Merge branch 'i2c/for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa...

[linux-2.6.git] / drivers / i2c / busses / i2c-nomadik.c

/*
 * Copyright (C) 2009 ST-Ericsson SA
 * Copyright (C) 2009 STMicroelectronics
 *
 * I2C master mode controller driver, used in Nomadik 8815
 * and Ux500 platforms.
 *
 * Author: Srinidhi Kasagar <srinidhi.kasagar@stericsson.com>
 * Author: Sachin Verma <sachin.verma@st.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2, as
 * published by the Free Software Foundation.
 */
#include <linux/init.h>
#include <linux/module.h>
#include <linux/amba/bus.h>
#include <linux/slab.h>
#include <linux/interrupt.h>
#include <linux/i2c.h>
#include <linux/err.h>
#include <linux/clk.h>
#include <linux/io.h>
#include <linux/pm_runtime.h>
#include <linux/platform_data/i2c-nomadik.h>
#include <linux/of.h>
#include <linux/of_i2c.h>
#include <linux/pinctrl/consumer.h>

#define DRIVER_NAME "nmk-i2c"

/* I2C Controller register offsets */
#define I2C_CR          (0x000)
#define I2C_SCR         (0x004)
#define I2C_HSMCR       (0x008)
#define I2C_MCR         (0x00C)
#define I2C_TFR         (0x010)
#define I2C_SR          (0x014)
#define I2C_RFR         (0x018)
#define I2C_TFTR        (0x01C)
#define I2C_RFTR        (0x020)
#define I2C_DMAR        (0x024)
#define I2C_BRCR        (0x028)
#define I2C_IMSCR       (0x02C)
#define I2C_RISR        (0x030)
#define I2C_MISR        (0x034)
#define I2C_ICR         (0x038)

/* Control registers */
#define I2C_CR_PE               (0x1 << 0)      /* Peripheral Enable */
#define I2C_CR_OM               (0x3 << 1)      /* Operating mode */
#define I2C_CR_SAM              (0x1 << 3)      /* Slave addressing mode */
#define I2C_CR_SM               (0x3 << 4)      /* Speed mode */
#define I2C_CR_SGCM             (0x1 << 6)      /* Slave general call mode */
#define I2C_CR_FTX              (0x1 << 7)      /* Flush Transmit */
#define I2C_CR_FRX              (0x1 << 8)      /* Flush Receive */
#define I2C_CR_DMA_TX_EN        (0x1 << 9)      /* DMA Tx enable */
#define I2C_CR_DMA_RX_EN        (0x1 << 10)     /* DMA Rx Enable */
#define I2C_CR_DMA_SLE          (0x1 << 11)     /* DMA sync. logic enable */
#define I2C_CR_LM               (0x1 << 12)     /* Loopback mode */
#define I2C_CR_FON              (0x3 << 13)     /* Filtering on */
#define I2C_CR_FS               (0x3 << 15)     /* Force stop enable */

/* Master controller (MCR) register */
#define I2C_MCR_OP              (0x1 << 0)      /* Operation */
#define I2C_MCR_A7              (0x7f << 1)     /* 7-bit address */
#define I2C_MCR_EA10            (0x7 << 8)      /* 10-bit Extended address */
#define I2C_MCR_SB              (0x1 << 11)     /* Extended address */
#define I2C_MCR_AM              (0x3 << 12)     /* Address type */
#define I2C_MCR_STOP            (0x1 << 14)     /* Stop condition */
#define I2C_MCR_LENGTH          (0x7ff << 15)   /* Transaction length */

/* Status register (SR) */
#define I2C_SR_OP               (0x3 << 0)      /* Operation */
#define I2C_SR_STATUS           (0x3 << 2)      /* controller status */
#define I2C_SR_CAUSE            (0x7 << 4)      /* Abort cause */
#define I2C_SR_TYPE             (0x3 << 7)      /* Receive type */
#define I2C_SR_LENGTH           (0x7ff << 9)    /* Transfer length */

/* Interrupt mask set/clear (IMSCR) bits */
#define I2C_IT_TXFE             (0x1 << 0)
#define I2C_IT_TXFNE            (0x1 << 1)
#define I2C_IT_TXFF             (0x1 << 2)
#define I2C_IT_TXFOVR           (0x1 << 3)
#define I2C_IT_RXFE             (0x1 << 4)
#define I2C_IT_RXFNF            (0x1 << 5)
#define I2C_IT_RXFF             (0x1 << 6)
#define I2C_IT_RFSR             (0x1 << 16)
#define I2C_IT_RFSE             (0x1 << 17)
#define I2C_IT_WTSR             (0x1 << 18)
#define I2C_IT_MTD              (0x1 << 19)
#define I2C_IT_STD              (0x1 << 20)
#define I2C_IT_MAL              (0x1 << 24)
#define I2C_IT_BERR             (0x1 << 25)
#define I2C_IT_MTDWS            (0x1 << 28)

