// SPDX-License-Identifier: GPL-2.0-only
/*
 * Driver for Cirrus Logic EP93xx SPI controller.
 *
 * Copyright (C) 2010-2011 Mika Westerberg
 *
 * Explicit FIFO handling code was inspired by amba-pl022 driver.
 *
 * Chip select support using other than built-in GPIOs by H. Hartley Sweeten.
 *
 * For more information about the SPI controller see documentation on Cirrus
 * Logic web site:
 *     https://www.cirrus.com/en/pubs/manual/EP93xx_Users_Guide_UM1.pdf
 */

#include <linux/io.h>
#include <linux/clk.h>
#include <linux/err.h>
#include <linux/delay.h>
#include <linux/device.h>
#include <linux/dma-direction.h>
#include <linux/dma-mapping.h>
#include <linux/dmaengine.h>
#include <linux/bitops.h>
#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/property.h>
#include <linux/platform_device.h>
#include <linux/sched.h>
#include <linux/scatterlist.h>
#include <linux/spi/spi.h>

#define SSPCR0                  0x0000
#define SSPCR0_SPO              BIT(6)
#define SSPCR0_SPH              BIT(7)
#define SSPCR0_SCR_SHIFT        8

#define SSPCR1                  0x0004
#define SSPCR1_RIE              BIT(0)
#define SSPCR1_TIE              BIT(1)
#define SSPCR1_RORIE            BIT(2)
#define SSPCR1_LBM              BIT(3)
#define SSPCR1_SSE              BIT(4)
#define SSPCR1_MS               BIT(5)
#define SSPCR1_SOD              BIT(6)

#define SSPDR                   0x0008

#define SSPSR                   0x000c
#define SSPSR_TFE               BIT(0)
#define SSPSR_TNF               BIT(1)
#define SSPSR_RNE               BIT(2)
#define SSPSR_RFF               BIT(3)
#define SSPSR_BSY               BIT(4)
#define SSPCPSR                 0x0010

#define SSPIIR                  0x0014
#define SSPIIR_RIS              BIT(0)
#define SSPIIR_TIS              BIT(1)
#define SSPIIR_RORIS            BIT(2)
#define SSPICR                  SSPIIR

/* timeout in milliseconds */
#define SPI_TIMEOUT             5
/* maximum depth of RX/TX FIFO */
#define SPI_FIFO_SIZE           8

/**
 * struct ep93xx_spi - EP93xx SPI controller structure
 * @clk: clock for the controller
 * @mmio: pointer to ioremap()'d registers
 * @sspdr_phys: physical address of the SSPDR register
 * @tx: current byte in transfer to transmit
 * @rx: current byte in transfer to receive
 * @fifo_level: how full is FIFO (%0..%SPI_FIFO_SIZE - %1). Receiving one
 *              frame decreases this level and sending one frame increases it.
 * @dma_rx: RX DMA channel
 * @dma_tx: TX DMA channel
 * @rx_sgt: sg table for RX transfers
 * @tx_sgt: sg table for TX transfers
 * @zeropage: dummy page used as RX buffer when only TX buffer is passed in by
 *            the client
 */
struct ep93xx_spi {
        struct clk                      *clk;
        void __iomem                    *mmio;
        unsigned long                   sspdr_phys;
        size_t                          tx;
        size_t                          rx;
        size_t                          fifo_level;
        struct dma_chan                 *dma_rx;
        struct dma_chan                 *dma_tx;
        struct sg_table                 rx_sgt;
        struct sg_table                 tx_sgt;
        void                            *zeropage;
};

/* converts bits per word to CR0.DSS value */
#define bits_per_word_to_dss(bpw)       ((bpw) - 1)

/**
 * ep93xx_spi_calc_divisors() - calculates SPI clock divisors
 * @host: SPI host
 * @rate: desired SPI output clock rate
 * @div_cpsr: pointer to return the cpsr (pre-scaler) divider
 * @div_scr: pointer to return the scr divider
 */
static int ep93xx_spi_calc_divisors(struct spi_controller *host,
                                    u32 rate, u8 *div_cpsr, u8 *div_scr)
{
        struct ep93xx_spi *espi = spi_controller_get_devdata(host);
        unsigned long spi_clk_rate = clk_get_rate(espi->clk);
        int cpsr, scr;

