/*
 * drivers/i2c/busses/i2c-tegra.c
 *
 * Copyright (C) 2010 Google, Inc.
 * Author: Colin Cross <ccross@android.com>
 *
 * This software is licensed under the terms of the GNU General Public
 * License version 2, as published by the Free Software Foundation, and
 * may be copied, distributed, and modified under those terms.
 *
 * 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/kernel.h>
#include <linux/init.h>
#include <linux/platform_device.h>
#include <linux/clk.h>
#include <linux/err.h>
#include <linux/i2c.h>
#include <linux/io.h>
#include <linux/interrupt.h>
#include <linux/delay.h>
#include <linux/slab.h>
#include <linux/of_i2c.h>
#include <linux/of_device.h>
#include <linux/module.h>
#include <linux/clk/tegra.h>

#include <asm/unaligned.h>

#define TEGRA_I2C_TIMEOUT (msecs_to_jiffies(1000))
#define BYTES_PER_FIFO_WORD 4

#define I2C_CNFG                                0x000
#define I2C_CNFG_DEBOUNCE_CNT_SHIFT             12
#define I2C_CNFG_PACKET_MODE_EN                 (1<<10)
#define I2C_CNFG_NEW_MASTER_FSM                 (1<<11)
#define I2C_STATUS                              0x01C
#define I2C_SL_CNFG                             0x020
#define I2C_SL_CNFG_NACK                        (1<<1)
#define I2C_SL_CNFG_NEWSL                       (1<<2)
#define I2C_SL_ADDR1                            0x02c
#define I2C_SL_ADDR2                            0x030
#define I2C_TX_FIFO                             0x050
#define I2C_RX_FIFO                             0x054
#define I2C_PACKET_TRANSFER_STATUS              0x058
#define I2C_FIFO_CONTROL                        0x05c
#define I2C_FIFO_CONTROL_TX_FLUSH               (1<<1)
#define I2C_FIFO_CONTROL_RX_FLUSH               (1<<0)
#define I2C_FIFO_CONTROL_TX_TRIG_SHIFT          5
#define I2C_FIFO_CONTROL_RX_TRIG_SHIFT          2
#define I2C_FIFO_STATUS                         0x060
#define I2C_FIFO_STATUS_TX_MASK                 0xF0
#define I2C_FIFO_STATUS_TX_SHIFT                4
#define I2C_FIFO_STATUS_RX_MASK                 0x0F
#define I2C_FIFO_STATUS_RX_SHIFT                0
#define I2C_INT_MASK                            0x064
#define I2C_INT_STATUS                          0x068
#define I2C_INT_PACKET_XFER_COMPLETE            (1<<7)
#define I2C_INT_ALL_PACKETS_XFER_COMPLETE       (1<<6)
#define I2C_INT_TX_FIFO_OVERFLOW                (1<<5)
#define I2C_INT_RX_FIFO_UNDERFLOW               (1<<4)
#define I2C_INT_NO_ACK                          (1<<3)
#define I2C_INT_ARBITRATION_LOST                (1<<2)
#define I2C_INT_TX_FIFO_DATA_REQ                (1<<1)
#define I2C_INT_RX_FIFO_DATA_REQ                (1<<0)
#define I2C_CLK_DIVISOR                         0x06c
#define I2C_CLK_DIVISOR_STD_FAST_MODE_SHIFT     16
#define I2C_CLK_MULTIPLIER_STD_FAST_MODE        8

#define DVC_CTRL_REG1                           0x000
#define DVC_CTRL_REG1_INTR_EN                   (1<<10)
#define DVC_CTRL_REG2                           0x004
#define DVC_CTRL_REG3                           0x008
#define DVC_CTRL_REG3_SW_PROG                   (1<<26)
#define DVC_CTRL_REG3_I2C_DONE_INTR_EN          (1<<30)
#define DVC_STATUS                              0x00c
#define DVC_STATUS_I2C_DONE_INTR                (1<<30)

#define I2C_ERR_NONE                            0x00
#define I2C_ERR_NO_ACK                          0x01
#define I2C_ERR_ARBITRATION_LOST                0x02
#define I2C_ERR_UNKNOWN_INTERRUPT               0x04

#define PACKET_HEADER0_HEADER_SIZE_SHIFT        28
#define PACKET_HEADER0_PACKET_ID_SHIFT          16
#define PACKET_HEADER0_CONT_ID_SHIFT            12
#define PACKET_HEADER0_PROTOCOL_I2C             (1<<4)

