scsi: qedf: Fix a potential NULL pointer dereference

[mirror_ubuntu-artful-kernel.git] / drivers / i2c / busses / i2c-designware-core.c

/*
 * Synopsys DesignWare I2C adapter driver (master only).
 *
 * Based on the TI DAVINCI I2C adapter driver.
 *
 * Copyright (C) 2006 Texas Instruments.
 * Copyright (C) 2007 MontaVista Software Inc.
 * Copyright (C) 2009 Provigent Ltd.
 *
 * ----------------------------------------------------------------------------
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * ----------------------------------------------------------------------------
 *
 */
#include <linux/export.h>
#include <linux/errno.h>
#include <linux/err.h>
#include <linux/i2c.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/pm_runtime.h>
#include <linux/delay.h>
#include <linux/module.h>
#include "i2c-designware-core.h"

/*
 * Registers offset
 */
#define DW_IC_CON               0x0
#define DW_IC_TAR               0x4
#define DW_IC_DATA_CMD          0x10
#define DW_IC_SS_SCL_HCNT       0x14
#define DW_IC_SS_SCL_LCNT       0x18
#define DW_IC_FS_SCL_HCNT       0x1c
#define DW_IC_FS_SCL_LCNT       0x20
#define DW_IC_HS_SCL_HCNT       0x24
#define DW_IC_HS_SCL_LCNT       0x28
#define DW_IC_INTR_STAT         0x2c
#define DW_IC_INTR_MASK         0x30
#define DW_IC_RAW_INTR_STAT     0x34
#define DW_IC_RX_TL             0x38
#define DW_IC_TX_TL             0x3c
#define DW_IC_CLR_INTR          0x40
#define DW_IC_CLR_RX_UNDER      0x44
#define DW_IC_CLR_RX_OVER       0x48
#define DW_IC_CLR_TX_OVER       0x4c
#define DW_IC_CLR_RD_REQ        0x50
#define DW_IC_CLR_TX_ABRT       0x54
#define DW_IC_CLR_RX_DONE       0x58
#define DW_IC_CLR_ACTIVITY      0x5c
#define DW_IC_CLR_STOP_DET      0x60
#define DW_IC_CLR_START_DET     0x64
#define DW_IC_CLR_GEN_CALL      0x68
#define DW_IC_ENABLE            0x6c
#define DW_IC_STATUS            0x70
#define DW_IC_TXFLR             0x74
#define DW_IC_RXFLR             0x78
#define DW_IC_SDA_HOLD          0x7c
#define DW_IC_TX_ABRT_SOURCE    0x80
#define DW_IC_ENABLE_STATUS     0x9c
#define DW_IC_COMP_PARAM_1      0xf4
#define DW_IC_COMP_VERSION      0xf8
#define DW_IC_SDA_HOLD_MIN_VERS 0x3131312A
#define DW_IC_COMP_TYPE         0xfc
#define DW_IC_COMP_TYPE_VALUE   0x44570140

#define DW_IC_INTR_RX_UNDER     0x001
#define DW_IC_INTR_RX_OVER      0x002
#define DW_IC_INTR_RX_FULL      0x004
#define DW_IC_INTR_TX_OVER      0x008
#define DW_IC_INTR_TX_EMPTY     0x010
#define DW_IC_INTR_RD_REQ       0x020
#define DW_IC_INTR_TX_ABRT      0x040
#define DW_IC_INTR_RX_DONE      0x080
#define DW_IC_INTR_ACTIVITY     0x100
#define DW_IC_INTR_STOP_DET     0x200
#define DW_IC_INTR_START_DET    0x400
#define DW_IC_INTR_GEN_CALL     0x800

#define DW_IC_INTR_DEFAULT_MASK         (DW_IC_INTR_RX_FULL | \
                                         DW_IC_INTR_TX_EMPTY | \
                                         DW_IC_INTR_TX_ABRT | \
                                         DW_IC_INTR_STOP_DET)

#define DW_IC_STATUS_ACTIVITY   0x1

#define DW_IC_SDA_HOLD_RX_SHIFT         16
#define DW_IC_SDA_HOLD_RX_MASK          GENMASK(23, DW_IC_SDA_HOLD_RX_SHIFT)

#define DW_IC_ERR_TX_ABRT       0x1

#define DW_IC_TAR_10BITADDR_MASTER BIT(12)

#define DW_IC_COMP_PARAM_1_SPEED_MODE_HIGH      (BIT(2) | BIT(3))
#define DW_IC_COMP_PARAM_1_SPEED_MODE_MASK      GENMASK(3, 2)

/*
 * status codes
 */
#define STATUS_IDLE                     0x0
#define STATUS_WRITE_IN_PROGRESS        0x1
#define STATUS_READ_IN_PROGRESS         0x2

