spi/xilinx: Simplify spi_fill_tx_fifo

[mirror_ubuntu-artful-kernel.git] / drivers / spi / spi-xilinx.c

/*
 * Xilinx SPI controller driver (master 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.

 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#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_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;

        u8 *rx_ptr;             /* pointer in the Tx buffer */
        const u8 *tx_ptr;       /* pointer in the Rx buffer */
        int remaining_bytes;    /* the number of bytes left to transfer */
        u8 bits_per_word;
        int buffer_size;        /* buffer size in words */
        unsigned int (*read_fn)(void __iomem *);
        void (*write_fn)(u32, void __iomem *);
        void (*tx_fn)(struct xilinx_spi *);
        void (*rx_fn)(struct xilinx_spi *);
};

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 xspi_tx8(struct xilinx_spi *xspi)
{
        xspi->write_fn(*xspi->tx_ptr, xspi->regs + XSPI_TXD_OFFSET);
        xspi->tx_ptr++;
}

static void xspi_tx16(struct xilinx_spi *xspi)
{
        xspi->write_fn(*(u16 *)(xspi->tx_ptr), xspi->regs + XSPI_TXD_OFFSET);
        xspi->tx_ptr += 2;
}

static void xspi_tx32(struct xilinx_spi *xspi)
{
        xspi->write_fn(*(u32 *)(xspi->tx_ptr), xspi->regs + XSPI_TXD_OFFSET);
        xspi->tx_ptr += 4;
}

static void xspi_rx8(struct xilinx_spi *xspi)
{
        u32 data = xspi->read_fn(xspi->regs + XSPI_RXD_OFFSET);
        if (xspi->rx_ptr) {
                *xspi->rx_ptr = data & 0xff;
                xspi->rx_ptr++;
        }
}

static void xspi_rx16(struct xilinx_spi *xspi)
{
        u32 data = xspi->read_fn(xspi->regs + XSPI_RXD_OFFSET);
        if (xspi->rx_ptr) {
                *(u16 *)(xspi->rx_ptr) = data & 0xffff;
                xspi->rx_ptr += 2;
        }
}

static void xspi_rx32(struct xilinx_spi *xspi)
{
        u32 data = xspi->read_fn(xspi->regs + XSPI_RXD_OFFSET);
        if (xspi->rx_ptr) {
                *(u32 *)(xspi->rx_ptr) = data;
                xspi->rx_ptr += 4;
        }
}

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);
        /* Disable all the interrupts just in case */
        xspi->write_fn(0, regs_base + XIPIF_V123B_IIER_OFFSET);
        /* Enable the global IPIF interrupt */
        xspi->write_fn(XIPIF_V123B_GINTR_ENABLE,
                regs_base + XIPIF_V123B_DGIER_OFFSET);
        /* Deselect the slave on the SPI bus */
        xspi->write_fn(0xffff, regs_base + XSPI_SSR_OFFSET);
        /* Disable the transmitter, enable Manual Slave Select Assertion,
         * put SPI controller into master mode, and enable it */
        xspi->write_fn(XSPI_CR_TRANS_INHIBIT | 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_master_get_devdata(spi->master);

        if (is_on == BITBANG_CS_INACTIVE) {
                /* Deselect the slave on the SPI bus */
                xspi->write_fn(0xffff, xspi->regs + XSPI_SSR_OFFSET);
        } else if (is_on == BITBANG_CS_ACTIVE) {
                /* Set the SPI clock phase and polarity */
                u16 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)
                 */

                /* Activate the chip select */
                xspi->write_fn(~(0x0001 << spi->chip_select),
                        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)
{
        return 0;
}

static void xilinx_spi_fill_tx_fifo(struct xilinx_spi *xspi, int n_words)
{
        xspi->remaining_bytes -= n_words * xspi->bits_per_word / 8;

        while (n_words--)
                if (xspi->tx_ptr)
                        xspi->tx_fn(xspi);
                else
                        xspi->write_fn(0, xspi->regs + XSPI_TXD_OFFSET);
        return;
}

static int xilinx_spi_txrx_bufs(struct spi_device *spi, struct spi_transfer *t)
{
        struct xilinx_spi *xspi = spi_master_get_devdata(spi->master);
        u32 ipif_ier;

        /* We get here with transmitter inhibited */

        xspi->tx_ptr = t->tx_buf;
        xspi->rx_ptr = t->rx_buf;
        xspi->remaining_bytes = t->len;
        reinit_completion(&xspi->done);