#define GEN_MASK(val, mask, sb)  (((val) << (sb)) & (mask))

/* some bits in ICR are reserved */
#define I2C_CLEAR_ALL_INTS      0x131f007f

/* first three msb bits are reserved */
#define IRQ_MASK(mask)          (mask & 0x1fffffff)

/* maximum threshold value */
#define MAX_I2C_FIFO_THRESHOLD  15

/**
 * struct i2c_vendor_data - per-vendor variations
 * @has_mtdws: variant has the MTDWS bit
 * @fifodepth: variant FIFO depth
 */
struct i2c_vendor_data {
        bool has_mtdws;
        u32 fifodepth;
};

enum i2c_status {
        I2C_NOP,
        I2C_ON_GOING,
        I2C_OK,
        I2C_ABORT
};

/* operation */
enum i2c_operation {
        I2C_NO_OPERATION = 0xff,
        I2C_WRITE = 0x00,
        I2C_READ = 0x01
};

/**
 * struct i2c_nmk_client - client specific data
 * @slave_adr: 7-bit slave address
 * @count: no. bytes to be transferred
 * @buffer: client data buffer
 * @xfer_bytes: bytes transferred till now
 * @operation: current I2C operation
 */
struct i2c_nmk_client {
        unsigned short          slave_adr;
        unsigned long           count;
        unsigned char           *buffer;
        unsigned long           xfer_bytes;
        enum i2c_operation      operation;
};

/**
 * struct nmk_i2c_dev - private data structure of the controller.
 * @vendor: vendor data for this variant.
 * @adev: parent amba device.
 * @adap: corresponding I2C adapter.
 * @irq: interrupt line for the controller.
 * @virtbase: virtual io memory area.
 * @clk: hardware i2c block clock.
 * @cfg: machine provided controller configuration.
 * @cli: holder of client specific data.
 * @stop: stop condition.
 * @xfer_complete: acknowledge completion for a I2C message.
 * @result: controller propogated result.
 * @busy: Busy doing transfer.
 */
struct nmk_i2c_dev {
        struct i2c_vendor_data          *vendor;
        struct amba_device              *adev;
        struct i2c_adapter              adap;
        int                             irq;
        void __iomem                    *virtbase;
        struct clk                      *clk;
        struct nmk_i2c_controller       cfg;
        struct i2c_nmk_client           cli;
        int                             stop;
        struct completion               xfer_complete;
        int                             result;
        bool                            busy;
};

/* controller's abort causes */
static const char *abort_causes[] = {
        "no ack received after address transmission",
        "no ack received during data phase",
        "ack received after xmission of master code",
        "master lost arbitration",
        "slave restarts",
        "slave reset",
        "overflow, maxsize is 2047 bytes",
};

static inline void i2c_set_bit(void __iomem *reg, u32 mask)
{
        writel(readl(reg) | mask, reg);
}

static inline void i2c_clr_bit(void __iomem *reg, u32 mask)
{
        writel(readl(reg) & ~mask, reg);
}

/**
 * flush_i2c_fifo() - This function flushes the I2C FIFO
 * @dev: private data of I2C Driver
 *
 * This function flushes the I2C Tx and Rx FIFOs. It returns
 * 0 on successful flushing of FIFO
 */
static int flush_i2c_fifo(struct nmk_i2c_dev *dev)
{
#define LOOP_ATTEMPTS 10
        int i;
        unsigned long timeout;

        /*
         * flush the transmit and receive FIFO. The flushing
         * operation takes several cycles before to be completed.
         * On the completion, the I2C internal logic clears these
         * bits, until then no one must access Tx, Rx FIFO and
         * should poll on these bits waiting for the completion.
         */
        writel((I2C_CR_FTX | I2C_CR_FRX), dev->virtbase + I2C_CR);

        for (i = 0; i < LOOP_ATTEMPTS; i++) {
                timeout = jiffies + dev->adap.timeout;

                while (!time_after(jiffies, timeout)) {
                        if ((readl(dev->virtbase + I2C_CR) &
                                (I2C_CR_FTX | I2C_CR_FRX)) == 0)
                                        return 0;
                }
        }

        dev_err(&dev->adev->dev,
                "flushing operation timed out giving up after %d attempts",
                LOOP_ATTEMPTS);

        return -ETIMEDOUT;
}

/**
 * disable_all_interrupts() - Disable all interrupts of this I2c Bus
 * @dev: private data of I2C Driver
 */
static void disable_all_interrupts(struct nmk_i2c_dev *dev)
{
        u32 mask = IRQ_MASK(0);
        writel(mask, dev->virtbase + I2C_IMSCR);
}

/**
 * clear_all_interrupts() - Clear all interrupts of I2C Controller
 * @dev: private data of I2C Driver
 */
static void clear_all_interrupts(struct nmk_i2c_dev *dev)
{
        u32 mask;
        mask = IRQ_MASK(I2C_CLEAR_ALL_INTS);
        writel(mask, dev->virtbase + I2C_ICR);
}

