/*
 * MPC512x PSC in SPI mode driver.
 *
 * Copyright (C) 2007,2008 Freescale Semiconductor Inc.
 * Original port from 52xx driver:
 *      Hongjun Chen <hong-jun.chen@freescale.com>
 *
 * Fork of mpc52xx_psc_spi.c:
 *      Copyright (C) 2006 TOPTICA Photonics AG., Dragos Carp
 *
 * 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.
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/errno.h>
#include <linux/interrupt.h>
#include <linux/of_address.h>
#include <linux/of_platform.h>
#include <linux/completion.h>
#include <linux/io.h>
#include <linux/delay.h>
#include <linux/clk.h>
#include <linux/spi/spi.h>
#include <linux/fsl_devices.h>
#include <linux/gpio.h>
#include <asm/mpc52xx_psc.h>

struct mpc512x_psc_spi {
        void (*cs_control)(struct spi_device *spi, bool on);

        /* driver internal data */
        struct mpc52xx_psc __iomem *psc;
        struct mpc512x_psc_fifo __iomem *fifo;
        unsigned int irq;
        u8 bits_per_word;
        struct clk *clk_mclk;
        u32 mclk_rate;

        struct completion txisrdone;
};

/* controller state */
struct mpc512x_psc_spi_cs {
        int bits_per_word;
        int speed_hz;
};

/* set clock freq, clock ramp, bits per work
 * if t is NULL then reset the values to the default values
 */
static int mpc512x_psc_spi_transfer_setup(struct spi_device *spi,
                                          struct spi_transfer *t)
{
        struct mpc512x_psc_spi_cs *cs = spi->controller_state;

        cs->speed_hz = (t && t->speed_hz)
            ? t->speed_hz : spi->max_speed_hz;
        cs->bits_per_word = (t && t->bits_per_word)
            ? t->bits_per_word : spi->bits_per_word;
        cs->bits_per_word = ((cs->bits_per_word + 7) / 8) * 8;
        return 0;
}

static void mpc512x_psc_spi_activate_cs(struct spi_device *spi)
{
        struct mpc512x_psc_spi_cs *cs = spi->controller_state;
        struct mpc512x_psc_spi *mps = spi_master_get_devdata(spi->master);
        struct mpc52xx_psc __iomem *psc = mps->psc;
        u32 sicr;
        u32 ccr;
        int speed;
        u16 bclkdiv;

        sicr = in_be32(&psc->sicr);

        /* Set clock phase and polarity */
        if (spi->mode & SPI_CPHA)
                sicr |= 0x00001000;
        else
                sicr &= ~0x00001000;

        if (spi->mode & SPI_CPOL)
                sicr |= 0x00002000;
        else
                sicr &= ~0x00002000;

        if (spi->mode & SPI_LSB_FIRST)
                sicr |= 0x10000000;
        else
                sicr &= ~0x10000000;
        out_be32(&psc->sicr, sicr);

        ccr = in_be32(&psc->ccr);
        ccr &= 0xFF000000;
        speed = cs->speed_hz;
        if (!speed)
                speed = 1000000;        /* default 1MHz */
        bclkdiv = (mps->mclk_rate / speed) - 1;

        ccr |= (((bclkdiv & 0xff) << 16) | (((bclkdiv >> 8) & 0xff) << 8));
        out_be32(&psc->ccr, ccr);
        mps->bits_per_word = cs->bits_per_word;

        if (mps->cs_control && gpio_is_valid(spi->cs_gpio))
                mps->cs_control(spi, (spi->mode & SPI_CS_HIGH) ? 1 : 0);
}

static void mpc512x_psc_spi_deactivate_cs(struct spi_device *spi)
{
        struct mpc512x_psc_spi *mps = spi_master_get_devdata(spi->master);

        if (mps->cs_control && gpio_is_valid(spi->cs_gpio))
                mps->cs_control(spi, (spi->mode & SPI_CS_HIGH) ? 0 : 1);

}

/* extract and scale size field in txsz or rxsz */
#define MPC512x_PSC_FIFO_SZ(sz) ((sz & 0x7ff) << 2);