#define I2C_HEADER_HIGHSPEED_MODE               (1<<22)
#define I2C_HEADER_CONT_ON_NAK                  (1<<21)
#define I2C_HEADER_SEND_START_BYTE              (1<<20)
#define I2C_HEADER_READ                         (1<<19)
#define I2C_HEADER_10BIT_ADDR                   (1<<18)
#define I2C_HEADER_IE_ENABLE                    (1<<17)
#define I2C_HEADER_REPEAT_START                 (1<<16)
#define I2C_HEADER_CONTINUE_XFER                (1<<15)
#define I2C_HEADER_MASTER_ADDR_SHIFT            12
#define I2C_HEADER_SLAVE_ADDR_SHIFT             1
/*
 * msg_end_type: The bus control which need to be send at end of transfer.
 * @MSG_END_STOP: Send stop pulse at end of transfer.
 * @MSG_END_REPEAT_START: Send repeat start at end of transfer.
 * @MSG_END_CONTINUE: The following on message is coming and so do not send
 *              stop or repeat start.
 */
enum msg_end_type {
        MSG_END_STOP,
        MSG_END_REPEAT_START,
        MSG_END_CONTINUE,
};

/**
 * struct tegra_i2c_hw_feature : Different HW support on Tegra
 * @has_continue_xfer_support: Continue transfer supports.
 * @has_per_pkt_xfer_complete_irq: Has enable/disable capability for transfer
 *              complete interrupt per packet basis.
 * @has_single_clk_source: The i2c controller has single clock source. Tegra30
 *              and earlier Socs has two clock sources i.e. div-clk and
 *              fast-clk.
 * @clk_divisor_hs_mode: Clock divisor in HS mode.
 * @clk_divisor_std_fast_mode: Clock divisor in standard/fast mode. It is
 *              applicable if there is no fast clock source i.e. single clock
 *              source.
 */

struct tegra_i2c_hw_feature {
        bool has_continue_xfer_support;
        bool has_per_pkt_xfer_complete_irq;
        bool has_single_clk_source;
        int clk_divisor_hs_mode;
        int clk_divisor_std_fast_mode;
};

/**
 * struct tegra_i2c_dev - per device i2c context
 * @dev: device reference for power management
 * @hw: Tegra i2c hw feature.
 * @adapter: core i2c layer adapter information
 * @div_clk: clock reference for div clock of i2c controller.
 * @fast_clk: clock reference for fast clock of i2c controller.
 * @base: ioremapped registers cookie
 * @cont_id: i2c controller id, used for for packet header
 * @irq: irq number of transfer complete interrupt
 * @is_dvc: identifies the DVC i2c controller, has a different register layout
 * @msg_complete: transfer completion notifier
 * @msg_err: error code for completed message
 * @msg_buf: pointer to current message data
 * @msg_buf_remaining: size of unsent data in the message buffer
 * @msg_read: identifies read transfers
 * @bus_clk_rate: current i2c bus clock rate
 * @is_suspended: prevents i2c controller accesses after suspend is called
 */
struct tegra_i2c_dev {
        struct device *dev;
        const struct tegra_i2c_hw_feature *hw;
        struct i2c_adapter adapter;
        struct clk *div_clk;
        struct clk *fast_clk;
        void __iomem *base;
        int cont_id;
        int irq;
        bool irq_disabled;
        int is_dvc;
        struct completion msg_complete;
        int msg_err;
        u8 *msg_buf;
        size_t msg_buf_remaining;
        int msg_read;
        u32 bus_clk_rate;
        bool is_suspended;
};

static void dvc_writel(struct tegra_i2c_dev *i2c_dev, u32 val, unsigned long reg)
{
        writel(val, i2c_dev->base + reg);
}

static u32 dvc_readl(struct tegra_i2c_dev *i2c_dev, unsigned long reg)
{
        return readl(i2c_dev->base + reg);
}

/*
 * i2c_writel and i2c_readl will offset the register if necessary to talk
 * to the I2C block inside the DVC block
 */
static unsigned long tegra_i2c_reg_addr(struct tegra_i2c_dev *i2c_dev,
        unsigned long reg)
{
        if (i2c_dev->is_dvc)
                reg += (reg >= I2C_TX_FIFO) ? 0x10 : 0x40;
        return reg;
}

static void i2c_writel(struct tegra_i2c_dev *i2c_dev, u32 val,
        unsigned long reg)
{
        writel(val, i2c_dev->base + tegra_i2c_reg_addr(i2c_dev, reg));

