tx;
        up.rs485_stop_tx = serial8250_em485_stop_tx;
        up.port.has_sysrq = IS_ENABLED(CONFIG_SERIAL_8250_CONSOLE);

        ret = of_alias_get_id(np, "serial");
        if (ret < 0) {
                dev_err(&pdev->dev, "failed to get alias\n");
                return ret;
        }
        up.port.line = ret;

        if (of_property_read_u32(np, "clock-frequency", &up.port.uartclk)) {
                struct clk *clk;

                clk = devm_clk_get(&pdev->dev, NULL);
                if (IS_ERR(clk)) {
                        if (PTR_ERR(clk) == -EPROBE_DEFER)
                                return -EPROBE_DEFER;
                } else {
                        up.port.uartclk = clk_get_rate(clk);
                }
        }

        priv->wakeirq = irq_of_parse_and_map(np, 1);

        pdata = of_device_get_match_data(&pdev->dev);
        if (pdata)
                priv->habit |= pdata->habit;

        if (!up.port.uartclk) {
                up.port.uartclk = DEFAULT_CLK_SPEED;
                dev_warn(&pdev->dev,
                         "No clock speed specified: using default: %d\n",
                         DEFAULT_CLK_SPEED);
        }

        priv->latency = PM_QOS_CPU_LATENCY_DEFAULT_VALUE;
        priv->calc_latency = PM_QOS_CPU_LATENCY_DEFAULT_VALUE;
        cpu_latency_qos_add_request(&priv->pm_qos_request, priv->latency);
        INIT_WORK(&priv->qos_work, omap8250_uart_qos_work);

        spin_lock_init(&priv->rx_dma_lock);

        device_init_wakeup(&pdev->dev, true);
        pm_runtime_enable(&pdev->dev);
        pm_runtime_use_autosuspend(&pdev->dev);

        /*
         * Disable runtime PM until autosuspend delay unless specifically
         * enabled by the user via sysfs. This is the historic way to
         * prevent an unsafe default policy with lossy characters on wake-up.
         * For serdev devices this is not needed, the policy can be managed by
         * the serdev driver.
         */
        if (!of_get_available_child_count(pdev->dev.of_node))
                pm_runtime_set_autosuspend_delay(&pdev->dev, -1);

        pm_runtime_irq_safe(&pdev->dev);

        pm_runtime_get_sync(&pdev->dev);

        omap_serial_fill_features_erratas(&up, priv);
        up.port.handle_irq = omap8250_no_handle_irq;
        priv->rx_trigger = RX_TRIGGER;
        priv->tx_trigger = TX_TRIGGER;
#ifdef CONFIG_SERIAL_8250_DMA
        /*
         * Oh DMA support. If there are no DMA properties in the DT then
         * we will fall back to a generic DMA channel which does not
         * really work here. To ensure that we do not get a generic DMA
         * channel assigned, we have the the_no_dma_filter_fn() here.
         * To avoid "failed to request DMA" messages we check for DMA
         * properties in DT.
         */
        ret = of_property_count_strings(np, "dma-names");
        if (ret == 2) {
                struct omap8250_dma_params *dma_params = NULL;

                up.dma = &priv->omap8250_dma;
                up.dma->fn = the_no_dma_filter_fn;
                up.dma->tx_dma = omap_8250_tx_dma;
                up.dma->rx_dma = omap_8250_rx_dma;
                if (pdata)
                        dma_params = pdata->dma_params;

                if (dma_params) {
                        up.dma->rx_size = dma_params->rx_size;
                        up.dma->rxconf.src_maxburst = dma_params->rx_trigger;
                        up.dma->txconf.dst_maxburst = dma_params->tx_trigger;
                        priv->rx_trigger = dma_params->rx_trigger;
                        priv->tx_trigger = dma_params->tx_trigger;
                } else {
                        up.dma->rx_size = RX_TRIGGER;
                        up.dma->rxconf.src_maxburst = RX_TRIGGER;
                        up.dma->txconf.dst_maxburst = TX_TRIGGER;
                }
        }
#endif
        ret = serial8250_register_8250_port(&up);
        if (ret < 0) {
                dev_err(&pdev->dev, "unable to register 8250 port\n");
                goto err;
        }
        priv->line = ret;
        platform_set_drvdata(pdev, priv);
        pm_runtime_mark_last_busy(&pdev->dev);
        pm_runtime_put_autosuspend(&pdev->dev);
        return 0;
err:
        pm_runtime_dont_use_autosuspend(&pdev->dev);
        pm_runtime_put_sync(&pdev->dev);
        pm_runtime_disable(&pdev->dev);
        return ret;
}

