/*
 * Copyright (C) 2012-2013 Uwe Kleine-Koenig for Pengutronix
 *
 * 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/kernel.h>
#include <linux/io.h>
#include <linux/spi/spi.h>
#include <linux/spi/spi_bitbang.h>
#include <linux/gpio.h>
#include <linux/interrupt.h>
#include <linux/platform_device.h>
#include <linux/clk.h>
#include <linux/err.h>
#include <linux/module.h>
#include <linux/of_gpio.h>
#include <linux/platform_data/efm32-spi.h>

#define DRIVER_NAME "efm32-spi"

#define MASK_VAL(mask, val)		((val << __ffs(mask)) & mask)

#define REG_CTRL		0x00
#define REG_CTRL_SYNC			0x0001
#define REG_CTRL_CLKPOL			0x0100
#define REG_CTRL_CLKPHA			0x0200
#define REG_CTRL_MSBF			0x0400
#define REG_CTRL_TXBIL			0x1000

#define REG_FRAME		0x04
#define REG_FRAME_DATABITS__MASK	0x000f
#define REG_FRAME_DATABITS(n)		((n) - 3)

#define REG_CMD			0x0c
#define REG_CMD_RXEN			0x0001
#define REG_CMD_RXDIS			0x0002
#define REG_CMD_TXEN			0x0004
#define REG_CMD_TXDIS			0x0008
#define REG_CMD_MASTEREN		0x0010

#define REG_STATUS		0x10
#define REG_STATUS_TXENS		0x0002
#define REG_STATUS_TXC			0x0020
#define REG_STATUS_TXBL			0x0040
#define REG_STATUS_RXDATAV		0x0080

#define REG_CLKDIV		0x14

#define REG_RXDATAX		0x18
#define REG_RXDATAX_RXDATA__MASK	0x01ff
#define REG_RXDATAX_PERR		0x4000
#define REG_RXDATAX_FERR		0x8000

#define REG_TXDATA		0x34

#define REG_IF		0x40
#define REG_IF_TXBL			0x0002
#define REG_IF_RXDATAV			0x0004

#define REG_IFS		0x44
#define REG_IFC		0x48
#define REG_IEN		0x4c

#define REG_ROUTE		0x54
#define REG_ROUTE_RXPEN			0x0001
#define REG_ROUTE_TXPEN			0x0002
#define REG_ROUTE_CLKPEN		0x0008
#define REG_ROUTE_LOCATION__MASK	0x0700
#define REG_ROUTE_LOCATION(n)		MASK_VAL(REG_ROUTE_LOCATION__MASK, (n))

struct efm32_spi_ddata {
	struct spi_bitbang bitbang;

	spinlock_t lock;

	struct clk *clk;
	void __iomem *base;
	unsigned int rxirq, txirq;
	struct efm32_spi_pdata pdata;

	/* irq data */
	struct completion done;
	const u8 *tx_buf;
	u8 *rx_buf;
	unsigned tx_len, rx_len;

	/* chip selects */
	unsigned csgpio[];
};

#define ddata_to_dev(ddata)	(&(ddata->bitbang.master->dev))
#define efm32_spi_vdbg(ddata, format, arg...)	\
	dev_vdbg(ddata_to_dev(ddata), format, ##arg)

static void efm32_spi_write32(struct efm32_spi_ddata *ddata,
		u32 value, unsigned offset)
{
	writel_relaxed(value, ddata->base + offset);
}

static u32 efm32_spi_read32(struct efm32_spi_ddata *ddata, unsigned offset)
{
	return readl_relaxed(ddata->base + offset);
}

static void efm32_spi_chipselect(struct spi_device *spi, int is_on)
{
	struct efm32_spi_ddata *ddata = spi_master_get_devdata(spi->master);
	int value = !(spi->mode & SPI_CS_HIGH) == !(is_on == BITBANG_CS_ACTIVE);

	gpio_set_value(ddata->csgpio[spi->chip_select], value);
}

static int efm32_spi_setup_transfer(struct spi_device *spi,
		struct spi_transfer *t)
{
	struct efm32_spi_ddata *ddata = spi_master_get_devdata(spi->master);

	unsigned bpw = t->bits_per_word ?: spi->bits_per_word;
	unsigned speed = t->speed_hz ?: spi->max_speed_hz;
	unsigned long clkfreq = clk_get_rate(ddata->clk);
	u32 clkdiv;

