// SPDX-License-Identifier: GPL-2.0-only
/*
 * Xtensa xtfpga SPI controller driver
 *
 * Copyright (c) 2014 Cadence Design Systems Inc.
 */

#include <linux/delay.h>
#include <linux/io.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/spi/spi.h>
#include <linux/spi/spi_bitbang.h>

#define XTFPGA_SPI_NAME "xtfpga_spi"

#define XTFPGA_SPI_START        0x0
#define XTFPGA_SPI_BUSY         0x4
#define XTFPGA_SPI_DATA         0x8

#define BUSY_WAIT_US            100

struct xtfpga_spi {
        struct spi_bitbang bitbang;
        void __iomem *regs;
        u32 data;
        unsigned data_sz;
};

static inline void xtfpga_spi_write32(const struct xtfpga_spi *spi,
                                      unsigned addr, u32 val)
{
        __raw_writel(val, spi->regs + addr);
}

static inline unsigned int xtfpga_spi_read32(const struct xtfpga_spi *spi,
                                             unsigned addr)
{
        return __raw_readl(spi->regs + addr);
}

static inline void xtfpga_spi_wait_busy(struct xtfpga_spi *xspi)
{
        unsigned i;

        for (i = 0; xtfpga_spi_read32(xspi, XTFPGA_SPI_BUSY) &&
             i < BUSY_WAIT_US; ++i)
                udelay(1);
        WARN_ON_ONCE(i == BUSY_WAIT_US);
}

static u32 xtfpga_spi_txrx_word(struct spi_device *spi, unsigned nsecs,
                                u32 v, u8 bits, unsigned flags)
{
        struct xtfpga_spi *xspi = spi_controller_get_devdata(spi->controller);

        xspi->data = (xspi->data << bits) | (v & GENMASK(bits - 1, 0));
        xspi->data_sz += bits;
        if (xspi->data_sz >= 16) {
                xtfpga_spi_write32(xspi, XTFPGA_SPI_DATA,
                                   xspi->data >> (xspi->data_sz - 16));
                xspi->data_sz -= 16;
                xtfpga_spi_write32(xspi, XTFPGA_SPI_START, 1);
                xtfpga_spi_wait_busy(xspi);
                xtfpga_spi_write32(xspi, XTFPGA_SPI_START, 0);
        }

        return 0;
}

static void xtfpga_spi_chipselect(struct spi_device *spi, int is_on)
{
        struct xtfpga_spi *xspi = spi_controller_get_devdata(spi->controller);

        WARN_ON(xspi->data_sz != 0);
        xspi->data_sz = 0;
}

static int xtfpga_spi_probe(struct platform_device *pdev)
{
        struct xtfpga_spi *xspi;
        int ret;
        struct spi_controller *host;

        host = devm_spi_alloc_host(&pdev->dev, sizeof(struct xtfpga_spi));
        if (!host)
                return -ENOMEM;

        host->flags = SPI_CONTROLLER_NO_RX;
        host->bits_per_word_mask = SPI_BPW_RANGE_MASK(1, 16);
        host->bus_num = pdev->dev.id;

        xspi = spi_controller_get_devdata(host);
        xspi->bitbang.ctlr = host;
        xspi->bitbang.chipselect = xtfpga_spi_chipselect;
        xspi->bitbang.txrx_word[SPI_MODE_0] = xtfpga_spi_txrx_word;
        xspi->regs = devm_platform_ioremap_resource(pdev, 0);
        if (IS_ERR(xspi->regs))
                return PTR_ERR(xspi->regs);

        xtfpga_spi_write32(xspi, XTFPGA_SPI_START, 0);
        usleep_range(1000, 2000);
        if (xtfpga_spi_read32(xspi, XTFPGA_SPI_BUSY)) {
                dev_err(&pdev->dev, "Device stuck in busy state\n");
                return -EBUSY;
        }

        ret = spi_bitbang_start(&xspi->bitbang);
        if (ret < 0) {
                dev_err(&pdev->dev, "spi_bitbang_start failed\n");
                return ret;
        }

        platform_set_drvdata(pdev, host);
        return 0;
}

static void xtfpga_spi_remove(struct platform_device *pdev)
{
        struct spi_controller *host = platform_get_drvdata(pdev);
        struct xtfpga_spi *xspi = spi_controller_get_devdata(host);

        spi_bitbang_stop(&xspi->bitbang);
        spi_controller_put(host);
}

MODULE_ALIAS("platform:" XTFPGA_SPI_NAME);

#ifdef CONFIG_OF
static const struct of_device_id xtfpga_spi_of_match[] = {
        { .compatible = "cdns,xtfpga-spi", },
        {}
};
MODULE_DEVICE_TABLE(of, xtfpga_spi_of_match);
#endif

static struct platform_driver xtfpga_spi_driver = {
        .probe = xtfpga_spi_probe,
        .remove = xtfpga_spi_remove,
        .driver = {
                .name = XTFPGA_SPI_NAME,
                .of_match_table = of_match_ptr(xtfpga_spi_of_match),
        },
};
module_platform_driver(xtfpga_spi_driver);

MODULE_AUTHOR("Max Filippov <jcmvbkbc@gmail.com>");
MODULE_DESCRIPTION("xtensa xtfpga SPI driver");
MODULE_LICENSE("GPL");