/*
 * (C) Copyright 2009-2010
 * Nokia Siemens Networks, michael.lawnick.ext@nsn.com
 *
 * Portions Copyright (C) 2010, 2011 Cavium Networks, Inc.
 *
 * This is a driver for the i2c adapter in Cavium Networks' OCTEON processors.
 *
 * This file is licensed under the terms of the GNU General Public
 * License version 2. This program is licensed "as is" without any
 * warranty of any kind, whether express or implied.
 */

#include <linux/platform_device.h>
#include <linux/interrupt.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/delay.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/i2c.h>
#include <linux/io.h>
#include <linux/of.h>

#include <asm/octeon/octeon.h>

#define DRV_NAME "i2c-octeon"

/* The previous out-of-tree version was implicitly version 1.0. */
#define DRV_VERSION     "2.0"

/* register offsets */
#define SW_TWSI  0x00
#define TWSI_INT 0x10

/* Controller command patterns */
#define SW_TWSI_V               0x8000000000000000ull
#define SW_TWSI_EOP_TWSI_DATA   0x0C00000100000000ull
#define SW_TWSI_EOP_TWSI_CTL    0x0C00000200000000ull
#define SW_TWSI_EOP_TWSI_CLKCTL 0x0C00000300000000ull
#define SW_TWSI_EOP_TWSI_STAT   0x0C00000300000000ull
#define SW_TWSI_EOP_TWSI_RST    0x0C00000700000000ull
#define SW_TWSI_OP_TWSI_CLK     0x0800000000000000ull
#define SW_TWSI_R               0x0100000000000000ull

/* Controller command and status bits */
#define TWSI_CTL_CE   0x80
#define TWSI_CTL_ENAB 0x40
#define TWSI_CTL_STA  0x20
#define TWSI_CTL_STP  0x10
#define TWSI_CTL_IFLG 0x08
#define TWSI_CTL_AAK  0x04

/* Some status values */
#define STAT_START      0x08
#define STAT_RSTART     0x10
#define STAT_TXADDR_ACK 0x18
#define STAT_TXDATA_ACK 0x28
#define STAT_RXADDR_ACK 0x40
#define STAT_RXDATA_ACK 0x50
#define STAT_IDLE       0xF8

struct octeon_i2c {
        wait_queue_head_t queue;
        struct i2c_adapter adap;
        int irq;
        u32 twsi_freq;
        int sys_freq;
        resource_size_t twsi_phys;
        void __iomem *twsi_base;
        resource_size_t regsize;
        struct device *dev;
};

/**
 * octeon_i2c_write_sw - write an I2C core register.
 * @i2c: The struct octeon_i2c.
 * @eop_reg: Register selector.
 * @data: Value to be written.
 *
 * The I2C core registers are accessed indirectly via the SW_TWSI CSR.
 */
static void octeon_i2c_write_sw(struct octeon_i2c *i2c,
                                u64 eop_reg,
                                u8 data)
{
        u64 tmp;

        __raw_writeq(SW_TWSI_V | eop_reg | data, i2c->twsi_base + SW_TWSI);
        do {
                tmp = __raw_readq(i2c->twsi_base + SW_TWSI);
        } while ((tmp & SW_TWSI_V) != 0);
}

/**
 * octeon_i2c_read_sw - write an I2C core register.
 * @i2c: The struct octeon_i2c.
 * @eop_reg: Register selector.
 *
 * Returns the data.
 *
 * The I2C core registers are accessed indirectly via the SW_TWSI CSR.
 */
static u8 octeon_i2c_read_sw(struct octeon_i2c *i2c, u64 eop_reg)
{
        u64 tmp;

        __raw_writeq(SW_TWSI_V | eop_reg | SW_TWSI_R, i2c->twsi_base + SW_TWSI);
        do {
                tmp = __raw_readq(i2c->twsi_base + SW_TWSI);
        } while ((tmp & SW_TWSI_V) != 0);

        return tmp & 0xFF;
}

/**
 * octeon_i2c_write_int - write the TWSI_INT register
 * @i2c: The struct octeon_i2c.
 * @data: Value to be written.
 */
static void octeon_i2c_write_int(struct octeon_i2c *i2c, u64 data)
{
        __raw_writeq(data, i2c->twsi_base + TWSI_INT);
        __raw_readq(i2c->twsi_base + TWSI_INT);
}

