/*
 * ramips_spi.c -- Ralink RT288x/RT305x SPI controller driver
 *
 * Copyright (C) 2011 Sergiy <piratfm@gmail.com>
 * Copyright (C) 2011 Gabor Juhos <juhosg@openwrt.org>
 *
 * 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/init.h>
#include <linux/module.h>
#include <linux/clk.h>
#include <linux/err.h>
#include <linux/delay.h>
#include <linux/platform_device.h>
#include <linux/io.h>
#include <linux/spi/spi.h>

#define DRIVER_NAME			"ramips-spi"
#define RALINK_NUM_CHIPSELECTS		1 /* only one slave is supported*/
#define RALINK_SPI_WAIT_RDY_MAX_LOOP	2000 /* in usec */

#define RAMIPS_SPI_STAT			0x00
#define RAMIPS_SPI_CFG			0x10
#define RAMIPS_SPI_CTL			0x14
#define RAMIPS_SPI_DATA			0x20

/* SPISTAT register bit field */
#define SPISTAT_BUSY			BIT(0)

/* SPICFG register bit field */
#define SPICFG_LSBFIRST			0
#define SPICFG_MSBFIRST			BIT(8)
#define SPICFG_SPICLKPOL		BIT(6)
#define SPICFG_RXCLKEDGE_FALLING	BIT(5)
#define SPICFG_TXCLKEDGE_FALLING	BIT(4)
#define SPICFG_SPICLK_PRESCALE_MASK	0x7
#define SPICFG_SPICLK_DIV2		0
#define SPICFG_SPICLK_DIV4		1
#define SPICFG_SPICLK_DIV8		2
#define SPICFG_SPICLK_DIV16		3
#define SPICFG_SPICLK_DIV32		4
#define SPICFG_SPICLK_DIV64		5
#define SPICFG_SPICLK_DIV128		6
#define SPICFG_SPICLK_DISABLE		7

/* SPICTL register bit field */
#define SPICTL_HIZSDO			BIT(3)
#define SPICTL_STARTWR			BIT(2)
#define SPICTL_STARTRD			BIT(1)
#define SPICTL_SPIENA			BIT(0)

#ifdef DEBUG
#define spi_debug(args...) printk(args)
#else
#define spi_debug(args...)
#endif

struct ramips_spi {
	struct work_struct	work;

	/* Lock access to transfer list.*/
	spinlock_t		lock;

	struct list_head	msg_queue;
	struct spi_master	*master;
	void __iomem		*base;
	unsigned int		sys_freq;
	unsigned int		speed;

	struct clk		*clk;
};

static struct workqueue_struct *ramips_spi_wq;

static inline struct ramips_spi *ramips_spidev_to_rs(struct spi_device *spi)
{
	return spi_master_get_devdata(spi->master);
}

static inline u32 ramips_spi_read(struct ramips_spi *rs, u32 reg)
{
	return ioread32(rs->base + reg);
}

static inline void ramips_spi_write(struct ramips_spi *rs, u32 reg, u32 val)
{
	iowrite32(val, rs->base + reg);
}

static inline void ramips_spi_setbits(struct ramips_spi *rs, u32 reg, u32 mask)
{
	void __iomem *addr = rs->base + reg;
	u32 val;

	val = ioread32(addr);
	val |= mask;
	iowrite32(val, addr);
}

static inline void ramips_spi_clrbits(struct ramips_spi *rs, u32 reg, u32 mask)
{
	void __iomem *addr = rs->base + reg;
	u32 val;

	val = ioread32(addr);
	val &= ~mask;
	iowrite32(val, addr);
}

static int ramips_spi_baudrate_set(struct spi_device *spi, unsigned int speed)
{
	struct ramips_spi *rs = ramips_spidev_to_rs(spi);
	u32 rate;
	u32 prescale;
	u32 reg;

	spi_debug("%s: speed:%u\n", __func__, speed);

	/*
	 * the supported rates are: 2,4,8...128
	 * round up as we look for equal or less speed
	 */
	rate = DIV_ROUND_UP(rs->sys_freq, speed);
	spi_debug("%s: rate-1:%u\n", __func__, rate);
	rate = roundup_pow_of_two(rate);
	spi_debug("%s: rate-2:%u\n", __func__, rate);

