// SPDX-License-Identifier: GPL-2.0-only
/*
 * Xilinx SPI controller driver (host mode only)
 *
 * Author: MontaVista Software, Inc.
 *      source@mvista.com
 *
 * Copyright (c) 2010 Secret Lab Technologies, Ltd.
 * Copyright (c) 2009 Intel Corporation
 * 2002-2007 (c) MontaVista Software, Inc.

 */

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

#define XILINX_SPI_MAX_CS       32

#define XILINX_SPI_NAME "xilinx_spi"

/* Register definitions as per "OPB Serial Peripheral Interface (SPI) (v1.00e)
 * Product Specification", DS464
 */
#define XSPI_CR_OFFSET          0x60    /* Control Register */

#define XSPI_CR_LOOP            0x01
#define XSPI_CR_ENABLE          0x02
#define XSPI_CR_MASTER_MODE     0x04
#define XSPI_CR_CPOL            0x08
#define XSPI_CR_CPHA            0x10
#define XSPI_CR_MODE_MASK       (XSPI_CR_CPHA | XSPI_CR_CPOL | \
                                 XSPI_CR_LSB_FIRST | XSPI_CR_LOOP)
#define XSPI_CR_TXFIFO_RESET    0x20
#define XSPI_CR_RXFIFO_RESET    0x40
#define XSPI_CR_MANUAL_SSELECT  0x80
#define XSPI_CR_TRANS_INHIBIT   0x100
#define XSPI_CR_LSB_FIRST       0x200

#define XSPI_SR_OFFSET          0x64    /* Status Register */

#define XSPI_SR_RX_EMPTY_MASK   0x01    /* Receive FIFO is empty */
#define XSPI_SR_RX_FULL_MASK    0x02    /* Receive FIFO is full */
#define XSPI_SR_TX_EMPTY_MASK   0x04    /* Transmit FIFO is empty */
#define XSPI_SR_TX_FULL_MASK    0x08    /* Transmit FIFO is full */
#define XSPI_SR_MODE_FAULT_MASK 0x10    /* Mode fault error */

#define XSPI_TXD_OFFSET         0x68    /* Data Transmit Register */
#define XSPI_RXD_OFFSET         0x6c    /* Data Receive Register */

#define XSPI_SSR_OFFSET         0x70    /* 32-bit Slave Select Register */

/* Register definitions as per "OPB IPIF (v3.01c) Product Specification", DS414
 * IPIF registers are 32 bit
 */
#define XIPIF_V123B_DGIER_OFFSET        0x1c    /* IPIF global int enable reg */
#define XIPIF_V123B_GINTR_ENABLE        0x80000000

#define XIPIF_V123B_IISR_OFFSET         0x20    /* IPIF interrupt status reg */
#define XIPIF_V123B_IIER_OFFSET         0x28    /* IPIF interrupt enable reg */

#define XSPI_INTR_MODE_FAULT            0x01    /* Mode fault error */
#define XSPI_INTR_SLAVE_MODE_FAULT      0x02    /* Selected as slave while
                                                 * disabled */
#define XSPI_INTR_TX_EMPTY              0x04    /* TxFIFO is empty */
#define XSPI_INTR_TX_UNDERRUN           0x08    /* TxFIFO was underrun */
#define XSPI_INTR_RX_FULL               0x10    /* RxFIFO is full */
#define XSPI_INTR_RX_OVERRUN            0x20    /* RxFIFO was overrun */
#define XSPI_INTR_TX_HALF_EMPTY         0x40    /* TxFIFO is half empty */

