// SPDX-License-Identifier: GPL-2.0-only
/*
 * MPC52xx SPI bus driver.
 *
 * Copyright (C) 2008 Secret Lab Technologies Ltd.
 *
 * This is the driver for the MPC5200's dedicated SPI controller.
 *
 * Note: this driver does not support the MPC5200 PSC in SPI mode.  For
 * that driver see drivers/spi/mpc52xx_psc_spi.c
 */

#include <linux/module.h>
#include <linux/err.h>
#include <linux/errno.h>
#include <linux/of_platform.h>
#include <linux/interrupt.h>
#include <linux/delay.h>
#include <linux/gpio/consumer.h>
#include <linux/spi/spi.h>
#include <linux/io.h>
#include <linux/slab.h>
#include <linux/of_address.h>
#include <linux/of_irq.h>
#include <linux/platform_device.h>

#include <asm/time.h>
#include <asm/mpc52xx.h>

MODULE_AUTHOR("Grant Likely <grant.likely@secretlab.ca>");
MODULE_DESCRIPTION("MPC52xx SPI (non-PSC) Driver");
MODULE_LICENSE("GPL");

/* Register offsets */
#define SPI_CTRL1       0x00
#define SPI_CTRL1_SPIE          (1 << 7)
#define SPI_CTRL1_SPE           (1 << 6)
#define SPI_CTRL1_MSTR          (1 << 4)
#define SPI_CTRL1_CPOL          (1 << 3)
#define SPI_CTRL1_CPHA          (1 << 2)
#define SPI_CTRL1_SSOE          (1 << 1)
#define SPI_CTRL1_LSBFE         (1 << 0)

#define SPI_CTRL2       0x01
#define SPI_BRR         0x04

#define SPI_STATUS      0x05
#define SPI_STATUS_SPIF         (1 << 7)
#define SPI_STATUS_WCOL         (1 << 6)
#define SPI_STATUS_MODF         (1 << 4)

#define SPI_DATA        0x09
#define SPI_PORTDATA    0x0d
#define SPI_DATADIR     0x10

/* FSM state return values */
#define FSM_STOP        0       /* Nothing more for the state machine to */
                                /* do.  If something interesting happens */
                                /* then an IRQ will be received */
#define FSM_POLL        1       /* need to poll for completion, an IRQ is */
                                /* not expected */
#define FSM_CONTINUE    2       /* Keep iterating the state machine */

/* Driver internal data */
struct mpc52xx_spi {
        struct spi_controller *host;
        void __iomem *regs;
        int irq0;       /* MODF irq */
        int irq1;       /* SPIF irq */
        unsigned int ipb_freq;

        /* Statistics; not used now, but will be reintroduced for debugfs */
        int msg_count;
        int wcol_count;
        int wcol_ticks;
        u32 wcol_tx_timestamp;
        int modf_count;
        int byte_count;

        struct list_head queue;         /* queue of pending messages */
        spinlock_t lock;
        struct work_struct work;

        /* Details of current transfer (length, and buffer pointers) */
        struct spi_message *message;    /* current message */
        struct spi_transfer *transfer;  /* current transfer */
        int (*state)(int irq, struct mpc52xx_spi *ms, u8 status, u8 data);
        int len;
        int timestamp;
        u8 *rx_buf;
        const u8 *tx_buf;
        int cs_change;
        int gpio_cs_count;
        struct gpio_desc **gpio_cs;
};

/*
 * CS control function
 */
static void mpc52xx_spi_chipsel(struct mpc52xx_spi *ms, int value)
{
        int cs;

        if (ms->gpio_cs_count > 0) {
                cs = spi_get_chipselect(ms->message->spi, 0);
                gpiod_set_value(ms->gpio_cs[cs], value);
        } else {
                out_8(ms->regs + SPI_PORTDATA, value ? 0 : 0x08);
        }
}