        /* Read back register to make sure that register writes completed */
        if (reg != I2C_TX_FIFO)
                readl(i2c_dev->base + tegra_i2c_reg_addr(i2c_dev, reg));
}

static u32 i2c_readl(struct tegra_i2c_dev *i2c_dev, unsigned long reg)
{
        return readl(i2c_dev->base + tegra_i2c_reg_addr(i2c_dev, reg));
}

static void i2c_writesl(struct tegra_i2c_dev *i2c_dev, void *data,
        unsigned long reg, int len)
{
        writesl(i2c_dev->base + tegra_i2c_reg_addr(i2c_dev, reg), data, len);
}

static void i2c_readsl(struct tegra_i2c_dev *i2c_dev, void *data,
        unsigned long reg, int len)
{
        readsl(i2c_dev->base + tegra_i2c_reg_addr(i2c_dev, reg), data, len);
}

static void tegra_i2c_mask_irq(struct tegra_i2c_dev *i2c_dev, u32 mask)
{
        u32 int_mask = i2c_readl(i2c_dev, I2C_INT_MASK);
        int_mask &= ~mask;
        i2c_writel(i2c_dev, int_mask, I2C_INT_MASK);
}

static void tegra_i2c_unmask_irq(struct tegra_i2c_dev *i2c_dev, u32 mask)
{
        u32 int_mask = i2c_readl(i2c_dev, I2C_INT_MASK);
        int_mask |= mask;
        i2c_writel(i2c_dev, int_mask, I2C_INT_MASK);
}

static int tegra_i2c_flush_fifos(struct tegra_i2c_dev *i2c_dev)
{
        unsigned long timeout = jiffies + HZ;
        u32 val = i2c_readl(i2c_dev, I2C_FIFO_CONTROL);
        val |= I2C_FIFO_CONTROL_TX_FLUSH | I2C_FIFO_CONTROL_RX_FLUSH;
        i2c_writel(i2c_dev, val, I2C_FIFO_CONTROL);

        while (i2c_readl(i2c_dev, I2C_FIFO_CONTROL) &
                (I2C_FIFO_CONTROL_TX_FLUSH | I2C_FIFO_CONTROL_RX_FLUSH)) {
                if (time_after(jiffies, timeout)) {
                        dev_warn(i2c_dev->dev, "timeout waiting for fifo flush\n");
                        return -ETIMEDOUT;
                }
                msleep(1);
        }
        return 0;
}

static int tegra_i2c_empty_rx_fifo(struct tegra_i2c_dev *i2c_dev)
{
        u32 val;
        int rx_fifo_avail;
        u8 *buf = i2c_dev->msg_buf;
        size_t buf_remaining = i2c_dev->msg_buf_remaining;
        int words_to_transfer;

        val = i2c_readl(i2c_dev, I2C_FIFO_STATUS);
        rx_fifo_avail = (val & I2C_FIFO_STATUS_RX_MASK) >>
                I2C_FIFO_STATUS_RX_SHIFT;

        /* Rounds down to not include partial word at the end of buf */
        words_to_transfer = buf_remaining / BYTES_PER_FIFO_WORD;
        if (words_to_transfer > rx_fifo_avail)
                words_to_transfer = rx_fifo_avail;

        i2c_readsl(i2c_dev, buf, I2C_RX_FIFO, words_to_transfer);

        buf += words_to_transfer * BYTES_PER_FIFO_WORD;
        buf_remaining -= words_to_transfer * BYTES_PER_FIFO_WORD;
        rx_fifo_avail -= words_to_transfer;

        /*
         * If there is a partial word at the end of buf, handle it manually to
         * prevent overwriting past the end of buf
         */
        if (rx_fifo_avail > 0 && buf_remaining > 0) {
                BUG_ON(buf_remaining > 3);
                val = i2c_readl(i2c_dev, I2C_RX_FIFO);
                memcpy(buf, &val, buf_remaining);
                buf_remaining = 0;
                rx_fifo_avail--;
        }

        BUG_ON(rx_fifo_avail > 0 && buf_remaining > 0);
        i2c_dev->msg_buf_remaining = buf_remaining;
        i2c_dev->msg_buf = buf;
        return 0;
}

static int tegra_i2c_fill_tx_fifo(struct tegra_i2c_dev *i2c_dev)
{
        u32 val;
        int tx_fifo_avail;
        u8 *buf = i2c_dev->msg_buf;
        size_t buf_remaining = i2c_dev->msg_buf_remaining;
        int words_to_transfer;

        val = i2c_readl(i2c_dev, I2C_FIFO_STATUS);
        tx_fifo_avail = (val & I2C_FIFO_STATUS_TX_MASK) >>
                I2C_FIFO_STATUS_TX_SHIFT;

        /* Rounds down to not include partial word at the end of buf */
        words_to_transfer = buf_remaining / BYTES_PER_FIFO_WORD;

