// SPDX-License-Identifier: GPL-2.0
//
// Copyright 2018 SiFive, Inc.
//
// SiFive SPI controller driver (master mode only)
//
// Author: SiFive, Inc.
// sifive@sifive.com

#include <linux/clk.h>
#include <linux/module.h>
#include <linux/interrupt.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/spi/spi.h>
#include <linux/io.h>
#include <linux/log2.h>

#define SIFIVE_SPI_DRIVER_NAME           "sifive_spi"

#define SIFIVE_SPI_MAX_CS                32
#define SIFIVE_SPI_DEFAULT_DEPTH         8
#define SIFIVE_SPI_DEFAULT_MAX_BITS      8

/* register offsets */
#define SIFIVE_SPI_REG_SCKDIV            0x00 /* Serial clock divisor */
#define SIFIVE_SPI_REG_SCKMODE           0x04 /* Serial clock mode */
#define SIFIVE_SPI_REG_CSID              0x10 /* Chip select ID */
#define SIFIVE_SPI_REG_CSDEF             0x14 /* Chip select default */
#define SIFIVE_SPI_REG_CSMODE            0x18 /* Chip select mode */
#define SIFIVE_SPI_REG_DELAY0            0x28 /* Delay control 0 */
#define SIFIVE_SPI_REG_DELAY1            0x2c /* Delay control 1 */
#define SIFIVE_SPI_REG_FMT               0x40 /* Frame format */
#define SIFIVE_SPI_REG_TXDATA            0x48 /* Tx FIFO data */
#define SIFIVE_SPI_REG_RXDATA            0x4c /* Rx FIFO data */
#define SIFIVE_SPI_REG_TXMARK            0x50 /* Tx FIFO watermark */
#define SIFIVE_SPI_REG_RXMARK            0x54 /* Rx FIFO watermark */
#define SIFIVE_SPI_REG_FCTRL             0x60 /* SPI flash interface control */
#define SIFIVE_SPI_REG_FFMT              0x64 /* SPI flash instruction format */
#define SIFIVE_SPI_REG_IE                0x70 /* Interrupt Enable Register */
#define SIFIVE_SPI_REG_IP                0x74 /* Interrupt Pendings Register */

/* sckdiv bits */
#define SIFIVE_SPI_SCKDIV_DIV_MASK       0xfffU

/* sckmode bits */
#define SIFIVE_SPI_SCKMODE_PHA           BIT(0)
#define SIFIVE_SPI_SCKMODE_POL           BIT(1)
#define SIFIVE_SPI_SCKMODE_MODE_MASK     (SIFIVE_SPI_SCKMODE_PHA | \
                                          SIFIVE_SPI_SCKMODE_POL)

/* csmode bits */
#define SIFIVE_SPI_CSMODE_MODE_AUTO      0U
#define SIFIVE_SPI_CSMODE_MODE_HOLD      2U
#define SIFIVE_SPI_CSMODE_MODE_OFF       3U

/* delay0 bits */
#define SIFIVE_SPI_DELAY0_CSSCK(x)       ((u32)(x))
#define SIFIVE_SPI_DELAY0_CSSCK_MASK     0xffU
#define SIFIVE_SPI_DELAY0_SCKCS(x)       ((u32)(x) << 16)
#define SIFIVE_SPI_DELAY0_SCKCS_MASK     (0xffU << 16)

/* delay1 bits */
#define SIFIVE_SPI_DELAY1_INTERCS(x)     ((u32)(x))
#define SIFIVE_SPI_DELAY1_INTERCS_MASK   0xffU
#define SIFIVE_SPI_DELAY1_INTERXFR(x)    ((u32)(x) << 16)
#define SIFIVE_SPI_DELAY1_INTERXFR_MASK  (0xffU << 16)