        /*
         * Make sure that max value is between values supported by the
         * controller.
         */
        rate = clamp(rate, host->min_speed_hz, host->max_speed_hz);

        /*
         * Calculate divisors so that we can get speed according the
         * following formula:
         *      rate = spi_clock_rate / (cpsr * (1 + scr))
         *
         * cpsr must be even number and starts from 2, scr can be any number
         * between 0 and 255.
         */
        for (cpsr = 2; cpsr <= 254; cpsr += 2) {
                for (scr = 0; scr <= 255; scr++) {
                        if ((spi_clk_rate / (cpsr * (scr + 1))) <= rate) {
                                *div_scr = (u8)scr;
                                *div_cpsr = (u8)cpsr;
                                return 0;
                        }
                }
        }

        return -EINVAL;
}

static int ep93xx_spi_chip_setup(struct spi_controller *host,
                                 struct spi_device *spi,
                                 struct spi_transfer *xfer)
{
        struct ep93xx_spi *espi = spi_controller_get_devdata(host);
        u8 dss = bits_per_word_to_dss(xfer->bits_per_word);
        u8 div_cpsr = 0;
        u8 div_scr = 0;
        u16 cr0;
        int err;

        err = ep93xx_spi_calc_divisors(host, xfer->speed_hz,
                                       &div_cpsr, &div_scr);
        if (err)
                return err;

        cr0 = div_scr << SSPCR0_SCR_SHIFT;
        if (spi->mode & SPI_CPOL)
                cr0 |= SSPCR0_SPO;
        if (spi->mode & SPI_CPHA)
                cr0 |= SSPCR0_SPH;
        cr0 |= dss;

        dev_dbg(&host->dev, "setup: mode %d, cpsr %d, scr %d, dss %d\n",
                spi->mode, div_cpsr, div_scr, dss);
        dev_dbg(&host->dev, "setup: cr0 %#x\n", cr0);

        writel(div_cpsr, espi->mmio + SSPCPSR);
        writel(cr0, espi->mmio + SSPCR0);

        return 0;
}

static void ep93xx_do_write(struct spi_controller *host)
{
        struct ep93xx_spi *espi = spi_controller_get_devdata(host);
        struct spi_transfer *xfer = host->cur_msg->state;
        u32 val = 0;

        if (xfer->bits_per_word > 8) {
                if (xfer->tx_buf)
                        val = ((u16 *)xfer->tx_buf)[espi->tx];
                espi->tx += 2;
        } else {
                if (xfer->tx_buf)
                        val = ((u8 *)xfer->tx_buf)[espi->tx];
                espi->tx += 1;
        }
        writel(val, espi->mmio + SSPDR);
}

static void ep93xx_do_read(struct spi_controller *host)
{
        struct ep93xx_spi *espi = spi_controller_get_devdata(host);
        struct spi_transfer *xfer = host->cur_msg->state;
        u32 val;

        val = readl(espi->mmio + SSPDR);
        if (xfer->bits_per_word > 8) {
                if (xfer->rx_buf)
                        ((u16 *)xfer->rx_buf)[espi->rx] = val;
                espi->rx += 2;
        } else {
                if (xfer->rx_buf)
                        ((u8 *)xfer->rx_buf)[espi->rx] = val;
                espi->rx += 1;
        }
}

/**
 * ep93xx_spi_read_write() - perform next RX/TX transfer
 * @host: SPI host
 *
 * This function transfers next bytes (or half-words) to/from RX/TX FIFOs. If
 * called several times, the whole transfer will be completed. Returns
 * %-EINPROGRESS when current transfer was not yet completed otherwise %0.
 *
 * When this function is finished, RX FIFO should be empty and TX FIFO should be
 * full.
 */
static int ep93xx_spi_read_write(struct spi_controller *host)
{
        struct ep93xx_spi *espi = spi_controller_get_devdata(host);
        struct spi_transfer *xfer = host->cur_msg->state;

        /* read as long as RX FIFO has frames in it */
        while ((readl(espi->mmio + SSPSR) & SSPSR_RNE)) {
                ep93xx_do_read(host);
                espi->fifo_level--;
        }