#define TIMEOUT                 20 /* ms */

/*
 * hardware abort codes from the DW_IC_TX_ABRT_SOURCE register
 *
 * only expected abort codes are listed here
 * refer to the datasheet for the full list
 */
#define ABRT_7B_ADDR_NOACK      0
#define ABRT_10ADDR1_NOACK      1
#define ABRT_10ADDR2_NOACK      2
#define ABRT_TXDATA_NOACK       3
#define ABRT_GCALL_NOACK        4
#define ABRT_GCALL_READ         5
#define ABRT_SBYTE_ACKDET       7
#define ABRT_SBYTE_NORSTRT      9
#define ABRT_10B_RD_NORSTRT     10
#define ABRT_MASTER_DIS         11
#define ARB_LOST                12

#define DW_IC_TX_ABRT_7B_ADDR_NOACK     (1UL << ABRT_7B_ADDR_NOACK)
#define DW_IC_TX_ABRT_10ADDR1_NOACK     (1UL << ABRT_10ADDR1_NOACK)
#define DW_IC_TX_ABRT_10ADDR2_NOACK     (1UL << ABRT_10ADDR2_NOACK)
#define DW_IC_TX_ABRT_TXDATA_NOACK      (1UL << ABRT_TXDATA_NOACK)
#define DW_IC_TX_ABRT_GCALL_NOACK       (1UL << ABRT_GCALL_NOACK)
#define DW_IC_TX_ABRT_GCALL_READ        (1UL << ABRT_GCALL_READ)
#define DW_IC_TX_ABRT_SBYTE_ACKDET      (1UL << ABRT_SBYTE_ACKDET)
#define DW_IC_TX_ABRT_SBYTE_NORSTRT     (1UL << ABRT_SBYTE_NORSTRT)
#define DW_IC_TX_ABRT_10B_RD_NORSTRT    (1UL << ABRT_10B_RD_NORSTRT)
#define DW_IC_TX_ABRT_MASTER_DIS        (1UL << ABRT_MASTER_DIS)
#define DW_IC_TX_ARB_LOST               (1UL << ARB_LOST)

#define DW_IC_TX_ABRT_NOACK             (DW_IC_TX_ABRT_7B_ADDR_NOACK | \
                                         DW_IC_TX_ABRT_10ADDR1_NOACK | \
                                         DW_IC_TX_ABRT_10ADDR2_NOACK | \
                                         DW_IC_TX_ABRT_TXDATA_NOACK | \
                                         DW_IC_TX_ABRT_GCALL_NOACK)

static char *abort_sources[] = {
        [ABRT_7B_ADDR_NOACK] =
                "slave address not acknowledged (7bit mode)",
        [ABRT_10ADDR1_NOACK] =
                "first address byte not acknowledged (10bit mode)",
        [ABRT_10ADDR2_NOACK] =
                "second address byte not acknowledged (10bit mode)",
        [ABRT_TXDATA_NOACK] =
                "data not acknowledged",
        [ABRT_GCALL_NOACK] =
                "no acknowledgement for a general call",
        [ABRT_GCALL_READ] =
                "read after general call",
        [ABRT_SBYTE_ACKDET] =
                "start byte acknowledged",
        [ABRT_SBYTE_NORSTRT] =
                "trying to send start byte when restart is disabled",
        [ABRT_10B_RD_NORSTRT] =
                "trying to read when restart is disabled (10bit mode)",
        [ABRT_MASTER_DIS] =
                "trying to use disabled adapter",
        [ARB_LOST] =
                "lost arbitration",
};

static u32 dw_readl(struct dw_i2c_dev *dev, int offset)
{
        u32 value;

        if (dev->flags & ACCESS_16BIT)
                value = readw_relaxed(dev->base + offset) |
                        (readw_relaxed(dev->base + offset + 2) << 16);
        else
                value = readl_relaxed(dev->base + offset);

        if (dev->flags & ACCESS_SWAP)
                return swab32(value);
        else
                return value;
}

static void dw_writel(struct dw_i2c_dev *dev, u32 b, int offset)
{
        if (dev->flags & ACCESS_SWAP)
                b = swab32(b);

        if (dev->flags & ACCESS_16BIT) {
                writew_relaxed((u16)b, dev->base + offset);
                writew_relaxed((u16)(b >> 16), dev->base + offset + 2);
        } else {
                writel_relaxed(b, dev->base + offset);
        }
}