/* fmt bits */
#define SIFIVE_SPI_FMT_PROTO_SINGLE      0U
#define SIFIVE_SPI_FMT_PROTO_DUAL        1U
#define SIFIVE_SPI_FMT_PROTO_QUAD        2U
#define SIFIVE_SPI_FMT_PROTO_MASK        3U
#define SIFIVE_SPI_FMT_ENDIAN            BIT(2)
#define SIFIVE_SPI_FMT_DIR               BIT(3)
#define SIFIVE_SPI_FMT_LEN(x)            ((u32)(x) << 16)
#define SIFIVE_SPI_FMT_LEN_MASK          (0xfU << 16)

/* txdata bits */
#define SIFIVE_SPI_TXDATA_DATA_MASK      0xffU
#define SIFIVE_SPI_TXDATA_FULL           BIT(31)

/* rxdata bits */
#define SIFIVE_SPI_RXDATA_DATA_MASK      0xffU
#define SIFIVE_SPI_RXDATA_EMPTY          BIT(31)

/* ie and ip bits */
#define SIFIVE_SPI_IP_TXWM               BIT(0)
#define SIFIVE_SPI_IP_RXWM               BIT(1)

struct sifive_spi {
        void __iomem      *regs;        /* virt. address of control registers */
        struct clk        *clk;         /* bus clock */
        unsigned int      fifo_depth;   /* fifo depth in words */
        u32               cs_inactive;  /* level of the CS pins when inactive */
        struct completion done;         /* wake-up from interrupt */
};

static void sifive_spi_write(struct sifive_spi *spi, int offset, u32 value)
{
        iowrite32(value, spi->regs + offset);
}

static u32 sifive_spi_read(struct sifive_spi *spi, int offset)
{
        return ioread32(spi->regs + offset);
}

static void sifive_spi_init(struct sifive_spi *spi)
{
        /* Watermark interrupts are disabled by default */
        sifive_spi_write(spi, SIFIVE_SPI_REG_IE, 0);

        /* Default watermark FIFO threshold values */
        sifive_spi_write(spi, SIFIVE_SPI_REG_TXMARK, 1);
        sifive_spi_write(spi, SIFIVE_SPI_REG_RXMARK, 0);

        /* Set CS/SCK Delays and Inactive Time to defaults */
        sifive_spi_write(spi, SIFIVE_SPI_REG_DELAY0,
                         SIFIVE_SPI_DELAY0_CSSCK(1) |
                         SIFIVE_SPI_DELAY0_SCKCS(1));
        sifive_spi_write(spi, SIFIVE_SPI_REG_DELAY1,
                         SIFIVE_SPI_DELAY1_INTERCS(1) |
                         SIFIVE_SPI_DELAY1_INTERXFR(0));

        /* Exit specialized memory-mapped SPI flash mode */
        sifive_spi_write(spi, SIFIVE_SPI_REG_FCTRL, 0);
}

static int
sifive_spi_prepare_message(struct spi_controller *host, struct spi_message *msg)
{
        struct sifive_spi *spi = spi_controller_get_devdata(host);
        struct spi_device *device = msg->spi;

        /* Update the chip select polarity */
        if (device->mode & SPI_CS_HIGH)
                spi->cs_inactive &= ~BIT(spi_get_chipselect(device, 0));
        else
                spi->cs_inactive |= BIT(spi_get_chipselect(device, 0));
        sifive_spi_write(spi, SIFIVE_SPI_REG_CSDEF, spi->cs_inactive);

        /* Select the correct device */
        sifive_spi_write(spi, SIFIVE_SPI_REG_CSID, spi_get_chipselect(device, 0));

        /* Set clock mode */
        sifive_spi_write(spi, SIFIVE_SPI_REG_SCKMODE,
                         device->mode & SIFIVE_SPI_SCKMODE_MODE_MASK);

        return 0;
}

static void sifive_spi_set_cs(struct spi_device *device, bool is_high)
{
        struct sifive_spi *spi = spi_controller_get_devdata(device->controller);