#define XIPIF_V123B_RESETR_OFFSET       0x40    /* IPIF reset register */
#define XIPIF_V123B_RESET_MASK          0x0a    /* the value to write */

struct xilinx_spi {
        /* bitbang has to be first */
        struct spi_bitbang bitbang;
        struct completion done;
        void __iomem    *regs;  /* virt. address of the control registers */

        int             irq;
        bool force_irq;         /* force irq to setup host inhibit */
        u8 *rx_ptr;             /* pointer in the Tx buffer */
        const u8 *tx_ptr;       /* pointer in the Rx buffer */
        u8 bytes_per_word;
        int buffer_size;        /* buffer size in words */
        u32 cs_inactive;        /* Level of the CS pins when inactive*/
        unsigned int (*read_fn)(void __iomem *addr);
        void (*write_fn)(u32 val, void __iomem *addr);
};

static void xspi_write32(u32 val, void __iomem *addr)
{
        iowrite32(val, addr);
}

static unsigned int xspi_read32(void __iomem *addr)
{
        return ioread32(addr);
}

static void xspi_write32_be(u32 val, void __iomem *addr)
{
        iowrite32be(val, addr);
}

static unsigned int xspi_read32_be(void __iomem *addr)
{
        return ioread32be(addr);
}

static void xilinx_spi_tx(struct xilinx_spi *xspi)
{
        u32 data = 0;

        if (!xspi->tx_ptr) {
                xspi->write_fn(0, xspi->regs + XSPI_TXD_OFFSET);
                return;
        }

        switch (xspi->bytes_per_word) {
        case 1:
                data = *(u8 *)(xspi->tx_ptr);
                break;
        case 2:
                data = *(u16 *)(xspi->tx_ptr);
                break;
        case 4:
                data = *(u32 *)(xspi->tx_ptr);
                break;
        }

        xspi->write_fn(data, xspi->regs + XSPI_TXD_OFFSET);
        xspi->tx_ptr += xspi->bytes_per_word;
}

static void xilinx_spi_rx(struct xilinx_spi *xspi)
{
        u32 data = xspi->read_fn(xspi->regs + XSPI_RXD_OFFSET);

        if (!xspi->rx_ptr)
                return;

        switch (xspi->bytes_per_word) {
        case 1:
                *(u8 *)(xspi->rx_ptr) = data;
                break;
        case 2:
                *(u16 *)(xspi->rx_ptr) = data;
                break;
        case 4:
                *(u32 *)(xspi->rx_ptr) = data;
                break;
        }

        xspi->rx_ptr += xspi->bytes_per_word;
}

static void xspi_init_hw(struct xilinx_spi *xspi)
{
        void __iomem *regs_base = xspi->regs;

        /* Reset the SPI device */
        xspi->write_fn(XIPIF_V123B_RESET_MASK,
                regs_base + XIPIF_V123B_RESETR_OFFSET);
        /* Enable the transmit empty interrupt, which we use to determine
         * progress on the transmission.
         */
        xspi->write_fn(XSPI_INTR_TX_EMPTY,
                        regs_base + XIPIF_V123B_IIER_OFFSET);
        /* Disable the global IPIF interrupt */
        xspi->write_fn(0, regs_base + XIPIF_V123B_DGIER_OFFSET);
        /* Deselect the Target on the SPI bus */
        xspi->write_fn(0xffff, regs_base + XSPI_SSR_OFFSET);
        /* Disable the transmitter, enable Manual Target Select Assertion,
         * put SPI controller into host mode, and enable it */
        xspi->write_fn(XSPI_CR_MANUAL_SSELECT | XSPI_CR_MASTER_MODE |
                XSPI_CR_ENABLE | XSPI_CR_TXFIFO_RESET | XSPI_CR_RXFIFO_RESET,
                regs_base + XSPI_CR_OFFSET);
}

static void xilinx_spi_chipselect(struct spi_device *spi, int is_on)
{
        struct xilinx_spi *xspi = spi_controller_get_devdata(spi->controller);
        u16 cr;
        u32 cs;

        if (is_on == BITBANG_CS_INACTIVE) {
                /* Deselect the target on the SPI bus */
                xspi->write_fn(xspi->cs_inactive, xspi->regs + XSPI_SSR_OFFSET);
                return;
        }

        /* Set the SPI clock phase and polarity */
        cr = xspi->read_fn(xspi->regs + XSPI_CR_OFFSET) & ~XSPI_CR_MODE_MASK;
        if (spi->mode & SPI_CPHA)
                cr |= XSPI_CR_CPHA;
        if (spi->mode & SPI_CPOL)
                cr |= XSPI_CR_CPOL;
        if (spi->mode & SPI_LSB_FIRST)
                cr |= XSPI_CR_LSB_FIRST;
        if (spi->mode & SPI_LOOP)
                cr |= XSPI_CR_LOOP;
        xspi->write_fn(cr, xspi->regs + XSPI_CR_OFFSET);