        /* It's very common to have < 4 bytes, so optimize that case. */
        if (words_to_transfer) {
                if (words_to_transfer > tx_fifo_avail)
                        words_to_transfer = tx_fifo_avail;

                /*
                 * Update state before writing to FIFO.  If this casues us
                 * to finish writing all bytes (AKA buf_remaining goes to 0) we
                 * have a potential for an interrupt (PACKET_XFER_COMPLETE is
                 * not maskable).  We need to make sure that the isr sees
                 * buf_remaining as 0 and doesn't call us back re-entrantly.
                 */
                buf_remaining -= words_to_transfer * BYTES_PER_FIFO_WORD;
                tx_fifo_avail -= words_to_transfer;
                i2c_dev->msg_buf_remaining = buf_remaining;
                i2c_dev->msg_buf = buf +
                        words_to_transfer * BYTES_PER_FIFO_WORD;
                barrier();

                i2c_writesl(i2c_dev, buf, I2C_TX_FIFO, words_to_transfer);

                buf += words_to_transfer * BYTES_PER_FIFO_WORD;
        }

        /*
         * If there is a partial word at the end of buf, handle it manually to
         * prevent reading past the end of buf, which could cross a page
         * boundary and fault.
         */
        if (tx_fifo_avail > 0 && buf_remaining > 0) {
                BUG_ON(buf_remaining > 3);
                memcpy(&val, buf, buf_remaining);

                /* Again update before writing to FIFO to make sure isr sees. */
                i2c_dev->msg_buf_remaining = 0;
                i2c_dev->msg_buf = NULL;
                barrier();

                i2c_writel(i2c_dev, val, I2C_TX_FIFO);
        }

        return 0;
}

/*
 * One of the Tegra I2C blocks is inside the DVC (Digital Voltage Controller)
 * block.  This block is identical to the rest of the I2C blocks, except that
 * it only supports master mode, it has registers moved around, and it needs
 * some extra init to get it into I2C mode.  The register moves are handled
 * by i2c_readl and i2c_writel
 */
static void tegra_dvc_init(struct tegra_i2c_dev *i2c_dev)
{
        u32 val = 0;
        val = dvc_readl(i2c_dev, DVC_CTRL_REG3);
        val |= DVC_CTRL_REG3_SW_PROG;
        val |= DVC_CTRL_REG3_I2C_DONE_INTR_EN;
        dvc_writel(i2c_dev, val, DVC_CTRL_REG3);

        val = dvc_readl(i2c_dev, DVC_CTRL_REG1);
        val |= DVC_CTRL_REG1_INTR_EN;
        dvc_writel(i2c_dev, val, DVC_CTRL_REG1);
}

static inline int tegra_i2c_clock_enable(struct tegra_i2c_dev *i2c_dev)
{
        int ret;
        if (!i2c_dev->hw->has_single_clk_source) {
                ret = clk_prepare_enable(i2c_dev->fast_clk);
                if (ret < 0) {
                        dev_err(i2c_dev->dev,
                                "Enabling fast clk failed, err %d\n", ret);
                        return ret;
                }
        }
        ret = clk_prepare_enable(i2c_dev->div_clk);
        if (ret < 0) {
                dev_err(i2c_dev->dev,
                        "Enabling div clk failed, err %d\n", ret);
                clk_disable_unprepare(i2c_dev->fast_clk);
        }
        return ret;
}

static inline void tegra_i2c_clock_disable(struct tegra_i2c_dev *i2c_dev)
{
        clk_disable_unprepare(i2c_dev->div_clk);
        if (!i2c_dev->hw->has_single_clk_source)
                clk_disable_unprepare(i2c_dev->fast_clk);
}

static int tegra_i2c_init(struct tegra_i2c_dev *i2c_dev)
{
        u32 val;
        int err = 0;
        int clk_multiplier = I2C_CLK_MULTIPLIER_STD_FAST_MODE;
        u32 clk_divisor;

        err = tegra_i2c_clock_enable(i2c_dev);
        if (err < 0) {
                dev_err(i2c_dev->dev, "Clock enable failed %d\n", err);
                return err;
        }

        tegra_periph_reset_assert(i2c_dev->div_clk);
        udelay(2);
        tegra_periph_reset_deassert(i2c_dev->div_clk);

        if (i2c_dev->is_dvc)
                tegra_dvc_init(i2c_dev);

        val = I2C_CNFG_NEW_MASTER_FSM | I2C_CNFG_PACKET_MODE_EN |
                (0x2 << I2C_CNFG_DEBOUNCE_CNT_SHIFT);
        i2c_writel(i2c_dev, val, I2C_CNFG);
        i2c_writel(i2c_dev, 0, I2C_INT_MASK);

        clk_multiplier *= (i2c_dev->hw->clk_divisor_std_fast_mode + 1);
        clk_set_rate(i2c_dev->div_clk, i2c_dev->bus_clk_rate * clk_multiplier);