/**
 * init_hw() - initialize the I2C hardware
 * @dev: private data of I2C Driver
 */
static int init_hw(struct nmk_i2c_dev *dev)
{
        int stat;

        stat = flush_i2c_fifo(dev);
        if (stat)
                goto exit;

        /* disable the controller */
        i2c_clr_bit(dev->virtbase + I2C_CR , I2C_CR_PE);

        disable_all_interrupts(dev);

        clear_all_interrupts(dev);

        dev->cli.operation = I2C_NO_OPERATION;

exit:
        return stat;
}

/* enable peripheral, master mode operation */
#define DEFAULT_I2C_REG_CR      ((1 << 1) | I2C_CR_PE)

/**
 * load_i2c_mcr_reg() - load the MCR register
 * @dev: private data of controller
 * @flags: message flags
 */
static u32 load_i2c_mcr_reg(struct nmk_i2c_dev *dev, u16 flags)
{
        u32 mcr = 0;
        unsigned short slave_adr_3msb_bits;

        mcr |= GEN_MASK(dev->cli.slave_adr, I2C_MCR_A7, 1);

        if (unlikely(flags & I2C_M_TEN)) {
                /* 10-bit address transaction */
                mcr |= GEN_MASK(2, I2C_MCR_AM, 12);
                /*
                 * Get the top 3 bits.
                 * EA10 represents extended address in MCR. This includes
                 * the extension (MSB bits) of the 7 bit address loaded
                 * in A7
                 */
                slave_adr_3msb_bits = (dev->cli.slave_adr >> 7) & 0x7;

                mcr |= GEN_MASK(slave_adr_3msb_bits, I2C_MCR_EA10, 8);
        } else {
                /* 7-bit address transaction */
                mcr |= GEN_MASK(1, I2C_MCR_AM, 12);
        }

        /* start byte procedure not applied */
        mcr |= GEN_MASK(0, I2C_MCR_SB, 11);

        /* check the operation, master read/write? */
        if (dev->cli.operation == I2C_WRITE)
                mcr |= GEN_MASK(I2C_WRITE, I2C_MCR_OP, 0);
        else
                mcr |= GEN_MASK(I2C_READ, I2C_MCR_OP, 0);

        /* stop or repeated start? */
        if (dev->stop)
                mcr |= GEN_MASK(1, I2C_MCR_STOP, 14);
        else
                mcr &= ~(GEN_MASK(1, I2C_MCR_STOP, 14));

        mcr |= GEN_MASK(dev->cli.count, I2C_MCR_LENGTH, 15);

        return mcr;
}

/**
 * setup_i2c_controller() - setup the controller
 * @dev: private data of controller
 */
static void setup_i2c_controller(struct nmk_i2c_dev *dev)
{
        u32 brcr1, brcr2;
        u32 i2c_clk, div;

        writel(0x0, dev->virtbase + I2C_CR);
        writel(0x0, dev->virtbase + I2C_HSMCR);
        writel(0x0, dev->virtbase + I2C_TFTR);
        writel(0x0, dev->virtbase + I2C_RFTR);
        writel(0x0, dev->virtbase + I2C_DMAR);

        /*
         * set the slsu:
         *
         * slsu defines the data setup time after SCL clock
         * stretching in terms of i2c clk cycles. The
         * needed setup time for the three modes are 250ns,
         * 100ns, 10ns respectively thus leading to the values
         * of 14, 6, 2 for a 48 MHz i2c clk.
         */
        writel(dev->cfg.slsu << 16, dev->virtbase + I2C_SCR);

        i2c_clk = clk_get_rate(dev->clk);

        /*
         * The spec says, in case of std. mode the divider is
         * 2 whereas it is 3 for fast and fastplus mode of
         * operation. TODO - high speed support.
         */
        div = (dev->cfg.clk_freq > 100000) ? 3 : 2;

        /*
         * generate the mask for baud rate counters. The controller
         * has two baud rate counters. One is used for High speed
         * operation, and the other is for std, fast mode, fast mode
         * plus operation. Currently we do not supprt high speed mode
         * so set brcr1 to 0.
         */
        brcr1 = 0 << 16;
        brcr2 = (i2c_clk/(dev->cfg.clk_freq * div)) & 0xffff;

        /* set the baud rate counter register */
        writel((brcr1 | brcr2), dev->virtbase + I2C_BRCR);

        /*
         * set the speed mode. Currently we support
         * only standard and fast mode of operation
         * TODO - support for fast mode plus (up to 1Mb/s)
         * and high speed (up to 3.4 Mb/s)
         */
        if (dev->cfg.sm > I2C_FREQ_MODE_FAST) {
                dev_err(&dev->adev->dev,
                        "do not support this mode defaulting to std. mode\n");
                brcr2 = i2c_clk/(100000 * 2) & 0xffff;
                writel((brcr1 | brcr2), dev->virtbase + I2C_BRCR);
                writel(I2C_FREQ_MODE_STANDARD << 4,
                                dev->virtbase + I2C_CR);
        }
        writel(dev->cfg.sm << 4, dev->virtbase + I2C_CR);