	/* check if requested speed is too small */
	if (rate > 128)
		return -EINVAL;

	if (rate < 2)
		rate = 2;

	/* Convert the rate to SPI clock divisor value.	*/
	prescale = ilog2(rate/2);
	spi_debug("%s: prescale:%u\n", __func__, prescale);

	reg = ramips_spi_read(rs, RAMIPS_SPI_CFG);
	reg = ((reg & ~SPICFG_SPICLK_PRESCALE_MASK) | prescale);
	ramips_spi_write(rs, RAMIPS_SPI_CFG, reg);
	rs->speed = speed;
	return 0;
}

/*
 * called only when no transfer is active on the bus
 */
static int
ramips_spi_setup_transfer(struct spi_device *spi, struct spi_transfer *t)
{
	struct ramips_spi *rs = ramips_spidev_to_rs(spi);
	unsigned int speed = spi->max_speed_hz;
	int	rc;
	unsigned int bits_per_word = 8;

	if ((t != NULL) && t->speed_hz)
		speed = t->speed_hz;

	if ((t != NULL) && t->bits_per_word)
		bits_per_word = t->bits_per_word;

	if (rs->speed != speed) {
		spi_debug("%s: speed_hz:%u\n", __func__, speed);
		rc = ramips_spi_baudrate_set(spi, speed);
		if (rc)
			return rc;
	}

	if (bits_per_word != 8) {
		spi_debug("%s: bad bits_per_word: %u\n", __func__,
			  bits_per_word);
		return -EINVAL;
	}

	return 0;
}

static void ramips_spi_set_cs(struct ramips_spi *rs, int enable)
{
	if (enable)
		ramips_spi_clrbits(rs, RAMIPS_SPI_CTL, SPICTL_SPIENA);
	else
		ramips_spi_setbits(rs, RAMIPS_SPI_CTL, SPICTL_SPIENA);
}

static inline int ramips_spi_wait_till_ready(struct ramips_spi *rs)
{
	int i;

	for (i = 0; i < RALINK_SPI_WAIT_RDY_MAX_LOOP; i++) {
		u32 status;

		status = ramips_spi_read(rs, RAMIPS_SPI_STAT);
		if ((status & SPISTAT_BUSY) == 0)
			return 0;

		udelay(1);
	}

	return -ETIMEDOUT;
}

static unsigned int
ramips_spi_write_read(struct spi_device *spi, struct spi_transfer *xfer)
{
	struct ramips_spi *rs = ramips_spidev_to_rs(spi);
	unsigned count = 0;
	u8 *rx = xfer->rx_buf;
	const u8 *tx = xfer->tx_buf;
	int err;

	spi_debug("%s(%d): %s %s\n", __func__, xfer->len,
		  (tx != NULL) ? "tx" : "  ",
		  (rx != NULL) ? "rx" : "  ");

	if (tx) {
		for (count = 0; count < xfer->len; count++) {
			ramips_spi_write(rs, RAMIPS_SPI_DATA, tx[count]);
			ramips_spi_setbits(rs, RAMIPS_SPI_CTL, SPICTL_STARTWR);
			err = ramips_spi_wait_till_ready(rs);
			if (err) {
				dev_err(&spi->dev, "TX failed, err=%d\n", err);
				goto out;
			}
		}
	}

	if (rx) {
		for (count = 0; count < xfer->len; count++) {
			ramips_spi_setbits(rs, RAMIPS_SPI_CTL, SPICTL_STARTRD);
			err = ramips_spi_wait_till_ready(rs);
			if (err) {
				dev_err(&spi->dev, "RX failed, err=%d\n", err);
				goto out;
			}
			rx[count] = (u8) ramips_spi_read(rs, RAMIPS_SPI_DATA);
		}
	}

out:
	return count;
}

static void ramips_spi_work(struct work_struct *work)
{
	struct ramips_spi *rs =
		container_of(work, struct ramips_spi, work);

	spin_lock_irq(&rs->lock);
	while (!list_empty(&rs->msg_queue)) {
		struct spi_message *m;
		struct spi_device *spi;
		struct spi_transfer *t = NULL;
		int par_override = 0;
		int status = 0;
		int cs_active = 0;

		m = container_of(rs->msg_queue.next, struct spi_message,
				 queue);

		list_del_init(&m->queue);
		spin_unlock_irq(&rs->lock);

		spi = m->spi;