static u32
i2c_dw_scl_hcnt(u32 ic_clk, u32 tSYMBOL, u32 tf, int cond, int offset)
{
        /*
         * DesignWare I2C core doesn't seem to have solid strategy to meet
         * the tHD;STA timing spec.  Configuring _HCNT based on tHIGH spec
         * will result in violation of the tHD;STA spec.
         */
        if (cond)
                /*
                 * Conditional expression:
                 *
                 *   IC_[FS]S_SCL_HCNT + (1+4+3) >= IC_CLK * tHIGH
                 *
                 * This is based on the DW manuals, and represents an ideal
                 * configuration.  The resulting I2C bus speed will be
                 * faster than any of the others.
                 *
                 * If your hardware is free from tHD;STA issue, try this one.
                 */
                return (ic_clk * tSYMBOL + 500000) / 1000000 - 8 + offset;
        else
                /*
                 * Conditional expression:
                 *
                 *   IC_[FS]S_SCL_HCNT + 3 >= IC_CLK * (tHD;STA + tf)
                 *
                 * This is just experimental rule; the tHD;STA period turned
                 * out to be proportinal to (_HCNT + 3).  With this setting,
                 * we could meet both tHIGH and tHD;STA timing specs.
                 *
                 * If unsure, you'd better to take this alternative.
                 *
                 * The reason why we need to take into account "tf" here,
                 * is the same as described in i2c_dw_scl_lcnt().
                 */
                return (ic_clk * (tSYMBOL + tf) + 500000) / 1000000
                        - 3 + offset;
}

static u32 i2c_dw_scl_lcnt(u32 ic_clk, u32 tLOW, u32 tf, int offset)
{
        /*
         * Conditional expression:
         *
         *   IC_[FS]S_SCL_LCNT + 1 >= IC_CLK * (tLOW + tf)
         *
         * DW I2C core starts counting the SCL CNTs for the LOW period
         * of the SCL clock (tLOW) as soon as it pulls the SCL line.
         * In order to meet the tLOW timing spec, we need to take into
         * account the fall time of SCL signal (tf).  Default tf value
         * should be 0.3 us, for safety.
         */
        return ((ic_clk * (tLOW + tf) + 500000) / 1000000) - 1 + offset;
}

static void __i2c_dw_enable(struct dw_i2c_dev *dev, bool enable)
{
        dw_writel(dev, enable, DW_IC_ENABLE);
}

static void __i2c_dw_enable_and_wait(struct dw_i2c_dev *dev, bool enable)
{
        int timeout = 100;

        do {
                __i2c_dw_enable(dev, enable);
                if ((dw_readl(dev, DW_IC_ENABLE_STATUS) & 1) == enable)
                        return;

                /*
                 * Wait 10 times the signaling period of the highest I2C
                 * transfer supported by the driver (for 400KHz this is
                 * 25us) as described in the DesignWare I2C databook.
                 */
                usleep_range(25, 250);
        } while (timeout--);

        dev_warn(dev->dev, "timeout in %sabling adapter\n",
                 enable ? "en" : "dis");
}

static unsigned long i2c_dw_clk_rate(struct dw_i2c_dev *dev)
{
        /*
         * Clock is not necessary if we got LCNT/HCNT values directly from
         * the platform code.
         */
        if (WARN_ON_ONCE(!dev->get_clk_rate_khz))
                return 0;
        return dev->get_clk_rate_khz(dev);
}

static int i2c_dw_acquire_lock(struct dw_i2c_dev *dev)
{
        int ret;

        if (!dev->acquire_lock)
                return 0;

        ret = dev->acquire_lock(dev);
        if (!ret)
                return 0;

        dev_err(dev->dev, "couldn't acquire bus ownership\n");

        return ret;
}

static void i2c_dw_release_lock(struct dw_i2c_dev *dev)
{
        if (dev->release_lock)
                dev->release_lock(dev);
}

/**
 * i2c_dw_init() - initialize the designware i2c master hardware
 * @dev: device private data
 *
 * This functions configures and enables the I2C master.
 * This function is called during I2C init function, and in case of timeout at
 * run time.
 */
int i2c_dw_init(struct dw_i2c_dev *dev)
{
        u32 hcnt, lcnt;
        u32 reg, comp_param1;
        u32 sda_falling_time, scl_falling_time;
        int ret;

        ret = i2c_dw_acquire_lock(dev);
        if (ret)
                return ret;

        reg = dw_readl(dev, DW_IC_COMP_TYPE);
        if (reg == ___constant_swab32(DW_IC_COMP_TYPE_VALUE)) {
                /* Configure register endianess access */
                dev->flags |= ACCESS_SWAP;
        } else if (reg == (DW_IC_COMP_TYPE_VALUE & 0x0000ffff)) {
                /* Configure register access mode 16bit */
                dev->flags |= ACCESS_16BIT;
        } else if (reg != DW_IC_COMP_TYPE_VALUE) {
                dev_err(dev->dev, "Unknown Synopsys component type: "
                        "0x%08x\n", reg);
                i2c_dw_release_lock(dev);
                return -ENODEV;
        }

        comp_param1 = dw_readl(dev, DW_IC_COMP_PARAM_1);

        /* Disable the adapter */
        __i2c_dw_enable_and_wait(dev, false);

        /* set standard and fast speed deviders for high/low periods */

        sda_falling_time = dev->sda_falling_time ?: 300; /* ns */
        scl_falling_time = dev->scl_falling_time ?: 300; /* ns */