        /* set the Tx and Rx FIFO threshold */
        writel(dev->cfg.tft, dev->virtbase + I2C_TFTR);
        writel(dev->cfg.rft, dev->virtbase + I2C_RFTR);
}

/**
 * read_i2c() - Read from I2C client device
 * @dev: private data of I2C Driver
 * @flags: message flags
 *
 * This function reads from i2c client device when controller is in
 * master mode. There is a completion timeout. If there is no transfer
 * before timeout error is returned.
 */
static int read_i2c(struct nmk_i2c_dev *dev, u16 flags)
{
        u32 status = 0;
        u32 mcr, irq_mask;
        int timeout;

        mcr = load_i2c_mcr_reg(dev, flags);
        writel(mcr, dev->virtbase + I2C_MCR);

        /* load the current CR value */
        writel(readl(dev->virtbase + I2C_CR) | DEFAULT_I2C_REG_CR,
                        dev->virtbase + I2C_CR);

        /* enable the controller */
        i2c_set_bit(dev->virtbase + I2C_CR, I2C_CR_PE);

        init_completion(&dev->xfer_complete);

        /* enable interrupts by setting the mask */
        irq_mask = (I2C_IT_RXFNF | I2C_IT_RXFF |
                        I2C_IT_MAL | I2C_IT_BERR);

        if (dev->stop || !dev->vendor->has_mtdws)
                irq_mask |= I2C_IT_MTD;
        else
                irq_mask |= I2C_IT_MTDWS;

        irq_mask = I2C_CLEAR_ALL_INTS & IRQ_MASK(irq_mask);

        writel(readl(dev->virtbase + I2C_IMSCR) | irq_mask,
                        dev->virtbase + I2C_IMSCR);

        timeout = wait_for_completion_timeout(
                &dev->xfer_complete, dev->adap.timeout);

        if (timeout == 0) {
                /* Controller timed out */
                dev_err(&dev->adev->dev, "read from slave 0x%x timed out\n",
                                dev->cli.slave_adr);
                status = -ETIMEDOUT;
        }
        return status;
}

static void fill_tx_fifo(struct nmk_i2c_dev *dev, int no_bytes)
{
        int count;

        for (count = (no_bytes - 2);
                        (count > 0) &&
                        (dev->cli.count != 0);
                        count--) {
                /* write to the Tx FIFO */
                writeb(*dev->cli.buffer,
                        dev->virtbase + I2C_TFR);
                dev->cli.buffer++;
                dev->cli.count--;
                dev->cli.xfer_bytes++;
        }

}

/**
 * write_i2c() - Write data to I2C client.
 * @dev: private data of I2C Driver
 * @flags: message flags
 *
 * This function writes data to I2C client
 */
static int write_i2c(struct nmk_i2c_dev *dev, u16 flags)
{
        u32 status = 0;
        u32 mcr, irq_mask;
        int timeout;

        mcr = load_i2c_mcr_reg(dev, flags);

        writel(mcr, dev->virtbase + I2C_MCR);

        /* load the current CR value */
        writel(readl(dev->virtbase + I2C_CR) | DEFAULT_I2C_REG_CR,
                        dev->virtbase + I2C_CR);

        /* enable the controller */
        i2c_set_bit(dev->virtbase + I2C_CR , I2C_CR_PE);

        init_completion(&dev->xfer_complete);

        /* enable interrupts by settings the masks */
        irq_mask = (I2C_IT_TXFOVR | I2C_IT_MAL | I2C_IT_BERR);

        /* Fill the TX FIFO with transmit data */
        fill_tx_fifo(dev, MAX_I2C_FIFO_THRESHOLD);

        if (dev->cli.count != 0)
                irq_mask |= I2C_IT_TXFNE;

        /*
         * check if we want to transfer a single or multiple bytes, if so
         * set the MTDWS bit (Master Transaction Done Without Stop)
         * to start repeated start operation
         */
        if (dev->stop || !dev->vendor->has_mtdws)
                irq_mask |= I2C_IT_MTD;
        else
                irq_mask |= I2C_IT_MTDWS;

        irq_mask = I2C_CLEAR_ALL_INTS & IRQ_MASK(irq_mask);

        writel(readl(dev->virtbase + I2C_IMSCR) | irq_mask,
                        dev->virtbase + I2C_IMSCR);

        timeout = wait_for_completion_timeout(
                &dev->xfer_complete, dev->adap.timeout);

        if (timeout == 0) {
                /* Controller timed out */
                dev_err(&dev->adev->dev, "write to slave 0x%x timed out\n",
                                dev->cli.slave_adr);
                status = -ETIMEDOUT;
        }

        return status;
}

/**
 * nmk_i2c_xfer_one() - transmit a single I2C message
 * @dev: device with a message encoded into it
 * @flags: message flags
 */
static int nmk_i2c_xfer_one(struct nmk_i2c_dev *dev, u16 flags)
{
        int status;