/**
 * octeon_i2c_int_enable - enable the TS interrupt.
 * @i2c: The struct octeon_i2c.
 *
 * The interrupt will be asserted when there is non-STAT_IDLE state in
 * the SW_TWSI_EOP_TWSI_STAT register.
 */
static void octeon_i2c_int_enable(struct octeon_i2c *i2c)
{
        octeon_i2c_write_int(i2c, 0x40);
}

/**
 * octeon_i2c_int_disable - disable the TS interrupt.
 * @i2c: The struct octeon_i2c.
 */
static void octeon_i2c_int_disable(struct octeon_i2c *i2c)
{
        octeon_i2c_write_int(i2c, 0);
}

/**
 * octeon_i2c_unblock - unblock the bus.
 * @i2c: The struct octeon_i2c.
 *
 * If there was a reset while a device was driving 0 to bus,
 * bus is blocked. We toggle it free manually by some clock
 * cycles and send a stop.
 */
static void octeon_i2c_unblock(struct octeon_i2c *i2c)
{
        int i;

        dev_dbg(i2c->dev, "%s\n", __func__);
        for (i = 0; i < 9; i++) {
                octeon_i2c_write_int(i2c, 0x0);
                udelay(5);
                octeon_i2c_write_int(i2c, 0x200);
                udelay(5);
        }
        octeon_i2c_write_int(i2c, 0x300);
        udelay(5);
        octeon_i2c_write_int(i2c, 0x100);
        udelay(5);
        octeon_i2c_write_int(i2c, 0x0);
}

/**
 * octeon_i2c_isr - the interrupt service routine.
 * @int: The irq, unused.
 * @dev_id: Our struct octeon_i2c.
 */
static irqreturn_t octeon_i2c_isr(int irq, void *dev_id)
{
        struct octeon_i2c *i2c = dev_id;

        octeon_i2c_int_disable(i2c);
        wake_up(&i2c->queue);

        return IRQ_HANDLED;
}


static int octeon_i2c_test_iflg(struct octeon_i2c *i2c)
{
        return (octeon_i2c_read_sw(i2c, SW_TWSI_EOP_TWSI_CTL) & TWSI_CTL_IFLG) != 0;
}

/**
 * octeon_i2c_wait - wait for the IFLG to be set.
 * @i2c: The struct octeon_i2c.
 *
 * Returns 0 on success, otherwise a negative errno.
 */
static int octeon_i2c_wait(struct octeon_i2c *i2c)
{
        int result;

        octeon_i2c_int_enable(i2c);

        result = wait_event_timeout(i2c->queue,
                                        octeon_i2c_test_iflg(i2c),
                                        i2c->adap.timeout);

        octeon_i2c_int_disable(i2c);

        if (result < 0) {
                dev_dbg(i2c->dev, "%s: wait interrupted\n", __func__);
                return result;
        } else if (result == 0) {
                dev_dbg(i2c->dev, "%s: timeout\n", __func__);
                return -ETIMEDOUT;
        }

        return 0;
}

/**
 * octeon_i2c_start - send START to the bus.
 * @i2c: The struct octeon_i2c.
 *
 * Returns 0 on success, otherwise a negative errno.
 */
static int octeon_i2c_start(struct octeon_i2c *i2c)
{
        u8 data;
        int result;

        octeon_i2c_write_sw(i2c, SW_TWSI_EOP_TWSI_CTL,
                                TWSI_CTL_ENAB | TWSI_CTL_STA);

        result = octeon_i2c_wait(i2c);
        if (result) {
                if (octeon_i2c_read_sw(i2c, SW_TWSI_EOP_TWSI_STAT) == STAT_IDLE) {
                        /*
                         * Controller refused to send start flag May
                         * be a client is holding SDA low - let's try
                         * to free it.
                         */
                        octeon_i2c_unblock(i2c);
                        octeon_i2c_write_sw(i2c, SW_TWSI_EOP_TWSI_CTL,
                                            TWSI_CTL_ENAB | TWSI_CTL_STA);