#define EOFBYTE 1

static int mpc512x_psc_spi_transfer_rxtx(struct spi_device *spi,
                                         struct spi_transfer *t)
{
        struct mpc512x_psc_spi *mps = spi_master_get_devdata(spi->master);
        struct mpc512x_psc_fifo __iomem *fifo = mps->fifo;
        size_t tx_len = t->len;
        size_t rx_len = t->len;
        u8 *tx_buf = (u8 *)t->tx_buf;
        u8 *rx_buf = (u8 *)t->rx_buf;

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

        while (rx_len || tx_len) {
                size_t txcount;
                u8 data;
                size_t fifosz;
                size_t rxcount;
                int rxtries;

                /*
                 * send the TX bytes in as large a chunk as possible
                 * but neither exceed the TX nor the RX FIFOs
                 */
                fifosz = MPC512x_PSC_FIFO_SZ(in_be32(&fifo->txsz));
                txcount = min(fifosz, tx_len);
                fifosz = MPC512x_PSC_FIFO_SZ(in_be32(&fifo->rxsz));
                fifosz -= in_be32(&fifo->rxcnt) + 1;
                txcount = min(fifosz, txcount);
                if (txcount) {

                        /* fill the TX FIFO */
                        while (txcount-- > 0) {
                                data = tx_buf ? *tx_buf++ : 0;
                                if (tx_len == EOFBYTE && t->cs_change)
                                        setbits32(&fifo->txcmd,
                                                  MPC512x_PSC_FIFO_EOF);
                                out_8(&fifo->txdata_8, data);
                                tx_len--;
                        }

                        /* have the ISR trigger when the TX FIFO is empty */
                        INIT_COMPLETION(mps->txisrdone);
                        out_be32(&fifo->txisr, MPC512x_PSC_FIFO_EMPTY);
                        out_be32(&fifo->tximr, MPC512x_PSC_FIFO_EMPTY);
                        wait_for_completion(&mps->txisrdone);
                }

                /*
                 * consume as much RX data as the FIFO holds, while we
                 * iterate over the transfer's TX data length
                 *
                 * only insist in draining all the remaining RX bytes
                 * when the TX bytes were exhausted (that's at the very
                 * end of this transfer, not when still iterating over
                 * the transfer's chunks)
                 */
                rxtries = 50;
                do {

                        /*
                         * grab whatever was in the FIFO when we started
                         * looking, don't bother fetching what was added to
                         * the FIFO while we read from it -- we'll return
                         * here eventually and prefer sending out remaining
                         * TX data
                         */
                        fifosz = in_be32(&fifo->rxcnt);
                        rxcount = min(fifosz, rx_len);
                        while (rxcount-- > 0) {
                                data = in_8(&fifo->rxdata_8);
                                if (rx_buf)
                                        *rx_buf++ = data;
                                rx_len--;
                        }

                        /*
                         * come back later if there still is TX data to send,
                         * bail out of the RX drain loop if all of the TX data
                         * was sent and all of the RX data was received (i.e.
                         * when the transmission has completed)
                         */
                        if (tx_len)
                                break;
                        if (!rx_len)
                                break;

                        /*
                         * TX data transmission has completed while RX data
                         * is still pending -- that's a transient situation
                         * which depends on wire speed and specific
                         * hardware implementation details (buffering) yet
                         * should resolve very quickly
                         *
                         * just yield for a moment to not hog the CPU for
                         * too long when running SPI at low speed
                         *
                         * the timeout range is rather arbitrary and tries
                         * to balance throughput against system load; the
                         * chosen values result in a minimal timeout of 50
                         * times 10us and thus work at speeds as low as
                         * some 20kbps, while the maximum timeout at the
                         * transfer's end could be 5ms _if_ nothing else
                         * ticks in the system _and_ RX data still wasn't
                         * received, which only occurs in situations that
                         * are exceptional; removing the unpredictability
                         * of the timeout either decreases throughput
                         * (longer timeouts), or puts more load on the
                         * system (fixed short timeouts) or requires the
                         * use of a timeout API instead of a counter and an
                         * unknown inner delay
                         */
                        usleep_range(10, 100);

                } while (--rxtries > 0);
                if (!tx_len && rx_len && !rxtries) {
                        /*
                         * not enough RX bytes even after several retries
                         * and the resulting rather long timeout?
                         */
                        rxcount = in_be32(&fifo->rxcnt);
                        dev_warn(&spi->dev,
                                 "short xfer, missing %zd RX bytes, FIFO level %zd\n",
                                 rx_len, rxcount);
                }