        /* We do not check spi->max_speed_hz here as the SPI clock
         * frequency is not software programmable (the IP block design
         * parameter)
         */

        cs = xspi->cs_inactive;
        cs ^= BIT(spi_get_chipselect(spi, 0));

        /* Activate the chip select */
        xspi->write_fn(cs, xspi->regs + XSPI_SSR_OFFSET);
}

/* spi_bitbang requires custom setup_transfer() to be defined if there is a
 * custom txrx_bufs().
 */
static int xilinx_spi_setup_transfer(struct spi_device *spi,
                struct spi_transfer *t)
{
        struct xilinx_spi *xspi = spi_controller_get_devdata(spi->controller);

        if (spi->mode & SPI_CS_HIGH)
                xspi->cs_inactive &= ~BIT(spi_get_chipselect(spi, 0));
        else
                xspi->cs_inactive |= BIT(spi_get_chipselect(spi, 0));

        return 0;
}

static int xilinx_spi_txrx_bufs(struct spi_device *spi, struct spi_transfer *t)
{
        struct xilinx_spi *xspi = spi_controller_get_devdata(spi->controller);
        int remaining_words;    /* the number of words left to transfer */
        bool use_irq = false;
        u16 cr = 0;

        /* We get here with transmitter inhibited */

        xspi->tx_ptr = t->tx_buf;
        xspi->rx_ptr = t->rx_buf;
        remaining_words = t->len / xspi->bytes_per_word;

        if (xspi->irq >= 0 &&
            (xspi->force_irq || remaining_words > xspi->buffer_size)) {
                u32 isr;

                use_irq = true;
                /* Inhibit irq to avoid spurious irqs on tx_empty*/
                cr = xspi->read_fn(xspi->regs + XSPI_CR_OFFSET);
                xspi->write_fn(cr | XSPI_CR_TRANS_INHIBIT,
                               xspi->regs + XSPI_CR_OFFSET);
                /* ACK old irqs (if any) */
                isr = xspi->read_fn(xspi->regs + XIPIF_V123B_IISR_OFFSET);
                if (isr)
                        xspi->write_fn(isr,
                                       xspi->regs + XIPIF_V123B_IISR_OFFSET);
                /* Enable the global IPIF interrupt */
                xspi->write_fn(XIPIF_V123B_GINTR_ENABLE,
                                xspi->regs + XIPIF_V123B_DGIER_OFFSET);
                reinit_completion(&xspi->done);
        }

        while (remaining_words) {
                int n_words, tx_words, rx_words;
                u32 sr;
                int stalled;

                n_words = min(remaining_words, xspi->buffer_size);

                tx_words = n_words;
                while (tx_words--)
                        xilinx_spi_tx(xspi);

                /* Start the transfer by not inhibiting the transmitter any
                 * longer
                 */

                if (use_irq) {
                        xspi->write_fn(cr, xspi->regs + XSPI_CR_OFFSET);
                        wait_for_completion(&xspi->done);
                        /* A transmit has just completed. Process received data
                         * and check for more data to transmit. Always inhibit
                         * the transmitter while the Isr refills the transmit
                         * register/FIFO, or make sure it is stopped if we're
                         * done.
                         */
                        xspi->write_fn(cr | XSPI_CR_TRANS_INHIBIT,
                                       xspi->regs + XSPI_CR_OFFSET);
                        sr = XSPI_SR_TX_EMPTY_MASK;
                } else
                        sr = xspi->read_fn(xspi->regs + XSPI_SR_OFFSET);

                /* Read out all the data from the Rx FIFO */
                rx_words = n_words;
                stalled = 32;
                while (rx_words) {
                        if (rx_words == n_words && !(stalled--) &&
                            !(sr & XSPI_SR_TX_EMPTY_MASK) &&
                            (sr & XSPI_SR_RX_EMPTY_MASK)) {
                                dev_err(&spi->dev,
                                        "Detected stall. Check C_SPI_MODE and C_SPI_MEMORY\n");
                                xspi_init_hw(xspi);
                                return -EIO;
                        }