        /* Set SCL timing parameters for standard-mode */
        if (dev->ss_hcnt && dev->ss_lcnt) {
                hcnt = dev->ss_hcnt;
                lcnt = dev->ss_lcnt;
        } else {
                hcnt = i2c_dw_scl_hcnt(i2c_dw_clk_rate(dev),
                                        4000,   /* tHD;STA = tHIGH = 4.0 us */
                                        sda_falling_time,
                                        0,      /* 0: DW default, 1: Ideal */
                                        0);     /* No offset */
                lcnt = i2c_dw_scl_lcnt(i2c_dw_clk_rate(dev),
                                        4700,   /* tLOW = 4.7 us */
                                        scl_falling_time,
                                        0);     /* No offset */
        }
        dw_writel(dev, hcnt, DW_IC_SS_SCL_HCNT);
        dw_writel(dev, lcnt, DW_IC_SS_SCL_LCNT);
        dev_dbg(dev->dev, "Standard-mode HCNT:LCNT = %d:%d\n", hcnt, lcnt);

        /* Set SCL timing parameters for fast-mode or fast-mode plus */
        if ((dev->clk_freq == 1000000) && dev->fp_hcnt && dev->fp_lcnt) {
                hcnt = dev->fp_hcnt;
                lcnt = dev->fp_lcnt;
        } else if (dev->fs_hcnt && dev->fs_lcnt) {
                hcnt = dev->fs_hcnt;
                lcnt = dev->fs_lcnt;
        } else {
                hcnt = i2c_dw_scl_hcnt(i2c_dw_clk_rate(dev),
                                        600,    /* tHD;STA = tHIGH = 0.6 us */
                                        sda_falling_time,
                                        0,      /* 0: DW default, 1: Ideal */
                                        0);     /* No offset */
                lcnt = i2c_dw_scl_lcnt(i2c_dw_clk_rate(dev),
                                        1300,   /* tLOW = 1.3 us */
                                        scl_falling_time,
                                        0);     /* No offset */
        }
        dw_writel(dev, hcnt, DW_IC_FS_SCL_HCNT);
        dw_writel(dev, lcnt, DW_IC_FS_SCL_LCNT);
        dev_dbg(dev->dev, "Fast-mode HCNT:LCNT = %d:%d\n", hcnt, lcnt);

        if ((dev->master_cfg & DW_IC_CON_SPEED_MASK) ==
                DW_IC_CON_SPEED_HIGH) {
                if ((comp_param1 & DW_IC_COMP_PARAM_1_SPEED_MODE_MASK)
                        != DW_IC_COMP_PARAM_1_SPEED_MODE_HIGH) {
                        dev_err(dev->dev, "High Speed not supported!\n");
                        dev->master_cfg &= ~DW_IC_CON_SPEED_MASK;
                        dev->master_cfg |= DW_IC_CON_SPEED_FAST;
                } else if (dev->hs_hcnt && dev->hs_lcnt) {
                        hcnt = dev->hs_hcnt;
                        lcnt = dev->hs_lcnt;
                        dw_writel(dev, hcnt, DW_IC_HS_SCL_HCNT);
                        dw_writel(dev, lcnt, DW_IC_HS_SCL_LCNT);
                        dev_dbg(dev->dev, "HighSpeed-mode HCNT:LCNT = %d:%d\n",
                                hcnt, lcnt);
                }
        }

        /* Configure SDA Hold Time if required */
        reg = dw_readl(dev, DW_IC_COMP_VERSION);
        if (reg >= DW_IC_SDA_HOLD_MIN_VERS) {
                if (!dev->sda_hold_time) {
                        /* Keep previous hold time setting if no one set it */
                        dev->sda_hold_time = dw_readl(dev, DW_IC_SDA_HOLD);
                }
                /*
                 * Workaround for avoiding TX arbitration lost in case I2C
                 * slave pulls SDA down "too quickly" after falling egde of
                 * SCL by enabling non-zero SDA RX hold. Specification says it
                 * extends incoming SDA low to high transition while SCL is
                 * high but it apprears to help also above issue.
                 */
                if (!(dev->sda_hold_time & DW_IC_SDA_HOLD_RX_MASK))
                        dev->sda_hold_time |= 1 << DW_IC_SDA_HOLD_RX_SHIFT;
                dw_writel(dev, dev->sda_hold_time, DW_IC_SDA_HOLD);
        } else {
                dev_warn(dev->dev,
                        "Hardware too old to adjust SDA hold time.\n");
        }

        /* Configure Tx/Rx FIFO threshold levels */
        dw_writel(dev, dev->tx_fifo_depth / 2, DW_IC_TX_TL);
        dw_writel(dev, 0, DW_IC_RX_TL);

        /* configure the i2c master */
        dw_writel(dev, dev->master_cfg , DW_IC_CON);

        i2c_dw_release_lock(dev);

        return 0;
}
EXPORT_SYMBOL_GPL(i2c_dw_init);