        /* write as long as TX FIFO has room */
        while (espi->fifo_level < SPI_FIFO_SIZE && espi->tx < xfer->len) {
                ep93xx_do_write(host);
                espi->fifo_level++;
        }

        if (espi->rx == xfer->len)
                return 0;

        return -EINPROGRESS;
}

static enum dma_transfer_direction
ep93xx_dma_data_to_trans_dir(enum dma_data_direction dir)
{
        switch (dir) {
        case DMA_TO_DEVICE:
                return DMA_MEM_TO_DEV;
        case DMA_FROM_DEVICE:
                return DMA_DEV_TO_MEM;
        default:
                return DMA_TRANS_NONE;
        }
}

/**
 * ep93xx_spi_dma_prepare() - prepares a DMA transfer
 * @host: SPI host
 * @dir: DMA transfer direction
 *
 * Function configures the DMA, maps the buffer and prepares the DMA
 * descriptor. Returns a valid DMA descriptor in case of success and ERR_PTR
 * in case of failure.
 */
static struct dma_async_tx_descriptor *
ep93xx_spi_dma_prepare(struct spi_controller *host,
                       enum dma_data_direction dir)
{
        struct ep93xx_spi *espi = spi_controller_get_devdata(host);
        struct spi_transfer *xfer = host->cur_msg->state;
        struct dma_async_tx_descriptor *txd;
        enum dma_slave_buswidth buswidth;
        struct dma_slave_config conf;
        struct scatterlist *sg;
        struct sg_table *sgt;
        struct dma_chan *chan;
        const void *buf, *pbuf;
        size_t len = xfer->len;
        int i, ret, nents;

        if (xfer->bits_per_word > 8)
                buswidth = DMA_SLAVE_BUSWIDTH_2_BYTES;
        else
                buswidth = DMA_SLAVE_BUSWIDTH_1_BYTE;

        memset(&conf, 0, sizeof(conf));
        conf.direction = ep93xx_dma_data_to_trans_dir(dir);

        if (dir == DMA_FROM_DEVICE) {
                chan = espi->dma_rx;
                buf = xfer->rx_buf;
                sgt = &espi->rx_sgt;

                conf.src_addr = espi->sspdr_phys;
                conf.src_addr_width = buswidth;
        } else {
                chan = espi->dma_tx;
                buf = xfer->tx_buf;
                sgt = &espi->tx_sgt;

                conf.dst_addr = espi->sspdr_phys;
                conf.dst_addr_width = buswidth;
        }

        ret = dmaengine_slave_config(chan, &conf);
        if (ret)
                return ERR_PTR(ret);

        /*
         * We need to split the transfer into PAGE_SIZE'd chunks. This is
         * because we are using @espi->zeropage to provide a zero RX buffer
         * for the TX transfers and we have only allocated one page for that.
         *
         * For performance reasons we allocate a new sg_table only when
         * needed. Otherwise we will re-use the current one. Eventually the
         * last sg_table is released in ep93xx_spi_release_dma().
         */

        nents = DIV_ROUND_UP(len, PAGE_SIZE);
        if (nents != sgt->nents) {
                sg_free_table(sgt);

                ret = sg_alloc_table(sgt, nents, GFP_KERNEL);
                if (ret)
                        return ERR_PTR(ret);
        }

        pbuf = buf;
        for_each_sg(sgt->sgl, sg, sgt->nents, i) {
                size_t bytes = min_t(size_t, len, PAGE_SIZE);

                if (buf) {
                        sg_set_page(sg, virt_to_page(pbuf), bytes,
                                    offset_in_page(pbuf));
                } else {
                        sg_set_page(sg, virt_to_page(espi->zeropage),
                                    bytes, 0);
                }

                pbuf += bytes;
                len -= bytes;
        }

        if (WARN_ON(len)) {
                dev_warn(&host->dev, "len = %zu expected 0!\n", len);
                return ERR_PTR(-EINVAL);
        }

        nents = dma_map_sg(chan->device->dev, sgt->sgl, sgt->nents, dir);
        if (!nents)
                return ERR_PTR(-ENOMEM);

        txd = dmaengine_prep_slave_sg(chan, sgt->sgl, nents, conf.direction,
                                      DMA_CTRL_ACK);
        if (!txd) {
                dma_unmap_sg(chan->device->dev, sgt->sgl, sgt->nents, dir);
                return ERR_PTR(-ENOMEM);
        }
        return txd;
}