        if (flags & I2C_M_RD) {
                /* read operation */
                dev->cli.operation = I2C_READ;
                status = read_i2c(dev, flags);
        } else {
                /* write operation */
                dev->cli.operation = I2C_WRITE;
                status = write_i2c(dev, flags);
        }

        if (status || (dev->result)) {
                u32 i2c_sr;
                u32 cause;

                i2c_sr = readl(dev->virtbase + I2C_SR);
                /*
                 * Check if the controller I2C operation status
                 * is set to ABORT(11b).
                 */
                if (((i2c_sr >> 2) & 0x3) == 0x3) {
                        /* get the abort cause */
                        cause = (i2c_sr >> 4) & 0x7;
                        dev_err(&dev->adev->dev, "%s\n",
                                cause >= ARRAY_SIZE(abort_causes) ?
                                "unknown reason" :
                                abort_causes[cause]);
                }

                (void) init_hw(dev);

                status = status ? status : dev->result;
        }

        return status;
}

/**
 * nmk_i2c_xfer() - I2C transfer function used by kernel framework
 * @i2c_adap: Adapter pointer to the controller
 * @msgs: Pointer to data to be written.
 * @num_msgs: Number of messages to be executed
 *
 * This is the function called by the generic kernel i2c_transfer()
 * or i2c_smbus...() API calls. Note that this code is protected by the
 * semaphore set in the kernel i2c_transfer() function.
 *
 * NOTE:
 * READ TRANSFER : We impose a restriction of the first message to be the
 *              index message for any read transaction.
 *              - a no index is coded as '0',
 *              - 2byte big endian index is coded as '3'
 *              !!! msg[0].buf holds the actual index.
 *              This is compatible with generic messages of smbus emulator
 *              that send a one byte index.
 *              eg. a I2C transation to read 2 bytes from index 0
 *                      idx = 0;
 *                      msg[0].addr = client->addr;
 *                      msg[0].flags = 0x0;
 *                      msg[0].len = 1;
 *                      msg[0].buf = &idx;
 *
 *                      msg[1].addr = client->addr;
 *                      msg[1].flags = I2C_M_RD;
 *                      msg[1].len = 2;
 *                      msg[1].buf = rd_buff
 *                      i2c_transfer(adap, msg, 2);
 *
 * WRITE TRANSFER : The I2C standard interface interprets all data as payload.
 *              If you want to emulate an SMBUS write transaction put the
 *              index as first byte(or first and second) in the payload.
 *              eg. a I2C transation to write 2 bytes from index 1
 *                      wr_buff[0] = 0x1;
 *                      wr_buff[1] = 0x23;
 *                      wr_buff[2] = 0x46;
 *                      msg[0].flags = 0x0;
 *                      msg[0].len = 3;
 *                      msg[0].buf = wr_buff;
 *                      i2c_transfer(adap, msg, 1);
 *
 * To read or write a block of data (multiple bytes) using SMBUS emulation
 * please use the i2c_smbus_read_i2c_block_data()
 * or i2c_smbus_write_i2c_block_data() API
 */
static int nmk_i2c_xfer(struct i2c_adapter *i2c_adap,
                struct i2c_msg msgs[], int num_msgs)
{
        int status;
        int i;
        struct nmk_i2c_dev *dev = i2c_get_adapdata(i2c_adap);
        int j;

        dev->busy = true;

        pm_runtime_get_sync(&dev->adev->dev);

        status = clk_prepare_enable(dev->clk);
        if (status) {
                dev_err(&dev->adev->dev, "can't prepare_enable clock\n");
                goto out_clk;
        }

        /* Optionaly enable pins to be muxed in and configured */
        pinctrl_pm_select_default_state(&dev->adev->dev);

        status = init_hw(dev);
        if (status)
                goto out;

        /* Attempt three times to send the message queue */
        for (j = 0; j < 3; j++) {
                /* setup the i2c controller */
                setup_i2c_controller(dev);

                for (i = 0; i < num_msgs; i++) {
                        dev->cli.slave_adr      = msgs[i].addr;
                        dev->cli.buffer         = msgs[i].buf;
                        dev->cli.count          = msgs[i].len;
                        dev->stop = (i < (num_msgs - 1)) ? 0 : 1;
                        dev->result = 0;

                        status = nmk_i2c_xfer_one(dev, msgs[i].flags);
                        if (status != 0)
                                break;
                }
                if (status == 0)
                        break;
        }

out:
        clk_disable_unprepare(dev->clk);
out_clk:
        /* Optionally let pins go into idle state */
        pinctrl_pm_select_idle_state(&dev->adev->dev);

        pm_runtime_put_sync(&dev->adev->dev);

        dev->busy = false;

        /* return the no. messages processed */
        if (status)
                return status;
        else
                return num_msgs;
}

