/*
 * Driver for Broadcom BCM2835 SPI Controllers
 *
 * Copyright (C) 2012 Chris Boot
 * Copyright (C) 2013 Stephen Warren
 * Copyright (C) 2015 Martin Sperl
 *
 * This driver is inspired by:
 * spi-ath79.c, Copyright (C) 2009-2011 Gabor Juhos <juhosg@openwrt.org>
 * spi-atmel.c, Copyright (C) 2006 Atmel Corporation
 *
 * 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 program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 */

#include <asm/page.h>
#include <linux/clk.h>
#include <linux/completion.h>
#include <linux/delay.h>
#include <linux/dma-mapping.h>
#include <linux/dmaengine.h>
#include <linux/err.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/of_address.h>
#include <linux/of_device.h>
#include <linux/of_gpio.h>
#include <linux/of_irq.h>
#include <linux/spi/spi.h>

/* SPI register offsets */
#define BCM2835_SPI_CS                  0x00
#define BCM2835_SPI_FIFO                0x04
#define BCM2835_SPI_CLK                 0x08
#define BCM2835_SPI_DLEN                0x0c
#define BCM2835_SPI_LTOH                0x10
#define BCM2835_SPI_DC                  0x14

/* Bitfields in CS */
#define BCM2835_SPI_CS_LEN_LONG         0x02000000
#define BCM2835_SPI_CS_DMA_LEN          0x01000000
#define BCM2835_SPI_CS_CSPOL2           0x00800000
#define BCM2835_SPI_CS_CSPOL1           0x00400000
#define BCM2835_SPI_CS_CSPOL0           0x00200000
#define BCM2835_SPI_CS_RXF              0x00100000
#define BCM2835_SPI_CS_RXR              0x00080000
#define BCM2835_SPI_CS_TXD              0x00040000
#define BCM2835_SPI_CS_RXD              0x00020000
#define BCM2835_SPI_CS_DONE             0x00010000
#define BCM2835_SPI_CS_LEN              0x00002000
#define BCM2835_SPI_CS_REN              0x00001000
#define BCM2835_SPI_CS_ADCS             0x00000800
#define BCM2835_SPI_CS_INTR             0x00000400
#define BCM2835_SPI_CS_INTD             0x00000200
#define BCM2835_SPI_CS_DMAEN            0x00000100
#define BCM2835_SPI_CS_TA               0x00000080
#define BCM2835_SPI_CS_CSPOL            0x00000040
#define BCM2835_SPI_CS_CLEAR_RX         0x00000020
#define BCM2835_SPI_CS_CLEAR_TX         0x00000010
#define BCM2835_SPI_CS_CPOL             0x00000008
#define BCM2835_SPI_CS_CPHA             0x00000004
#define BCM2835_SPI_CS_CS_10            0x00000002
#define BCM2835_SPI_CS_CS_01            0x00000001

#define BCM2835_SPI_POLLING_LIMIT_US    30
#define BCM2835_SPI_POLLING_JIFFIES     2
#define BCM2835_SPI_DMA_MIN_LENGTH      96
#define BCM2835_SPI_MODE_BITS   (SPI_CPOL | SPI_CPHA | SPI_CS_HIGH \
                                | SPI_NO_CS | SPI_3WIRE)

#define DRV_NAME        "spi-bcm2835"

struct bcm2835_spi {
        void __iomem *regs;
        struct clk *clk;
        int irq;
        const u8 *tx_buf;
        u8 *rx_buf;
        int tx_len;
        int rx_len;
        bool dma_pending;
};

static inline u32 bcm2835_rd(struct bcm2835_spi *bs, unsigned reg)
{
        return readl(bs->regs + reg);
}

static inline void bcm2835_wr(struct bcm2835_spi *bs, unsigned reg, u32 val)
{
        writel(val, bs->regs + reg);
}

static inline void bcm2835_rd_fifo(struct bcm2835_spi *bs)
{
        u8 byte;

        while ((bs->rx_len) &&
               (bcm2835_rd(bs, BCM2835_SPI_CS) & BCM2835_SPI_CS_RXD)) {
                byte = bcm2835_rd(bs, BCM2835_SPI_FIFO);
                if (bs->rx_buf)
                        *bs->rx_buf++ = byte;
                bs->rx_len--;
        }
}

static inline void bcm2835_wr_fifo(struct bcm2835_spi *bs)
{
        u8 byte;

        while ((bs->tx_len) &&
               (bcm2835_rd(bs, BCM2835_SPI_CS) & BCM2835_SPI_CS_TXD)) {
                byte = bs->tx_buf ? *bs->tx_buf++ : 0;
                bcm2835_wr(bs, BCM2835_SPI_FIFO, byte);
                bs->tx_len--;
        }
}

static void bcm2835_spi_reset_hw(struct spi_master *master)
{
        struct bcm2835_spi *bs = spi_master_get_devdata(master);
        u32 cs = bcm2835_rd(bs, BCM2835_SPI_CS);