        /* Make sure clock divisor programmed correctly */
        clk_divisor = i2c_dev->hw->clk_divisor_hs_mode;
        clk_divisor |= i2c_dev->hw->clk_divisor_std_fast_mode <<
                                        I2C_CLK_DIVISOR_STD_FAST_MODE_SHIFT;
        i2c_writel(i2c_dev, clk_divisor, I2C_CLK_DIVISOR);

        if (!i2c_dev->is_dvc) {
                u32 sl_cfg = i2c_readl(i2c_dev, I2C_SL_CNFG);
                sl_cfg |= I2C_SL_CNFG_NACK | I2C_SL_CNFG_NEWSL;
                i2c_writel(i2c_dev, sl_cfg, I2C_SL_CNFG);
                i2c_writel(i2c_dev, 0xfc, I2C_SL_ADDR1);
                i2c_writel(i2c_dev, 0x00, I2C_SL_ADDR2);

        }

        val = 7 << I2C_FIFO_CONTROL_TX_TRIG_SHIFT |
                0 << I2C_FIFO_CONTROL_RX_TRIG_SHIFT;
        i2c_writel(i2c_dev, val, I2C_FIFO_CONTROL);

        if (tegra_i2c_flush_fifos(i2c_dev))
                err = -ETIMEDOUT;

        tegra_i2c_clock_disable(i2c_dev);

        if (i2c_dev->irq_disabled) {
                i2c_dev->irq_disabled = 0;
                enable_irq(i2c_dev->irq);
        }

        return err;
}

static irqreturn_t tegra_i2c_isr(int irq, void *dev_id)
{
        u32 status;
        const u32 status_err = I2C_INT_NO_ACK | I2C_INT_ARBITRATION_LOST;
        struct tegra_i2c_dev *i2c_dev = dev_id;

        status = i2c_readl(i2c_dev, I2C_INT_STATUS);

        if (status == 0) {
                dev_warn(i2c_dev->dev, "irq status 0 %08x %08x %08x\n",
                         i2c_readl(i2c_dev, I2C_PACKET_TRANSFER_STATUS),
                         i2c_readl(i2c_dev, I2C_STATUS),
                         i2c_readl(i2c_dev, I2C_CNFG));
                i2c_dev->msg_err |= I2C_ERR_UNKNOWN_INTERRUPT;

                if (!i2c_dev->irq_disabled) {
                        disable_irq_nosync(i2c_dev->irq);
                        i2c_dev->irq_disabled = 1;
                }
                goto err;
        }

        if (unlikely(status & status_err)) {
                if (status & I2C_INT_NO_ACK)
                        i2c_dev->msg_err |= I2C_ERR_NO_ACK;
                if (status & I2C_INT_ARBITRATION_LOST)
                        i2c_dev->msg_err |= I2C_ERR_ARBITRATION_LOST;
                goto err;
        }

        if (i2c_dev->msg_read && (status & I2C_INT_RX_FIFO_DATA_REQ)) {
                if (i2c_dev->msg_buf_remaining)
                        tegra_i2c_empty_rx_fifo(i2c_dev);
                else
                        BUG();
        }

        if (!i2c_dev->msg_read && (status & I2C_INT_TX_FIFO_DATA_REQ)) {
                if (i2c_dev->msg_buf_remaining)
                        tegra_i2c_fill_tx_fifo(i2c_dev);
                else
                        tegra_i2c_mask_irq(i2c_dev, I2C_INT_TX_FIFO_DATA_REQ);
        }

        i2c_writel(i2c_dev, status, I2C_INT_STATUS);
        if (i2c_dev->is_dvc)
                dvc_writel(i2c_dev, DVC_STATUS_I2C_DONE_INTR, DVC_STATUS);

        if (status & I2C_INT_PACKET_XFER_COMPLETE) {
                BUG_ON(i2c_dev->msg_buf_remaining);
                complete(&i2c_dev->msg_complete);
        }
        return IRQ_HANDLED;
err:
        /* An error occurred, mask all interrupts */
        tegra_i2c_mask_irq(i2c_dev, I2C_INT_NO_ACK | I2C_INT_ARBITRATION_LOST |
                I2C_INT_PACKET_XFER_COMPLETE | I2C_INT_TX_FIFO_DATA_REQ |
                I2C_INT_RX_FIFO_DATA_REQ);
        i2c_writel(i2c_dev, status, I2C_INT_STATUS);
        if (i2c_dev->is_dvc)
                dvc_writel(i2c_dev, DVC_STATUS_I2C_DONE_INTR, DVC_STATUS);