/**
 * ep93xx_spi_dma_finish() - finishes with a DMA transfer
 * @host: SPI host
 * @dir: DMA transfer direction
 *
 * Function finishes with the DMA transfer. After this, the DMA buffer is
 * unmapped.
 */
static void ep93xx_spi_dma_finish(struct spi_controller *host,
                                  enum dma_data_direction dir)
{
        struct ep93xx_spi *espi = spi_controller_get_devdata(host);
        struct dma_chan *chan;
        struct sg_table *sgt;

        if (dir == DMA_FROM_DEVICE) {
                chan = espi->dma_rx;
                sgt = &espi->rx_sgt;
        } else {
                chan = espi->dma_tx;
                sgt = &espi->tx_sgt;
        }

        dma_unmap_sg(chan->device->dev, sgt->sgl, sgt->nents, dir);
}

static void ep93xx_spi_dma_callback(void *callback_param)
{
        struct spi_controller *host = callback_param;

        ep93xx_spi_dma_finish(host, DMA_TO_DEVICE);
        ep93xx_spi_dma_finish(host, DMA_FROM_DEVICE);

        spi_finalize_current_transfer(host);
}

static int ep93xx_spi_dma_transfer(struct spi_controller *host)
{
        struct ep93xx_spi *espi = spi_controller_get_devdata(host);
        struct dma_async_tx_descriptor *rxd, *txd;

        rxd = ep93xx_spi_dma_prepare(host, DMA_FROM_DEVICE);
        if (IS_ERR(rxd)) {
                dev_err(&host->dev, "DMA RX failed: %ld\n", PTR_ERR(rxd));
                return PTR_ERR(rxd);
        }

        txd = ep93xx_spi_dma_prepare(host, DMA_TO_DEVICE);
        if (IS_ERR(txd)) {
                ep93xx_spi_dma_finish(host, DMA_FROM_DEVICE);
                dev_err(&host->dev, "DMA TX failed: %ld\n", PTR_ERR(txd));
                return PTR_ERR(txd);
        }

        /* We are ready when RX is done */
        rxd->callback = ep93xx_spi_dma_callback;
        rxd->callback_param = host;

        /* Now submit both descriptors and start DMA */
        dmaengine_submit(rxd);
        dmaengine_submit(txd);

        dma_async_issue_pending(espi->dma_rx);
        dma_async_issue_pending(espi->dma_tx);

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

static irqreturn_t ep93xx_spi_interrupt(int irq, void *dev_id)
{
        struct spi_controller *host = dev_id;
        struct ep93xx_spi *espi = spi_controller_get_devdata(host);
        u32 val;

        /*
         * If we got ROR (receive overrun) interrupt we know that something is
         * wrong. Just abort the message.
         */
        if (readl(espi->mmio + SSPIIR) & SSPIIR_RORIS) {
                /* clear the overrun interrupt */
                writel(0, espi->mmio + SSPICR);
                dev_warn(&host->dev,
                         "receive overrun, aborting the message\n");
                host->cur_msg->status = -EIO;
        } else {
                /*
                 * Interrupt is either RX (RIS) or TX (TIS). For both cases we
                 * simply execute next data transfer.
                 */
                if (ep93xx_spi_read_write(host)) {
                        /*
                         * In normal case, there still is some processing left
                         * for current transfer. Let's wait for the next
                         * interrupt then.
                         */
                        return IRQ_HANDLED;
                }
        }