        /* Disable SPI interrupts and transfer */
        cs &= ~(BCM2835_SPI_CS_INTR |
                BCM2835_SPI_CS_INTD |
                BCM2835_SPI_CS_DMAEN |
                BCM2835_SPI_CS_TA);
        /* and reset RX/TX FIFOS */
        cs |= BCM2835_SPI_CS_CLEAR_RX | BCM2835_SPI_CS_CLEAR_TX;

        /* and reset the SPI_HW */
        bcm2835_wr(bs, BCM2835_SPI_CS, cs);
        /* as well as DLEN */
        bcm2835_wr(bs, BCM2835_SPI_DLEN, 0);
}

static irqreturn_t bcm2835_spi_interrupt(int irq, void *dev_id)
{
        struct spi_master *master = dev_id;
        struct bcm2835_spi *bs = spi_master_get_devdata(master);

        /* Read as many bytes as possible from FIFO */
        bcm2835_rd_fifo(bs);
        /* Write as many bytes as possible to FIFO */
        bcm2835_wr_fifo(bs);

        /* based on flags decide if we can finish the transfer */
        if (bcm2835_rd(bs, BCM2835_SPI_CS) & BCM2835_SPI_CS_DONE) {
                /* Transfer complete - reset SPI HW */
                bcm2835_spi_reset_hw(master);
                /* wake up the framework */
                complete(&master->xfer_completion);
        }

        return IRQ_HANDLED;
}

static int bcm2835_spi_transfer_one_irq(struct spi_master *master,
                                        struct spi_device *spi,
                                        struct spi_transfer *tfr,
                                        u32 cs)
{
        struct bcm2835_spi *bs = spi_master_get_devdata(master);

        /* fill in fifo if we have gpio-cs
         * note that there have been rare events where the native-CS
         * flapped for <1us which may change the behaviour
         * with gpio-cs this does not happen, so it is implemented
         * only for this case
         */
        if (gpio_is_valid(spi->cs_gpio)) {
                /* enable HW block, but without interrupts enabled
                 * this would triggern an immediate interrupt
                 */
                bcm2835_wr(bs, BCM2835_SPI_CS,
                           cs | BCM2835_SPI_CS_TA);
                /* fill in tx fifo as much as possible */
                bcm2835_wr_fifo(bs);
        }

        /*
         * Enable the HW block. This will immediately trigger a DONE (TX
         * empty) interrupt, upon which we will fill the TX FIFO with the
         * first TX bytes. Pre-filling the TX FIFO here to avoid the
         * interrupt doesn't work:-(
         */
        cs |= BCM2835_SPI_CS_INTR | BCM2835_SPI_CS_INTD | BCM2835_SPI_CS_TA;
        bcm2835_wr(bs, BCM2835_SPI_CS, cs);

        /* signal that we need to wait for completion */
        return 1;
}

/*
 * DMA support
 *
 * this implementation has currently a few issues in so far as it does
 * not work arrount limitations of the HW.
 *
 * the main one being that DMA transfers are limited to 16 bit
 * (so 0 to 65535 bytes) by the SPI HW due to BCM2835_SPI_DLEN
 *
 * also we currently assume that the scatter-gather fragments are
 * all multiple of 4 (except the last) - otherwise we would need
 * to reset the FIFO before subsequent transfers...
 * this also means that tx/rx transfers sg's need to be of equal size!
 *
 * there may be a few more border-cases we may need to address as well
 * but unfortunately this would mean splitting up the scatter-gather
 * list making it slightly unpractical...
 */
static void bcm2835_spi_dma_done(void *data)
{
        struct spi_master *master = data;
        struct bcm2835_spi *bs = spi_master_get_devdata(master);

        /* reset fifo and HW */
        bcm2835_spi_reset_hw(master);