/**
 * disable_interrupts() - disable the interrupts
 * @dev: private data of controller
 * @irq: interrupt number
 */
static int disable_interrupts(struct nmk_i2c_dev *dev, u32 irq)
{
        irq = IRQ_MASK(irq);
        writel(readl(dev->virtbase + I2C_IMSCR) & ~(I2C_CLEAR_ALL_INTS & irq),
                        dev->virtbase + I2C_IMSCR);
        return 0;
}

/**
 * i2c_irq_handler() - interrupt routine
 * @irq: interrupt number
 * @arg: data passed to the handler
 *
 * This is the interrupt handler for the i2c driver. Currently
 * it handles the major interrupts like Rx & Tx FIFO management
 * interrupts, master transaction interrupts, arbitration and
 * bus error interrupts. The rest of the interrupts are treated as
 * unhandled.
 */
static irqreturn_t i2c_irq_handler(int irq, void *arg)
{
        struct nmk_i2c_dev *dev = arg;
        u32 tft, rft;
        u32 count;
        u32 misr, src;

        /* load Tx FIFO and Rx FIFO threshold values */
        tft = readl(dev->virtbase + I2C_TFTR);
        rft = readl(dev->virtbase + I2C_RFTR);

        /* read interrupt status register */
        misr = readl(dev->virtbase + I2C_MISR);

        src = __ffs(misr);
        switch ((1 << src)) {

        /* Transmit FIFO nearly empty interrupt */
        case I2C_IT_TXFNE:
        {
                if (dev->cli.operation == I2C_READ) {
                        /*
                         * in read operation why do we care for writing?
                         * so disable the Transmit FIFO interrupt
                         */
                        disable_interrupts(dev, I2C_IT_TXFNE);
                } else {
                        fill_tx_fifo(dev, (MAX_I2C_FIFO_THRESHOLD - tft));
                        /*
                         * if done, close the transfer by disabling the
                         * corresponding TXFNE interrupt
                         */
                        if (dev->cli.count == 0)
                                disable_interrupts(dev, I2C_IT_TXFNE);
                }
        }
        break;

        /*
         * Rx FIFO nearly full interrupt.
         * This is set when the numer of entries in Rx FIFO is
         * greater or equal than the threshold value programmed
         * in RFT
         */
        case I2C_IT_RXFNF:
                for (count = rft; count > 0; count--) {
                        /* Read the Rx FIFO */
                        *dev->cli.buffer = readb(dev->virtbase + I2C_RFR);
                        dev->cli.buffer++;
                }
                dev->cli.count -= rft;
                dev->cli.xfer_bytes += rft;
                break;

        /* Rx FIFO full */
        case I2C_IT_RXFF:
                for (count = MAX_I2C_FIFO_THRESHOLD; count > 0; count--) {
                        *dev->cli.buffer = readb(dev->virtbase + I2C_RFR);
                        dev->cli.buffer++;
                }
                dev->cli.count -= MAX_I2C_FIFO_THRESHOLD;
                dev->cli.xfer_bytes += MAX_I2C_FIFO_THRESHOLD;
                break;

        /* Master Transaction Done with/without stop */
        case I2C_IT_MTD:
        case I2C_IT_MTDWS:
                if (dev->cli.operation == I2C_READ) {
                        while (!(readl(dev->virtbase + I2C_RISR)
                                 & I2C_IT_RXFE)) {
                                if (dev->cli.count == 0)
                                        break;
                                *dev->cli.buffer =
                                        readb(dev->virtbase + I2C_RFR);
                                dev->cli.buffer++;
                                dev->cli.count--;
                                dev->cli.xfer_bytes++;
                        }
                }

                disable_all_interrupts(dev);
                clear_all_interrupts(dev);

                if (dev->cli.count) {
                        dev->result = -EIO;
                        dev_err(&dev->adev->dev,
                                "%lu bytes still remain to be xfered\n",
                                dev->cli.count);
                        (void) init_hw(dev);
                }
                complete(&dev->xfer_complete);

                break;

        /* Master Arbitration lost interrupt */
        case I2C_IT_MAL:
                dev->result = -EIO;
                (void) init_hw(dev);

                i2c_set_bit(dev->virtbase + I2C_ICR, I2C_IT_MAL);
                complete(&dev->xfer_complete);

                break;

        /*
         * Bus Error interrupt.
         * This happens when an unexpected start/stop condition occurs
         * during the transaction.
         */
        case I2C_IT_BERR:
                dev->result = -EIO;
                /* get the status */
                if (((readl(dev->virtbase + I2C_SR) >> 2) & 0x3) == I2C_ABORT)
                        (void) init_hw(dev);

                i2c_set_bit(dev->virtbase + I2C_ICR, I2C_IT_BERR);
                complete(&dev->xfer_complete);

                break;

        /*
         * Tx FIFO overrun interrupt.
         * This is set when a write operation in Tx FIFO is performed and
         * the Tx FIFO is full.
         */
        case I2C_IT_TXFOVR:
                dev->result = -EIO;
                (void) init_hw(dev);

                dev_err(&dev->adev->dev, "Tx Fifo Over run\n");
                complete(&dev->xfer_complete);

                break;