        complete(&i2c_dev->msg_complete);
        return IRQ_HANDLED;
}

static int tegra_i2c_xfer_msg(struct tegra_i2c_dev *i2c_dev,
        struct i2c_msg *msg, enum msg_end_type end_state)
{
        u32 packet_header;
        u32 int_mask;
        int ret;

        tegra_i2c_flush_fifos(i2c_dev);

        if (msg->len == 0)
                return -EINVAL;

        i2c_dev->msg_buf = msg->buf;
        i2c_dev->msg_buf_remaining = msg->len;
        i2c_dev->msg_err = I2C_ERR_NONE;
        i2c_dev->msg_read = (msg->flags & I2C_M_RD);
        INIT_COMPLETION(i2c_dev->msg_complete);

        packet_header = (0 << PACKET_HEADER0_HEADER_SIZE_SHIFT) |
                        PACKET_HEADER0_PROTOCOL_I2C |
                        (i2c_dev->cont_id << PACKET_HEADER0_CONT_ID_SHIFT) |
                        (1 << PACKET_HEADER0_PACKET_ID_SHIFT);
        i2c_writel(i2c_dev, packet_header, I2C_TX_FIFO);

        packet_header = msg->len - 1;
        i2c_writel(i2c_dev, packet_header, I2C_TX_FIFO);

        packet_header = I2C_HEADER_IE_ENABLE;
        if (end_state == MSG_END_CONTINUE)
                packet_header |= I2C_HEADER_CONTINUE_XFER;
        else if (end_state == MSG_END_REPEAT_START)
                packet_header |= I2C_HEADER_REPEAT_START;
        if (msg->flags & I2C_M_TEN) {
                packet_header |= msg->addr;
                packet_header |= I2C_HEADER_10BIT_ADDR;
        } else {
                packet_header |= msg->addr << I2C_HEADER_SLAVE_ADDR_SHIFT;
        }
        if (msg->flags & I2C_M_IGNORE_NAK)
                packet_header |= I2C_HEADER_CONT_ON_NAK;
        if (msg->flags & I2C_M_RD)
                packet_header |= I2C_HEADER_READ;
        i2c_writel(i2c_dev, packet_header, I2C_TX_FIFO);

        if (!(msg->flags & I2C_M_RD))
                tegra_i2c_fill_tx_fifo(i2c_dev);

        int_mask = I2C_INT_NO_ACK | I2C_INT_ARBITRATION_LOST;
        if (i2c_dev->hw->has_per_pkt_xfer_complete_irq)
                int_mask |= I2C_INT_PACKET_XFER_COMPLETE;
        if (msg->flags & I2C_M_RD)
                int_mask |= I2C_INT_RX_FIFO_DATA_REQ;
        else if (i2c_dev->msg_buf_remaining)
                int_mask |= I2C_INT_TX_FIFO_DATA_REQ;
        tegra_i2c_unmask_irq(i2c_dev, int_mask);
        dev_dbg(i2c_dev->dev, "unmasked irq: %02x\n",
                i2c_readl(i2c_dev, I2C_INT_MASK));

        ret = wait_for_completion_timeout(&i2c_dev->msg_complete, TEGRA_I2C_TIMEOUT);
        tegra_i2c_mask_irq(i2c_dev, int_mask);

        if (ret == 0) {
                dev_err(i2c_dev->dev, "i2c transfer timed out\n");

                tegra_i2c_init(i2c_dev);
                return -ETIMEDOUT;
        }

        dev_dbg(i2c_dev->dev, "transfer complete: %d %d %d\n",
                ret, completion_done(&i2c_dev->msg_complete), i2c_dev->msg_err);

        if (likely(i2c_dev->msg_err == I2C_ERR_NONE))
                return 0;

        /*
         * NACK interrupt is generated before the I2C controller generates the
         * STOP condition on the bus. So wait for 2 clock periods before resetting
         * the controller so that STOP condition has been delivered properly.
         */
        if (i2c_dev->msg_err == I2C_ERR_NO_ACK)
                udelay(DIV_ROUND_UP(2 * 1000000, i2c_dev->bus_clk_rate));

        tegra_i2c_init(i2c_dev);
        if (i2c_dev->msg_err == I2C_ERR_NO_ACK) {
                if (msg->flags & I2C_M_IGNORE_NAK)
                        return 0;
                return -EREMOTEIO;
        }

        return -EIO;
}

static int tegra_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[],
        int num)
{
        struct tegra_i2c_dev *i2c_dev = i2c_get_adapdata(adap);
        int i;
        int ret = 0;