        /* and terminate tx-dma as we do not have an irq for it
         * because when the rx dma will terminate and this callback
         * is called the tx-dma must have finished - can't get to this
         * situation otherwise...
         */
        dmaengine_terminate_all(master->dma_tx);

        /* mark as no longer pending */
        bs->dma_pending = 0;

        /* and mark as completed */;
        complete(&master->xfer_completion);
}

static int bcm2835_spi_prepare_sg(struct spi_master *master,
                                  struct spi_transfer *tfr,
                                  bool is_tx)
{
        struct dma_chan *chan;
        struct scatterlist *sgl;
        unsigned int nents;
        enum dma_transfer_direction dir;
        unsigned long flags;

        struct dma_async_tx_descriptor *desc;
        dma_cookie_t cookie;

        if (is_tx) {
                dir   = DMA_MEM_TO_DEV;
                chan  = master->dma_tx;
                nents = tfr->tx_sg.nents;
                sgl   = tfr->tx_sg.sgl;
                flags = 0 /* no  tx interrupt */;

        } else {
                dir   = DMA_DEV_TO_MEM;
                chan  = master->dma_rx;
                nents = tfr->rx_sg.nents;
                sgl   = tfr->rx_sg.sgl;
                flags = DMA_PREP_INTERRUPT;
        }
        /* prepare the channel */
        desc = dmaengine_prep_slave_sg(chan, sgl, nents, dir, flags);
        if (!desc)
                return -EINVAL;

        /* set callback for rx */
        if (!is_tx) {
                desc->callback = bcm2835_spi_dma_done;
                desc->callback_param = master;
        }

        /* submit it to DMA-engine */
        cookie = dmaengine_submit(desc);

        return dma_submit_error(cookie);
}

static inline int bcm2835_check_sg_length(struct sg_table *sgt)
{
        int i;
        struct scatterlist *sgl;

        /* check that the sg entries are word-sized (except for last) */
        for_each_sg(sgt->sgl, sgl, (int)sgt->nents - 1, i) {
                if (sg_dma_len(sgl) % 4)
                        return -EFAULT;
        }

        return 0;
}

static int bcm2835_spi_transfer_one_dma(struct spi_master *master,
                                        struct spi_device *spi,
                                        struct spi_transfer *tfr,
                                        u32 cs)
{
        struct bcm2835_spi *bs = spi_master_get_devdata(master);
        int ret;

        /* check that the scatter gather segments are all a multiple of 4 */
        if (bcm2835_check_sg_length(&tfr->tx_sg) ||
            bcm2835_check_sg_length(&tfr->rx_sg)) {
                dev_warn_once(&spi->dev,
                              "scatter gather segment length is not a multiple of 4 - falling back to interrupt mode\n");
                return bcm2835_spi_transfer_one_irq(master, spi, tfr, cs);
        }

        /* setup tx-DMA */
        ret = bcm2835_spi_prepare_sg(master, tfr, true);
        if (ret)
                return ret;

        /* start TX early */
        dma_async_issue_pending(master->dma_tx);

        /* mark as dma pending */
        bs->dma_pending = 1;

        /* set the DMA length */
        bcm2835_wr(bs, BCM2835_SPI_DLEN, tfr->len);

        /* start the HW */
        bcm2835_wr(bs, BCM2835_SPI_CS,
                   cs | BCM2835_SPI_CS_TA | BCM2835_SPI_CS_DMAEN);

        /* setup rx-DMA late - to run transfers while
         * mapping of the rx buffers still takes place
         * this saves 10us or more.
         */
        ret = bcm2835_spi_prepare_sg(master, tfr, false);
        if (ret) {
                /* need to reset on errors */
                dmaengine_terminate_all(master->dma_tx);
                bcm2835_spi_reset_hw(master);
                return ret;
        }

        /* start rx dma late */
        dma_async_issue_pending(master->dma_rx);

        /* wait for wakeup in framework */
        return 1;
}

static bool bcm2835_spi_can_dma(struct spi_master *master,
                                struct spi_device *spi,
                                struct spi_transfer *tfr)
{
        /* only run for gpio_cs */
        if (!gpio_is_valid(spi->cs_gpio))
                return false;

        /* we start DMA efforts only on bigger transfers */
        if (tfr->len < BCM2835_SPI_DMA_MIN_LENGTH)
                return false;