static int omap8250_remove(struct platform_device *pdev)
{
        struct omap8250_priv *priv = platform_get_drvdata(pdev);

        pm_runtime_dont_use_autosuspend(&pdev->dev);
        pm_runtime_put_sync(&pdev->dev);
        pm_runtime_disable(&pdev->dev);
        serial8250_unregister_port(priv->line);
        cpu_latency_qos_remove_request(&priv->pm_qos_request);
        device_init_wakeup(&pdev->dev, false);
        return 0;
}

#ifdef CONFIG_PM_SLEEP
static int omap8250_prepare(struct device *dev)
{
        struct omap8250_priv *priv = dev_get_drvdata(dev);

        if (!priv)
                return 0;
        priv->is_suspending = true;
        return 0;
}

static void omap8250_complete(struct device *dev)
{
        struct omap8250_priv *priv = dev_get_drvdata(dev);

        if (!priv)
                return;
        priv->is_suspending = false;
}

static int omap8250_suspend(struct device *dev)
{
        struct omap8250_priv *priv = dev_get_drvdata(dev);
        struct uart_8250_port *up = serial8250_get_port(priv->line);

        serial8250_suspend_port(priv->line);

        pm_runtime_get_sync(dev);
        if (!device_may_wakeup(dev))
                priv->wer = 0;
        serial_out(up, UART_OMAP_WER, priv->wer);
        pm_runtime_mark_last_busy(dev);
        pm_runtime_put_autosuspend(dev);

        flush_work(&priv->qos_work);
        return 0;
}

static int omap8250_resume(struct device *dev)
{
        struct omap8250_priv *priv = dev_get_drvdata(dev);

        serial8250_resume_port(priv->line);
        return 0;
}
#else
#define omap8250_prepare NULL
#define omap8250_complete NULL
#endif

#ifdef CONFIG_PM
static int omap8250_lost_context(struct uart_8250_port *up)
{
        u32 val;

        val = serial_in(up, UART_OMAP_SCR);
        /*
         * If we lose context, then SCR is set to its reset value of zero.
         * After set_termios() we set bit 3 of SCR (TX_EMPTY_CTL_IT) to 1,
         * among other bits, to never set the register back to zero again.
         */
        if (!val)
                return 1;
        return 0;
}

/* TODO: in future, this should happen via API in drivers/reset/ */
static int omap8250_soft_reset(struct device *dev)
{
        struct omap8250_priv *priv = dev_get_drvdata(dev);
        struct uart_8250_port *up = serial8250_get_port(priv->line);
        int timeout = 100;
        int sysc;
        int syss;

        /*
         * At least on omap4, unused uarts may not idle after reset without
         * a basic scr dma configuration even with no dma in use. The
         * module clkctrl status bits will be 1 instead of 3 blocking idle
         * for the whole clockdomain. The softreset below will clear scr,
         * and we restore it on resume so this is safe to do on all SoCs
         * needing omap8250_soft_reset() quirk. Do it in two writes as
         * recommended in the comment for omap8250_update_scr().
         */
        serial_out(up, UART_OMAP_SCR, OMAP_UART_SCR_DMAMODE_1);
        serial_out(up, UART_OMAP_SCR,
                   OMAP_UART_SCR_DMAMODE_1 | OMAP_UART_SCR_DMAMODE_CTL);

        sysc = serial_in(up, UART_OMAP_SYSC);

        /* softreset the UART */
        sysc |= OMAP_UART_SYSC_SOFTRESET;
        serial_out(up, UART_OMAP_SYSC, sysc);