	efm32_spi_write32(ddata, REG_CTRL_SYNC | REG_CTRL_MSBF |
			(spi->mode & SPI_CPHA ? REG_CTRL_CLKPHA : 0) |
			(spi->mode & SPI_CPOL ? REG_CTRL_CLKPOL : 0), REG_CTRL);

	efm32_spi_write32(ddata,
			REG_FRAME_DATABITS(bpw), REG_FRAME);

	if (2 * speed >= clkfreq)
		clkdiv = 0;
	else
		clkdiv = 64 * (DIV_ROUND_UP(2 * clkfreq, speed) - 4);

	if (clkdiv > (1U << 21))
		return -EINVAL;

	efm32_spi_write32(ddata, clkdiv, REG_CLKDIV);
	efm32_spi_write32(ddata, REG_CMD_MASTEREN, REG_CMD);
	efm32_spi_write32(ddata, REG_CMD_RXEN | REG_CMD_TXEN, REG_CMD);

	return 0;
}

static void efm32_spi_tx_u8(struct efm32_spi_ddata *ddata)
{
	u8 val = 0;

	if (ddata->tx_buf) {
		val = *ddata->tx_buf;
		ddata->tx_buf++;
	}

	ddata->tx_len--;
	efm32_spi_write32(ddata, val, REG_TXDATA);
	efm32_spi_vdbg(ddata, "%s: tx 0x%x\n", __func__, val);
}

static void efm32_spi_rx_u8(struct efm32_spi_ddata *ddata)
{
	u32 rxdata = efm32_spi_read32(ddata, REG_RXDATAX);
	efm32_spi_vdbg(ddata, "%s: rx 0x%x\n", __func__, rxdata);

	if (ddata->rx_buf) {
		*ddata->rx_buf = rxdata;
		ddata->rx_buf++;
	}

	ddata->rx_len--;
}

static void efm32_spi_filltx(struct efm32_spi_ddata *ddata)
{
	while (ddata->tx_len &&
			ddata->tx_len + 2 > ddata->rx_len &&
			efm32_spi_read32(ddata, REG_STATUS) & REG_STATUS_TXBL) {
		efm32_spi_tx_u8(ddata);
	}
}

static int efm32_spi_txrx_bufs(struct spi_device *spi, struct spi_transfer *t)
{
	struct efm32_spi_ddata *ddata = spi_master_get_devdata(spi->master);
	int ret = -EBUSY;

	spin_lock_irq(&ddata->lock);

	if (ddata->tx_buf || ddata->rx_buf)
		goto out_unlock;

	ddata->tx_buf = t->tx_buf;
	ddata->rx_buf = t->rx_buf;
	ddata->tx_len = ddata->rx_len =
		t->len * DIV_ROUND_UP(t->bits_per_word, 8);

	efm32_spi_filltx(ddata);

	init_completion(&ddata->done);

	efm32_spi_write32(ddata, REG_IF_TXBL | REG_IF_RXDATAV, REG_IEN);

	spin_unlock_irq(&ddata->lock);

	wait_for_completion(&ddata->done);

	spin_lock_irq(&ddata->lock);

	ret = t->len - max(ddata->tx_len, ddata->rx_len);

	efm32_spi_write32(ddata, 0, REG_IEN);
	ddata->tx_buf = ddata->rx_buf = NULL;

out_unlock:
	spin_unlock_irq(&ddata->lock);

	return ret;
}

static irqreturn_t efm32_spi_rxirq(int irq, void *data)
{
	struct efm32_spi_ddata *ddata = data;
	irqreturn_t ret = IRQ_NONE;

	spin_lock(&ddata->lock);

	while (ddata->rx_len > 0 &&
			efm32_spi_read32(ddata, REG_STATUS) &
			REG_STATUS_RXDATAV) {
		efm32_spi_rx_u8(ddata);

		ret = IRQ_HANDLED;
	}

	if (!ddata->rx_len) {
		u32 ien = efm32_spi_read32(ddata, REG_IEN);

		ien &= ~REG_IF_RXDATAV;

		efm32_spi_write32(ddata, ien, REG_IEN);

		complete(&ddata->done);
	}

	spin_unlock(&ddata->lock);