        /* BCM2835_SPI_DLEN has defined a max transfer size as
         * 16 bit, so max is 65535
         * we can revisit this by using an alternative transfer
         * method - ideally this would get done without any more
         * interaction...
         */
        if (tfr->len > 65535) {
                dev_warn_once(&spi->dev,
                              "transfer size of %d too big for dma-transfer\n",
                              tfr->len);
                return false;
        }

        /* if we run rx/tx_buf with word aligned addresses then we are OK */
        if ((((size_t)tfr->rx_buf & 3) == 0) &&
            (((size_t)tfr->tx_buf & 3) == 0))
                return true;

        /* otherwise we only allow transfers within the same page
         * to avoid wasting time on dma_mapping when it is not practical
         */
        if (((size_t)tfr->tx_buf & (PAGE_SIZE - 1)) + tfr->len > PAGE_SIZE) {
                dev_warn_once(&spi->dev,
                              "Unaligned spi tx-transfer bridging page\n");
                return false;
        }
        if (((size_t)tfr->rx_buf & (PAGE_SIZE - 1)) + tfr->len > PAGE_SIZE) {
                dev_warn_once(&spi->dev,
                              "Unaligned spi rx-transfer bridging page\n");
                return false;
        }

        /* return OK */
        return true;
}

static void bcm2835_dma_release(struct spi_master *master)
{
        if (master->dma_tx) {
                dmaengine_terminate_all(master->dma_tx);
                dma_release_channel(master->dma_tx);
                master->dma_tx = NULL;
        }
        if (master->dma_rx) {
                dmaengine_terminate_all(master->dma_rx);
                dma_release_channel(master->dma_rx);
                master->dma_rx = NULL;
        }
}

static void bcm2835_dma_init(struct spi_master *master, struct device *dev)
{
        struct dma_slave_config slave_config;
        const __be32 *addr;
        dma_addr_t dma_reg_base;
        int ret;

        /* base address in dma-space */
        addr = of_get_address(master->dev.of_node, 0, NULL, NULL);
        if (!addr) {
                dev_err(dev, "could not get DMA-register address - not using dma mode\n");
                goto err;
        }
        dma_reg_base = be32_to_cpup(addr);

        /* get tx/rx dma */
        master->dma_tx = dma_request_slave_channel(dev, "tx");
        if (!master->dma_tx) {
                dev_err(dev, "no tx-dma configuration found - not using dma mode\n");
                goto err;
        }
        master->dma_rx = dma_request_slave_channel(dev, "rx");
        if (!master->dma_rx) {
                dev_err(dev, "no rx-dma configuration found - not using dma mode\n");
                goto err_release;
        }

        /* configure DMAs */
        slave_config.direction = DMA_MEM_TO_DEV;
        slave_config.dst_addr = (u32)(dma_reg_base + BCM2835_SPI_FIFO);
        slave_config.dst_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;

        ret = dmaengine_slave_config(master->dma_tx, &slave_config);
        if (ret)
                goto err_config;

        slave_config.direction = DMA_DEV_TO_MEM;
        slave_config.src_addr = (u32)(dma_reg_base + BCM2835_SPI_FIFO);
        slave_config.src_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;

        ret = dmaengine_slave_config(master->dma_rx, &slave_config);
        if (ret)
                goto err_config;

        /* all went well, so set can_dma */
        master->can_dma = bcm2835_spi_can_dma;
        master->max_dma_len = 65535; /* limitation by BCM2835_SPI_DLEN */
        /* need to do TX AND RX DMA, so we need dummy buffers */
        master->flags = SPI_MASTER_MUST_RX | SPI_MASTER_MUST_TX;

        return;

err_config:
        dev_err(dev, "issue configuring dma: %d - not using DMA mode\n",
                ret);
err_release:
        bcm2835_dma_release(master);
err:
        return;
}

static int bcm2835_spi_transfer_one_poll(struct spi_master *master,
                                         struct spi_device *spi,
                                         struct spi_transfer *tfr,
                                         u32 cs,
                                         unsigned long long xfer_time_us)
{
        struct bcm2835_spi *bs = spi_master_get_devdata(master);
        unsigned long timeout;

        /* enable HW block without interrupts */
        bcm2835_wr(bs, BCM2835_SPI_CS, cs | BCM2835_SPI_CS_TA);

        /* fill in the fifo before timeout calculations
         * if we are interrupted here, then the data is
         * getting transferred by the HW while we are interrupted
         */
        bcm2835_wr_fifo(bs);

