/*
 * SPI_PPC4XX SPI controller driver.
 *
 * Copyright (C) 2007 Gary Jennejohn <garyj@denx.de>
 * Copyright 2008 Stefan Roese <sr@denx.de>, DENX Software Engineering
 * Copyright 2009 Harris Corporation, Steven A. Falco <sfalco@harris.com>
 *
 * Based in part on drivers/spi/spi_s3c24xx.c
 *
 * Copyright (c) 2006 Ben Dooks
 * Copyright (c) 2006 Simtec Electronics
 *      Ben Dooks <ben@simtec.co.uk>
 *
 * 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.
 */

/*
 * The PPC4xx SPI controller has no FIFO so each sent/received byte will
 * generate an interrupt to the CPU. This can cause high CPU utilization.
 * This driver allows platforms to reduce the interrupt load on the CPU
 * during SPI transfers by setting max_speed_hz via the device tree.
 */

#include <linux/module.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/errno.h>
#include <linux/wait.h>
#include <linux/of_address.h>
#include <linux/of_irq.h>
#include <linux/of_platform.h>
#include <linux/of_gpio.h>
#include <linux/interrupt.h>
#include <linux/delay.h>

#include <linux/gpio.h>
#include <linux/spi/spi.h>
#include <linux/spi/spi_bitbang.h>

#include <asm/io.h>
#include <asm/dcr.h>
#include <asm/dcr-regs.h>

/* bits in mode register - bit 0 is MSb */

/*
 * SPI_PPC4XX_MODE_SCP = 0 means "data latched on trailing edge of clock"
 * SPI_PPC4XX_MODE_SCP = 1 means "data latched on leading edge of clock"
 * Note: This is the inverse of CPHA.
 */
#define SPI_PPC4XX_MODE_SCP     (0x80 >> 3)

/* SPI_PPC4XX_MODE_SPE = 1 means "port enabled" */
#define SPI_PPC4XX_MODE_SPE     (0x80 >> 4)

/*
 * SPI_PPC4XX_MODE_RD = 0 means "MSB first" - this is the normal mode
 * SPI_PPC4XX_MODE_RD = 1 means "LSB first" - this is bit-reversed mode
 * Note: This is identical to SPI_LSB_FIRST.
 */
#define SPI_PPC4XX_MODE_RD      (0x80 >> 5)

/*
 * SPI_PPC4XX_MODE_CI = 0 means "clock idles low"
 * SPI_PPC4XX_MODE_CI = 1 means "clock idles high"
 * Note: This is identical to CPOL.
 */
#define SPI_PPC4XX_MODE_CI      (0x80 >> 6)

/*
 * SPI_PPC4XX_MODE_IL = 0 means "loopback disable"
 * SPI_PPC4XX_MODE_IL = 1 means "loopback enable"
 */
#define SPI_PPC4XX_MODE_IL      (0x80 >> 7)

/* bits in control register */
/* starts a transfer when set */
#define SPI_PPC4XX_CR_STR       (0x80 >> 7)

/* bits in status register */
/* port is busy with a transfer */
#define SPI_PPC4XX_SR_BSY       (0x80 >> 6)
/* RxD ready */
#define SPI_PPC4XX_SR_RBR       (0x80 >> 7)

/* clock settings (SCP and CI) for various SPI modes */
#define SPI_CLK_MODE0   (SPI_PPC4XX_MODE_SCP | 0)
#define SPI_CLK_MODE1   (0 | 0)
#define SPI_CLK_MODE2   (SPI_PPC4XX_MODE_SCP | SPI_PPC4XX_MODE_CI)
#define SPI_CLK_MODE3   (0 | SPI_PPC4XX_MODE_CI)

#define DRIVER_NAME     "spi_ppc4xx_of"

struct spi_ppc4xx_regs {
        u8 mode;
        u8 rxd;
        u8 txd;
        u8 cr;
        u8 sr;
        u8 dummy;
        /*
         * Clock divisor modulus register
         * This uses the following formula:
         *    SCPClkOut = OPBCLK/(4(CDM + 1))
         * or
         *    CDM = (OPBCLK/4*SCPClkOut) - 1
         * bit 0 is the MSb!
         */
        u8 cdm;
};

/* SPI Controller driver's private data. */
struct ppc4xx_spi {
        /* bitbang has to be first */
        struct spi_bitbang bitbang;
        struct completion done;

        u64 mapbase;
        u64 mapsize;
        int irqnum;
        /* need this to set the SPI clock */
        unsigned int opb_freq;

        /* for transfers */
        int len;
        int count;
        /* data buffers */
        const unsigned char *tx;
        unsigned char *rx;

        int *gpios;

        struct spi_ppc4xx_regs __iomem *regs; /* pointer to the registers */
        struct spi_master *master;
        struct device *dev;
};