	return ret;
}

static irqreturn_t efm32_spi_txirq(int irq, void *data)
{
	struct efm32_spi_ddata *ddata = data;

	efm32_spi_vdbg(ddata,
			"%s: txlen = %u, rxlen = %u, if=0x%08x, stat=0x%08x\n",
			__func__, ddata->tx_len, ddata->rx_len,
			efm32_spi_read32(ddata, REG_IF),
			efm32_spi_read32(ddata, REG_STATUS));

	spin_lock(&ddata->lock);

	efm32_spi_filltx(ddata);

	efm32_spi_vdbg(ddata, "%s: txlen = %u, rxlen = %u\n",
			__func__, ddata->tx_len, ddata->rx_len);

	if (!ddata->tx_len) {
		u32 ien = efm32_spi_read32(ddata, REG_IEN);

		ien &= ~REG_IF_TXBL;

		efm32_spi_write32(ddata, ien, REG_IEN);
		efm32_spi_vdbg(ddata, "disable TXBL\n");
	}

	spin_unlock(&ddata->lock);

	return IRQ_HANDLED;
}

static u32 efm32_spi_get_configured_location(struct efm32_spi_ddata *ddata)
{
	u32 reg = efm32_spi_read32(ddata, REG_ROUTE);

	return (reg & REG_ROUTE_LOCATION__MASK) >> __ffs(REG_ROUTE_LOCATION__MASK);
}

static int efm32_spi_probe_dt(struct platform_device *pdev,
		struct spi_master *master, struct efm32_spi_ddata *ddata)
{
	struct device_node *np = pdev->dev.of_node;
	u32 location;
	int ret;

	if (!np)
		return 1;

	ret = of_property_read_u32(np, "location", &location);
	if (!ret) {
		dev_dbg(&pdev->dev, "using location %u\n", location);
	} else {
		/* default to location configured in hardware */
		location = efm32_spi_get_configured_location(ddata);

		dev_info(&pdev->dev, "fall back to location %u\n", location);
	}

	ddata->pdata.location = location;

	/* spi core takes care about the bus number using an alias */
	master->bus_num = -1;

	return 0;
}

static int efm32_spi_probe(struct platform_device *pdev)
{
	struct efm32_spi_ddata *ddata;
	struct resource *res;
	int ret;
	struct spi_master *master;
	struct device_node *np = pdev->dev.of_node;
	unsigned int num_cs, i;

	num_cs = of_gpio_named_count(np, "cs-gpios");

	master = spi_alloc_master(&pdev->dev,
			sizeof(*ddata) + num_cs * sizeof(unsigned));
	if (!master) {
		dev_dbg(&pdev->dev,
				"failed to allocate spi master controller\n");
		return -ENOMEM;
	}
	platform_set_drvdata(pdev, master);

	master->dev.of_node = pdev->dev.of_node;

	master->num_chipselect = num_cs;
	master->mode_bits = SPI_CPOL | SPI_CPHA | SPI_CS_HIGH;
	master->bits_per_word_mask = SPI_BPW_RANGE_MASK(4, 16);

	ddata = spi_master_get_devdata(master);

	ddata->bitbang.master = master;
	ddata->bitbang.chipselect = efm32_spi_chipselect;
	ddata->bitbang.setup_transfer = efm32_spi_setup_transfer;
	ddata->bitbang.txrx_bufs = efm32_spi_txrx_bufs;

	spin_lock_init(&ddata->lock);

	ddata->clk = devm_clk_get(&pdev->dev, NULL);
	if (IS_ERR(ddata->clk)) {
		ret = PTR_ERR(ddata->clk);
		dev_err(&pdev->dev, "failed to get clock: %d\n", ret);
		goto err;
	}

	for (i = 0; i < num_cs; ++i) {
		ret = of_get_named_gpio(np, "cs-gpios", i);
		if (ret < 0) {
			dev_err(&pdev->dev, "failed to get csgpio#%u (%d)\n",
					i, ret);
			goto err;
		}
		ddata->csgpio[i] = ret;
		dev_dbg(&pdev->dev, "csgpio#%u = %u\n", i, ddata->csgpio[i]);
		ret = devm_gpio_request_one(&pdev->dev, ddata->csgpio[i],
				GPIOF_OUT_INIT_LOW, DRIVER_NAME);
		if (ret < 0) {
			dev_err(&pdev->dev,
					"failed to configure csgpio#%u (%d)\n",
					i, ret);
			goto err;
		}
	}

