/*
 * MicroWire interface driver for OMAP
 *
 * Copyright 2003 MontaVista Software Inc. <source@mvista.com>
 *
 * Ported to 2.6 OMAP uwire interface.
 * Copyright (C) 2004 Texas Instruments.
 *
 * Generalization patches by Juha Yrjola <juha.yrjola@nokia.com>
 *
 * Copyright (C) 2005 David Brownell (ported to 2.6 SPI interface)
 * Copyright (C) 2006 Nokia
 *
 * Many updates by Imre Deak <imre.deak@nokia.com>
 *
 * 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 SOFTWARE IS PROVIDED "AS IS" AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/delay.h>
#include <linux/platform_device.h>
#include <linux/interrupt.h>
#include <linux/err.h>
#include <linux/clk.h>
#include <linux/slab.h>
#include <linux/device.h>

#include <linux/spi/spi.h>
#include <linux/spi/spi_bitbang.h>
#include <linux/module.h>
#include <linux/io.h>

#include <asm/mach-types.h>
#include <linux/soc/ti/omap1-io.h>
#include <linux/soc/ti/omap1-soc.h>
#include <linux/soc/ti/omap1-mux.h>

/* FIXME address is now a platform device resource,
 * and irqs should show there too...
 */
#define UWIRE_BASE_PHYS         0xFFFB3000

/* uWire Registers: */
#define UWIRE_IO_SIZE 0x20
#define UWIRE_TDR     0x00
#define UWIRE_RDR     0x00
#define UWIRE_CSR     0x01
#define UWIRE_SR1     0x02
#define UWIRE_SR2     0x03
#define UWIRE_SR3     0x04
#define UWIRE_SR4     0x05
#define UWIRE_SR5     0x06

/* CSR bits */
#define RDRB    (1 << 15)
#define CSRB    (1 << 14)
#define START   (1 << 13)
#define CS_CMD  (1 << 12)

/* SR1 or SR2 bits */
#define UWIRE_READ_FALLING_EDGE         0x0001
#define UWIRE_READ_RISING_EDGE          0x0000
#define UWIRE_WRITE_FALLING_EDGE        0x0000
#define UWIRE_WRITE_RISING_EDGE         0x0002
#define UWIRE_CS_ACTIVE_LOW             0x0000
#define UWIRE_CS_ACTIVE_HIGH            0x0004
#define UWIRE_FREQ_DIV_2                0x0000
#define UWIRE_FREQ_DIV_4                0x0008
#define UWIRE_FREQ_DIV_8                0x0010
#define UWIRE_CHK_READY                 0x0020
#define UWIRE_CLK_INVERTED              0x0040


struct uwire_spi {
        struct spi_bitbang      bitbang;
        struct clk              *ck;
};

struct uwire_state {
        unsigned        div1_idx;
};

/* REVISIT compile time constant for idx_shift? */
/*
 * Or, put it in a structure which is used throughout the driver;
 * that avoids having to issue two loads for each bit of static data.
 */
static unsigned int uwire_idx_shift = 2;
static void __iomem *uwire_base;

static inline void uwire_write_reg(int idx, u16 val)
{
        __raw_writew(val, uwire_base + (idx << uwire_idx_shift));
}

static inline u16 uwire_read_reg(int idx)
{
        return __raw_readw(uwire_base + (idx << uwire_idx_shift));
}

static inline void omap_uwire_configure_mode(u8 cs, unsigned long flags)
{
        u16     w, val = 0;
        int     shift, reg;

        if (flags & UWIRE_CLK_INVERTED)
                val ^= 0x03;
        val = flags & 0x3f;
        if (cs & 1)
                shift = 6;
        else
                shift = 0;
        if (cs <= 1)
                reg = UWIRE_SR1;
        else
                reg = UWIRE_SR2;

        w = uwire_read_reg(reg);
        w &= ~(0x3f << shift);
        w |= val << shift;
        uwire_write_reg(reg, w);
}