/*
 * Waiting for bus not busy
 */
static int i2c_dw_wait_bus_not_busy(struct dw_i2c_dev *dev)
{
        int timeout = TIMEOUT;

        while (dw_readl(dev, DW_IC_STATUS) & DW_IC_STATUS_ACTIVITY) {
                if (timeout <= 0) {
                        dev_warn(dev->dev, "timeout waiting for bus ready\n");
                        return -ETIMEDOUT;
                }
                timeout--;
                usleep_range(1000, 1100);
        }

        return 0;
}

static void i2c_dw_xfer_init(struct dw_i2c_dev *dev)
{
        struct i2c_msg *msgs = dev->msgs;
        u32 ic_con, ic_tar = 0;

        /* Disable the adapter */
        __i2c_dw_enable_and_wait(dev, false);

        /* if the slave address is ten bit address, enable 10BITADDR */
        ic_con = dw_readl(dev, DW_IC_CON);
        if (msgs[dev->msg_write_idx].flags & I2C_M_TEN) {
                ic_con |= DW_IC_CON_10BITADDR_MASTER;
                /*
                 * If I2C_DYNAMIC_TAR_UPDATE is set, the 10-bit addressing
                 * mode has to be enabled via bit 12 of IC_TAR register.
                 * We set it always as I2C_DYNAMIC_TAR_UPDATE can't be
                 * detected from registers.
                 */
                ic_tar = DW_IC_TAR_10BITADDR_MASTER;
        } else {
                ic_con &= ~DW_IC_CON_10BITADDR_MASTER;
        }

        dw_writel(dev, ic_con, DW_IC_CON);

        /*
         * Set the slave (target) address and enable 10-bit addressing mode
         * if applicable.
         */
        dw_writel(dev, msgs[dev->msg_write_idx].addr | ic_tar, DW_IC_TAR);

        /* enforce disabled interrupts (due to HW issues) */
        i2c_dw_disable_int(dev);

        /* Enable the adapter */
        __i2c_dw_enable(dev, true);

        /* Clear and enable interrupts */
        dw_readl(dev, DW_IC_CLR_INTR);
        dw_writel(dev, DW_IC_INTR_DEFAULT_MASK, DW_IC_INTR_MASK);
}

/*
 * Initiate (and continue) low level master read/write transaction.
 * This function is only called from i2c_dw_isr, and pumping i2c_msg
 * messages into the tx buffer.  Even if the size of i2c_msg data is
 * longer than the size of the tx buffer, it handles everything.
 */
static void
i2c_dw_xfer_msg(struct dw_i2c_dev *dev)
{
        struct i2c_msg *msgs = dev->msgs;
        u32 intr_mask;
        int tx_limit, rx_limit;
        u32 addr = msgs[dev->msg_write_idx].addr;
        u32 buf_len = dev->tx_buf_len;
        u8 *buf = dev->tx_buf;
        bool need_restart = false;

        intr_mask = DW_IC_INTR_DEFAULT_MASK;

        for (; dev->msg_write_idx < dev->msgs_num; dev->msg_write_idx++) {
                u32 flags = msgs[dev->msg_write_idx].flags;

                /*
                 * if target address has changed, we need to
                 * reprogram the target address in the i2c
                 * adapter when we are done with this transfer
                 */
                if (msgs[dev->msg_write_idx].addr != addr) {
                        dev_err(dev->dev,
                                "%s: invalid target address\n", __func__);
                        dev->msg_err = -EINVAL;
                        break;
                }

                if (msgs[dev->msg_write_idx].len == 0) {
                        dev_err(dev->dev,
                                "%s: invalid message length\n", __func__);
                        dev->msg_err = -EINVAL;
                        break;
                }

                if (!(dev->status & STATUS_WRITE_IN_PROGRESS)) {
                        /* new i2c_msg */
                        buf = msgs[dev->msg_write_idx].buf;
                        buf_len = msgs[dev->msg_write_idx].len;

                        /* If both IC_EMPTYFIFO_HOLD_MASTER_EN and
                         * IC_RESTART_EN are set, we must manually
                         * set restart bit between messages.
                         */
                        if ((dev->master_cfg & DW_IC_CON_RESTART_EN) &&
                                        (dev->msg_write_idx > 0))
                                need_restart = true;
                }

                tx_limit = dev->tx_fifo_depth - dw_readl(dev, DW_IC_TXFLR);
                rx_limit = dev->rx_fifo_depth - dw_readl(dev, DW_IC_RXFLR);

                while (buf_len > 0 && tx_limit > 0 && rx_limit > 0) {
                        u32 cmd = 0;

                        /*
                         * If IC_EMPTYFIFO_HOLD_MASTER_EN is set we must
                         * manually set the stop bit. However, it cannot be
                         * detected from the registers so we set it always
                         * when writing/reading the last byte.
                         */

                        /*
                         * i2c-core.c always sets the buffer length of
                         * I2C_FUNC_SMBUS_BLOCK_DATA to 1. The length will
                         * be adjusted when receiving the first byte.
                         * Thus we can't stop the transaction here.
                         */
                        if (dev->msg_write_idx == dev->msgs_num - 1 &&
                            buf_len == 1 && !(flags & I2C_M_RECV_LEN))
                                cmd |= BIT(9);