        /* Reverse polarity is handled by SCMR/CPOL. Not inverted CS. */
        if (device->mode & SPI_CS_HIGH)
                is_high = !is_high;

        sifive_spi_write(spi, SIFIVE_SPI_REG_CSMODE, is_high ?
                         SIFIVE_SPI_CSMODE_MODE_AUTO :
                         SIFIVE_SPI_CSMODE_MODE_HOLD);
}

static int
sifive_spi_prep_transfer(struct sifive_spi *spi, struct spi_device *device,
                         struct spi_transfer *t)
{
        u32 cr;
        unsigned int mode;

        /* Calculate and program the clock rate */
        cr = DIV_ROUND_UP(clk_get_rate(spi->clk) >> 1, t->speed_hz) - 1;
        cr &= SIFIVE_SPI_SCKDIV_DIV_MASK;
        sifive_spi_write(spi, SIFIVE_SPI_REG_SCKDIV, cr);

        mode = max_t(unsigned int, t->rx_nbits, t->tx_nbits);

        /* Set frame format */
        cr = SIFIVE_SPI_FMT_LEN(t->bits_per_word);
        switch (mode) {
        case SPI_NBITS_QUAD:
                cr |= SIFIVE_SPI_FMT_PROTO_QUAD;
                break;
        case SPI_NBITS_DUAL:
                cr |= SIFIVE_SPI_FMT_PROTO_DUAL;
                break;
        default:
                cr |= SIFIVE_SPI_FMT_PROTO_SINGLE;
                break;
        }
        if (device->mode & SPI_LSB_FIRST)
                cr |= SIFIVE_SPI_FMT_ENDIAN;
        if (!t->rx_buf)
                cr |= SIFIVE_SPI_FMT_DIR;
        sifive_spi_write(spi, SIFIVE_SPI_REG_FMT, cr);

        /* We will want to poll if the time we need to wait is
         * less than the context switching time.
         * Let's call that threshold 5us. The operation will take:
         *    (8/mode) * fifo_depth / hz <= 5 * 10^-6
         *    1600000 * fifo_depth <= hz * mode
         */
        return 1600000 * spi->fifo_depth <= t->speed_hz * mode;
}

static irqreturn_t sifive_spi_irq(int irq, void *dev_id)
{
        struct sifive_spi *spi = dev_id;
        u32 ip = sifive_spi_read(spi, SIFIVE_SPI_REG_IP);

        if (ip & (SIFIVE_SPI_IP_TXWM | SIFIVE_SPI_IP_RXWM)) {
                /* Disable interrupts until next transfer */
                sifive_spi_write(spi, SIFIVE_SPI_REG_IE, 0);
                complete(&spi->done);
                return IRQ_HANDLED;
        }

        return IRQ_NONE;
}

static void sifive_spi_wait(struct sifive_spi *spi, u32 bit, int poll)
{
        if (poll) {
                u32 cr;

                do {
                        cr = sifive_spi_read(spi, SIFIVE_SPI_REG_IP);
                } while (!(cr & bit));
        } else {
                reinit_completion(&spi->done);
                sifive_spi_write(spi, SIFIVE_SPI_REG_IE, bit);
                wait_for_completion(&spi->done);
        }
}

static void sifive_spi_tx(struct sifive_spi *spi, const u8 *tx_ptr)
{
        WARN_ON_ONCE((sifive_spi_read(spi, SIFIVE_SPI_REG_TXDATA)
                                & SIFIVE_SPI_TXDATA_FULL) != 0);
        sifive_spi_write(spi, SIFIVE_SPI_REG_TXDATA,
                         *tx_ptr & SIFIVE_SPI_TXDATA_DATA_MASK);
}

static void sifive_spi_rx(struct sifive_spi *spi, u8 *rx_ptr)
{
        u32 data = sifive_spi_read(spi, SIFIVE_SPI_REG_RXDATA);