static int wait_uwire_csr_flag(u16 mask, u16 val, int might_not_catch)
{
        u16 w;
        int c = 0;
        unsigned long max_jiffies = jiffies + HZ;

        for (;;) {
                w = uwire_read_reg(UWIRE_CSR);
                if ((w & mask) == val)
                        break;
                if (time_after(jiffies, max_jiffies)) {
                        printk(KERN_ERR "%s: timeout. reg=%#06x "
                                        "mask=%#06x val=%#06x\n",
                               __func__, w, mask, val);
                        return -1;
                }
                c++;
                if (might_not_catch && c > 64)
                        break;
        }
        return 0;
}

static void uwire_set_clk1_div(int div1_idx)
{
        u16 w;

        w = uwire_read_reg(UWIRE_SR3);
        w &= ~(0x03 << 1);
        w |= div1_idx << 1;
        uwire_write_reg(UWIRE_SR3, w);
}

static void uwire_chipselect(struct spi_device *spi, int value)
{
        struct  uwire_state *ust = spi->controller_state;
        u16     w;
        int     old_cs;


        BUG_ON(wait_uwire_csr_flag(CSRB, 0, 0));

        w = uwire_read_reg(UWIRE_CSR);
        old_cs = (w >> 10) & 0x03;
        if (value == BITBANG_CS_INACTIVE || old_cs != spi_get_chipselect(spi, 0)) {
                /* Deselect this CS, or the previous CS */
                w &= ~CS_CMD;
                uwire_write_reg(UWIRE_CSR, w);
        }
        /* activate specfied chipselect */
        if (value == BITBANG_CS_ACTIVE) {
                uwire_set_clk1_div(ust->div1_idx);
                /* invert clock? */
                if (spi->mode & SPI_CPOL)
                        uwire_write_reg(UWIRE_SR4, 1);
                else
                        uwire_write_reg(UWIRE_SR4, 0);

                w = spi_get_chipselect(spi, 0) << 10;
                w |= CS_CMD;
                uwire_write_reg(UWIRE_CSR, w);
        }
}

static int uwire_txrx(struct spi_device *spi, struct spi_transfer *t)
{
        unsigned        len = t->len;
        unsigned        bits = t->bits_per_word;
        unsigned        bytes;
        u16             val, w;
        int             status = 0;

        if (!t->tx_buf && !t->rx_buf)
                return 0;

        w = spi_get_chipselect(spi, 0) << 10;
        w |= CS_CMD;

        if (t->tx_buf) {
                const u8        *buf = t->tx_buf;

                /* NOTE:  DMA could be used for TX transfers */

                /* write one or two bytes at a time */
                while (len >= 1) {
                        /* tx bit 15 is first sent; we byteswap multibyte words
                         * (msb-first) on the way out from memory.
                         */
                        val = *buf++;
                        if (bits > 8) {
                                bytes = 2;
                                val |= *buf++ << 8;
                        } else
                                bytes = 1;
                        val <<= 16 - bits;

#ifdef  VERBOSE
                        pr_debug("%s: write-%d =%04x\n",
                                        dev_name(&spi->dev), bits, val);
#endif
                        if (wait_uwire_csr_flag(CSRB, 0, 0))
                                goto eio;

                        uwire_write_reg(UWIRE_TDR, val);

                        /* start write */
                        val = START | w | (bits << 5);

                        uwire_write_reg(UWIRE_CSR, val);
                        len -= bytes;

                        /* Wait till write actually starts.
                         * This is needed with MPU clock 60+ MHz.
                         * REVISIT: we may not have time to catch it...
                         */
                        if (wait_uwire_csr_flag(CSRB, CSRB, 1))
                                goto eio;

                        status += bytes;
                }

                /* REVISIT:  save this for later to get more i/o overlap */
                if (wait_uwire_csr_flag(CSRB, 0, 0))
                        goto eio;

        } else if (t->rx_buf) {
                u8              *buf = t->rx_buf;

                /* read one or two bytes at a time */
                while (len) {
                        if (bits > 8) {
                                bytes = 2;
                        } else
                                bytes = 1;