        /* set the timeout */
        timeout = jiffies + BCM2835_SPI_POLLING_JIFFIES;

        /* loop until finished the transfer */
        while (bs->rx_len) {
                /* fill in tx fifo with remaining data */
                bcm2835_wr_fifo(bs);

                /* read from fifo as much as possible */
                bcm2835_rd_fifo(bs);

                /* if there is still data pending to read
                 * then check the timeout
                 */
                if (bs->rx_len && time_after(jiffies, timeout)) {
                        dev_dbg_ratelimited(&spi->dev,
                                            "timeout period reached: jiffies: %lu remaining tx/rx: %d/%d - falling back to interrupt mode\n",
                                            jiffies - timeout,
                                            bs->tx_len, bs->rx_len);
                        /* fall back to interrupt mode */
                        return bcm2835_spi_transfer_one_irq(master, spi,
                                                            tfr, cs);
                }
        }

        /* Transfer complete - reset SPI HW */
        bcm2835_spi_reset_hw(master);
        /* and return without waiting for completion */
        return 0;
}

static int bcm2835_spi_transfer_one(struct spi_master *master,
                                    struct spi_device *spi,
                                    struct spi_transfer *tfr)
{
        struct bcm2835_spi *bs = spi_master_get_devdata(master);
        unsigned long spi_hz, clk_hz, cdiv;
        unsigned long spi_used_hz;
        unsigned long long xfer_time_us;
        u32 cs = bcm2835_rd(bs, BCM2835_SPI_CS);

        /* set clock */
        spi_hz = tfr->speed_hz;
        clk_hz = clk_get_rate(bs->clk);

        if (spi_hz >= clk_hz / 2) {
                cdiv = 2; /* clk_hz/2 is the fastest we can go */
        } else if (spi_hz) {
                /* CDIV must be a multiple of two */
                cdiv = DIV_ROUND_UP(clk_hz, spi_hz);
                cdiv += (cdiv % 2);

                if (cdiv >= 65536)
                        cdiv = 0; /* 0 is the slowest we can go */
        } else {
                cdiv = 0; /* 0 is the slowest we can go */
        }
        spi_used_hz = cdiv ? (clk_hz / cdiv) : (clk_hz / 65536);
        bcm2835_wr(bs, BCM2835_SPI_CLK, cdiv);

        /* handle all the 3-wire mode */
        if ((spi->mode & SPI_3WIRE) && (tfr->rx_buf))
                cs |= BCM2835_SPI_CS_REN;
        else
                cs &= ~BCM2835_SPI_CS_REN;

        /* for gpio_cs set dummy CS so that no HW-CS get changed
         * we can not run this in bcm2835_spi_set_cs, as it does
         * not get called for cs_gpio cases, so we need to do it here
         */
        if (gpio_is_valid(spi->cs_gpio) || (spi->mode & SPI_NO_CS))
                cs |= BCM2835_SPI_CS_CS_10 | BCM2835_SPI_CS_CS_01;

        /* set transmit buffers and length */
        bs->tx_buf = tfr->tx_buf;
        bs->rx_buf = tfr->rx_buf;
        bs->tx_len = tfr->len;
        bs->rx_len = tfr->len;

        /* calculate the estimated time in us the transfer runs */
        xfer_time_us = (unsigned long long)tfr->len
                * 9 /* clocks/byte - SPI-HW waits 1 clock after each byte */
                * 1000000;
        do_div(xfer_time_us, spi_used_hz);

        /* for short requests run polling*/
        if (xfer_time_us <= BCM2835_SPI_POLLING_LIMIT_US)
                return bcm2835_spi_transfer_one_poll(master, spi, tfr,
                                                     cs, xfer_time_us);

        /* run in dma mode if conditions are right */
        if (master->can_dma && bcm2835_spi_can_dma(master, spi, tfr))
                return bcm2835_spi_transfer_one_dma(master, spi, tfr, cs);