        /* unhandled interrupts by this driver - TODO*/
        case I2C_IT_TXFE:
        case I2C_IT_TXFF:
        case I2C_IT_RXFE:
        case I2C_IT_RFSR:
        case I2C_IT_RFSE:
        case I2C_IT_WTSR:
        case I2C_IT_STD:
                dev_err(&dev->adev->dev, "unhandled Interrupt\n");
                break;
        default:
                dev_err(&dev->adev->dev, "spurious Interrupt..\n");
                break;
        }

        return IRQ_HANDLED;
}


#ifdef CONFIG_PM
static int nmk_i2c_suspend(struct device *dev)
{
        struct amba_device *adev = to_amba_device(dev);
        struct nmk_i2c_dev *nmk_i2c = amba_get_drvdata(adev);

        if (nmk_i2c->busy)
                return -EBUSY;

        pinctrl_pm_select_sleep_state(dev);

        return 0;
}

static int nmk_i2c_resume(struct device *dev)
{
        /* First go to the default state */
        pinctrl_pm_select_default_state(dev);
        /* Then let's idle the pins until the next transfer happens */
        pinctrl_pm_select_idle_state(dev);

        return 0;
}
#else
#define nmk_i2c_suspend NULL
#define nmk_i2c_resume  NULL
#endif

/*
 * We use noirq so that we suspend late and resume before the wakeup interrupt
 * to ensure that we do the !pm_runtime_suspended() check in resume before
 * there has been a regular pm runtime resume (via pm_runtime_get_sync()).
 */
static const struct dev_pm_ops nmk_i2c_pm = {
        .suspend_noirq  = nmk_i2c_suspend,
        .resume_noirq   = nmk_i2c_resume,
};

static unsigned int nmk_i2c_functionality(struct i2c_adapter *adap)
{
        return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL | I2C_FUNC_10BIT_ADDR;
}

static const struct i2c_algorithm nmk_i2c_algo = {
        .master_xfer    = nmk_i2c_xfer,
        .functionality  = nmk_i2c_functionality
};

static struct nmk_i2c_controller u8500_i2c = {
        /*
         * Slave data setup time; 250ns, 100ns, and 10ns, which
         * is 14, 6 and 2 respectively for a 48Mhz i2c clock.
         */
        .slsu           = 0xe,
        .tft            = 1,      /* Tx FIFO threshold */
        .rft            = 8,      /* Rx FIFO threshold */
        .clk_freq       = 400000, /* fast mode operation */
        .timeout        = 200,    /* Slave response timeout(ms) */
        .sm             = I2C_FREQ_MODE_FAST,
};

static void nmk_i2c_of_probe(struct device_node *np,
                        struct nmk_i2c_controller *pdata)
{
        of_property_read_u32(np, "clock-frequency", &pdata->clk_freq);

        /* This driver only supports 'standard' and 'fast' modes of operation. */
        if (pdata->clk_freq <= 100000)
                pdata->sm = I2C_FREQ_MODE_STANDARD;
        else
                pdata->sm = I2C_FREQ_MODE_FAST;
}

static int nmk_i2c_probe(struct amba_device *adev, const struct amba_id *id)
{
        int ret = 0;
        struct nmk_i2c_controller *pdata = adev->dev.platform_data;
        struct device_node *np = adev->dev.of_node;
        struct nmk_i2c_dev      *dev;
        struct i2c_adapter *adap;
        struct i2c_vendor_data *vendor = id->data;
        u32 max_fifo_threshold = (vendor->fifodepth / 2) - 1;

        if (!pdata) {
                if (np) {
                        pdata = devm_kzalloc(&adev->dev, sizeof(*pdata), GFP_KERNEL);
                        if (!pdata) {
                                ret = -ENOMEM;
                                goto err_no_mem;
                        }
                        /* Provide the default configuration as a base. */
                        memcpy(pdata, &u8500_i2c, sizeof(struct nmk_i2c_controller));
                        nmk_i2c_of_probe(np, pdata);
                } else
                        /* No i2c configuration found, using the default. */
                        pdata = &u8500_i2c;
        }

        if (pdata->tft > max_fifo_threshold) {
                dev_warn(&adev->dev, "requested TX FIFO threshold %u, adjusted down to %u\n",
                        pdata->tft, max_fifo_threshold);
                pdata->tft = max_fifo_threshold;
        }

        if (pdata->rft > max_fifo_threshold) {
                dev_warn(&adev->dev, "requested RX FIFO threshold %u, adjusted down to %u\n",
                        pdata->rft, max_fifo_threshold);
                pdata->rft = max_fifo_threshold;
        }

        dev = kzalloc(sizeof(struct nmk_i2c_dev), GFP_KERNEL);
        if (!dev) {
                dev_err(&adev->dev, "cannot allocate memory\n");
                ret = -ENOMEM;
                goto err_no_mem;
        }
        dev->vendor = vendor;
        dev->busy = false;
        dev->adev = adev;
        amba_set_drvdata(adev, dev);