	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	if (!res) {
		ret = -ENODEV;
		dev_err(&pdev->dev, "failed to determine base address\n");
		goto err;
	}

	if (resource_size(res) < 0x60) {
		ret = -EINVAL;
		dev_err(&pdev->dev, "memory resource too small\n");
		goto err;
	}

	ddata->base = devm_ioremap_resource(&pdev->dev, res);
	if (IS_ERR(ddata->base)) {
		ret = PTR_ERR(ddata->base);
		goto err;
	}

	ret = platform_get_irq(pdev, 0);
	if (ret <= 0) {
		dev_err(&pdev->dev, "failed to get rx irq (%d)\n", ret);
		goto err;
	}

	ddata->rxirq = ret;

	ret = platform_get_irq(pdev, 1);
	if (ret <= 0)
		ret = ddata->rxirq + 1;

	ddata->txirq = ret;

	ret = clk_prepare_enable(ddata->clk);
	if (ret < 0) {
		dev_err(&pdev->dev, "failed to enable clock (%d)\n", ret);
		goto err;
	}

	ret = efm32_spi_probe_dt(pdev, master, ddata);
	if (ret > 0) {
		/* not created by device tree */
		const struct efm32_spi_pdata *pdata =
			dev_get_platdata(&pdev->dev);

		if (pdata)
			ddata->pdata = *pdata;
		else
			ddata->pdata.location =
				efm32_spi_get_configured_location(ddata);

		master->bus_num = pdev->id;

	} else if (ret < 0) {
		goto err_disable_clk;
	}

	efm32_spi_write32(ddata, 0, REG_IEN);
	efm32_spi_write32(ddata, REG_ROUTE_TXPEN | REG_ROUTE_RXPEN |
			REG_ROUTE_CLKPEN |
			REG_ROUTE_LOCATION(ddata->pdata.location), REG_ROUTE);

	ret = request_irq(ddata->rxirq, efm32_spi_rxirq,
			0, DRIVER_NAME " rx", ddata);
	if (ret) {
		dev_err(&pdev->dev, "failed to register rxirq (%d)\n", ret);
		goto err_disable_clk;
	}

	ret = request_irq(ddata->txirq, efm32_spi_txirq,
			0, DRIVER_NAME " tx", ddata);
	if (ret) {
		dev_err(&pdev->dev, "failed to register txirq (%d)\n", ret);
		goto err_free_rx_irq;
	}

	ret = spi_bitbang_start(&ddata->bitbang);
	if (ret) {
		dev_err(&pdev->dev, "spi_bitbang_start failed (%d)\n", ret);

		free_irq(ddata->txirq, ddata);
err_free_rx_irq:
		free_irq(ddata->rxirq, ddata);
err_disable_clk:
		clk_disable_unprepare(ddata->clk);
err:
		spi_master_put(master);
	}

	return ret;
}

static int efm32_spi_remove(struct platform_device *pdev)
{
	struct spi_master *master = platform_get_drvdata(pdev);
	struct efm32_spi_ddata *ddata = spi_master_get_devdata(master);

	spi_bitbang_stop(&ddata->bitbang);

	efm32_spi_write32(ddata, 0, REG_IEN);

	free_irq(ddata->txirq, ddata);
	free_irq(ddata->rxirq, ddata);
	clk_disable_unprepare(ddata->clk);
	spi_master_put(master);

	return 0;
}

static const struct of_device_id efm32_spi_dt_ids[] = {
	{
		.compatible = "efm32,spi",
	}, {
		/* sentinel */
	}
};
MODULE_DEVICE_TABLE(of, efm32_spi_dt_ids);

static struct platform_driver efm32_spi_driver = {
	.probe = efm32_spi_probe,
	.remove = efm32_spi_remove,

	.driver = {
		.name = DRIVER_NAME,
		.owner = THIS_MODULE,
		.of_match_table = efm32_spi_dt_ids,
	},
};
module_platform_driver(efm32_spi_driver);

MODULE_AUTHOR("Uwe Kleine-Koenig <u.kleine-koenig@pengutronix.de>");
MODULE_DESCRIPTION("EFM32 SPI driver");
MODULE_LICENSE("GPL v2");
MODULE_ALIAS("platform:" DRIVER_NAME);