		/* Load defaults */
		status = ramips_spi_setup_transfer(spi, NULL);

		if (status < 0)
			goto msg_done;

		list_for_each_entry(t, &m->transfers, transfer_list) {
			if (par_override || t->speed_hz || t->bits_per_word) {
				par_override = 1;
				status = ramips_spi_setup_transfer(spi, t);
				if (status < 0)
					break;
				if (!t->speed_hz && !t->bits_per_word)
					par_override = 0;
			}

			if (!cs_active) {
				ramips_spi_set_cs(rs, 1);
				cs_active = 1;
			}

			if (t->len)
				m->actual_length +=
					ramips_spi_write_read(spi, t);

			if (t->delay_usecs)
				udelay(t->delay_usecs);

			if (t->cs_change) {
				ramips_spi_set_cs(rs, 0);
				cs_active = 0;
			}
		}

msg_done:
		if (cs_active)
			ramips_spi_set_cs(rs, 0);

		m->status = status;
		m->complete(m->context);

		spin_lock_irq(&rs->lock);
	}

	spin_unlock_irq(&rs->lock);
}

static int ramips_spi_setup(struct spi_device *spi)
{
	struct ramips_spi *rs = ramips_spidev_to_rs(spi);

	if ((spi->max_speed_hz == 0) ||
	    (spi->max_speed_hz > (rs->sys_freq / 2)))
		spi->max_speed_hz = (rs->sys_freq / 2);

	if (spi->max_speed_hz < (rs->sys_freq/128)) {
		dev_err(&spi->dev, "setup: requested speed too low %d Hz\n",
			spi->max_speed_hz);
		return -EINVAL;
	}

	if (spi->bits_per_word != 0 && spi->bits_per_word != 8) {
		dev_err(&spi->dev,
			"setup: requested bits per words - os wrong %d bpw\n",
			spi->bits_per_word);
		return -EINVAL;
	}

	if (spi->bits_per_word == 0)
		spi->bits_per_word = 8;

	/*
	 * baudrate & width will be set ramips_spi_setup_transfer
	 */
	return 0;
}

static int ramips_spi_transfer(struct spi_device *spi, struct spi_message *m)
{
	struct ramips_spi *rs;
	struct spi_transfer *t = NULL;
	unsigned long flags;

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

	/* reject invalid messages and transfers */
	if (list_empty(&m->transfers) || !m->complete)
		return -EINVAL;

	rs = ramips_spidev_to_rs(spi);

	list_for_each_entry(t, &m->transfers, transfer_list) {
		unsigned int bits_per_word = spi->bits_per_word;

		if (t->tx_buf == NULL && t->rx_buf == NULL && t->len) {
			dev_err(&spi->dev,
				"message rejected : "
				"invalid transfer data buffers\n");
			goto msg_rejected;
		}

		if (t->bits_per_word)
			bits_per_word = t->bits_per_word;

		if (bits_per_word != 8) {
			dev_err(&spi->dev,
				"message rejected : "
				"invalid transfer bits_per_word (%d bits)\n",
				bits_per_word);
			goto msg_rejected;
		}

		if (t->speed_hz && t->speed_hz < (rs->sys_freq/128)) {
			dev_err(&spi->dev,
				"message rejected : "
				"device min speed (%d Hz) exceeds "
				"required transfer speed (%d Hz)\n",
				(rs->sys_freq/128), t->speed_hz);
			goto msg_rejected;
		}
	}


	spin_lock_irqsave(&rs->lock, flags);
	list_add_tail(&m->queue, &rs->msg_queue);
	queue_work(ramips_spi_wq, &rs->work);
	spin_unlock_irqrestore(&rs->lock, flags);

	return 0;
msg_rejected:
	/* Message rejected and not queued */
	m->status = -EINVAL;
	if (m->complete)
		m->complete(m->context);
	return -EINVAL;
}

static void __init ramips_spi_reset(struct ramips_spi *rs)
{
	ramips_spi_write(rs, RAMIPS_SPI_CFG,
			 SPICFG_MSBFIRST | SPICFG_TXCLKEDGE_FALLING |
			 SPICFG_SPICLK_DIV16 | SPICFG_SPICLKPOL);
	ramips_spi_write(rs, RAMIPS_SPI_CTL, SPICTL_HIZSDO | SPICTL_SPIENA);
}

static int __init ramips_spi_probe(struct platform_device *pdev)
{
	struct spi_master *master;
	struct ramips_spi *rs;
	struct resource *r;
	int status = 0;

	master = spi_alloc_master(&pdev->dev, sizeof(*rs));
	if (master == NULL) {
		dev_dbg(&pdev->dev, "master allocation failed\n");
		return -ENOMEM;
	}

	if (pdev->id != -1)
		master->bus_num = pdev->id;