        WARN_ON_ONCE((data & SIFIVE_SPI_RXDATA_EMPTY) != 0);
        *rx_ptr = data & SIFIVE_SPI_RXDATA_DATA_MASK;
}

static int
sifive_spi_transfer_one(struct spi_controller *host, struct spi_device *device,
                        struct spi_transfer *t)
{
        struct sifive_spi *spi = spi_controller_get_devdata(host);
        int poll = sifive_spi_prep_transfer(spi, device, t);
        const u8 *tx_ptr = t->tx_buf;
        u8 *rx_ptr = t->rx_buf;
        unsigned int remaining_words = t->len;

        while (remaining_words) {
                unsigned int n_words = min(remaining_words, spi->fifo_depth);
                unsigned int i;

                /* Enqueue n_words for transmission */
                for (i = 0; i < n_words; i++)
                        sifive_spi_tx(spi, tx_ptr++);

                if (rx_ptr) {
                        /* Wait for transmission + reception to complete */
                        sifive_spi_write(spi, SIFIVE_SPI_REG_RXMARK,
                                         n_words - 1);
                        sifive_spi_wait(spi, SIFIVE_SPI_IP_RXWM, poll);

                        /* Read out all the data from the RX FIFO */
                        for (i = 0; i < n_words; i++)
                                sifive_spi_rx(spi, rx_ptr++);
                } else {
                        /* Wait for transmission to complete */
                        sifive_spi_wait(spi, SIFIVE_SPI_IP_TXWM, poll);
                }

                remaining_words -= n_words;
        }

        return 0;
}

static int sifive_spi_probe(struct platform_device *pdev)
{
        struct sifive_spi *spi;
        int ret, irq, num_cs;
        u32 cs_bits, max_bits_per_word;
        struct spi_controller *host;

        host = spi_alloc_host(&pdev->dev, sizeof(struct sifive_spi));
        if (!host) {
                dev_err(&pdev->dev, "out of memory\n");
                return -ENOMEM;
        }

        spi = spi_controller_get_devdata(host);
        init_completion(&spi->done);
        platform_set_drvdata(pdev, host);

        spi->regs = devm_platform_ioremap_resource(pdev, 0);
        if (IS_ERR(spi->regs)) {
                ret = PTR_ERR(spi->regs);
                goto put_host;
        }

        spi->clk = devm_clk_get(&pdev->dev, NULL);
        if (IS_ERR(spi->clk)) {
                dev_err(&pdev->dev, "Unable to find bus clock\n");
                ret = PTR_ERR(spi->clk);
                goto put_host;
        }

        irq = platform_get_irq(pdev, 0);
        if (irq < 0) {
                ret = irq;
                goto put_host;
        }

        /* Optional parameters */
        ret =
          of_property_read_u32(pdev->dev.of_node, "sifive,fifo-depth",
                               &spi->fifo_depth);
        if (ret < 0)
                spi->fifo_depth = SIFIVE_SPI_DEFAULT_DEPTH;

        ret =
          of_property_read_u32(pdev->dev.of_node, "sifive,max-bits-per-word",
                               &max_bits_per_word);

        if (!ret && max_bits_per_word < 8) {
                dev_err(&pdev->dev, "Only 8bit SPI words supported by the driver\n");
                ret = -EINVAL;
                goto put_host;
        }

        /* Spin up the bus clock before hitting registers */
        ret = clk_prepare_enable(spi->clk);
        if (ret) {
                dev_err(&pdev->dev, "Unable to enable bus clock\n");
                goto put_host;
        }

        /* probe the number of CS lines */
        spi->cs_inactive = sifive_spi_read(spi, SIFIVE_SPI_REG_CSDEF);
        sifive_spi_write(spi, SIFIVE_SPI_REG_CSDEF, 0xffffffffU);
        cs_bits = sifive_spi_read(spi, SIFIVE_SPI_REG_CSDEF);
        sifive_spi_write(spi, SIFIVE_SPI_REG_CSDEF, spi->cs_inactive);
        if (!cs_bits) {
                dev_err(&pdev->dev, "Could not auto probe CS lines\n");
                ret = -EINVAL;
                goto disable_clk;
        }

        num_cs = ilog2(cs_bits) + 1;
        if (num_cs > SIFIVE_SPI_MAX_CS) {
                dev_err(&pdev->dev, "Invalid number of spi targets\n");
                ret = -EINVAL;
                goto disable_clk;
        }

