/*
   * 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
  ", __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
  ", __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);
  
  	reinit_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
  ",
  			__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
  ",
  			__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
  ");
  	}
  
  	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 void 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;
  
  	ret = of_property_read_u32(np, "energymicro,location", &location);
  
  	if (ret)
  		/* fall back to wrongly namespaced property */
  		ret = of_property_read_u32(np, "efm32,location", &location);
  
  	if (ret)
  		/* fall back to old and (wrongly) generic property "location" */
  		ret = of_property_read_u32(np, "location", &location);
  
  	if (!ret) {
  		dev_dbg(&pdev->dev, "using location %u
  ", location);
  	} else {
  		/* default to location configured in hardware */
  		location = efm32_spi_get_configured_location(ddata);
  
  		dev_info(&pdev->dev, "fall back to location %u
  ", location);
  	}
  
  	ddata->pdata.location = location;
  }
  
  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;
  	int num_cs, i;
  
  	if (!np)
  		return -EINVAL;
  
  	num_cs = of_gpio_named_count(np, "cs-gpios");
  	if (num_cs < 0)
  		return num_cs;
  
  	master = spi_alloc_master(&pdev->dev,
  			sizeof(*ddata) + num_cs * sizeof(unsigned));
  	if (!master) {
  		dev_dbg(&pdev->dev,
  				"failed to allocate spi master controller
  ");
  		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);
  	init_completion(&ddata->done);
  
  	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
  ", 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)
  ",
  					i, ret);
  			goto err;
  		}
  		ddata->csgpio[i] = ret;
  		dev_dbg(&pdev->dev, "csgpio#%u = %u
  ", 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)
  ",
  					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
  ");
  		goto err;
  	}
  
  	if (resource_size(res) < 0x60) {
  		ret = -EINVAL;
  		dev_err(&pdev->dev, "memory resource too small
  ");
  		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)
  ", 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)
  ", ret);
  		goto err;
  	}
  
  	efm32_spi_probe_dt(pdev, master, ddata);
  
  	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)
  ", 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)
  ", ret);
  		goto err_free_rx_irq;
  	}
  
  	ret = spi_bitbang_start(&ddata->bitbang);
  	if (ret) {
  		dev_err(&pdev->dev, "spi_bitbang_start failed (%d)
  ", 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 = "energymicro,efm32-spi",
  	}, {
  		/* doesn't follow the "vendor,device" scheme, don't use */
  		.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,
  		.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);