/*
 * Start a new transfer.  This is called both by the idle state
 * for the first transfer in a message, and by the wait state when the
 * previous transfer in a message is complete.
 */
static void mpc52xx_spi_start_transfer(struct mpc52xx_spi *ms)
{
        ms->rx_buf = ms->transfer->rx_buf;
        ms->tx_buf = ms->transfer->tx_buf;
        ms->len = ms->transfer->len;

        /* Activate the chip select */
        if (ms->cs_change)
                mpc52xx_spi_chipsel(ms, 1);
        ms->cs_change = ms->transfer->cs_change;

        /* Write out the first byte */
        ms->wcol_tx_timestamp = mftb();
        if (ms->tx_buf)
                out_8(ms->regs + SPI_DATA, *ms->tx_buf++);
        else
                out_8(ms->regs + SPI_DATA, 0);
}

/* Forward declaration of state handlers */
static int mpc52xx_spi_fsmstate_transfer(int irq, struct mpc52xx_spi *ms,
                                         u8 status, u8 data);
static int mpc52xx_spi_fsmstate_wait(int irq, struct mpc52xx_spi *ms,
                                     u8 status, u8 data);

/*
 * IDLE state
 *
 * No transfers are in progress; if another transfer is pending then retrieve
 * it and kick it off.  Otherwise, stop processing the state machine
 */
static int
mpc52xx_spi_fsmstate_idle(int irq, struct mpc52xx_spi *ms, u8 status, u8 data)
{
        struct spi_device *spi;
        int spr, sppr;
        u8 ctrl1;

        if (status && irq)
                dev_err(&ms->host->dev, "spurious irq, status=0x%.2x\n",
                        status);

        /* Check if there is another transfer waiting. */
        if (list_empty(&ms->queue))
                return FSM_STOP;

        /* get the head of the queue */
        ms->message = list_first_entry(&ms->queue, struct spi_message, queue);
        list_del_init(&ms->message->queue);

        /* Setup the controller parameters */
        ctrl1 = SPI_CTRL1_SPIE | SPI_CTRL1_SPE | SPI_CTRL1_MSTR;
        spi = ms->message->spi;
        if (spi->mode & SPI_CPHA)
                ctrl1 |= SPI_CTRL1_CPHA;
        if (spi->mode & SPI_CPOL)
                ctrl1 |= SPI_CTRL1_CPOL;
        if (spi->mode & SPI_LSB_FIRST)
                ctrl1 |= SPI_CTRL1_LSBFE;
        out_8(ms->regs + SPI_CTRL1, ctrl1);

        /* Setup the controller speed */
        /* minimum divider is '2'.  Also, add '1' to force rounding the
         * divider up. */
        sppr = ((ms->ipb_freq / ms->message->spi->max_speed_hz) + 1) >> 1;
        spr = 0;
        if (sppr < 1)
                sppr = 1;
        while (((sppr - 1) & ~0x7) != 0) {
                sppr = (sppr + 1) >> 1; /* add '1' to force rounding up */
                spr++;
        }
        sppr--;         /* sppr quantity in register is offset by 1 */
        if (spr > 7) {
                /* Don't overrun limits of SPI baudrate register */
                spr = 7;
                sppr = 7;
        }
        out_8(ms->regs + SPI_BRR, sppr << 4 | spr); /* Set speed */

        ms->cs_change = 1;
        ms->transfer = container_of(ms->message->transfers.next,
                                    struct spi_transfer, transfer_list);

        mpc52xx_spi_start_transfer(ms);
        ms->state = mpc52xx_spi_fsmstate_transfer;

        return FSM_CONTINUE;
}

/*
 * TRANSFER state
 *
 * In the middle of a transfer.  If the SPI core has completed processing
 * a byte, then read out the received data and write out the next byte
 * (unless this transfer is finished; in which case go on to the wait
 * state)
 */
static int mpc52xx_spi_fsmstate_transfer(int irq, struct mpc52xx_spi *ms,
                                         u8 status, u8 data)
{
        if (!status)
                return ms->irq0 ? FSM_STOP : FSM_POLL;