                /*
                 * drain and drop RX data which "should not be there" in
                 * the first place, for undisturbed transmission this turns
                 * into a NOP (except for the FIFO level fetch)
                 */
                if (!tx_len && !rx_len) {
                        while (in_be32(&fifo->rxcnt))
                                in_8(&fifo->rxdata_8);
                }

        }
        return 0;
}

static int mpc512x_psc_spi_msg_xfer(struct spi_master *master,
                                    struct spi_message *m)
{
        struct spi_device *spi;
        unsigned cs_change;
        int status;
        struct spi_transfer *t;

        spi = m->spi;
        cs_change = 1;
        status = 0;
        list_for_each_entry(t, &m->transfers, transfer_list) {
                if (t->bits_per_word || t->speed_hz) {
                        status = mpc512x_psc_spi_transfer_setup(spi, t);
                        if (status < 0)
                                break;
                }

                if (cs_change)
                        mpc512x_psc_spi_activate_cs(spi);
                cs_change = t->cs_change;

                status = mpc512x_psc_spi_transfer_rxtx(spi, t);
                if (status)
                        break;
                m->actual_length += t->len;

                if (t->delay_usecs)
                        udelay(t->delay_usecs);

                if (cs_change)
                        mpc512x_psc_spi_deactivate_cs(spi);
        }

        m->status = status;
        m->complete(m->context);

        if (status || !cs_change)
                mpc512x_psc_spi_deactivate_cs(spi);

        mpc512x_psc_spi_transfer_setup(spi, NULL);

        spi_finalize_current_message(master);
        return status;
}

static int mpc512x_psc_spi_prep_xfer_hw(struct spi_master *master)
{
        struct mpc512x_psc_spi *mps = spi_master_get_devdata(master);
        struct mpc52xx_psc __iomem *psc = mps->psc;

        dev_dbg(&master->dev, "%s()\n", __func__);

        /* Zero MR2 */
        in_8(&psc->mode);
        out_8(&psc->mode, 0x0);

        /* enable transmitter/receiver */
        out_8(&psc->command, MPC52xx_PSC_TX_ENABLE | MPC52xx_PSC_RX_ENABLE);

        return 0;
}

static int mpc512x_psc_spi_unprep_xfer_hw(struct spi_master *master)
{
        struct mpc512x_psc_spi *mps = spi_master_get_devdata(master);
        struct mpc52xx_psc __iomem *psc = mps->psc;
        struct mpc512x_psc_fifo __iomem *fifo = mps->fifo;

        dev_dbg(&master->dev, "%s()\n", __func__);

        /* disable transmitter/receiver and fifo interrupt */
        out_8(&psc->command, MPC52xx_PSC_TX_DISABLE | MPC52xx_PSC_RX_DISABLE);
        out_be32(&fifo->tximr, 0);

        return 0;
}

static int mpc512x_psc_spi_setup(struct spi_device *spi)
{
        struct mpc512x_psc_spi_cs *cs = spi->controller_state;
        int ret;

        if (spi->bits_per_word % 8)
                return -EINVAL;

        if (!cs) {
                cs = kzalloc(sizeof *cs, GFP_KERNEL);
                if (!cs)
                        return -ENOMEM;

                if (gpio_is_valid(spi->cs_gpio)) {
                        ret = gpio_request(spi->cs_gpio, dev_name(&spi->dev));
                        if (ret) {
                                dev_err(&spi->dev, "can't get CS gpio: %d\n",
                                        ret);
                                kfree(cs);
                                return ret;
                        }
                        gpio_direction_output(spi->cs_gpio,
                                        spi->mode & SPI_CS_HIGH ? 0 : 1);
                }

                spi->controller_state = cs;
        }

        cs->bits_per_word = spi->bits_per_word;
        cs->speed_hz = spi->max_speed_hz;

        return 0;
}

static void mpc512x_psc_spi_cleanup(struct spi_device *spi)
{
        if (gpio_is_valid(spi->cs_gpio))
                gpio_free(spi->cs_gpio);
        kfree(spi->controller_state);
}

static int mpc512x_psc_spi_port_config(struct spi_master *master,
                                       struct mpc512x_psc_spi *mps)
{
        struct mpc52xx_psc __iomem *psc = mps->psc;
        struct mpc512x_psc_fifo __iomem *fifo = mps->fifo;
        u32 sicr;
        u32 ccr;
        int speed;
        u16 bclkdiv;