        /* Select default pin state */
        pinctrl_pm_select_default_state(&adev->dev);
        /* If possible, let's go to idle until the first transfer */
        pinctrl_pm_select_idle_state(&adev->dev);

        dev->virtbase = ioremap(adev->res.start, resource_size(&adev->res));
        if (!dev->virtbase) {
                ret = -ENOMEM;
                goto err_no_ioremap;
        }

        dev->irq = adev->irq[0];
        ret = request_irq(dev->irq, i2c_irq_handler, 0,
                                DRIVER_NAME, dev);
        if (ret) {
                dev_err(&adev->dev, "cannot claim the irq %d\n", dev->irq);
                goto err_irq;
        }

        pm_suspend_ignore_children(&adev->dev, true);

        dev->clk = clk_get(&adev->dev, NULL);
        if (IS_ERR(dev->clk)) {
                dev_err(&adev->dev, "could not get i2c clock\n");
                ret = PTR_ERR(dev->clk);
                goto err_no_clk;
        }

        adap = &dev->adap;
        adap->dev.of_node = np;
        adap->dev.parent = &adev->dev;
        adap->owner     = THIS_MODULE;
        adap->class     = I2C_CLASS_HWMON | I2C_CLASS_SPD;
        adap->algo      = &nmk_i2c_algo;
        adap->timeout   = msecs_to_jiffies(pdata->timeout);
        snprintf(adap->name, sizeof(adap->name),
                 "Nomadik I2C at %pR", &adev->res);

        /* fetch the controller configuration from machine */
        dev->cfg.clk_freq = pdata->clk_freq;
        dev->cfg.slsu   = pdata->slsu;
        dev->cfg.tft    = pdata->tft;
        dev->cfg.rft    = pdata->rft;
        dev->cfg.sm     = pdata->sm;

        i2c_set_adapdata(adap, dev);

        dev_info(&adev->dev,
                 "initialize %s on virtual base %p\n",
                 adap->name, dev->virtbase);

        ret = i2c_add_adapter(adap);
        if (ret) {
                dev_err(&adev->dev, "failed to add adapter\n");
                goto err_add_adap;
        }

        of_i2c_register_devices(adap);

        pm_runtime_put(&adev->dev);

        return 0;

 err_add_adap:
        clk_put(dev->clk);
 err_no_clk:
        free_irq(dev->irq, dev);
 err_irq:
        iounmap(dev->virtbase);
 err_no_ioremap:
        kfree(dev);
 err_no_mem:

        return ret;
}

static int nmk_i2c_remove(struct amba_device *adev)
{
        struct resource *res = &adev->res;
        struct nmk_i2c_dev *dev = amba_get_drvdata(adev);

        i2c_del_adapter(&dev->adap);
        flush_i2c_fifo(dev);
        disable_all_interrupts(dev);
        clear_all_interrupts(dev);
        /* disable the controller */
        i2c_clr_bit(dev->virtbase + I2C_CR, I2C_CR_PE);
        free_irq(dev->irq, dev);
        iounmap(dev->virtbase);
        if (res)
                release_mem_region(res->start, resource_size(res));
        clk_put(dev->clk);
        pm_runtime_disable(&adev->dev);
        kfree(dev);

        return 0;
}

static struct i2c_vendor_data vendor_stn8815 = {
        .has_mtdws = false,
        .fifodepth = 16, /* Guessed from TFTR/RFTR = 7 */
};

static struct i2c_vendor_data vendor_db8500 = {
        .has_mtdws = true,
        .fifodepth = 32, /* Guessed from TFTR/RFTR = 15 */
};

static struct amba_id nmk_i2c_ids[] = {
        {
                .id     = 0x00180024,
                .mask   = 0x00ffffff,
                .data   = &vendor_stn8815,
        },
        {
                .id     = 0x00380024,
                .mask   = 0x00ffffff,
                .data   = &vendor_db8500,
        },
        {},
};

MODULE_DEVICE_TABLE(amba, nmk_i2c_ids);

static struct amba_driver nmk_i2c_driver = {
        .drv = {
                .owner = THIS_MODULE,
                .name = DRIVER_NAME,
                .pm = &nmk_i2c_pm,
        },
        .id_table = nmk_i2c_ids,
        .probe = nmk_i2c_probe,
        .remove = nmk_i2c_remove,
};

static int __init nmk_i2c_init(void)
{
        return amba_driver_register(&nmk_i2c_driver);
}

static void __exit nmk_i2c_exit(void)
{
        amba_driver_unregister(&nmk_i2c_driver);
}

subsys_initcall(nmk_i2c_init);
module_exit(nmk_i2c_exit);

MODULE_AUTHOR("Sachin Verma, Srinidhi KASAGAR");
MODULE_DESCRIPTION("Nomadik/Ux500 I2C driver");
MODULE_LICENSE("GPL");