        if (status & SPI_STATUS_WCOL) {
                /* The SPI controller is stoopid.  At slower speeds, it may
                 * raise the SPIF flag before the state machine is actually
                 * finished, which causes a collision (internal to the state
                 * machine only).  The manual recommends inserting a delay
                 * between receiving the interrupt and sending the next byte,
                 * but it can also be worked around simply by retrying the
                 * transfer which is what we do here. */
                ms->wcol_count++;
                ms->wcol_ticks += mftb() - ms->wcol_tx_timestamp;
                ms->wcol_tx_timestamp = mftb();
                data = 0;
                if (ms->tx_buf)
                        data = *(ms->tx_buf - 1);
                out_8(ms->regs + SPI_DATA, data); /* try again */
                return FSM_CONTINUE;
        } else if (status & SPI_STATUS_MODF) {
                ms->modf_count++;
                dev_err(&ms->host->dev, "mode fault\n");
                mpc52xx_spi_chipsel(ms, 0);
                ms->message->status = -EIO;
                if (ms->message->complete)
                        ms->message->complete(ms->message->context);
                ms->state = mpc52xx_spi_fsmstate_idle;
                return FSM_CONTINUE;
        }

        /* Read data out of the spi device */
        ms->byte_count++;
        if (ms->rx_buf)
                *ms->rx_buf++ = data;

        /* Is the transfer complete? */
        ms->len--;
        if (ms->len == 0) {
                ms->timestamp = mftb();
                if (ms->transfer->delay.unit == SPI_DELAY_UNIT_USECS)
                        ms->timestamp += ms->transfer->delay.value *
                                         tb_ticks_per_usec;
                ms->state = mpc52xx_spi_fsmstate_wait;
                return FSM_CONTINUE;
        }

        /* Write out the next byte */
        ms->wcol_tx_timestamp = mftb();
        if (ms->tx_buf)
                out_8(ms->regs + SPI_DATA, *ms->tx_buf++);
        else
                out_8(ms->regs + SPI_DATA, 0);

        return FSM_CONTINUE;
}

/*
 * WAIT state
 *
 * A transfer has completed; need to wait for the delay period to complete
 * before starting the next transfer
 */
static int
mpc52xx_spi_fsmstate_wait(int irq, struct mpc52xx_spi *ms, u8 status, u8 data)
{
        if (status && irq)
                dev_err(&ms->host->dev, "spurious irq, status=0x%.2x\n",
                        status);

        if (((int)mftb()) - ms->timestamp < 0)
                return FSM_POLL;

        ms->message->actual_length += ms->transfer->len;

        /* Check if there is another transfer in this message.  If there
         * aren't then deactivate CS, notify sender, and drop back to idle
         * to start the next message. */
        if (ms->transfer->transfer_list.next == &ms->message->transfers) {
                ms->msg_count++;
                mpc52xx_spi_chipsel(ms, 0);
                ms->message->status = 0;
                if (ms->message->complete)
                        ms->message->complete(ms->message->context);
                ms->state = mpc52xx_spi_fsmstate_idle;
                return FSM_CONTINUE;
        }

        /* There is another transfer; kick it off */

        if (ms->cs_change)
                mpc52xx_spi_chipsel(ms, 0);

        ms->transfer = container_of(ms->transfer->transfer_list.next,
                                    struct spi_transfer, transfer_list);
        mpc52xx_spi_start_transfer(ms);
        ms->state = mpc52xx_spi_fsmstate_transfer;
        return FSM_CONTINUE;
}

