// SPDX-License-Identifier: GPL-2.0-only
/*
 * OpenCores tiny SPI host driver
 *
 * https://opencores.org/project,tiny_spi
 *
 * Copyright (C) 2011 Thomas Chou <thomas@wytron.com.tw>
 *
 * Based on spi_s3c24xx.c, which is:
 * Copyright (c) 2006 Ben Dooks
 * Copyright (c) 2006 Simtec Electronics
 *      Ben Dooks <ben@simtec.co.uk>
 */

#include <linux/interrupt.h>
#include <linux/errno.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/spi/spi.h>
#include <linux/spi/spi_bitbang.h>
#include <linux/spi/spi_oc_tiny.h>
#include <linux/io.h>
#include <linux/of.h>

#define DRV_NAME "spi_oc_tiny"

#define TINY_SPI_RXDATA 0
#define TINY_SPI_TXDATA 4
#define TINY_SPI_STATUS 8
#define TINY_SPI_CONTROL 12
#define TINY_SPI_BAUD 16

#define TINY_SPI_STATUS_TXE 0x1
#define TINY_SPI_STATUS_TXR 0x2

struct tiny_spi {
        /* bitbang has to be first */
        struct spi_bitbang bitbang;
        struct completion done;

        void __iomem *base;
        int irq;
        unsigned int freq;
        unsigned int baudwidth;
        unsigned int baud;
        unsigned int speed_hz;
        unsigned int mode;
        unsigned int len;
        unsigned int txc, rxc;
        const u8 *txp;
        u8 *rxp;
};

static inline struct tiny_spi *tiny_spi_to_hw(struct spi_device *sdev)
{
        return spi_controller_get_devdata(sdev->controller);
}

static unsigned int tiny_spi_baud(struct spi_device *spi, unsigned int hz)
{
        struct tiny_spi *hw = tiny_spi_to_hw(spi);

        return min(DIV_ROUND_UP(hw->freq, hz * 2), (1U << hw->baudwidth)) - 1;
}

static int tiny_spi_setup_transfer(struct spi_device *spi,
                                   struct spi_transfer *t)
{
        struct tiny_spi *hw = tiny_spi_to_hw(spi);
        unsigned int baud = hw->baud;

        if (t) {
                if (t->speed_hz && t->speed_hz != hw->speed_hz)
                        baud = tiny_spi_baud(spi, t->speed_hz);
        }
        writel(baud, hw->base + TINY_SPI_BAUD);
        writel(hw->mode, hw->base + TINY_SPI_CONTROL);
        return 0;
}

static int tiny_spi_setup(struct spi_device *spi)
{
        struct tiny_spi *hw = tiny_spi_to_hw(spi);

        if (spi->max_speed_hz != hw->speed_hz) {
                hw->speed_hz = spi->max_speed_hz;
                hw->baud = tiny_spi_baud(spi, hw->speed_hz);
        }
        hw->mode = spi->mode & SPI_MODE_X_MASK;
        return 0;
}

static inline void tiny_spi_wait_txr(struct tiny_spi *hw)
{
        while (!(readb(hw->base + TINY_SPI_STATUS) &
                 TINY_SPI_STATUS_TXR))
                cpu_relax();
}

static inline void tiny_spi_wait_txe(struct tiny_spi *hw)
{
        while (!(readb(hw->base + TINY_SPI_STATUS) &
                 TINY_SPI_STATUS_TXE))
                cpu_relax();
}

static int tiny_spi_txrx_bufs(struct spi_device *spi, struct spi_transfer *t)
{
        struct tiny_spi *hw = tiny_spi_to_hw(spi);
        const u8 *txp = t->tx_buf;
        u8 *rxp = t->rx_buf;
        unsigned int i;

        if (hw->irq >= 0) {
                /* use interrupt driven data transfer */
                hw->len = t->len;
                hw->txp = t->tx_buf;
                hw->rxp = t->rx_buf;
                hw->txc = 0;
                hw->rxc = 0;

                /* send the first byte */
                if (t->len > 1) {
                        writeb(hw->txp ? *hw->txp++ : 0,
                               hw->base + TINY_SPI_TXDATA);
                        hw->txc++;
                        writeb(hw->txp ? *hw->txp++ : 0,
                               hw->base + TINY_SPI_TXDATA);
                        hw->txc++;
                        writeb(TINY_SPI_STATUS_TXR, hw->base + TINY_SPI_STATUS);
                } else {
                        writeb(hw->txp ? *hw->txp++ : 0,
                               hw->base + TINY_SPI_TXDATA);
                        hw->txc++;
                        writeb(TINY_SPI_STATUS_TXE, hw->base + TINY_SPI_STATUS);
                }

                wait_for_completion(&hw->done);
        } else {
                /* we need to tighten the transfer loop */
                writeb(txp ? *txp++ : 0, hw->base + TINY_SPI_TXDATA);
                for (i = 1; i < t->len; i++) {
                        writeb(txp ? *txp++ : 0, hw->base + TINY_SPI_TXDATA);