/* need this so we can set the clock in the chipselect routine */
struct spi_ppc4xx_cs {
        u8 mode;
};

static int spi_ppc4xx_txrx(struct spi_device *spi, struct spi_transfer *t)
{
        struct ppc4xx_spi *hw;
        u8 data;

        dev_dbg(&spi->dev, "txrx: tx %p, rx %p, len %d\n",
                t->tx_buf, t->rx_buf, t->len);

        hw = spi_master_get_devdata(spi->master);

        hw->tx = t->tx_buf;
        hw->rx = t->rx_buf;
        hw->len = t->len;
        hw->count = 0;

        /* send the first byte */
        data = hw->tx ? hw->tx[0] : 0;
        out_8(&hw->regs->txd, data);
        out_8(&hw->regs->cr, SPI_PPC4XX_CR_STR);
        wait_for_completion(&hw->done);

        return hw->count;
}

static int spi_ppc4xx_setupxfer(struct spi_device *spi, struct spi_transfer *t)
{
        struct ppc4xx_spi *hw = spi_master_get_devdata(spi->master);
        struct spi_ppc4xx_cs *cs = spi->controller_state;
        int scr;
        u8 cdm = 0;
        u32 speed;
        u8 bits_per_word;

        /* Start with the generic configuration for this device. */
        bits_per_word = spi->bits_per_word;
        speed = spi->max_speed_hz;

        /*
         * Modify the configuration if the transfer overrides it.  Do not allow
         * the transfer to overwrite the generic configuration with zeros.
         */
        if (t) {
                if (t->bits_per_word)
                        bits_per_word = t->bits_per_word;

                if (t->speed_hz)
                        speed = min(t->speed_hz, spi->max_speed_hz);
        }

        if (!speed || (speed > spi->max_speed_hz)) {
                dev_err(&spi->dev, "invalid speed_hz (%d)\n", speed);
                return -EINVAL;
        }

        /* Write new configuration */
        out_8(&hw->regs->mode, cs->mode);

        /* Set the clock */
        /* opb_freq was already divided by 4 */
        scr = (hw->opb_freq / speed) - 1;
        if (scr > 0)
                cdm = min(scr, 0xff);

        dev_dbg(&spi->dev, "setting pre-scaler to %d (hz %d)\n", cdm, speed);

        if (in_8(&hw->regs->cdm) != cdm)
                out_8(&hw->regs->cdm, cdm);

        mutex_lock(&hw->bitbang.lock);
        if (!hw->bitbang.busy) {
                hw->bitbang.chipselect(spi, BITBANG_CS_INACTIVE);
                /* Need to ndelay here? */
        }
        mutex_unlock(&hw->bitbang.lock);

        return 0;
}

static int spi_ppc4xx_setup(struct spi_device *spi)
{
        struct spi_ppc4xx_cs *cs = spi->controller_state;

        if (!spi->max_speed_hz) {
                dev_err(&spi->dev, "invalid max_speed_hz (must be non-zero)\n");
                return -EINVAL;
        }

        if (cs == NULL) {
                cs = kzalloc(sizeof *cs, GFP_KERNEL);
                if (!cs)
                        return -ENOMEM;
                spi->controller_state = cs;
        }

        /*
         * We set all bits of the SPI0_MODE register, so,
         * no need to read-modify-write
         */
        cs->mode = SPI_PPC4XX_MODE_SPE;

        switch (spi->mode & (SPI_CPHA | SPI_CPOL)) {
        case SPI_MODE_0:
                cs->mode |= SPI_CLK_MODE0;
                break;
        case SPI_MODE_1:
                cs->mode |= SPI_CLK_MODE1;
                break;
        case SPI_MODE_2:
                cs->mode |= SPI_CLK_MODE2;
                break;
        case SPI_MODE_3:
                cs->mode |= SPI_CLK_MODE3;
                break;
        }

        if (spi->mode & SPI_LSB_FIRST)
                cs->mode |= SPI_PPC4XX_MODE_RD;

        return 0;
}

static void spi_ppc4xx_chipsel(struct spi_device *spi, int value)
{
        struct ppc4xx_spi *hw = spi_master_get_devdata(spi->master);
        unsigned int cs = spi->chip_select;
        unsigned int cspol;

        /*
         * If there are no chip selects at all, or if this is the special
         * case of a non-existent (dummy) chip select, do nothing.
         */

        if (!hw->master->num_chipselect || hw->gpios[cs] == -EEXIST)
                return;

        cspol = spi->mode & SPI_CS_HIGH ? 1 : 0;
        if (value == BITBANG_CS_INACTIVE)
                cspol = !cspol;

        gpio_set_value(hw->gpios[cs], cspol);
}

static irqreturn_t spi_ppc4xx_int(int irq, void *dev_id)
{
        struct ppc4xx_spi *hw;
        u8 status;
        u8 data;
        unsigned int count;

        hw = (struct ppc4xx_spi *)dev_id;

        status = in_8(&hw->regs->sr);
        if (!status)
                return IRQ_NONE;