                        result = octeon_i2c_wait(i2c);
                }
                if (result)
                        return result;
        }

        data = octeon_i2c_read_sw(i2c, SW_TWSI_EOP_TWSI_STAT);
        if ((data != STAT_START) && (data != STAT_RSTART)) {
                dev_err(i2c->dev, "%s: bad status (0x%x)\n", __func__, data);
                return -EIO;
        }

        return 0;
}

/**
 * octeon_i2c_stop - send STOP to the bus.
 * @i2c: The struct octeon_i2c.
 *
 * Returns 0 on success, otherwise a negative errno.
 */
static int octeon_i2c_stop(struct octeon_i2c *i2c)
{
        u8 data;

        octeon_i2c_write_sw(i2c, SW_TWSI_EOP_TWSI_CTL,
                            TWSI_CTL_ENAB | TWSI_CTL_STP);

        data = octeon_i2c_read_sw(i2c, SW_TWSI_EOP_TWSI_STAT);

        if (data != STAT_IDLE) {
                dev_err(i2c->dev, "%s: bad status(0x%x)\n", __func__, data);
                return -EIO;
        }
        return 0;
}

/**
 * octeon_i2c_write - send data to the bus.
 * @i2c: The struct octeon_i2c.
 * @target: Target address.
 * @data: Pointer to the data to be sent.
 * @length: Length of the data.
 *
 * The address is sent over the bus, then the data.
 *
 * Returns 0 on success, otherwise a negative errno.
 */
static int octeon_i2c_write(struct octeon_i2c *i2c, int target,
                            const u8 *data, int length)
{
        int i, result;
        u8 tmp;

        result = octeon_i2c_start(i2c);
        if (result)
                return result;

        octeon_i2c_write_sw(i2c, SW_TWSI_EOP_TWSI_DATA, target << 1);
        octeon_i2c_write_sw(i2c, SW_TWSI_EOP_TWSI_CTL, TWSI_CTL_ENAB);

        result = octeon_i2c_wait(i2c);
        if (result)
                return result;

        for (i = 0; i < length; i++) {
                tmp = octeon_i2c_read_sw(i2c, SW_TWSI_EOP_TWSI_STAT);
                if ((tmp != STAT_TXADDR_ACK) && (tmp != STAT_TXDATA_ACK)) {
                        dev_err(i2c->dev,
                                "%s: bad status before write (0x%x)\n",
                                __func__, tmp);
                        return -EIO;
                }

                octeon_i2c_write_sw(i2c, SW_TWSI_EOP_TWSI_DATA, data[i]);
                octeon_i2c_write_sw(i2c, SW_TWSI_EOP_TWSI_CTL, TWSI_CTL_ENAB);

                result = octeon_i2c_wait(i2c);
                if (result)
                        return result;
        }

        return 0;
}

/**
 * octeon_i2c_read - receive data from the bus.
 * @i2c: The struct octeon_i2c.
 * @target: Target address.
 * @data: Pointer to the location to store the datae .
 * @length: Length of the data.
 *
 * The address is sent over the bus, then the data is read.
 *
 * Returns 0 on success, otherwise a negative errno.
 */
static int octeon_i2c_read(struct octeon_i2c *i2c, int target,
                           u8 *data, int length)
{
        int i, result;
        u8 tmp;

        if (length < 1)
                return -EINVAL;

        result = octeon_i2c_start(i2c);
        if (result)
                return result;

        octeon_i2c_write_sw(i2c, SW_TWSI_EOP_TWSI_DATA, (target<<1) | 1);
        octeon_i2c_write_sw(i2c, SW_TWSI_EOP_TWSI_CTL, TWSI_CTL_ENAB);

        result = octeon_i2c_wait(i2c);
        if (result)
                return result;

        for (i = 0; i < length; i++) {
                tmp = octeon_i2c_read_sw(i2c, SW_TWSI_EOP_TWSI_STAT);
                if ((tmp != STAT_RXDATA_ACK) && (tmp != STAT_RXADDR_ACK)) {
                        dev_err(i2c->dev,
                                "%s: bad status before read (0x%x)\n",
                                __func__, tmp);
                        return -EIO;
                }

                if (i+1 < length)
                        octeon_i2c_write_sw(i2c, SW_TWSI_EOP_TWSI_CTL,
                                                TWSI_CTL_ENAB | TWSI_CTL_AAK);
                else
                        octeon_i2c_write_sw(i2c, SW_TWSI_EOP_TWSI_CTL,
                                                TWSI_CTL_ENAB);

                result = octeon_i2c_wait(i2c);
                if (result)
                        return result;

                data[i] = octeon_i2c_read_sw(i2c, SW_TWSI_EOP_TWSI_DATA);
        }
        return 0;
}