                        if (rxp || (i != t->len - 1))
                                tiny_spi_wait_txr(hw);
                        if (rxp)
                                *rxp++ = readb(hw->base + TINY_SPI_TXDATA);
                }
                tiny_spi_wait_txe(hw);
                if (rxp)
                        *rxp++ = readb(hw->base + TINY_SPI_RXDATA);
        }

        return t->len;
}

static irqreturn_t tiny_spi_irq(int irq, void *dev)
{
        struct tiny_spi *hw = dev;

        writeb(0, hw->base + TINY_SPI_STATUS);
        if (hw->rxc + 1 == hw->len) {
                if (hw->rxp)
                        *hw->rxp++ = readb(hw->base + TINY_SPI_RXDATA);
                hw->rxc++;
                complete(&hw->done);
        } else {
                if (hw->rxp)
                        *hw->rxp++ = readb(hw->base + TINY_SPI_TXDATA);
                hw->rxc++;
                if (hw->txc < hw->len) {
                        writeb(hw->txp ? *hw->txp++ : 0,
                               hw->base + TINY_SPI_TXDATA);
                        hw->txc++;
                        writeb(TINY_SPI_STATUS_TXR,
                               hw->base + TINY_SPI_STATUS);
                } else {
                        writeb(TINY_SPI_STATUS_TXE,
                               hw->base + TINY_SPI_STATUS);
                }
        }
        return IRQ_HANDLED;
}

#ifdef CONFIG_OF
static int tiny_spi_of_probe(struct platform_device *pdev)
{
        struct tiny_spi *hw = platform_get_drvdata(pdev);
        struct device_node *np = pdev->dev.of_node;
        u32 val;

        if (!np)
                return 0;
        if (!of_property_read_u32(np, "clock-frequency", &val))
                hw->freq = val;
        if (!of_property_read_u32(np, "baud-width", &val))
                hw->baudwidth = val;
        return 0;
}
#else /* !CONFIG_OF */
static int tiny_spi_of_probe(struct platform_device *pdev)
{
        return 0;
}
#endif /* CONFIG_OF */

static int tiny_spi_probe(struct platform_device *pdev)
{
        struct tiny_spi_platform_data *platp = dev_get_platdata(&pdev->dev);
        struct tiny_spi *hw;
        struct spi_controller *host;
        int err = -ENODEV;

        host = spi_alloc_host(&pdev->dev, sizeof(struct tiny_spi));
        if (!host)
                return err;

        /* setup the host state. */
        host->bus_num = pdev->id;
        host->mode_bits = SPI_CPOL | SPI_CPHA | SPI_CS_HIGH;
        host->setup = tiny_spi_setup;
        host->use_gpio_descriptors = true;

        hw = spi_controller_get_devdata(host);
        platform_set_drvdata(pdev, hw);

        /* setup the state for the bitbang driver */
        hw->bitbang.ctlr = host;
        hw->bitbang.setup_transfer = tiny_spi_setup_transfer;
        hw->bitbang.txrx_bufs = tiny_spi_txrx_bufs;

        /* find and map our resources */
        hw->base = devm_platform_ioremap_resource(pdev, 0);
        if (IS_ERR(hw->base)) {
                err = PTR_ERR(hw->base);
                goto exit;
        }
        /* irq is optional */
        hw->irq = platform_get_irq(pdev, 0);
        if (hw->irq >= 0) {
                init_completion(&hw->done);
                err = devm_request_irq(&pdev->dev, hw->irq, tiny_spi_irq, 0,
                                       pdev->name, hw);
                if (err)
                        goto exit;
        }
        /* find platform data */
        if (platp) {
                hw->freq = platp->freq;
                hw->baudwidth = platp->baudwidth;
        } else {
                err = tiny_spi_of_probe(pdev);
                if (err)
                        goto exit;
        }

        /* register our spi controller */
        err = spi_bitbang_start(&hw->bitbang);
        if (err)
                goto exit;
        dev_info(&pdev->dev, "base %p, irq %d\n", hw->base, hw->irq);

        return 0;

exit:
        spi_controller_put(host);
        return err;
}

static void tiny_spi_remove(struct platform_device *pdev)
{
        struct tiny_spi *hw = platform_get_drvdata(pdev);
        struct spi_controller *host = hw->bitbang.ctlr;

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

#ifdef CONFIG_OF
static const struct of_device_id tiny_spi_match[] = {
        { .compatible = "opencores,tiny-spi-rtlsvn2", },
        {},
};
MODULE_DEVICE_TABLE(of, tiny_spi_match);
#endif /* CONFIG_OF */

static struct platform_driver tiny_spi_driver = {
        .probe = tiny_spi_probe,
        .remove = tiny_spi_remove,
        .driver = {
                .name = DRV_NAME,
                .pm = NULL,
                .of_match_table = of_match_ptr(tiny_spi_match),
        },
};
module_platform_driver(tiny_spi_driver);

MODULE_DESCRIPTION("OpenCores tiny SPI driver");
MODULE_AUTHOR("Thomas Chou <thomas@wytron.com.tw>");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:" DRV_NAME);