        /*
         * BSY de-asserts one cycle after the transfer is complete.  The
         * interrupt is asserted after the transfer is complete.  The exact
         * relationship is not documented, hence this code.
         */

        if (unlikely(status & SPI_PPC4XX_SR_BSY)) {
                u8 lstatus;
                int cnt = 0;

                dev_dbg(hw->dev, "got interrupt but spi still busy?\n");
                do {
                        ndelay(10);
                        lstatus = in_8(&hw->regs->sr);
                } while (++cnt < 100 && lstatus & SPI_PPC4XX_SR_BSY);

                if (cnt >= 100) {
                        dev_err(hw->dev, "busywait: too many loops!\n");
                        complete(&hw->done);
                        return IRQ_HANDLED;
                } else {
                        /* status is always 1 (RBR) here */
                        status = in_8(&hw->regs->sr);
                        dev_dbg(hw->dev, "loops %d status %x\n", cnt, status);
                }
        }

        count = hw->count;
        hw->count++;

        /* RBR triggered this interrupt.  Therefore, data must be ready. */
        data = in_8(&hw->regs->rxd);
        if (hw->rx)
                hw->rx[count] = data;

        count++;

        if (count < hw->len) {
                data = hw->tx ? hw->tx[count] : 0;
                out_8(&hw->regs->txd, data);
                out_8(&hw->regs->cr, SPI_PPC4XX_CR_STR);
        } else {
                complete(&hw->done);
        }

        return IRQ_HANDLED;
}

static void spi_ppc4xx_cleanup(struct spi_device *spi)
{
        kfree(spi->controller_state);
}

static void spi_ppc4xx_enable(struct ppc4xx_spi *hw)
{
        /*
         * On all 4xx PPC's the SPI bus is shared/multiplexed with
         * the 2nd I2C bus. We need to enable the the SPI bus before
         * using it.
         */

        /* need to clear bit 14 to enable SPC */
        dcri_clrset(SDR0, SDR0_PFC1, 0x80000000 >> 14, 0);
}

static void free_gpios(struct ppc4xx_spi *hw)
{
        if (hw->master->num_chipselect) {
                int i;
                for (i = 0; i < hw->master->num_chipselect; i++)
                        if (gpio_is_valid(hw->gpios[i]))
                                gpio_free(hw->gpios[i]);

                kfree(hw->gpios);
                hw->gpios = NULL;
        }
}

/*
 * platform_device layer stuff...
 */
static int spi_ppc4xx_of_probe(struct platform_device *op)
{
        struct ppc4xx_spi *hw;
        struct spi_master *master;
        struct spi_bitbang *bbp;
        struct resource resource;
        struct device_node *np = op->dev.of_node;
        struct device *dev = &op->dev;
        struct device_node *opbnp;
        int ret;
        int num_gpios;
        const unsigned int *clk;

        master = spi_alloc_master(dev, sizeof *hw);
        if (master == NULL)
                return -ENOMEM;
        master->dev.of_node = np;
        platform_set_drvdata(op, master);
        hw = spi_master_get_devdata(master);
        hw->master = master;
        hw->dev = dev;

        init_completion(&hw->done);

        /*
         * A count of zero implies a single SPI device without any chip-select.
         * Note that of_gpio_count counts all gpios assigned to this spi master.
         * This includes both "null" gpio's and real ones.
         */
        num_gpios = of_gpio_count(np);
        if (num_gpios > 0) {
                int i;

                hw->gpios = kcalloc(num_gpios, sizeof(*hw->gpios), GFP_KERNEL);
                if (!hw->gpios) {
                        ret = -ENOMEM;
                        goto free_master;
                }

                for (i = 0; i < num_gpios; i++) {
                        int gpio;
                        enum of_gpio_flags flags;

                        gpio = of_get_gpio_flags(np, i, &flags);
                        hw->gpios[i] = gpio;

                        if (gpio_is_valid(gpio)) {
                                /* Real CS - set the initial state. */
                                ret = gpio_request(gpio, np->name);
                                if (ret < 0) {
                                        dev_err(dev,
                                                "can't request gpio #%d: %d\n",
                                                i, ret);
                                        goto free_gpios;
                                }

                                gpio_direction_output(gpio,
                                                !!(flags & OF_GPIO_ACTIVE_LOW));
                        } else if (gpio == -EEXIST) {
                                ; /* No CS, but that's OK. */
                        } else {
                                dev_err(dev, "invalid gpio #%d: %d\n", i, gpio);
                                ret = -EINVAL;
                                goto free_gpios;
                        }
                }
        }

