/*
 * xilinx_spi.c
 *
 * Xilinx SPI controller driver (master mode only)
 *
 * Author: MontaVista Software, Inc.
 *      source@mvista.com
 *
 * 2002-2007 (c) MontaVista Software, Inc.  This file is licensed under the
 * terms of the GNU General Public License version 2.  This program is licensed
 * "as is" without any warranty of any kind, whether express or implied.
 */

#include <linux/module.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/platform_device.h>

#include <linux/of_platform.h>
#include <linux/of_device.h>
#include <linux/of_spi.h>

#include <linux/spi/spi.h>
#include <linux/spi/spi_bitbang.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          0x62    /* 16-bit Control Register */

#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)
#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_SR_OFFSET          0x67    /* 8-bit 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         0x6b    /* 8-bit Data Transmit Register */
#define XSPI_RXD_OFFSET         0x6f    /* 8-bit 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 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 */

        u32             irq;

        u32             speed_hz; /* SCK has a fixed frequency of speed_hz Hz */

        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 */
};

static void xspi_init_hw(void __iomem *regs_base)
{
        /* Reset the SPI device */
        out_be32(regs_base + XIPIF_V123B_RESETR_OFFSET,
                 XIPIF_V123B_RESET_MASK);
        /* Disable all the interrupts just in case */
        out_be32(regs_base + XIPIF_V123B_IIER_OFFSET, 0);
        /* Enable the global IPIF interrupt */
        out_be32(regs_base + XIPIF_V123B_DGIER_OFFSET,
                 XIPIF_V123B_GINTR_ENABLE);
        /* Deselect the slave on the SPI bus */
        out_be32(regs_base + XSPI_SSR_OFFSET, 0xffff);
        /* Disable the transmitter, enable Manual Slave Select Assertion,
         * put SPI controller into master mode, and enable it */
        out_be16(regs_base + XSPI_CR_OFFSET,
                 XSPI_CR_TRANS_INHIBIT | XSPI_CR_MANUAL_SSELECT
                 | XSPI_CR_MASTER_MODE | XSPI_CR_ENABLE);
}

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 */
                out_be32(xspi->regs + XSPI_SSR_OFFSET, 0xffff);
        } else if (is_on == BITBANG_CS_ACTIVE) {
                /* Set the SPI clock phase and polarity */
                u16 cr = in_be16(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;
                out_be16(xspi->regs + XSPI_CR_OFFSET, cr);

                /* 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 */
                out_be32(xspi->regs + XSPI_SSR_OFFSET,
                         ~(0x0001 << spi->chip_select));
        }
}

/* spi_bitbang requires custom setup_transfer() to be defined if there is a
 * custom txrx_bufs(). We have nothing to setup here as the SPI IP block
 * supports just 8 bits per word, and SPI clock can't be changed in software.
 * Check for 8 bits per word. Chip select delay calculations could be
 * added here as soon as bitbang_work() can be made aware of the delay value.
 */
static int xilinx_spi_setup_transfer(struct spi_device *spi,
                struct spi_transfer *t)
{
        u8 bits_per_word;

        bits_per_word = (t) ? t->bits_per_word : spi->bits_per_word;
        if (bits_per_word != 8) {
                dev_err(&spi->dev, "%s, unsupported bits_per_word=%d\n",
                        __func__, bits_per_word);
                return -EINVAL;
        }

        return 0;
}

static int xilinx_spi_setup(struct spi_device *spi)
{
        struct spi_bitbang *bitbang;
        struct xilinx_spi *xspi;
        int retval;

        xspi = spi_master_get_devdata(spi->master);
        bitbang = &xspi->bitbang;

        retval = xilinx_spi_setup_transfer(spi, NULL);
        if (retval < 0)
                return retval;

        return 0;
}

static void xilinx_spi_fill_tx_fifo(struct xilinx_spi *xspi)
{
        u8 sr;