                        if ((sr & XSPI_SR_TX_EMPTY_MASK) && (rx_words > 1)) {
                                xilinx_spi_rx(xspi);
                                rx_words--;
                                continue;
                        }

                        sr = xspi->read_fn(xspi->regs + XSPI_SR_OFFSET);
                        if (!(sr & XSPI_SR_RX_EMPTY_MASK)) {
                                xilinx_spi_rx(xspi);
                                rx_words--;
                        }
                }

                remaining_words -= n_words;
        }

        if (use_irq) {
                xspi->write_fn(0, xspi->regs + XIPIF_V123B_DGIER_OFFSET);
                xspi->write_fn(cr, xspi->regs + XSPI_CR_OFFSET);
        }

        return t->len;
}


/* This driver supports single host mode only. Hence Tx FIFO Empty
 * is the only interrupt we care about.
 * Receive FIFO Overrun, Transmit FIFO Underrun, Mode Fault, and Target Mode
 * Fault are not to happen.
 */
static irqreturn_t xilinx_spi_irq(int irq, void *dev_id)
{
        struct xilinx_spi *xspi = dev_id;
        u32 ipif_isr;

        /* Get the IPIF interrupts, and clear them immediately */
        ipif_isr = xspi->read_fn(xspi->regs + XIPIF_V123B_IISR_OFFSET);
        xspi->write_fn(ipif_isr, xspi->regs + XIPIF_V123B_IISR_OFFSET);

        if (ipif_isr & XSPI_INTR_TX_EMPTY) {    /* Transmission completed */
                complete(&xspi->done);
                return IRQ_HANDLED;
        }

        return IRQ_NONE;
}

static int xilinx_spi_find_buffer_size(struct xilinx_spi *xspi)
{
        u8 sr;
        int n_words = 0;

        /*
         * Before the buffer_size detection we reset the core
         * to make sure we start with a clean state.
         */
        xspi->write_fn(XIPIF_V123B_RESET_MASK,
                xspi->regs + XIPIF_V123B_RESETR_OFFSET);

        /* Fill the Tx FIFO with as many words as possible */
        do {
                xspi->write_fn(0, xspi->regs + XSPI_TXD_OFFSET);
                sr = xspi->read_fn(xspi->regs + XSPI_SR_OFFSET);
                n_words++;
        } while (!(sr & XSPI_SR_TX_FULL_MASK));

        return n_words;
}

static const struct of_device_id xilinx_spi_of_match[] = {
        { .compatible = "xlnx,axi-quad-spi-1.00.a", },
        { .compatible = "xlnx,xps-spi-2.00.a", },
        { .compatible = "xlnx,xps-spi-2.00.b", },
        {}
};
MODULE_DEVICE_TABLE(of, xilinx_spi_of_match);

static int xilinx_spi_probe(struct platform_device *pdev)
{
        struct xilinx_spi *xspi;
        struct xspi_platform_data *pdata;
        struct resource *res;
        int ret, num_cs = 0, bits_per_word;
        struct spi_controller *host;
        bool force_irq = false;
        u32 tmp;
        u8 i;

        pdata = dev_get_platdata(&pdev->dev);
        if (pdata) {
                num_cs = pdata->num_chipselect;
                bits_per_word = pdata->bits_per_word;
                force_irq = pdata->force_irq;
        } else {
                device_property_read_u32(&pdev->dev, "xlnx,num-ss-bits",
                                         &num_cs);
                ret = device_property_read_u32(&pdev->dev,
                                               "xlnx,num-transfer-bits",
                                               &bits_per_word);
                if (ret)
                        bits_per_word = 8;
        }

        if (!num_cs) {
                dev_err(&pdev->dev,
                        "Missing target select configuration data\n");
                return -EINVAL;
        }

        if (num_cs > XILINX_SPI_MAX_CS) {
                dev_err(&pdev->dev, "Invalid number of spi targets\n");
                return -EINVAL;
        }