        /* Reset the PSC into a known state */
        out_8(&psc->command, MPC52xx_PSC_RST_RX);
        out_8(&psc->command, MPC52xx_PSC_RST_TX);
        out_8(&psc->command, MPC52xx_PSC_TX_DISABLE | MPC52xx_PSC_RX_DISABLE);

        /* Disable psc interrupts all useful interrupts are in fifo */
        out_be16(&psc->isr_imr.imr, 0);

        /* Disable fifo interrupts, will be enabled later */
        out_be32(&fifo->tximr, 0);
        out_be32(&fifo->rximr, 0);

        /* Setup fifo slice address and size */
        /*out_be32(&fifo->txsz, 0x0fe00004);*/
        /*out_be32(&fifo->rxsz, 0x0ff00004);*/

        sicr =  0x01000000 |    /* SIM = 0001 -- 8 bit */
                0x00800000 |    /* GenClk = 1 -- internal clk */
                0x00008000 |    /* SPI = 1 */
                0x00004000 |    /* MSTR = 1   -- SPI master */
                0x00000800;     /* UseEOF = 1 -- SS low until EOF */

        out_be32(&psc->sicr, sicr);

        ccr = in_be32(&psc->ccr);
        ccr &= 0xFF000000;
        speed = 1000000;        /* default 1MHz */
        bclkdiv = (mps->mclk_rate / speed) - 1;
        ccr |= (((bclkdiv & 0xff) << 16) | (((bclkdiv >> 8) & 0xff) << 8));
        out_be32(&psc->ccr, ccr);

        /* Set 2ms DTL delay */
        out_8(&psc->ctur, 0x00);
        out_8(&psc->ctlr, 0x82);

        /* we don't use the alarms */
        out_be32(&fifo->rxalarm, 0xfff);
        out_be32(&fifo->txalarm, 0);

        /* Enable FIFO slices for Rx/Tx */
        out_be32(&fifo->rxcmd,
                 MPC512x_PSC_FIFO_ENABLE_SLICE | MPC512x_PSC_FIFO_ENABLE_DMA);
        out_be32(&fifo->txcmd,
                 MPC512x_PSC_FIFO_ENABLE_SLICE | MPC512x_PSC_FIFO_ENABLE_DMA);

        mps->bits_per_word = 8;

        return 0;
}

static irqreturn_t mpc512x_psc_spi_isr(int irq, void *dev_id)
{
        struct mpc512x_psc_spi *mps = (struct mpc512x_psc_spi *)dev_id;
        struct mpc512x_psc_fifo __iomem *fifo = mps->fifo;

        /* clear interrupt and wake up the rx/tx routine */
        if (in_be32(&fifo->txisr) &
            in_be32(&fifo->tximr) & MPC512x_PSC_FIFO_EMPTY) {
                out_be32(&fifo->txisr, MPC512x_PSC_FIFO_EMPTY);
                out_be32(&fifo->tximr, 0);
                complete(&mps->txisrdone);
                return IRQ_HANDLED;
        }
        return IRQ_NONE;
}

static void mpc512x_spi_cs_control(struct spi_device *spi, bool onoff)
{
        gpio_set_value(spi->cs_gpio, onoff);
}

/* bus_num is used only for the case dev->platform_data == NULL */
static int mpc512x_psc_spi_do_probe(struct device *dev, u32 regaddr,
                                              u32 size, unsigned int irq,
                                              s16 bus_num)
{
        struct fsl_spi_platform_data *pdata = dev_get_platdata(dev);
        struct mpc512x_psc_spi *mps;
        struct spi_master *master;
        int ret;
        void *tempp;
        int psc_num;
        char clk_name[16];
        struct clk *clk;

        master = spi_alloc_master(dev, sizeof *mps);
        if (master == NULL)
                return -ENOMEM;

        dev_set_drvdata(dev, master);
        mps = spi_master_get_devdata(master);
        mps->irq = irq;

        if (pdata == NULL) {
                mps->cs_control = mpc512x_spi_cs_control;
                master->bus_num = bus_num;
        } else {
                mps->cs_control = pdata->cs_control;
                master->bus_num = pdata->bus_num;
                master->num_chipselect = pdata->max_chipselect;
        }