        if (i2c_dev->is_suspended)
                return -EBUSY;

        ret = tegra_i2c_clock_enable(i2c_dev);
        if (ret < 0) {
                dev_err(i2c_dev->dev, "Clock enable failed %d\n", ret);
                return ret;
        }

        for (i = 0; i < num; i++) {
                enum msg_end_type end_type = MSG_END_STOP;
                if (i < (num - 1)) {
                        if (msgs[i + 1].flags & I2C_M_NOSTART)
                                end_type = MSG_END_CONTINUE;
                        else
                                end_type = MSG_END_REPEAT_START;
                }
                ret = tegra_i2c_xfer_msg(i2c_dev, &msgs[i], end_type);
                if (ret)
                        break;
        }
        tegra_i2c_clock_disable(i2c_dev);
        return ret ?: i;
}

static u32 tegra_i2c_func(struct i2c_adapter *adap)
{
        struct tegra_i2c_dev *i2c_dev = i2c_get_adapdata(adap);
        u32 ret = I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL | I2C_FUNC_10BIT_ADDR |
                                I2C_FUNC_PROTOCOL_MANGLING;

        if (i2c_dev->hw->has_continue_xfer_support)
                ret |= I2C_FUNC_NOSTART;
        return ret;
}

static const struct i2c_algorithm tegra_i2c_algo = {
        .master_xfer    = tegra_i2c_xfer,
        .functionality  = tegra_i2c_func,
};

static const struct tegra_i2c_hw_feature tegra20_i2c_hw = {
        .has_continue_xfer_support = false,
        .has_per_pkt_xfer_complete_irq = false,
        .has_single_clk_source = false,
        .clk_divisor_hs_mode = 3,
        .clk_divisor_std_fast_mode = 0,
};

static const struct tegra_i2c_hw_feature tegra30_i2c_hw = {
        .has_continue_xfer_support = true,
        .has_per_pkt_xfer_complete_irq = false,
        .has_single_clk_source = false,
        .clk_divisor_hs_mode = 3,
        .clk_divisor_std_fast_mode = 0,
};

static const struct tegra_i2c_hw_feature tegra114_i2c_hw = {
        .has_continue_xfer_support = true,
        .has_per_pkt_xfer_complete_irq = true,
        .has_single_clk_source = true,
        .clk_divisor_hs_mode = 1,
        .clk_divisor_std_fast_mode = 0x19,
};

/* Match table for of_platform binding */
static const struct of_device_id tegra_i2c_of_match[] = {
        { .compatible = "nvidia,tegra114-i2c", .data = &tegra114_i2c_hw, },
        { .compatible = "nvidia,tegra30-i2c", .data = &tegra30_i2c_hw, },
        { .compatible = "nvidia,tegra20-i2c", .data = &tegra20_i2c_hw, },
        { .compatible = "nvidia,tegra20-i2c-dvc", .data = &tegra20_i2c_hw, },
        {},
};
MODULE_DEVICE_TABLE(of, tegra_i2c_of_match);

static int tegra_i2c_probe(struct platform_device *pdev)
{
        struct tegra_i2c_dev *i2c_dev;
        struct resource *res;
        struct clk *div_clk;
        struct clk *fast_clk;
        void __iomem *base;
        int irq;
        int ret = 0;

        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        base = devm_ioremap_resource(&pdev->dev, res);
        if (IS_ERR(base))
                return PTR_ERR(base);

        res = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
        if (!res) {
                dev_err(&pdev->dev, "no irq resource\n");
                return -EINVAL;
        }
        irq = res->start;

        div_clk = devm_clk_get(&pdev->dev, "div-clk");
        if (IS_ERR(div_clk)) {
                dev_err(&pdev->dev, "missing controller clock");
                return PTR_ERR(div_clk);
        }

        i2c_dev = devm_kzalloc(&pdev->dev, sizeof(*i2c_dev), GFP_KERNEL);
        if (!i2c_dev) {
                dev_err(&pdev->dev, "Could not allocate struct tegra_i2c_dev");
                return -ENOMEM;
        }

        i2c_dev->base = base;
        i2c_dev->div_clk = div_clk;
        i2c_dev->adapter.algo = &tegra_i2c_algo;
        i2c_dev->irq = irq;
        i2c_dev->cont_id = pdev->id;
        i2c_dev->dev = &pdev->dev;

        ret = of_property_read_u32(i2c_dev->dev->of_node, "clock-frequency",
                                        &i2c_dev->bus_clk_rate);
        if (ret)
                i2c_dev->bus_clk_rate = 100000; /* default clock rate */