        /* Define our host */
        host->bus_num = pdev->id;
        host->num_chipselect = num_cs;
        host->mode_bits = SPI_CPHA | SPI_CPOL
                          | SPI_CS_HIGH | SPI_LSB_FIRST
                          | SPI_TX_DUAL | SPI_TX_QUAD
                          | SPI_RX_DUAL | SPI_RX_QUAD;
        /* TODO: add driver support for bits_per_word < 8
         * we need to "left-align" the bits (unless SPI_LSB_FIRST)
         */
        host->bits_per_word_mask = SPI_BPW_MASK(8);
        host->flags = SPI_CONTROLLER_MUST_TX | SPI_CONTROLLER_GPIO_SS;
        host->prepare_message = sifive_spi_prepare_message;
        host->set_cs = sifive_spi_set_cs;
        host->transfer_one = sifive_spi_transfer_one;

        pdev->dev.dma_mask = NULL;
        /* Configure the SPI host hardware */
        sifive_spi_init(spi);

        /* Register for SPI Interrupt */
        ret = devm_request_irq(&pdev->dev, irq, sifive_spi_irq, 0,
                               dev_name(&pdev->dev), spi);
        if (ret) {
                dev_err(&pdev->dev, "Unable to bind to interrupt\n");
                goto disable_clk;
        }

        dev_info(&pdev->dev, "mapped; irq=%d, cs=%d\n",
                 irq, host->num_chipselect);

        ret = devm_spi_register_controller(&pdev->dev, host);
        if (ret < 0) {
                dev_err(&pdev->dev, "spi_register_host failed\n");
                goto disable_clk;
        }

        return 0;

disable_clk:
        clk_disable_unprepare(spi->clk);
put_host:
        spi_controller_put(host);

        return ret;
}

static void sifive_spi_remove(struct platform_device *pdev)
{
        struct spi_controller *host = platform_get_drvdata(pdev);
        struct sifive_spi *spi = spi_controller_get_devdata(host);

        /* Disable all the interrupts just in case */
        sifive_spi_write(spi, SIFIVE_SPI_REG_IE, 0);
        clk_disable_unprepare(spi->clk);
}

static int sifive_spi_suspend(struct device *dev)
{
        struct spi_controller *host = dev_get_drvdata(dev);
        struct sifive_spi *spi = spi_controller_get_devdata(host);
        int ret;

        ret = spi_controller_suspend(host);
        if (ret)
                return ret;

        /* Disable all the interrupts just in case */
        sifive_spi_write(spi, SIFIVE_SPI_REG_IE, 0);

        clk_disable_unprepare(spi->clk);

        return ret;
}

static int sifive_spi_resume(struct device *dev)
{
        struct spi_controller *host = dev_get_drvdata(dev);
        struct sifive_spi *spi = spi_controller_get_devdata(host);
        int ret;

        ret = clk_prepare_enable(spi->clk);
        if (ret)
                return ret;
        ret = spi_controller_resume(host);
        if (ret)
                clk_disable_unprepare(spi->clk);

        return ret;
}

static DEFINE_SIMPLE_DEV_PM_OPS(sifive_spi_pm_ops,
                                sifive_spi_suspend, sifive_spi_resume);


static const struct of_device_id sifive_spi_of_match[] = {
        { .compatible = "sifive,spi0", },
        {}
};
MODULE_DEVICE_TABLE(of, sifive_spi_of_match);

static struct platform_driver sifive_spi_driver = {
        .probe = sifive_spi_probe,
        .remove = sifive_spi_remove,
        .driver = {
                .name = SIFIVE_SPI_DRIVER_NAME,
                .pm = &sifive_spi_pm_ops,
                .of_match_table = sifive_spi_of_match,
        },
};
module_platform_driver(sifive_spi_driver);

MODULE_AUTHOR("SiFive, Inc. <sifive@sifive.com>");
MODULE_DESCRIPTION("SiFive SPI driver");
MODULE_LICENSE("GPL");