        /* Fill the Tx FIFO with as many bytes as possible */
        sr = in_8(xspi->regs + XSPI_SR_OFFSET);
        while ((sr & XSPI_SR_TX_FULL_MASK) == 0 && xspi->remaining_bytes > 0) {
                if (xspi->tx_ptr) {
                        out_8(xspi->regs + XSPI_TXD_OFFSET, *xspi->tx_ptr++);
                } else {
                        out_8(xspi->regs + XSPI_TXD_OFFSET, 0);
                }
                xspi->remaining_bytes--;
                sr = in_8(xspi->regs + XSPI_SR_OFFSET);
        }
}

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;
        u16 cr;

        /* We get here with transmitter inhibited */

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

        xilinx_spi_fill_tx_fifo(xspi);

        /* Enable the transmit empty interrupt, which we use to determine
         * progress on the transmission.
         */
        ipif_ier = in_be32(xspi->regs + XIPIF_V123B_IIER_OFFSET);
        out_be32(xspi->regs + XIPIF_V123B_IIER_OFFSET,
                 ipif_ier | XSPI_INTR_TX_EMPTY);

        /* Start the transfer by not inhibiting the transmitter any longer */
        cr = in_be16(xspi->regs + XSPI_CR_OFFSET) & ~XSPI_CR_TRANS_INHIBIT;
        out_be16(xspi->regs + XSPI_CR_OFFSET, cr);

        wait_for_completion(&xspi->done);

        /* Disable the transmit empty interrupt */
        out_be32(xspi->regs + XIPIF_V123B_IIER_OFFSET, ipif_ier);

        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 = in_be32(xspi->regs + XIPIF_V123B_IISR_OFFSET);
        out_be32(xspi->regs + XIPIF_V123B_IISR_OFFSET, ipif_isr);

        if (ipif_isr & XSPI_INTR_TX_EMPTY) {    /* Transmission completed */
                u16 cr;
                u8 sr;

                /* 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 = in_be16(xspi->regs + XSPI_CR_OFFSET);
                out_be16(xspi->regs + XSPI_CR_OFFSET,
                         cr | XSPI_CR_TRANS_INHIBIT);

                /* Read out all the data from the Rx FIFO */
                sr = in_8(xspi->regs + XSPI_SR_OFFSET);
                while ((sr & XSPI_SR_RX_EMPTY_MASK) == 0) {
                        u8 data;

                        data = in_8(xspi->regs + XSPI_RXD_OFFSET);
                        if (xspi->rx_ptr) {
                                *xspi->rx_ptr++ = data;
                        }
                        sr = in_8(xspi->regs + XSPI_SR_OFFSET);
                }

                /* See if there is more data to send */
                if (xspi->remaining_bytes > 0) {
                        xilinx_spi_fill_tx_fifo(xspi);
                        /* Start the transfer by not inhibiting the
                         * transmitter any longer
                         */
                        out_be16(xspi->regs + XSPI_CR_OFFSET, cr);
                } else {
                        /* No more data to send.
                         * Indicate the transfer is completed.
                         */
                        complete(&xspi->done);
                }
        }

        return IRQ_HANDLED;
}

static int __init xilinx_spi_of_probe(struct of_device *ofdev,
                                        const struct of_device_id *match)
{
        struct spi_master *master;
        struct xilinx_spi *xspi;
        struct resource r_irq_struct;
        struct resource r_mem_struct;

        struct resource *r_irq = &r_irq_struct;
        struct resource *r_mem = &r_mem_struct;
        int rc = 0;
        const u32 *prop;
        int len;

        /* Get resources(memory, IRQ) associated with the device */
        master = spi_alloc_master(&ofdev->dev, sizeof(struct xilinx_spi));

        if (master == NULL) {
                return -ENOMEM;
        }

        dev_set_drvdata(&ofdev->dev, master);

        rc = of_address_to_resource(ofdev->node, 0, r_mem);
        if (rc) {
                dev_warn(&ofdev->dev, "invalid address\n");
                goto put_master;
        }

        rc = of_irq_to_resource(ofdev->node, 0, r_irq);
        if (rc == NO_IRQ) {
                dev_warn(&ofdev->dev, "no IRQ found\n");
                goto put_master;
        }