        /* By experiments, 1us enough for reset complete on AM335x */
        do {
                udelay(1);
                syss = serial_in(up, UART_OMAP_SYSS);
        } while (--timeout && !(syss & OMAP_UART_SYSS_RESETDONE));

        if (!timeout) {
                dev_err(dev, "timed out waiting for reset done\n");
                return -ETIMEDOUT;
        }

        return 0;
}

static int omap8250_runtime_suspend(struct device *dev)
{
        struct omap8250_priv *priv = dev_get_drvdata(dev);
        struct uart_8250_port *up;

        /* In case runtime-pm tries this before we are setup */
        if (!priv)
                return 0;

        up = serial8250_get_port(priv->line);
        /*
         * When using 'no_console_suspend', the console UART must not be
         * suspended. Since driver suspend is managed by runtime suspend,
         * preventing runtime suspend (by returning error) will keep device
         * active during suspend.
         */
        if (priv->is_suspending && !console_suspend_enabled) {
                if (uart_console(&up->port))
                        return -EBUSY;
        }

        if (priv->habit & UART_ERRATA_CLOCK_DISABLE) {
                int ret;

                ret = omap8250_soft_reset(dev);
                if (ret)
                        return ret;

                /* Restore to UART mode after reset (for wakeup) */
                omap8250_update_mdr1(up, priv);
                /* Restore wakeup enable register */
                serial_out(up, UART_OMAP_WER, priv->wer);
        }

        if (up->dma && up->dma->rxchan)
                omap_8250_rx_dma_flush(up);

        priv->latency = PM_QOS_CPU_LATENCY_DEFAULT_VALUE;
        schedule_work(&priv->qos_work);

        return 0;
}

static int omap8250_runtime_resume(struct device *dev)
{
        struct omap8250_priv *priv = dev_get_drvdata(dev);
        struct uart_8250_port *up;

        /* In case runtime-pm tries this before we are setup */
        if (!priv)
                return 0;

        up = serial8250_get_port(priv->line);

        if (omap8250_lost_context(up))
                omap8250_restore_regs(up);

        if (up->dma && up->dma->rxchan && !(priv->habit & UART_HAS_EFR2))
                omap_8250_rx_dma(up);

        priv->latency = priv->calc_latency;
        schedule_work(&priv->qos_work);
        return 0;
}
#endif

#ifdef CONFIG_SERIAL_8250_OMAP_TTYO_FIXUP
static int __init omap8250_console_fixup(void)
{
        char *omap_str;
        char *options;
        u8 idx;

        if (strstr(boot_command_line, "console=ttyS"))
                /* user set a ttyS based name for the console */
                return 0;

        omap_str = strstr(boot_command_line, "console=ttyO");
        if (!omap_str)
                /* user did not set ttyO based console, so we don't care */
                return 0;

        omap_str += 12;
        if ('0' <= *omap_str && *omap_str <= '9')
                idx = *omap_str - '0';
        else
                return 0;

        omap_str++;
        if (omap_str[0] == ',') {
                omap_str++;
                options = omap_str;
        } else {
                options = NULL;
        }

        add_preferred_console("ttyS", idx, options);
        pr_err("WARNING: Your 'console=ttyO%d' has been replaced by 'ttyS%d'\n",
               idx, idx);
        pr_err("This ensures that you still see kernel messages. Please\n");
        pr_err("update your kernel commandline.\n");
        return 0;
}
console_initcall(omap8250_console_fixup);
#endif

static const struct dev_pm_ops omap8250_dev_pm_ops = {
        SET_SYSTEM_SLEEP_PM_OPS(omap8250_suspend, omap8250_resume)
        SET_RUNTIME_PM_OPS(omap8250_runtime_suspend,
                           omap8250_runtime_resume, NULL)
        .prepare        = omap8250_prepare,
        .complete       = omap8250_complete,
};

static struct platform_driver omap8250_platform_driver = {
        .driver = {
                .name           = "omap8250",
                .pm             = &omap8250_dev_pm_ops,
                .of_match_table = omap8250_dt_ids,
        },
        .probe                  = omap8250_probe,
        .remove                 = omap8250_remove,
};
module_platform_driver(omap8250_platform_driver);

MODULE_AUTHOR("Sebastian Andrzej Siewior");
MODULE_DESCRIPTION("OMAP 8250 Driver");
MODULE_LICENSE("GPL v2");