        /*
         * Current transfer is finished, either with error or with success. In
         * any case we disable interrupts and notify the worker to handle
         * any post-processing of the message.
         */
        val = readl(espi->mmio + SSPCR1);
        val &= ~(SSPCR1_RORIE | SSPCR1_TIE | SSPCR1_RIE);
        writel(val, espi->mmio + SSPCR1);

        spi_finalize_current_transfer(host);

        return IRQ_HANDLED;
}

static int ep93xx_spi_transfer_one(struct spi_controller *host,
                                   struct spi_device *spi,
                                   struct spi_transfer *xfer)
{
        struct ep93xx_spi *espi = spi_controller_get_devdata(host);
        u32 val;
        int ret;

        ret = ep93xx_spi_chip_setup(host, spi, xfer);
        if (ret) {
                dev_err(&host->dev, "failed to setup chip for transfer\n");
                return ret;
        }

        host->cur_msg->state = xfer;
        espi->rx = 0;
        espi->tx = 0;

        /*
         * There is no point of setting up DMA for the transfers which will
         * fit into the FIFO and can be transferred with a single interrupt.
         * So in these cases we will be using PIO and don't bother for DMA.
         */
        if (espi->dma_rx && xfer->len > SPI_FIFO_SIZE)
                return ep93xx_spi_dma_transfer(host);

        /* Using PIO so prime the TX FIFO and enable interrupts */
        ep93xx_spi_read_write(host);

        val = readl(espi->mmio + SSPCR1);
        val |= (SSPCR1_RORIE | SSPCR1_TIE | SSPCR1_RIE);
        writel(val, espi->mmio + SSPCR1);

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

static int ep93xx_spi_prepare_message(struct spi_controller *host,
                                      struct spi_message *msg)
{
        struct ep93xx_spi *espi = spi_controller_get_devdata(host);
        unsigned long timeout;

        /*
         * Just to be sure: flush any data from RX FIFO.
         */
        timeout = jiffies + msecs_to_jiffies(SPI_TIMEOUT);
        while (readl(espi->mmio + SSPSR) & SSPSR_RNE) {
                if (time_after(jiffies, timeout)) {
                        dev_warn(&host->dev,
                                 "timeout while flushing RX FIFO\n");
                        return -ETIMEDOUT;
                }
                readl(espi->mmio + SSPDR);
        }

        /*
         * We explicitly handle FIFO level. This way we don't have to check TX
         * FIFO status using %SSPSR_TNF bit which may cause RX FIFO overruns.
         */
        espi->fifo_level = 0;

        return 0;
}

static int ep93xx_spi_prepare_hardware(struct spi_controller *host)
{
        struct ep93xx_spi *espi = spi_controller_get_devdata(host);
        u32 val;
        int ret;

        ret = clk_prepare_enable(espi->clk);
        if (ret)
                return ret;

        val = readl(espi->mmio + SSPCR1);
        val |= SSPCR1_SSE;
        writel(val, espi->mmio + SSPCR1);

        return 0;
}

static int ep93xx_spi_unprepare_hardware(struct spi_controller *host)
{
        struct ep93xx_spi *espi = spi_controller_get_devdata(host);
        u32 val;

        val = readl(espi->mmio + SSPCR1);
        val &= ~SSPCR1_SSE;
        writel(val, espi->mmio + SSPCR1);

        clk_disable_unprepare(espi->clk);

        return 0;
}

static int ep93xx_spi_setup_dma(struct device *dev, struct ep93xx_spi *espi)
{
        int ret;

        espi->zeropage = (void *)get_zeroed_page(GFP_KERNEL);
        if (!espi->zeropage)
                return -ENOMEM;

        espi->dma_rx = dma_request_chan(dev, "rx");
        if (IS_ERR(espi->dma_rx)) {
                ret = dev_err_probe(dev, PTR_ERR(espi->dma_rx), "rx DMA setup failed");
                goto fail_free_page;
        }

        espi->dma_tx = dma_request_chan(dev, "tx");
        if (IS_ERR(espi->dma_tx)) {
                ret = dev_err_probe(dev, PTR_ERR(espi->dma_tx), "tx DMA setup failed");
                goto fail_release_rx;
        }

        return 0;

fail_release_rx:
        dma_release_channel(espi->dma_rx);
        espi->dma_rx = NULL;
fail_free_page:
        free_page((unsigned long)espi->zeropage);

        return ret;
}

static void ep93xx_spi_release_dma(struct ep93xx_spi *espi)
{
        if (espi->dma_rx) {
                dma_release_channel(espi->dma_rx);
                sg_free_table(&espi->rx_sgt);
        }
        if (espi->dma_tx) {
                dma_release_channel(espi->dma_tx);
                sg_free_table(&espi->tx_sgt);
        }

        if (espi->zeropage)
                free_page((unsigned long)espi->zeropage);
}

static int ep93xx_spi_probe(struct platform_device *pdev)
{
        struct spi_controller *host;
        struct ep93xx_spi *espi;
        struct resource *res;
        int irq;
        int error;

        irq = platform_get_irq(pdev, 0);
        if (irq < 0)
                return irq;