                        /* start read */
                        val = START | w | (bits << 0);
                        uwire_write_reg(UWIRE_CSR, val);
                        len -= bytes;

                        /* Wait till read actually starts */
                        (void) wait_uwire_csr_flag(CSRB, CSRB, 1);

                        if (wait_uwire_csr_flag(RDRB | CSRB,
                                                RDRB, 0))
                                goto eio;

                        /* rx bit 0 is last received; multibyte words will
                         * be properly byteswapped on the way to memory.
                         */
                        val = uwire_read_reg(UWIRE_RDR);
                        val &= (1 << bits) - 1;
                        *buf++ = (u8) val;
                        if (bytes == 2)
                                *buf++ = val >> 8;
                        status += bytes;
#ifdef  VERBOSE
                        pr_debug("%s: read-%d =%04x\n",
                                        dev_name(&spi->dev), bits, val);
#endif

                }
        }
        return status;
eio:
        return -EIO;
}

static int uwire_setup_transfer(struct spi_device *spi, struct spi_transfer *t)
{
        struct uwire_state      *ust = spi->controller_state;
        struct uwire_spi        *uwire;
        unsigned                flags = 0;
        unsigned                hz;
        unsigned long           rate;
        int                     div1_idx;
        int                     div1;
        int                     div2;
        int                     status;

        uwire = spi_controller_get_devdata(spi->controller);

        /* mode 0..3, clock inverted separately;
         * standard nCS signaling;
         * don't treat DI=high as "not ready"
         */
        if (spi->mode & SPI_CS_HIGH)
                flags |= UWIRE_CS_ACTIVE_HIGH;

        if (spi->mode & SPI_CPOL)
                flags |= UWIRE_CLK_INVERTED;

        switch (spi->mode & SPI_MODE_X_MASK) {
        case SPI_MODE_0:
        case SPI_MODE_3:
                flags |= UWIRE_WRITE_FALLING_EDGE | UWIRE_READ_RISING_EDGE;
                break;
        case SPI_MODE_1:
        case SPI_MODE_2:
                flags |= UWIRE_WRITE_RISING_EDGE | UWIRE_READ_FALLING_EDGE;
                break;
        }

        /* assume it's already enabled */
        rate = clk_get_rate(uwire->ck);

        if (t != NULL)
                hz = t->speed_hz;
        else
                hz = spi->max_speed_hz;

        if (!hz) {
                pr_debug("%s: zero speed?\n", dev_name(&spi->dev));
                status = -EINVAL;
                goto done;
        }

        /* F_INT = mpu_xor_clk / DIV1 */
        for (div1_idx = 0; div1_idx < 4; div1_idx++) {
                switch (div1_idx) {
                case 0:
                        div1 = 2;
                        break;
                case 1:
                        div1 = 4;
                        break;
                case 2:
                        div1 = 7;
                        break;
                default:
                case 3:
                        div1 = 10;
                        break;
                }
                div2 = (rate / div1 + hz - 1) / hz;
                if (div2 <= 8)
                        break;
        }
        if (div1_idx == 4) {
                pr_debug("%s: lowest clock %ld, need %d\n",
                        dev_name(&spi->dev), rate / 10 / 8, hz);
                status = -EDOM;
                goto done;
        }

        /* we have to cache this and reset in uwire_chipselect as this is a
         * global parameter and another uwire device can change it under
         * us */
        ust->div1_idx = div1_idx;
        uwire_set_clk1_div(div1_idx);

        rate /= div1;

        switch (div2) {
        case 0:
        case 1:
        case 2:
                flags |= UWIRE_FREQ_DIV_2;
                rate /= 2;
                break;
        case 3:
        case 4:
                flags |= UWIRE_FREQ_DIV_4;
                rate /= 4;
                break;
        case 5:
        case 6:
        case 7:
        case 8:
                flags |= UWIRE_FREQ_DIV_8;
                rate /= 8;
                break;
        }
        omap_uwire_configure_mode(spi_get_chipselect(spi, 0), flags);
        pr_debug("%s: uwire flags %02x, armxor %lu KHz, SCK %lu KHz\n",
                        __func__, flags,
                        clk_get_rate(uwire->ck) / 1000,
                        rate / 1000);
        status = 0;
done:
        return status;
}