        /* run in interrupt-mode */
        return bcm2835_spi_transfer_one_irq(master, spi, tfr, cs);
}

static int bcm2835_spi_prepare_message(struct spi_master *master,
                                       struct spi_message *msg)
{
        struct spi_device *spi = msg->spi;
        struct bcm2835_spi *bs = spi_master_get_devdata(master);
        u32 cs = bcm2835_rd(bs, BCM2835_SPI_CS);

        cs &= ~(BCM2835_SPI_CS_CPOL | BCM2835_SPI_CS_CPHA);

        if (spi->mode & SPI_CPOL)
                cs |= BCM2835_SPI_CS_CPOL;
        if (spi->mode & SPI_CPHA)
                cs |= BCM2835_SPI_CS_CPHA;

        bcm2835_wr(bs, BCM2835_SPI_CS, cs);

        return 0;
}

static void bcm2835_spi_handle_err(struct spi_master *master,
                                   struct spi_message *msg)
{
        struct bcm2835_spi *bs = spi_master_get_devdata(master);

        /* if an error occurred and we have an active dma, then terminate */
        if (bs->dma_pending) {
                dmaengine_terminate_all(master->dma_tx);
                dmaengine_terminate_all(master->dma_rx);
                bs->dma_pending = 0;
        }
        /* and reset */
        bcm2835_spi_reset_hw(master);
}

static void bcm2835_spi_set_cs(struct spi_device *spi, bool gpio_level)
{
        /*
         * we can assume that we are "native" as per spi_set_cs
         *   calling us ONLY when cs_gpio is not set
         * we can also assume that we are CS < 3 as per bcm2835_spi_setup
         *   we would not get called because of error handling there.
         * the level passed is the electrical level not enabled/disabled
         *   so it has to get translated back to enable/disable
         *   see spi_set_cs in spi.c for the implementation
         */

        struct spi_master *master = spi->master;
        struct bcm2835_spi *bs = spi_master_get_devdata(master);
        u32 cs = bcm2835_rd(bs, BCM2835_SPI_CS);
        bool enable;

        /* calculate the enable flag from the passed gpio_level */
        enable = (spi->mode & SPI_CS_HIGH) ? gpio_level : !gpio_level;

        /* set flags for "reverse" polarity in the registers */
        if (spi->mode & SPI_CS_HIGH) {
                /* set the correct CS-bits */
                cs |= BCM2835_SPI_CS_CSPOL;
                cs |= BCM2835_SPI_CS_CSPOL0 << spi->chip_select;
        } else {
                /* clean the CS-bits */
                cs &= ~BCM2835_SPI_CS_CSPOL;
                cs &= ~(BCM2835_SPI_CS_CSPOL0 << spi->chip_select);
        }

        /* select the correct chip_select depending on disabled/enabled */
        if (enable) {
                /* set cs correctly */
                if (spi->mode & SPI_NO_CS) {
                        /* use the "undefined" chip-select */
                        cs |= BCM2835_SPI_CS_CS_10 | BCM2835_SPI_CS_CS_01;
                } else {
                        /* set the chip select */
                        cs &= ~(BCM2835_SPI_CS_CS_10 | BCM2835_SPI_CS_CS_01);
                        cs |= spi->chip_select;
                }
        } else {
                /* disable CSPOL which puts HW-CS into deselected state */
                cs &= ~BCM2835_SPI_CS_CSPOL;
                /* use the "undefined" chip-select as precaution */
                cs |= BCM2835_SPI_CS_CS_10 | BCM2835_SPI_CS_CS_01;
        }

        /* finally set the calculated flags in SPI_CS */
        bcm2835_wr(bs, BCM2835_SPI_CS, cs);
}

static int chip_match_name(struct gpio_chip *chip, void *data)
{
        return !strcmp(chip->label, data);
}

static int bcm2835_spi_setup(struct spi_device *spi)
{
        int err;
        struct gpio_chip *chip;
        /*
         * sanity checking the native-chipselects
         */
        if (spi->mode & SPI_NO_CS)
                return 0;
        if (gpio_is_valid(spi->cs_gpio))
                return 0;
        if (spi->chip_select > 1) {
                /* error in the case of native CS requested with CS > 1
                 * officially there is a CS2, but it is not documented
                 * which GPIO is connected with that...
                 */
                dev_err(&spi->dev,
                        "setup: only two native chip-selects are supported\n");
                return -EINVAL;
        }
        /* now translate native cs to GPIO */

        /* get the gpio chip for the base */
        chip = gpiochip_find("pinctrl-bcm2835", chip_match_name);
        if (!chip)
                return 0;

        /* and calculate the real CS */
        spi->cs_gpio = chip->base + 8 - spi->chip_select;

        /* and set up the "mode" and level */
        dev_info(&spi->dev, "setting up native-CS%i as GPIO %i\n",
                 spi->chip_select, spi->cs_gpio);