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

        host->use_gpio_descriptors = true;
        host->prepare_transfer_hardware = ep93xx_spi_prepare_hardware;
        host->unprepare_transfer_hardware = ep93xx_spi_unprepare_hardware;
        host->prepare_message = ep93xx_spi_prepare_message;
        host->transfer_one = ep93xx_spi_transfer_one;
        host->bus_num = pdev->id;
        host->mode_bits = SPI_CPOL | SPI_CPHA | SPI_CS_HIGH;
        host->bits_per_word_mask = SPI_BPW_RANGE_MASK(4, 16);
        /*
         * The SPI core will count the number of GPIO descriptors to figure
         * out the number of chip selects available on the platform.
         */
        host->num_chipselect = 0;

        platform_set_drvdata(pdev, host);

        espi = spi_controller_get_devdata(host);

        espi->clk = devm_clk_get(&pdev->dev, NULL);
        if (IS_ERR(espi->clk)) {
                dev_err(&pdev->dev, "unable to get spi clock\n");
                error = PTR_ERR(espi->clk);
                goto fail_release_host;
        }

        /*
         * Calculate maximum and minimum supported clock rates
         * for the controller.
         */
        host->max_speed_hz = clk_get_rate(espi->clk) / 2;
        host->min_speed_hz = clk_get_rate(espi->clk) / (254 * 256);

        espi->mmio = devm_platform_get_and_ioremap_resource(pdev, 0, &res);
        if (IS_ERR(espi->mmio)) {
                error = PTR_ERR(espi->mmio);
                goto fail_release_host;
        }
        espi->sspdr_phys = res->start + SSPDR;

        error = devm_request_irq(&pdev->dev, irq, ep93xx_spi_interrupt,
                                0, "ep93xx-spi", host);
        if (error) {
                dev_err(&pdev->dev, "failed to request irq\n");
                goto fail_release_host;
        }

        error = ep93xx_spi_setup_dma(&pdev->dev, espi);
        if (error == -EPROBE_DEFER)
                goto fail_release_host;

        if (error)
                dev_warn(&pdev->dev, "DMA setup failed. Falling back to PIO\n");

        /* make sure that the hardware is disabled */
        writel(0, espi->mmio + SSPCR1);

        error = devm_spi_register_controller(&pdev->dev, host);
        if (error) {
                dev_err(&pdev->dev, "failed to register SPI host\n");
                goto fail_free_dma;
        }

        dev_info(&pdev->dev, "EP93xx SPI Controller at 0x%08lx irq %d\n",
                 (unsigned long)res->start, irq);

        return 0;

fail_free_dma:
        ep93xx_spi_release_dma(espi);
fail_release_host:
        spi_controller_put(host);

        return error;
}

static void ep93xx_spi_remove(struct platform_device *pdev)
{
        struct spi_controller *host = platform_get_drvdata(pdev);
        struct ep93xx_spi *espi = spi_controller_get_devdata(host);

        ep93xx_spi_release_dma(espi);
}

static const struct of_device_id ep93xx_spi_of_ids[] = {
        { .compatible = "cirrus,ep9301-spi" },
        { /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, ep93xx_spi_of_ids);

static struct platform_driver ep93xx_spi_driver = {
        .driver         = {
                .name   = "ep93xx-spi",
                .of_match_table = ep93xx_spi_of_ids,
        },
        .probe          = ep93xx_spi_probe,
        .remove         = ep93xx_spi_remove,
};
module_platform_driver(ep93xx_spi_driver);

MODULE_DESCRIPTION("EP93xx SPI Controller driver");
MODULE_AUTHOR("Mika Westerberg <mika.westerberg@iki.fi>");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:ep93xx-spi");