/**
 * mpc52xx_spi_fsm_process - Finite State Machine iteration function
 * @irq: irq number that triggered the FSM or 0 for polling
 * @ms: pointer to mpc52xx_spi driver data
 */
static void mpc52xx_spi_fsm_process(int irq, struct mpc52xx_spi *ms)
{
        int rc = FSM_CONTINUE;
        u8 status, data;

        while (rc == FSM_CONTINUE) {
                /* Interrupt cleared by read of STATUS followed by
                 * read of DATA registers */
                status = in_8(ms->regs + SPI_STATUS);
                data = in_8(ms->regs + SPI_DATA);
                rc = ms->state(irq, ms, status, data);
        }

        if (rc == FSM_POLL)
                schedule_work(&ms->work);
}

/**
 * mpc52xx_spi_irq - IRQ handler
 */
static irqreturn_t mpc52xx_spi_irq(int irq, void *_ms)
{
        struct mpc52xx_spi *ms = _ms;
        spin_lock(&ms->lock);
        mpc52xx_spi_fsm_process(irq, ms);
        spin_unlock(&ms->lock);
        return IRQ_HANDLED;
}

/**
 * mpc52xx_spi_wq - Workqueue function for polling the state machine
 */
static void mpc52xx_spi_wq(struct work_struct *work)
{
        struct mpc52xx_spi *ms = container_of(work, struct mpc52xx_spi, work);
        unsigned long flags;

        spin_lock_irqsave(&ms->lock, flags);
        mpc52xx_spi_fsm_process(0, ms);
        spin_unlock_irqrestore(&ms->lock, flags);
}

/*
 * spi_controller ops
 */

static int mpc52xx_spi_transfer(struct spi_device *spi, struct spi_message *m)
{
        struct mpc52xx_spi *ms = spi_controller_get_devdata(spi->controller);
        unsigned long flags;

        m->actual_length = 0;
        m->status = -EINPROGRESS;

        spin_lock_irqsave(&ms->lock, flags);
        list_add_tail(&m->queue, &ms->queue);
        spin_unlock_irqrestore(&ms->lock, flags);
        schedule_work(&ms->work);

        return 0;
}

/*
 * OF Platform Bus Binding
 */
static int mpc52xx_spi_probe(struct platform_device *op)
{
        struct spi_controller *host;
        struct mpc52xx_spi *ms;
        struct gpio_desc *gpio_cs;
        void __iomem *regs;
        u8 ctrl1;
        int rc, i = 0;

        /* MMIO registers */
        dev_dbg(&op->dev, "probing mpc5200 SPI device\n");
        regs = of_iomap(op->dev.of_node, 0);
        if (!regs)
                return -ENODEV;

        /* initialize the device */
        ctrl1 = SPI_CTRL1_SPIE | SPI_CTRL1_SPE | SPI_CTRL1_MSTR;
        out_8(regs + SPI_CTRL1, ctrl1);
        out_8(regs + SPI_CTRL2, 0x0);
        out_8(regs + SPI_DATADIR, 0xe); /* Set output pins */
        out_8(regs + SPI_PORTDATA, 0x8);        /* Deassert /SS signal */

        /* Clear the status register and re-read it to check for a MODF
         * failure.  This driver cannot currently handle multiple hosts
         * on the SPI bus.  This fault will also occur if the SPI signals
         * are not connected to any pins (port_config setting) */
        in_8(regs + SPI_STATUS);
        out_8(regs + SPI_CTRL1, ctrl1);

        in_8(regs + SPI_DATA);
        if (in_8(regs + SPI_STATUS) & SPI_STATUS_MODF) {
                dev_err(&op->dev, "mode fault; is port_config correct?\n");
                rc = -EIO;
                goto err_init;
        }

        dev_dbg(&op->dev, "allocating spi_controller struct\n");
        host = spi_alloc_host(&op->dev, sizeof(*ms));
        if (!host) {
                rc = -ENOMEM;
                goto err_alloc;
        }

        host->transfer = mpc52xx_spi_transfer;
        host->mode_bits = SPI_CPOL | SPI_CPHA | SPI_LSB_FIRST;
        host->bits_per_word_mask = SPI_BPW_MASK(8);

        platform_set_drvdata(op, host);