                        if (need_restart) {
                                cmd |= BIT(10);
                                need_restart = false;
                        }

                        if (msgs[dev->msg_write_idx].flags & I2C_M_RD) {

                                /* avoid rx buffer overrun */
                                if (dev->rx_outstanding >= dev->rx_fifo_depth)
                                        break;

                                dw_writel(dev, cmd | 0x100, DW_IC_DATA_CMD);
                                rx_limit--;
                                dev->rx_outstanding++;
                        } else
                                dw_writel(dev, cmd | *buf++, DW_IC_DATA_CMD);
                        tx_limit--; buf_len--;
                }

                dev->tx_buf = buf;
                dev->tx_buf_len = buf_len;

                /*
                 * Because we don't know the buffer length in the
                 * I2C_FUNC_SMBUS_BLOCK_DATA case, we can't stop
                 * the transaction here.
                 */
                if (buf_len > 0 || flags & I2C_M_RECV_LEN) {
                        /* more bytes to be written */
                        dev->status |= STATUS_WRITE_IN_PROGRESS;
                        break;
                } else
                        dev->status &= ~STATUS_WRITE_IN_PROGRESS;
        }

        /*
         * If i2c_msg index search is completed, we don't need TX_EMPTY
         * interrupt any more.
         */
        if (dev->msg_write_idx == dev->msgs_num)
                intr_mask &= ~DW_IC_INTR_TX_EMPTY;

        if (dev->msg_err)
                intr_mask = 0;

        dw_writel(dev, intr_mask,  DW_IC_INTR_MASK);
}

static u8
i2c_dw_recv_len(struct dw_i2c_dev *dev, u8 len)
{
        struct i2c_msg *msgs = dev->msgs;
        u32 flags = msgs[dev->msg_read_idx].flags;

        /*
         * Adjust the buffer length and mask the flag
         * after receiving the first byte.
         */
        len += (flags & I2C_CLIENT_PEC) ? 2 : 1;
        dev->tx_buf_len = len - min_t(u8, len, dev->rx_outstanding);
        msgs[dev->msg_read_idx].len = len;
        msgs[dev->msg_read_idx].flags &= ~I2C_M_RECV_LEN;

        return len;
}

static void
i2c_dw_read(struct dw_i2c_dev *dev)
{
        struct i2c_msg *msgs = dev->msgs;
        int rx_valid;

        for (; dev->msg_read_idx < dev->msgs_num; dev->msg_read_idx++) {
                u32 len;
                u8 *buf;

                if (!(msgs[dev->msg_read_idx].flags & I2C_M_RD))
                        continue;

                if (!(dev->status & STATUS_READ_IN_PROGRESS)) {
                        len = msgs[dev->msg_read_idx].len;
                        buf = msgs[dev->msg_read_idx].buf;
                } else {
                        len = dev->rx_buf_len;
                        buf = dev->rx_buf;
                }

                rx_valid = dw_readl(dev, DW_IC_RXFLR);

                for (; len > 0 && rx_valid > 0; len--, rx_valid--) {
                        u32 flags = msgs[dev->msg_read_idx].flags;

                        *buf = dw_readl(dev, DW_IC_DATA_CMD);
                        /* Ensure length byte is a valid value */
                        if (flags & I2C_M_RECV_LEN &&
                                *buf <= I2C_SMBUS_BLOCK_MAX && *buf > 0) {
                                len = i2c_dw_recv_len(dev, *buf);
                        }
                        buf++;
                        dev->rx_outstanding--;
                }

                if (len > 0) {
                        dev->status |= STATUS_READ_IN_PROGRESS;
                        dev->rx_buf_len = len;
                        dev->rx_buf = buf;
                        return;
                } else
                        dev->status &= ~STATUS_READ_IN_PROGRESS;
        }
}

static int i2c_dw_handle_tx_abort(struct dw_i2c_dev *dev)
{
        unsigned long abort_source = dev->abort_source;
        int i;

        if (abort_source & DW_IC_TX_ABRT_NOACK) {
                for_each_set_bit(i, &abort_source, ARRAY_SIZE(abort_sources))
                        dev_dbg(dev->dev,
                                "%s: %s\n", __func__, abort_sources[i]);
                return -EREMOTEIO;
        }

        for_each_set_bit(i, &abort_source, ARRAY_SIZE(abort_sources))
                dev_err(dev->dev, "%s: %s\n", __func__, abort_sources[i]);

        if (abort_source & DW_IC_TX_ARB_LOST)
                return -EAGAIN;
        else if (abort_source & DW_IC_TX_ABRT_GCALL_READ)
                return -EINVAL; /* wrong msgs[] data */
        else
                return -EIO;
}