	/* we support only mode 0, and no options */
	master->mode_bits = 0;

	master->setup = ramips_spi_setup;
	master->transfer = ramips_spi_transfer;
	master->num_chipselect = RALINK_NUM_CHIPSELECTS;

	dev_set_drvdata(&pdev->dev, master);

	rs = spi_master_get_devdata(master);
	rs->master = master;

	rs->clk = clk_get(NULL, "sys");
	if (IS_ERR(rs->clk)) {
		status = PTR_ERR(rs->clk);
		dev_err(&pdev->dev, "unable to get SYS clock, err=%d\n",
			status);
		goto out_put_master;
	}

	status = clk_enable(rs->clk);
	if (status)
		goto out_put_clk;

	rs->sys_freq = clk_get_rate(rs->clk);
	spi_debug("%s: sys_freq: %ld\n", __func__, rs->sys_freq);

	r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	if (r == NULL) {
		status = -ENODEV;
		goto out_disable_clk;
	}

	if (!request_mem_region(r->start, (r->end - r->start) + 1,
				dev_name(&pdev->dev))) {
		status = -EBUSY;
		goto out_disable_clk;
	}

	rs->base = ioremap(r->start, resource_size(r));
	if (rs->base == NULL) {
		dev_err(&pdev->dev, "ioremap failed\n");
		status = -ENOMEM;
		goto out_rel_mem;
	}

	INIT_WORK(&rs->work, ramips_spi_work);

	spin_lock_init(&rs->lock);
	INIT_LIST_HEAD(&rs->msg_queue);

	ramips_spi_reset(rs);

	status = spi_register_master(master);
	if (status)
		goto out_unmap_base;

	return 0;

out_unmap_base:
	iounmap(rs->base);
out_rel_mem:
	release_mem_region(r->start, (r->end - r->start) + 1);
out_disable_clk:
	clk_disable(rs->clk);
out_put_clk:
	clk_put(rs->clk);
out_put_master:
	spi_master_put(master);
	return status;
}

static int ramips_spi_remove(struct platform_device *pdev)
{
	struct spi_master *master;
	struct ramips_spi *rs;
	struct resource *r;

	master = dev_get_drvdata(&pdev->dev);
	rs = spi_master_get_devdata(master);

	cancel_work_sync(&rs->work);

	iounmap(rs->base);
	r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	release_mem_region(r->start, (r->end - r->start) + 1);

	clk_disable(rs->clk);
	clk_put(rs->clk);
	spi_unregister_master(master);

	return 0;
}

MODULE_ALIAS("platform:" DRIVER_NAME);

static struct platform_driver ramips_spi_driver = {
	.driver = {
		.name	= DRIVER_NAME,
		.owner	= THIS_MODULE,
	},
	.remove		= ramips_spi_remove,
};

static int __init ramips_spi_init(void)
{
	ramips_spi_wq = create_singlethread_workqueue(
				ramips_spi_driver.driver.name);
	if (ramips_spi_wq == NULL)
		return -ENOMEM;

	return platform_driver_probe(&ramips_spi_driver, ramips_spi_probe);
}
module_init(ramips_spi_init);

static void __exit ramips_spi_exit(void)
{
	flush_workqueue(ramips_spi_wq);
	platform_driver_unregister(&ramips_spi_driver);

	destroy_workqueue(ramips_spi_wq);
}
module_exit(ramips_spi_exit);

MODULE_DESCRIPTION("Ralink SPI driver");
MODULE_AUTHOR("Sergiy <piratfm@gmail.com>");
MODULE_AUTHOR("Gabor Juhos <juhosg@openwrt.org>");
MODULE_LICENSE("GPL");