        master->mode_bits = SPI_CPOL | SPI_CPHA | SPI_CS_HIGH | SPI_LSB_FIRST;
        master->setup = mpc512x_psc_spi_setup;
        master->prepare_transfer_hardware = mpc512x_psc_spi_prep_xfer_hw;
        master->transfer_one_message = mpc512x_psc_spi_msg_xfer;
        master->unprepare_transfer_hardware = mpc512x_psc_spi_unprep_xfer_hw;
        master->cleanup = mpc512x_psc_spi_cleanup;
        master->dev.of_node = dev->of_node;

        tempp = ioremap(regaddr, size);
        if (!tempp) {
                dev_err(dev, "could not ioremap I/O port range\n");
                ret = -EFAULT;
                goto free_master;
        }
        mps->psc = tempp;
        mps->fifo =
                (struct mpc512x_psc_fifo *)(tempp + sizeof(struct mpc52xx_psc));

        ret = request_irq(mps->irq, mpc512x_psc_spi_isr, IRQF_SHARED,
                          "mpc512x-psc-spi", mps);
        if (ret)
                goto free_master;
        init_completion(&mps->txisrdone);

        psc_num = master->bus_num;
        snprintf(clk_name, sizeof(clk_name), "psc%d_mclk", psc_num);
        clk = devm_clk_get(dev, clk_name);
        if (IS_ERR(clk)) {
                ret = PTR_ERR(clk);
                goto free_irq;
        }
        ret = clk_prepare_enable(clk);
        if (ret)
                goto free_irq;
        mps->clk_mclk = clk;
        mps->mclk_rate = clk_get_rate(clk);

        ret = mpc512x_psc_spi_port_config(master, mps);
        if (ret < 0)
                goto free_clock;

        ret = spi_register_master(master);
        if (ret < 0)
                goto free_clock;

        return ret;

free_clock:
        clk_disable_unprepare(mps->clk_mclk);
free_irq:
        free_irq(mps->irq, mps);
free_master:
        if (mps->psc)
                iounmap(mps->psc);
        spi_master_put(master);

        return ret;
}

static int mpc512x_psc_spi_do_remove(struct device *dev)
{
        struct spi_master *master = spi_master_get(dev_get_drvdata(dev));
        struct mpc512x_psc_spi *mps = spi_master_get_devdata(master);

        spi_unregister_master(master);
        clk_disable_unprepare(mps->clk_mclk);
        free_irq(mps->irq, mps);
        if (mps->psc)
                iounmap(mps->psc);
        spi_master_put(master);

        return 0;
}

static int mpc512x_psc_spi_of_probe(struct platform_device *op)
{
        const u32 *regaddr_p;
        u64 regaddr64, size64;
        s16 id = -1;

        regaddr_p = of_get_address(op->dev.of_node, 0, &size64, NULL);
        if (!regaddr_p) {
                dev_err(&op->dev, "Invalid PSC address\n");
                return -EINVAL;
        }
        regaddr64 = of_translate_address(op->dev.of_node, regaddr_p);

        /* get PSC id (0..11, used by port_config) */
        id = of_alias_get_id(op->dev.of_node, "spi");
        if (id < 0) {
                dev_err(&op->dev, "no alias id for %s\n",
                        op->dev.of_node->full_name);
                return id;
        }

        return mpc512x_psc_spi_do_probe(&op->dev, (u32) regaddr64, (u32) size64,
                                irq_of_parse_and_map(op->dev.of_node, 0), id);
}

static int mpc512x_psc_spi_of_remove(struct platform_device *op)
{
        return mpc512x_psc_spi_do_remove(&op->dev);
}

static struct of_device_id mpc512x_psc_spi_of_match[] = {
        { .compatible = "fsl,mpc5121-psc-spi", },
        {},
};

MODULE_DEVICE_TABLE(of, mpc512x_psc_spi_of_match);

static struct platform_driver mpc512x_psc_spi_of_driver = {
        .probe = mpc512x_psc_spi_of_probe,
        .remove = mpc512x_psc_spi_of_remove,
        .driver = {
                .name = "mpc512x-psc-spi",
                .owner = THIS_MODULE,
                .of_match_table = mpc512x_psc_spi_of_match,
        },
};
module_platform_driver(mpc512x_psc_spi_of_driver);

MODULE_AUTHOR("John Rigby");
MODULE_DESCRIPTION("MPC512x PSC SPI Driver");
MODULE_LICENSE("GPL");