/**
 * octeon_i2c_xfer - The driver's master_xfer function.
 * @adap: Pointer to the i2c_adapter structure.
 * @msgs: Pointer to the messages to be processed.
 * @num: Length of the MSGS array.
 *
 * Returns the number of messages processed, or a negative errno on
 * failure.
 */
static int octeon_i2c_xfer(struct i2c_adapter *adap,
                           struct i2c_msg *msgs,
                           int num)
{
        struct i2c_msg *pmsg;
        int i;
        int ret = 0;
        struct octeon_i2c *i2c = i2c_get_adapdata(adap);

        for (i = 0; ret == 0 && i < num; i++) {
                pmsg = &msgs[i];
                dev_dbg(i2c->dev,
                        "Doing %s %d byte(s) to/from 0x%02x - %d of %d messages\n",
                         pmsg->flags & I2C_M_RD ? "read" : "write",
                         pmsg->len, pmsg->addr, i + 1, num);
                if (pmsg->flags & I2C_M_RD)
                        ret = octeon_i2c_read(i2c, pmsg->addr, pmsg->buf,
                                                pmsg->len);
                else
                        ret = octeon_i2c_write(i2c, pmsg->addr, pmsg->buf,
                                                pmsg->len);
        }
        octeon_i2c_stop(i2c);

        return (ret != 0) ? ret : num;
}

static u32 octeon_i2c_functionality(struct i2c_adapter *adap)
{
        return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
}

static const struct i2c_algorithm octeon_i2c_algo = {
        .master_xfer = octeon_i2c_xfer,
        .functionality = octeon_i2c_functionality,
};

static struct i2c_adapter octeon_i2c_ops = {
        .owner = THIS_MODULE,
        .name = "OCTEON adapter",
        .algo = &octeon_i2c_algo,
        .timeout = HZ / 50,
};

/**
 * octeon_i2c_setclock - Calculate and set clock divisors.
 */
static int octeon_i2c_setclock(struct octeon_i2c *i2c)
{
        int tclk, thp_base, inc, thp_idx, mdiv_idx, ndiv_idx, foscl, diff;
        int thp = 0x18, mdiv = 2, ndiv = 0, delta_hz = 1000000;

        for (ndiv_idx = 0; ndiv_idx < 8 && delta_hz != 0; ndiv_idx++) {
                /*
                 * An mdiv value of less than 2 seems to not work well
                 * with ds1337 RTCs, so we constrain it to larger
                 * values.
                 */
                for (mdiv_idx = 15; mdiv_idx >= 2 && delta_hz != 0; mdiv_idx--) {
                        /*
                         * For given ndiv and mdiv values check the
                         * two closest thp values.
                         */
                        tclk = i2c->twsi_freq * (mdiv_idx + 1) * 10;
                        tclk *= (1 << ndiv_idx);
                        thp_base = (i2c->sys_freq / (tclk * 2)) - 1;
                        for (inc = 0; inc <= 1; inc++) {
                                thp_idx = thp_base + inc;
                                if (thp_idx < 5 || thp_idx > 0xff)
                                        continue;

                                foscl = i2c->sys_freq / (2 * (thp_idx + 1));
                                foscl = foscl / (1 << ndiv_idx);
                                foscl = foscl / (mdiv_idx + 1) / 10;
                                diff = abs(foscl - i2c->twsi_freq);
                                if (diff < delta_hz) {
                                        delta_hz = diff;
                                        thp = thp_idx;
                                        mdiv = mdiv_idx;
                                        ndiv = ndiv_idx;
                                }
                        }
                }
        }
        octeon_i2c_write_sw(i2c, SW_TWSI_OP_TWSI_CLK, thp);
        octeon_i2c_write_sw(i2c, SW_TWSI_EOP_TWSI_CLKCTL, (mdiv << 3) | ndiv);

        return 0;
}

static int octeon_i2c_initlowlevel(struct octeon_i2c *i2c)
{
        u8 status;
        int tries;

        /* disable high level controller, enable bus access */
        octeon_i2c_write_sw(i2c, SW_TWSI_EOP_TWSI_CTL, TWSI_CTL_ENAB);