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

        /* the spi->mode bits understood by this driver: */
        host->mode_bits = SPI_CPOL | SPI_CPHA | SPI_LSB_FIRST | SPI_LOOP |
                          SPI_CS_HIGH;

        xspi = spi_controller_get_devdata(host);
        xspi->cs_inactive = 0xffffffff;
        xspi->bitbang.ctlr = host;
        xspi->bitbang.chipselect = xilinx_spi_chipselect;
        xspi->bitbang.setup_transfer = xilinx_spi_setup_transfer;
        xspi->bitbang.txrx_bufs = xilinx_spi_txrx_bufs;
        init_completion(&xspi->done);

        xspi->regs = devm_platform_get_and_ioremap_resource(pdev, 0, &res);
        if (IS_ERR(xspi->regs))
                return PTR_ERR(xspi->regs);

        host->bus_num = pdev->id;
        host->num_chipselect = num_cs;

        /*
         * Detect endianess on the IP via loop bit in CR. Detection
         * must be done before reset is sent because incorrect reset
         * value generates error interrupt.
         * Setup little endian helper functions first and try to use them
         * and check if bit was correctly setup or not.
         */
        xspi->read_fn = xspi_read32;
        xspi->write_fn = xspi_write32;

        xspi->write_fn(XSPI_CR_LOOP, xspi->regs + XSPI_CR_OFFSET);
        tmp = xspi->read_fn(xspi->regs + XSPI_CR_OFFSET);
        tmp &= XSPI_CR_LOOP;
        if (tmp != XSPI_CR_LOOP) {
                xspi->read_fn = xspi_read32_be;
                xspi->write_fn = xspi_write32_be;
        }

        host->bits_per_word_mask = SPI_BPW_MASK(bits_per_word);
        xspi->bytes_per_word = bits_per_word / 8;
        xspi->buffer_size = xilinx_spi_find_buffer_size(xspi);

        xspi->irq = platform_get_irq_optional(pdev, 0);
        if (xspi->irq < 0 && xspi->irq != -ENXIO) {
                return xspi->irq;
        } else if (xspi->irq >= 0) {
                /* Register for SPI Interrupt */
                ret = devm_request_irq(&pdev->dev, xspi->irq, xilinx_spi_irq, 0,
                                dev_name(&pdev->dev), xspi);
                if (ret)
                        return ret;

                xspi->force_irq = force_irq;
        }

        /* SPI controller initializations */
        xspi_init_hw(xspi);

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

        dev_info(&pdev->dev, "at %pR, irq=%d\n", res, xspi->irq);

        if (pdata) {
                for (i = 0; i < pdata->num_devices; i++)
                        spi_new_device(host, pdata->devices + i);
        }

        platform_set_drvdata(pdev, host);
        return 0;
}

static void xilinx_spi_remove(struct platform_device *pdev)
{
        struct spi_controller *host = platform_get_drvdata(pdev);
        struct xilinx_spi *xspi = spi_controller_get_devdata(host);
        void __iomem *regs_base = xspi->regs;

        spi_bitbang_stop(&xspi->bitbang);

        /* Disable all the interrupts just in case */
        xspi->write_fn(0, regs_base + XIPIF_V123B_IIER_OFFSET);
        /* Disable the global IPIF interrupt */
        xspi->write_fn(0, regs_base + XIPIF_V123B_DGIER_OFFSET);

        spi_controller_put(xspi->bitbang.ctlr);
}

/* work with hotplug and coldplug */
MODULE_ALIAS("platform:" XILINX_SPI_NAME);

static struct platform_driver xilinx_spi_driver = {
        .probe = xilinx_spi_probe,
        .remove = xilinx_spi_remove,
        .driver = {
                .name = XILINX_SPI_NAME,
                .of_match_table = xilinx_spi_of_match,
        },
};
module_platform_driver(xilinx_spi_driver);

MODULE_AUTHOR("MontaVista Software, Inc. <source@mvista.com>");
MODULE_DESCRIPTION("Xilinx SPI driver");
MODULE_LICENSE("GPL");