/*
 * Prepare controller for a transaction and call i2c_dw_xfer_msg
 */
static int
i2c_dw_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num)
{
        struct dw_i2c_dev *dev = i2c_get_adapdata(adap);
        int ret;

        dev_dbg(dev->dev, "%s: msgs: %d\n", __func__, num);

        pm_runtime_get_sync(dev->dev);

        reinit_completion(&dev->cmd_complete);
        dev->msgs = msgs;
        dev->msgs_num = num;
        dev->cmd_err = 0;
        dev->msg_write_idx = 0;
        dev->msg_read_idx = 0;
        dev->msg_err = 0;
        dev->status = STATUS_IDLE;
        dev->abort_source = 0;
        dev->rx_outstanding = 0;

        ret = i2c_dw_acquire_lock(dev);
        if (ret)
                goto done_nolock;

        ret = i2c_dw_wait_bus_not_busy(dev);
        if (ret < 0)
                goto done;

        /* start the transfers */
        i2c_dw_xfer_init(dev);

        /* wait for tx to complete */
        if (!wait_for_completion_timeout(&dev->cmd_complete, adap->timeout)) {
                dev_err(dev->dev, "controller timed out\n");
                /* i2c_dw_init implicitly disables the adapter */
                i2c_dw_init(dev);
                ret = -ETIMEDOUT;
                goto done;
        }

        /*
         * We must disable the adapter before returning and signaling the end
         * of the current transfer. Otherwise the hardware might continue
         * generating interrupts which in turn causes a race condition with
         * the following transfer.  Needs some more investigation if the
         * additional interrupts are a hardware bug or this driver doesn't
         * handle them correctly yet.
         */
        __i2c_dw_enable(dev, false);

        if (dev->msg_err) {
                ret = dev->msg_err;
                goto done;
        }

        /* no error */
        if (likely(!dev->cmd_err && !dev->status)) {
                ret = num;
                goto done;
        }

        /* We have an error */
        if (dev->cmd_err == DW_IC_ERR_TX_ABRT) {
                ret = i2c_dw_handle_tx_abort(dev);
                goto done;
        }

        if (dev->status)
                dev_err(dev->dev,
                        "transfer terminated early - interrupt latency too high?\n");

        ret = -EIO;

done:
        i2c_dw_release_lock(dev);

done_nolock:
        pm_runtime_mark_last_busy(dev->dev);
        pm_runtime_put_autosuspend(dev->dev);

        return ret;
}

static u32 i2c_dw_func(struct i2c_adapter *adap)
{
        struct dw_i2c_dev *dev = i2c_get_adapdata(adap);
        return dev->functionality;
}

static const struct i2c_algorithm i2c_dw_algo = {
        .master_xfer    = i2c_dw_xfer,
        .functionality  = i2c_dw_func,
};

static u32 i2c_dw_read_clear_intrbits(struct dw_i2c_dev *dev)
{
        u32 stat;

        /*
         * The IC_INTR_STAT register just indicates "enabled" interrupts.
         * Ths unmasked raw version of interrupt status bits are available
         * in the IC_RAW_INTR_STAT register.
         *
         * That is,
         *   stat = dw_readl(IC_INTR_STAT);
         * equals to,
         *   stat = dw_readl(IC_RAW_INTR_STAT) & dw_readl(IC_INTR_MASK);
         *
         * The raw version might be useful for debugging purposes.
         */
        stat = dw_readl(dev, DW_IC_INTR_STAT);

        /*
         * Do not use the IC_CLR_INTR register to clear interrupts, or
         * you'll miss some interrupts, triggered during the period from
         * dw_readl(IC_INTR_STAT) to dw_readl(IC_CLR_INTR).
         *
         * Instead, use the separately-prepared IC_CLR_* registers.
         */
        if (stat & DW_IC_INTR_RX_UNDER)
                dw_readl(dev, DW_IC_CLR_RX_UNDER);
        if (stat & DW_IC_INTR_RX_OVER)
                dw_readl(dev, DW_IC_CLR_RX_OVER);
        if (stat & DW_IC_INTR_TX_OVER)
                dw_readl(dev, DW_IC_CLR_TX_OVER);
        if (stat & DW_IC_INTR_RD_REQ)
                dw_readl(dev, DW_IC_CLR_RD_REQ);
        if (stat & DW_IC_INTR_TX_ABRT) {
                /*
                 * The IC_TX_ABRT_SOURCE register is cleared whenever
                 * the IC_CLR_TX_ABRT is read.  Preserve it beforehand.
                 */
                dev->abort_source = dw_readl(dev, DW_IC_TX_ABRT_SOURCE);
                dw_readl(dev, DW_IC_CLR_TX_ABRT);
        }
        if (stat & DW_IC_INTR_RX_DONE)
                dw_readl(dev, DW_IC_CLR_RX_DONE);
        if (stat & DW_IC_INTR_ACTIVITY)
                dw_readl(dev, DW_IC_CLR_ACTIVITY);
        if (stat & DW_IC_INTR_STOP_DET)
                dw_readl(dev, DW_IC_CLR_STOP_DET);
        if (stat & DW_IC_INTR_START_DET)
                dw_readl(dev, DW_IC_CLR_START_DET);
        if (stat & DW_IC_INTR_GEN_CALL)
                dw_readl(dev, DW_IC_CLR_GEN_CALL);