        /* Enable the transmit empty interrupt, which we use to determine
         * progress on the transmission.
         */
        ipif_ier = xspi->read_fn(xspi->regs + XIPIF_V123B_IIER_OFFSET);
        xspi->write_fn(ipif_ier | XSPI_INTR_TX_EMPTY,
                xspi->regs + XIPIF_V123B_IIER_OFFSET);

        for (;;) {
                u16 cr;
                int n_words;

                n_words = (xspi->remaining_bytes * 8) / xspi->bits_per_word;
                n_words = min(n_words, xspi->buffer_size);

                xilinx_spi_fill_tx_fifo(xspi, n_words);

                /* Start the transfer by not inhibiting the transmitter any
                 * longer
                 */
                cr = xspi->read_fn(xspi->regs + XSPI_CR_OFFSET) &
                                                        ~XSPI_CR_TRANS_INHIBIT;
                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.
                 */
                cr = xspi->read_fn(xspi->regs + XSPI_CR_OFFSET);
                xspi->write_fn(cr | XSPI_CR_TRANS_INHIBIT,
                               xspi->regs + XSPI_CR_OFFSET);

                /* Read out all the data from the Rx FIFO */
                while (n_words--)
                        xspi->rx_fn(xspi);

                /* See if there is more data to send */
                if (xspi->remaining_bytes <= 0)
                        break;
        }

        /* Disable the transmit empty interrupt */
        xspi->write_fn(ipif_ier, xspi->regs + XIPIF_V123B_IIER_OFFSET);

        return t->len - xspi->remaining_bytes;
}


/* This driver supports single master mode only. Hence Tx FIFO Empty
 * is the only interrupt we care about.
 * Receive FIFO Overrun, Transmit FIFO Underrun, Mode Fault, and Slave 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;
}

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,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 = 8;
        struct spi_master *master;
        u32 tmp;
        u8 i;

        pdata = dev_get_platdata(&pdev->dev);
        if (pdata) {
                num_cs = pdata->num_chipselect;
                bits_per_word = pdata->bits_per_word;
        } else {
                of_property_read_u32(pdev->dev.of_node, "xlnx,num-ss-bits",
                                          &num_cs);
        }

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

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

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

        xspi = spi_master_get_devdata(master);
        xspi->bitbang.master = master;
        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);

        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        xspi->regs = devm_ioremap_resource(&pdev->dev, res);
        if (IS_ERR(xspi->regs)) {
                ret = PTR_ERR(xspi->regs);
                goto put_master;
        }

        master->bus_num = pdev->id;
        master->num_chipselect = num_cs;
        master->dev.of_node = pdev->dev.of_node;

        /*
         * 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;
        }

        master->bits_per_word_mask = SPI_BPW_MASK(bits_per_word);
        xspi->bits_per_word = bits_per_word;
        if (xspi->bits_per_word == 8) {
                xspi->tx_fn = xspi_tx8;
                xspi->rx_fn = xspi_rx8;
        } else if (xspi->bits_per_word == 16) {
                xspi->tx_fn = xspi_tx16;
                xspi->rx_fn = xspi_rx16;
        } else if (xspi->bits_per_word == 32) {
                xspi->tx_fn = xspi_tx32;
                xspi->rx_fn = xspi_rx32;
        } else {
                ret = -EINVAL;
                goto put_master;
        }

        xspi->buffer_size = xilinx_spi_find_buffer_size(xspi);

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

        xspi->irq = platform_get_irq(pdev, 0);
        if (xspi->irq < 0) {
                ret = xspi->irq;
                goto put_master;
        }

        /* Register for SPI Interrupt */
        ret = devm_request_irq(&pdev->dev, xspi->irq, xilinx_spi_irq, 0,
                               dev_name(&pdev->dev), xspi);
        if (ret)
                goto put_master;

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

        dev_info(&pdev->dev, "at 0x%08llX mapped to 0x%p, irq=%d\n",
                (unsigned long long)res->start, xspi->regs, xspi->irq);

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

        platform_set_drvdata(pdev, master);
        return 0;

put_master:
        spi_master_put(master);

        return ret;
}

static int xilinx_spi_remove(struct platform_device *pdev)
{
        struct spi_master *master = platform_get_drvdata(pdev);
        struct xilinx_spi *xspi = spi_master_get_devdata(master);
        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_master_put(xspi->bitbang.master);

        return 0;
}

/* 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");