        i2c_dev->hw = &tegra20_i2c_hw;

        if (pdev->dev.of_node) {
                const struct of_device_id *match;
                match = of_match_device(tegra_i2c_of_match, &pdev->dev);
                i2c_dev->hw = match->data;
                i2c_dev->is_dvc = of_device_is_compatible(pdev->dev.of_node,
                                                "nvidia,tegra20-i2c-dvc");
        } else if (pdev->id == 3) {
                i2c_dev->is_dvc = 1;
        }
        init_completion(&i2c_dev->msg_complete);

        if (!i2c_dev->hw->has_single_clk_source) {
                fast_clk = devm_clk_get(&pdev->dev, "fast-clk");
                if (IS_ERR(fast_clk)) {
                        dev_err(&pdev->dev, "missing fast clock");
                        return PTR_ERR(fast_clk);
                }
                i2c_dev->fast_clk = fast_clk;
        }

        platform_set_drvdata(pdev, i2c_dev);

        ret = tegra_i2c_init(i2c_dev);
        if (ret) {
                dev_err(&pdev->dev, "Failed to initialize i2c controller");
                return ret;
        }

        ret = devm_request_irq(&pdev->dev, i2c_dev->irq,
                        tegra_i2c_isr, 0, dev_name(&pdev->dev), i2c_dev);
        if (ret) {
                dev_err(&pdev->dev, "Failed to request irq %i\n", i2c_dev->irq);
                return ret;
        }

        i2c_set_adapdata(&i2c_dev->adapter, i2c_dev);
        i2c_dev->adapter.owner = THIS_MODULE;
        i2c_dev->adapter.class = I2C_CLASS_HWMON;
        strlcpy(i2c_dev->adapter.name, "Tegra I2C adapter",
                sizeof(i2c_dev->adapter.name));
        i2c_dev->adapter.algo = &tegra_i2c_algo;
        i2c_dev->adapter.dev.parent = &pdev->dev;
        i2c_dev->adapter.nr = pdev->id;
        i2c_dev->adapter.dev.of_node = pdev->dev.of_node;

        ret = i2c_add_numbered_adapter(&i2c_dev->adapter);
        if (ret) {
                dev_err(&pdev->dev, "Failed to add I2C adapter\n");
                return ret;
        }

        of_i2c_register_devices(&i2c_dev->adapter);

        return 0;
}

static int tegra_i2c_remove(struct platform_device *pdev)
{
        struct tegra_i2c_dev *i2c_dev = platform_get_drvdata(pdev);
        i2c_del_adapter(&i2c_dev->adapter);
        return 0;
}

#ifdef CONFIG_PM_SLEEP
static int tegra_i2c_suspend(struct device *dev)
{
        struct tegra_i2c_dev *i2c_dev = dev_get_drvdata(dev);

        i2c_lock_adapter(&i2c_dev->adapter);
        i2c_dev->is_suspended = true;
        i2c_unlock_adapter(&i2c_dev->adapter);

        return 0;
}

static int tegra_i2c_resume(struct device *dev)
{
        struct tegra_i2c_dev *i2c_dev = dev_get_drvdata(dev);
        int ret;

        i2c_lock_adapter(&i2c_dev->adapter);

        ret = tegra_i2c_init(i2c_dev);

        if (ret) {
                i2c_unlock_adapter(&i2c_dev->adapter);
                return ret;
        }

        i2c_dev->is_suspended = false;

        i2c_unlock_adapter(&i2c_dev->adapter);

        return 0;
}

static SIMPLE_DEV_PM_OPS(tegra_i2c_pm, tegra_i2c_suspend, tegra_i2c_resume);
#define TEGRA_I2C_PM    (&tegra_i2c_pm)
#else
#define TEGRA_I2C_PM    NULL
#endif

static struct platform_driver tegra_i2c_driver = {
        .probe   = tegra_i2c_probe,
        .remove  = tegra_i2c_remove,
        .driver  = {
                .name  = "tegra-i2c",
                .owner = THIS_MODULE,
                .of_match_table = tegra_i2c_of_match,
                .pm    = TEGRA_I2C_PM,
        },
};

static int __init tegra_i2c_init_driver(void)
{
        return platform_driver_register(&tegra_i2c_driver);
}

static void __exit tegra_i2c_exit_driver(void)
{
        platform_driver_unregister(&tegra_i2c_driver);
}

subsys_initcall(tegra_i2c_init_driver);
module_exit(tegra_i2c_exit_driver);

MODULE_DESCRIPTION("nVidia Tegra2 I2C Bus Controller driver");
MODULE_AUTHOR("Colin Cross");
MODULE_LICENSE("GPL v2");