        return stat;
}

/*
 * Interrupt service routine. This gets called whenever an I2C interrupt
 * occurs.
 */
static irqreturn_t i2c_dw_isr(int this_irq, void *dev_id)
{
        struct dw_i2c_dev *dev = dev_id;
        u32 stat, enabled;

        enabled = dw_readl(dev, DW_IC_ENABLE);
        stat = dw_readl(dev, DW_IC_RAW_INTR_STAT);
        dev_dbg(dev->dev, "%s: enabled=%#x stat=%#x\n", __func__, enabled, stat);
        if (!enabled || !(stat & ~DW_IC_INTR_ACTIVITY))
                return IRQ_NONE;

        stat = i2c_dw_read_clear_intrbits(dev);

        if (stat & DW_IC_INTR_TX_ABRT) {
                dev->cmd_err |= DW_IC_ERR_TX_ABRT;
                dev->status = STATUS_IDLE;

                /*
                 * Anytime TX_ABRT is set, the contents of the tx/rx
                 * buffers are flushed.  Make sure to skip them.
                 */
                dw_writel(dev, 0, DW_IC_INTR_MASK);
                goto tx_aborted;
        }

        if (stat & DW_IC_INTR_RX_FULL)
                i2c_dw_read(dev);

        if (stat & DW_IC_INTR_TX_EMPTY)
                i2c_dw_xfer_msg(dev);

        /*
         * No need to modify or disable the interrupt mask here.
         * i2c_dw_xfer_msg() will take care of it according to
         * the current transmit status.
         */

tx_aborted:
        if ((stat & (DW_IC_INTR_TX_ABRT | DW_IC_INTR_STOP_DET)) || dev->msg_err)
                complete(&dev->cmd_complete);
        else if (unlikely(dev->flags & ACCESS_INTR_MASK)) {
                /* workaround to trigger pending interrupt */
                stat = dw_readl(dev, DW_IC_INTR_MASK);
                i2c_dw_disable_int(dev);
                dw_writel(dev, stat, DW_IC_INTR_MASK);
        }

        return IRQ_HANDLED;
}

void i2c_dw_disable(struct dw_i2c_dev *dev)
{
        /* Disable controller */
        __i2c_dw_enable_and_wait(dev, false);

        /* Disable all interupts */
        dw_writel(dev, 0, DW_IC_INTR_MASK);
        dw_readl(dev, DW_IC_CLR_INTR);
}
EXPORT_SYMBOL_GPL(i2c_dw_disable);

void i2c_dw_disable_int(struct dw_i2c_dev *dev)
{
        dw_writel(dev, 0, DW_IC_INTR_MASK);
}
EXPORT_SYMBOL_GPL(i2c_dw_disable_int);

u32 i2c_dw_read_comp_param(struct dw_i2c_dev *dev)
{
        return dw_readl(dev, DW_IC_COMP_PARAM_1);
}
EXPORT_SYMBOL_GPL(i2c_dw_read_comp_param);

int i2c_dw_probe(struct dw_i2c_dev *dev)
{
        struct i2c_adapter *adap = &dev->adapter;
        unsigned long irq_flags;
        int r;

        init_completion(&dev->cmd_complete);

        r = i2c_dw_init(dev);
        if (r)
                return r;

        snprintf(adap->name, sizeof(adap->name),
                 "Synopsys DesignWare I2C adapter");
        adap->retries = 3;
        adap->algo = &i2c_dw_algo;
        adap->dev.parent = dev->dev;
        i2c_set_adapdata(adap, dev);

        if (dev->pm_disabled) {
                dev_pm_syscore_device(dev->dev, true);
                irq_flags = IRQF_NO_SUSPEND;
        } else {
                irq_flags = IRQF_SHARED | IRQF_COND_SUSPEND;
        }

        i2c_dw_disable_int(dev);
        r = devm_request_irq(dev->dev, dev->irq, i2c_dw_isr, irq_flags,
                             dev_name(dev->dev), dev);
        if (r) {
                dev_err(dev->dev, "failure requesting irq %i: %d\n",
                        dev->irq, r);
                return r;
        }

        /*
         * Increment PM usage count during adapter registration in order to
         * avoid possible spurious runtime suspend when adapter device is
         * registered to the device core and immediate resume in case bus has
         * registered I2C slaves that do I2C transfers in their probe.
         */
        pm_runtime_get_noresume(dev->dev);
        r = i2c_add_numbered_adapter(adap);
        if (r)
                dev_err(dev->dev, "failure adding adapter: %d\n", r);
        pm_runtime_put_noidle(dev->dev);

        return r;
}
EXPORT_SYMBOL_GPL(i2c_dw_probe);

MODULE_DESCRIPTION("Synopsys DesignWare I2C bus adapter core");
MODULE_LICENSE("GPL");