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

        xspi = spi_master_get_devdata(master);
        xspi->bitbang.master = spi_master_get(master);
        xspi->bitbang.chipselect = xilinx_spi_chipselect;
        xspi->bitbang.setup_transfer = xilinx_spi_setup_transfer;
        xspi->bitbang.txrx_bufs = xilinx_spi_txrx_bufs;
        xspi->bitbang.master->setup = xilinx_spi_setup;
        init_completion(&xspi->done);

        xspi->irq = r_irq->start;

        if (!request_mem_region(r_mem->start,
                        r_mem->end - r_mem->start + 1, XILINX_SPI_NAME)) {
                rc = -ENXIO;
                dev_warn(&ofdev->dev, "memory request failure\n");
                goto put_master;
        }

        xspi->regs = ioremap(r_mem->start, r_mem->end - r_mem->start + 1);
        if (xspi->regs == NULL) {
                rc = -ENOMEM;
                dev_warn(&ofdev->dev, "ioremap failure\n");
                goto release_mem;
        }
        xspi->irq = r_irq->start;

        /* dynamic bus assignment */
        master->bus_num = -1;

        /* number of slave select bits is required */
        prop = of_get_property(ofdev->node, "xlnx,num-ss-bits", &len);
        if (!prop || len < sizeof(*prop)) {
                dev_warn(&ofdev->dev, "no 'xlnx,num-ss-bits' property\n");
                goto unmap_io;
        }
        master->num_chipselect = *prop;

        /* SPI controller initializations */
        xspi_init_hw(xspi->regs);

        /* Register for SPI Interrupt */
        rc = request_irq(xspi->irq, xilinx_spi_irq, 0, XILINX_SPI_NAME, xspi);
        if (rc != 0) {
                dev_warn(&ofdev->dev, "irq request failure: %d\n", xspi->irq);
                goto unmap_io;
        }

        rc = spi_bitbang_start(&xspi->bitbang);
        if (rc != 0) {
                dev_err(&ofdev->dev, "spi_bitbang_start FAILED\n");
                goto free_irq;
        }

        dev_info(&ofdev->dev, "at 0x%08X mapped to 0x%08X, irq=%d\n",
                        (unsigned int)r_mem->start, (u32)xspi->regs, xspi->irq);

        /* Add any subnodes on the SPI bus */
        of_register_spi_devices(master, ofdev->node);

        return rc;

free_irq:
        free_irq(xspi->irq, xspi);
unmap_io:
        iounmap(xspi->regs);
release_mem:
        release_mem_region(r_mem->start, resource_size(r_mem));
put_master:
        spi_master_put(master);
        return rc;
}

static int __devexit xilinx_spi_remove(struct of_device *ofdev)
{
        struct xilinx_spi *xspi;
        struct spi_master *master;
        struct resource r_mem;

        master = platform_get_drvdata(ofdev);
        xspi = spi_master_get_devdata(master);

        spi_bitbang_stop(&xspi->bitbang);
        free_irq(xspi->irq, xspi);
        iounmap(xspi->regs);
        if (!of_address_to_resource(ofdev->node, 0, &r_mem))
                release_mem_region(r_mem.start, resource_size(&r_mem));
        dev_set_drvdata(&ofdev->dev, 0);
        spi_master_put(xspi->bitbang.master);

        return 0;
}

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

static int __exit xilinx_spi_of_remove(struct of_device *op)
{
        return xilinx_spi_remove(op);
}

static 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 struct of_platform_driver xilinx_spi_of_driver = {
        .owner = THIS_MODULE,
        .name = "xilinx-xps-spi",
        .match_table = xilinx_spi_of_match,
        .probe = xilinx_spi_of_probe,
        .remove = __exit_p(xilinx_spi_of_remove),
        .driver = {
                .name = "xilinx-xps-spi",
                .owner = THIS_MODULE,
        },
};

static int __init xilinx_spi_init(void)
{
        return of_register_platform_driver(&xilinx_spi_of_driver);
}
module_init(xilinx_spi_init);

static void __exit xilinx_spi_exit(void)
{
        of_unregister_platform_driver(&xilinx_spi_of_driver);
}
module_exit(xilinx_spi_exit);
MODULE_AUTHOR("MontaVista Software, Inc. <source@mvista.com>");
MODULE_DESCRIPTION("Xilinx SPI driver");
MODULE_LICENSE("GPL");