        ms = spi_controller_get_devdata(host);
        ms->host = host;
        ms->regs = regs;
        ms->irq0 = irq_of_parse_and_map(op->dev.of_node, 0);
        ms->irq1 = irq_of_parse_and_map(op->dev.of_node, 1);
        ms->state = mpc52xx_spi_fsmstate_idle;
        ms->ipb_freq = mpc5xxx_get_bus_frequency(&op->dev);
        ms->gpio_cs_count = gpiod_count(&op->dev, NULL);
        if (ms->gpio_cs_count > 0) {
                host->num_chipselect = ms->gpio_cs_count;
                ms->gpio_cs = kmalloc_objs(*ms->gpio_cs, ms->gpio_cs_count);
                if (!ms->gpio_cs) {
                        rc = -ENOMEM;
                        goto err_alloc_gpio;
                }

                for (i = 0; i < ms->gpio_cs_count; i++) {
                        gpio_cs = gpiod_get_index(&op->dev,
                                                  NULL, i, GPIOD_OUT_LOW);
                        rc = PTR_ERR_OR_ZERO(gpio_cs);
                        if (rc) {
                                dev_err(&op->dev,
                                        "failed to get spi cs gpio #%d: %d\n",
                                        i, rc);
                                goto err_gpio;
                        }

                        ms->gpio_cs[i] = gpio_cs;
                }
        }

        spin_lock_init(&ms->lock);
        INIT_LIST_HEAD(&ms->queue);
        INIT_WORK(&ms->work, mpc52xx_spi_wq);

        /* Decide if interrupts can be used */
        if (ms->irq0 && ms->irq1) {
                rc = request_irq(ms->irq0, mpc52xx_spi_irq, 0,
                                  "mpc5200-spi-modf", ms);
                rc |= request_irq(ms->irq1, mpc52xx_spi_irq, 0,
                                  "mpc5200-spi-spif", ms);
                if (rc) {
                        free_irq(ms->irq0, ms);
                        free_irq(ms->irq1, ms);
                        ms->irq0 = ms->irq1 = 0;
                }
        } else {
                /* operate in polled mode */
                ms->irq0 = ms->irq1 = 0;
        }

        if (!ms->irq0)
                dev_info(&op->dev, "using polled mode\n");

        dev_dbg(&op->dev, "registering spi_controller struct\n");
        rc = spi_register_controller(host);
        if (rc)
                goto err_register;

        dev_info(&ms->host->dev, "registered MPC5200 SPI bus\n");

        return rc;

 err_register:
        dev_err(&ms->host->dev, "initialization failed\n");
 err_gpio:
        while (i-- > 0)
                gpiod_put(ms->gpio_cs[i]);

        kfree(ms->gpio_cs);
 err_alloc_gpio:
        spi_controller_put(host);
 err_alloc:
 err_init:
        iounmap(regs);
        return rc;
}

static void mpc52xx_spi_remove(struct platform_device *op)
{
        struct spi_controller *host = spi_controller_get(platform_get_drvdata(op));
        struct mpc52xx_spi *ms = spi_controller_get_devdata(host);
        int i;

        cancel_work_sync(&ms->work);
        free_irq(ms->irq0, ms);
        free_irq(ms->irq1, ms);

        for (i = 0; i < ms->gpio_cs_count; i++)
                gpiod_put(ms->gpio_cs[i]);

        kfree(ms->gpio_cs);
        spi_unregister_controller(host);
        iounmap(ms->regs);
        spi_controller_put(host);
}

static const struct of_device_id mpc52xx_spi_match[] = {
        { .compatible = "fsl,mpc5200-spi", },
        {}
};
MODULE_DEVICE_TABLE(of, mpc52xx_spi_match);

static struct platform_driver mpc52xx_spi_of_driver = {
        .driver = {
                .name = "mpc52xx-spi",
                .of_match_table = mpc52xx_spi_match,
        },
        .probe = mpc52xx_spi_probe,
        .remove = mpc52xx_spi_remove,
};
module_platform_driver(mpc52xx_spi_of_driver);