        /* reset controller */
        octeon_i2c_write_sw(i2c, SW_TWSI_EOP_TWSI_RST, 0);

        for (tries = 10; tries; tries--) {
                udelay(1);
                status = octeon_i2c_read_sw(i2c, SW_TWSI_EOP_TWSI_STAT);
                if (status == STAT_IDLE)
                        return 0;
        }
        dev_err(i2c->dev, "%s: TWSI_RST failed! (0x%x)\n", __func__, status);
        return -EIO;
}

static int octeon_i2c_probe(struct platform_device *pdev)
{
        int irq, result = 0;
        struct octeon_i2c *i2c;
        struct resource *res_mem;

        /* All adaptors have an irq.  */
        irq = platform_get_irq(pdev, 0);
        if (irq < 0)
                return irq;

        i2c = devm_kzalloc(&pdev->dev, sizeof(*i2c), GFP_KERNEL);
        if (!i2c) {
                dev_err(&pdev->dev, "kzalloc failed\n");
                result = -ENOMEM;
                goto out;
        }
        i2c->dev = &pdev->dev;

        res_mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);

        if (res_mem == NULL) {
                dev_err(i2c->dev, "found no memory resource\n");
                result = -ENXIO;
                goto out;
        }
        i2c->twsi_phys = res_mem->start;
        i2c->regsize = resource_size(res_mem);

        /*
         * "clock-rate" is a legacy binding, the official binding is
         * "clock-frequency".  Try the official one first and then
         * fall back if it doesn't exist.
         */
        if (of_property_read_u32(pdev->dev.of_node,
                                 "clock-frequency", &i2c->twsi_freq) &&
            of_property_read_u32(pdev->dev.of_node,
                                 "clock-rate", &i2c->twsi_freq)) {
                dev_err(i2c->dev,
                        "no I2C 'clock-rate' or 'clock-frequency' property\n");
                result = -ENXIO;
                goto out;
        }

        i2c->sys_freq = octeon_get_io_clock_rate();

        if (!devm_request_mem_region(&pdev->dev, i2c->twsi_phys, i2c->regsize,
                                      res_mem->name)) {
                dev_err(i2c->dev, "request_mem_region failed\n");
                goto out;
        }
        i2c->twsi_base = devm_ioremap(&pdev->dev, i2c->twsi_phys, i2c->regsize);

        init_waitqueue_head(&i2c->queue);

        i2c->irq = irq;

        result = devm_request_irq(&pdev->dev, i2c->irq,
                                  octeon_i2c_isr, 0, DRV_NAME, i2c);
        if (result < 0) {
                dev_err(i2c->dev, "failed to attach interrupt\n");
                goto out;
        }

        result = octeon_i2c_initlowlevel(i2c);
        if (result) {
                dev_err(i2c->dev, "init low level failed\n");
                goto  out;
        }

        result = octeon_i2c_setclock(i2c);
        if (result) {
                dev_err(i2c->dev, "clock init failed\n");
                goto  out;
        }

        i2c->adap = octeon_i2c_ops;
        i2c->adap.dev.parent = &pdev->dev;
        i2c->adap.dev.of_node = pdev->dev.of_node;
        i2c_set_adapdata(&i2c->adap, i2c);
        platform_set_drvdata(pdev, i2c);

        result = i2c_add_adapter(&i2c->adap);
        if (result < 0) {
                dev_err(i2c->dev, "failed to add adapter\n");
                goto out;
        }
        dev_info(i2c->dev, "version %s\n", DRV_VERSION);

        return 0;

out:
        return result;
};

static int octeon_i2c_remove(struct platform_device *pdev)
{
        struct octeon_i2c *i2c = platform_get_drvdata(pdev);

        i2c_del_adapter(&i2c->adap);
        return 0;
};

static struct of_device_id octeon_i2c_match[] = {
        {
                .compatible = "cavium,octeon-3860-twsi",
        },
        {},
};
MODULE_DEVICE_TABLE(of, octeon_i2c_match);

static struct platform_driver octeon_i2c_driver = {
        .probe          = octeon_i2c_probe,
        .remove         = octeon_i2c_remove,
        .driver         = {
                .owner  = THIS_MODULE,
                .name   = DRV_NAME,
                .of_match_table = octeon_i2c_match,
        },
};

module_platform_driver(octeon_i2c_driver);

MODULE_AUTHOR("Michael Lawnick <michael.lawnick.ext@nsn.com>");
MODULE_DESCRIPTION("I2C-Bus adapter for Cavium OCTEON processors");
MODULE_LICENSE("GPL");
MODULE_VERSION(DRV_VERSION);