static int uwire_setup(struct spi_device *spi)
{
        struct uwire_state *ust = spi->controller_state;
        bool initial_setup = false;
        int status;

        if (ust == NULL) {
                ust = kzalloc_obj(*ust);
                if (ust == NULL)
                        return -ENOMEM;
                spi->controller_state = ust;
                initial_setup = true;
        }

        status = uwire_setup_transfer(spi, NULL);
        if (status && initial_setup)
                kfree(ust);

        return status;
}

static void uwire_cleanup(struct spi_device *spi)
{
        kfree(spi->controller_state);
}

static void uwire_off(struct uwire_spi *uwire)
{
        uwire_write_reg(UWIRE_SR3, 0);
        clk_disable_unprepare(uwire->ck);
        spi_controller_put(uwire->bitbang.ctlr);
}

static int uwire_probe(struct platform_device *pdev)
{
        struct spi_controller   *host;
        struct uwire_spi        *uwire;
        int                     status;

        host = spi_alloc_host(&pdev->dev, sizeof(*uwire));
        if (!host)
                return -ENODEV;

        uwire = spi_controller_get_devdata(host);

        uwire_base = devm_ioremap(&pdev->dev, UWIRE_BASE_PHYS, UWIRE_IO_SIZE);
        if (!uwire_base) {
                dev_dbg(&pdev->dev, "can't ioremap UWIRE\n");
                spi_controller_put(host);
                return -ENOMEM;
        }

        platform_set_drvdata(pdev, uwire);

        uwire->ck = devm_clk_get(&pdev->dev, "fck");
        if (IS_ERR(uwire->ck)) {
                status = PTR_ERR(uwire->ck);
                dev_dbg(&pdev->dev, "no functional clock?\n");
                spi_controller_put(host);
                return status;
        }
        clk_prepare_enable(uwire->ck);

        uwire_write_reg(UWIRE_SR3, 1);

        /* the spi->mode bits understood by this driver: */
        host->mode_bits = SPI_CPOL | SPI_CPHA | SPI_CS_HIGH;
        host->bits_per_word_mask = SPI_BPW_RANGE_MASK(1, 16);
        host->flags = SPI_CONTROLLER_HALF_DUPLEX;

        host->bus_num = 2;      /* "official" */
        host->num_chipselect = 4;
        host->setup = uwire_setup;
        host->cleanup = uwire_cleanup;

        uwire->bitbang.ctlr = host;
        uwire->bitbang.chipselect = uwire_chipselect;
        uwire->bitbang.setup_transfer = uwire_setup_transfer;
        uwire->bitbang.txrx_bufs = uwire_txrx;

        status = spi_bitbang_start(&uwire->bitbang);
        if (status < 0) {
                uwire_off(uwire);
        }
        return status;
}

static void uwire_remove(struct platform_device *pdev)
{
        struct uwire_spi        *uwire = platform_get_drvdata(pdev);

        // FIXME remove all child devices, somewhere ...

        spi_bitbang_stop(&uwire->bitbang);
        uwire_off(uwire);
}

/* work with hotplug and coldplug */
MODULE_ALIAS("platform:omap_uwire");

static struct platform_driver uwire_driver = {
        .driver = {
                .name           = "omap_uwire",
        },
        .probe = uwire_probe,
        .remove = uwire_remove,
        // suspend ... unuse ck
        // resume ... use ck
};

static int __init omap_uwire_init(void)
{
        return platform_driver_register(&uwire_driver);
}

static void __exit omap_uwire_exit(void)
{
        platform_driver_unregister(&uwire_driver);
}

subsys_initcall(omap_uwire_init);
module_exit(omap_uwire_exit);

MODULE_DESCRIPTION("MicroWire interface driver for OMAP");
MODULE_LICENSE("GPL");