        /* set up GPIO as output and pull to the correct level */
        err = gpio_direction_output(spi->cs_gpio,
                                    (spi->mode & SPI_CS_HIGH) ? 0 : 1);
        if (err) {
                dev_err(&spi->dev,
                        "could not set CS%i gpio %i as output: %i",
                        spi->chip_select, spi->cs_gpio, err);
                return err;
        }

        return 0;
}

static int bcm2835_spi_probe(struct platform_device *pdev)
{
        struct spi_master *master;
        struct bcm2835_spi *bs;
        struct resource *res;
        int err;

        master = spi_alloc_master(&pdev->dev, sizeof(*bs));
        if (!master) {
                dev_err(&pdev->dev, "spi_alloc_master() failed\n");
                return -ENOMEM;
        }

        platform_set_drvdata(pdev, master);

        master->mode_bits = BCM2835_SPI_MODE_BITS;
        master->bits_per_word_mask = SPI_BPW_MASK(8);
        master->num_chipselect = 3;
        master->setup = bcm2835_spi_setup;
        master->set_cs = bcm2835_spi_set_cs;
        master->transfer_one = bcm2835_spi_transfer_one;
        master->handle_err = bcm2835_spi_handle_err;
        master->prepare_message = bcm2835_spi_prepare_message;
        master->dev.of_node = pdev->dev.of_node;

        bs = spi_master_get_devdata(master);

        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        bs->regs = devm_ioremap_resource(&pdev->dev, res);
        if (IS_ERR(bs->regs)) {
                err = PTR_ERR(bs->regs);
                goto out_master_put;
        }

        bs->clk = devm_clk_get(&pdev->dev, NULL);
        if (IS_ERR(bs->clk)) {
                err = PTR_ERR(bs->clk);
                dev_err(&pdev->dev, "could not get clk: %d\n", err);
                goto out_master_put;
        }

        bs->irq = platform_get_irq(pdev, 0);
        if (bs->irq <= 0) {
                dev_err(&pdev->dev, "could not get IRQ: %d\n", bs->irq);
                err = bs->irq ? bs->irq : -ENODEV;
                goto out_master_put;
        }

        clk_prepare_enable(bs->clk);

        bcm2835_dma_init(master, &pdev->dev);

        /* initialise the hardware with the default polarities */
        bcm2835_wr(bs, BCM2835_SPI_CS,
                   BCM2835_SPI_CS_CLEAR_RX | BCM2835_SPI_CS_CLEAR_TX);

        err = devm_request_irq(&pdev->dev, bs->irq, bcm2835_spi_interrupt, 0,
                               dev_name(&pdev->dev), master);
        if (err) {
                dev_err(&pdev->dev, "could not request IRQ: %d\n", err);
                goto out_clk_disable;
        }

        err = devm_spi_register_master(&pdev->dev, master);
        if (err) {
                dev_err(&pdev->dev, "could not register SPI master: %d\n", err);
                goto out_clk_disable;
        }

        return 0;

out_clk_disable:
        clk_disable_unprepare(bs->clk);
out_master_put:
        spi_master_put(master);
        return err;
}

static int bcm2835_spi_remove(struct platform_device *pdev)
{
        struct spi_master *master = platform_get_drvdata(pdev);
        struct bcm2835_spi *bs = spi_master_get_devdata(master);

        /* Clear FIFOs, and disable the HW block */
        bcm2835_wr(bs, BCM2835_SPI_CS,
                   BCM2835_SPI_CS_CLEAR_RX | BCM2835_SPI_CS_CLEAR_TX);

        clk_disable_unprepare(bs->clk);

        bcm2835_dma_release(master);

        return 0;
}

static const struct of_device_id bcm2835_spi_match[] = {
        { .compatible = "brcm,bcm2835-spi", },
        {}
};
MODULE_DEVICE_TABLE(of, bcm2835_spi_match);

static struct platform_driver bcm2835_spi_driver = {
        .driver         = {
                .name           = DRV_NAME,
                .of_match_table = bcm2835_spi_match,
        },
        .probe          = bcm2835_spi_probe,
        .remove         = bcm2835_spi_remove,
};
module_platform_driver(bcm2835_spi_driver);

MODULE_DESCRIPTION("SPI controller driver for Broadcom BCM2835");
MODULE_AUTHOR("Chris Boot <bootc@bootc.net>");
MODULE_LICENSE("GPL v2");