        /* Setup the state for the bitbang driver */
        bbp = &hw->bitbang;
        bbp->master = hw->master;
        bbp->setup_transfer = spi_ppc4xx_setupxfer;
        bbp->chipselect = spi_ppc4xx_chipsel;
        bbp->txrx_bufs = spi_ppc4xx_txrx;
        bbp->use_dma = 0;
        bbp->master->setup = spi_ppc4xx_setup;
        bbp->master->cleanup = spi_ppc4xx_cleanup;
        bbp->master->bits_per_word_mask = SPI_BPW_MASK(8);

        /* the spi->mode bits understood by this driver: */
        bbp->master->mode_bits =
                SPI_CPHA | SPI_CPOL | SPI_CS_HIGH | SPI_LSB_FIRST;

        /* this many pins in all GPIO controllers */
        bbp->master->num_chipselect = num_gpios > 0 ? num_gpios : 0;

        /* Get the clock for the OPB */
        opbnp = of_find_compatible_node(NULL, NULL, "ibm,opb");
        if (opbnp == NULL) {
                dev_err(dev, "OPB: cannot find node\n");
                ret = -ENODEV;
                goto free_gpios;
        }
        /* Get the clock (Hz) for the OPB */
        clk = of_get_property(opbnp, "clock-frequency", NULL);
        if (clk == NULL) {
                dev_err(dev, "OPB: no clock-frequency property set\n");
                of_node_put(opbnp);
                ret = -ENODEV;
                goto free_gpios;
        }
        hw->opb_freq = *clk;
        hw->opb_freq >>= 2;
        of_node_put(opbnp);

        ret = of_address_to_resource(np, 0, &resource);
        if (ret) {
                dev_err(dev, "error while parsing device node resource\n");
                goto free_gpios;
        }
        hw->mapbase = resource.start;
        hw->mapsize = resource_size(&resource);

        /* Sanity check */
        if (hw->mapsize < sizeof(struct spi_ppc4xx_regs)) {
                dev_err(dev, "too small to map registers\n");
                ret = -EINVAL;
                goto free_gpios;
        }

        /* Request IRQ */
        hw->irqnum = irq_of_parse_and_map(np, 0);
        ret = request_irq(hw->irqnum, spi_ppc4xx_int,
                          0, "spi_ppc4xx_of", (void *)hw);
        if (ret) {
                dev_err(dev, "unable to allocate interrupt\n");
                goto free_gpios;
        }

        if (!request_mem_region(hw->mapbase, hw->mapsize, DRIVER_NAME)) {
                dev_err(dev, "resource unavailable\n");
                ret = -EBUSY;
                goto request_mem_error;
        }

        hw->regs = ioremap(hw->mapbase, sizeof(struct spi_ppc4xx_regs));

        if (!hw->regs) {
                dev_err(dev, "unable to memory map registers\n");
                ret = -ENXIO;
                goto map_io_error;
        }

        spi_ppc4xx_enable(hw);

        /* Finally register our spi controller */
        dev->dma_mask = 0;
        ret = spi_bitbang_start(bbp);
        if (ret) {
                dev_err(dev, "failed to register SPI master\n");
                goto unmap_regs;
        }

        dev_info(dev, "driver initialized\n");

        return 0;

unmap_regs:
        iounmap(hw->regs);
map_io_error:
        release_mem_region(hw->mapbase, hw->mapsize);
request_mem_error:
        free_irq(hw->irqnum, hw);
free_gpios:
        free_gpios(hw);
free_master:
        spi_master_put(master);

        dev_err(dev, "initialization failed\n");
        return ret;
}

static int spi_ppc4xx_of_remove(struct platform_device *op)
{
        struct spi_master *master = platform_get_drvdata(op);
        struct ppc4xx_spi *hw = spi_master_get_devdata(master);

        spi_bitbang_stop(&hw->bitbang);
        release_mem_region(hw->mapbase, hw->mapsize);
        free_irq(hw->irqnum, hw);
        iounmap(hw->regs);
        free_gpios(hw);
        spi_master_put(master);
        return 0;
}

static const struct of_device_id spi_ppc4xx_of_match[] = {
        { .compatible = "ibm,ppc4xx-spi", },
        {},
};

MODULE_DEVICE_TABLE(of, spi_ppc4xx_of_match);

static struct platform_driver spi_ppc4xx_of_driver = {
        .probe = spi_ppc4xx_of_probe,
        .remove = spi_ppc4xx_of_remove,
        .driver = {
                .name = DRIVER_NAME,
                .of_match_table = spi_ppc4xx_of_match,
        },
};
module_platform_driver(spi_ppc4xx_of_driver);

MODULE_AUTHOR("Gary Jennejohn & Stefan Roese");
MODULE_DESCRIPTION("Simple PPC4xx SPI Driver");
MODULE_LICENSE("GPL");