/*
   * SPI controller driver for the Atheros AR71XX/AR724X/AR913X SoCs
   *
   * Copyright (C) 2009-2011 Gabor Juhos <juhosg@openwrt.org>
   *
   * This driver has been based on the spi-gpio.c:
   *	Copyright (C) 2006,2008 David Brownell
   *
   * 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/module.h>

  #include <linux/delay.h>
  #include <linux/spinlock.h>

  #include <linux/platform_device.h>
  #include <linux/io.h>
  #include <linux/spi/spi.h>
  #include <linux/spi/spi_bitbang.h>
  #include <linux/bitops.h>
  #include <linux/gpio.h>

  #include <linux/clk.h>
  #include <linux/err.h>

  
  #include <asm/mach-ath79/ar71xx_regs.h>
  #include <asm/mach-ath79/ath79_spi_platform.h>
  
  #define DRV_NAME	"ath79-spi"

  #define ATH79_SPI_RRW_DELAY_FACTOR	12000
  #define MHZ				(1000 * 1000)

  struct ath79_spi {
  	struct spi_bitbang	bitbang;
  	u32			ioc_base;
  	u32			reg_ctrl;
  	void __iomem		*base;

  	struct clk		*clk;

  	unsigned int		rrw_delay;

  };

  static inline u32 ath79_spi_rr(struct ath79_spi *sp, unsigned int reg)

  {
  	return ioread32(sp->base + reg);
  }

  static inline void ath79_spi_wr(struct ath79_spi *sp, unsigned int reg, u32 val)

  {
  	iowrite32(val, sp->base + reg);
  }
  
  static inline struct ath79_spi *ath79_spidev_to_sp(struct spi_device *spi)
  {
  	return spi_master_get_devdata(spi->master);
  }

  static inline void ath79_spi_delay(struct ath79_spi *sp, unsigned int nsecs)

  {
  	if (nsecs > sp->rrw_delay)
  		ndelay(nsecs - sp->rrw_delay);
  }

  static void ath79_spi_chipselect(struct spi_device *spi, int is_active)
  {
  	struct ath79_spi *sp = ath79_spidev_to_sp(spi);
  	int cs_high = (spi->mode & SPI_CS_HIGH) ? is_active : !is_active;
  
  	if (is_active) {
  		/* set initial clock polarity */
  		if (spi->mode & SPI_CPOL)
  			sp->ioc_base |= AR71XX_SPI_IOC_CLK;
  		else
  			sp->ioc_base &= ~AR71XX_SPI_IOC_CLK;
  
  		ath79_spi_wr(sp, AR71XX_SPI_REG_IOC, sp->ioc_base);
  	}

  	if (gpio_is_valid(spi->cs_gpio)) {

  		/* SPI is normally active-low */

  		gpio_set_value_cansleep(spi->cs_gpio, cs_high);

  	} else {

  		u32 cs_bit = AR71XX_SPI_IOC_CS(spi->chip_select);

  		if (cs_high)

  			sp->ioc_base |= cs_bit;

  		else

  			sp->ioc_base &= ~cs_bit;

  
  		ath79_spi_wr(sp, AR71XX_SPI_REG_IOC, sp->ioc_base);
  	}
  
  }

  static void ath79_spi_enable(struct ath79_spi *sp)

  {

  	/* enable GPIO mode */
  	ath79_spi_wr(sp, AR71XX_SPI_REG_FS, AR71XX_SPI_FS_GPIO);
  
  	/* save CTRL register */
  	sp->reg_ctrl = ath79_spi_rr(sp, AR71XX_SPI_REG_CTRL);
  	sp->ioc_base = ath79_spi_rr(sp, AR71XX_SPI_REG_IOC);
  
  	/* TODO: setup speed? */
  	ath79_spi_wr(sp, AR71XX_SPI_REG_CTRL, 0x43);

  }
  
  static void ath79_spi_disable(struct ath79_spi *sp)
  {
  	/* restore CTRL register */
  	ath79_spi_wr(sp, AR71XX_SPI_REG_CTRL, sp->reg_ctrl);
  	/* disable GPIO mode */
  	ath79_spi_wr(sp, AR71XX_SPI_REG_FS, 0);
  }
  
  static int ath79_spi_setup_cs(struct spi_device *spi)
  {

  	struct ath79_spi *sp = ath79_spidev_to_sp(spi);

  	int status;

  	status = 0;

  	if (gpio_is_valid(spi->cs_gpio)) {

  		unsigned long flags;
  
  		flags = GPIOF_DIR_OUT;
  		if (spi->mode & SPI_CS_HIGH)

  			flags |= GPIOF_INIT_LOW;

  		else
  			flags |= GPIOF_INIT_HIGH;

  		status = gpio_request_one(spi->cs_gpio, flags,

  					  dev_name(&spi->dev));

  	} else {

  		u32 cs_bit = AR71XX_SPI_IOC_CS(spi->chip_select);

  		if (spi->mode & SPI_CS_HIGH)

  			sp->ioc_base &= ~cs_bit;

  		else

  			sp->ioc_base |= cs_bit;

  
  		ath79_spi_wr(sp, AR71XX_SPI_REG_IOC, sp->ioc_base);

  	}

  	return status;

  }
  
  static void ath79_spi_cleanup_cs(struct spi_device *spi)
  {

  	if (gpio_is_valid(spi->cs_gpio))

  		gpio_free(spi->cs_gpio);

  }
  
  static int ath79_spi_setup(struct spi_device *spi)
  {
  	int status = 0;

  	if (!spi->controller_state) {
  		status = ath79_spi_setup_cs(spi);
  		if (status)
  			return status;
  	}
  
  	status = spi_bitbang_setup(spi);
  	if (status && !spi->controller_state)
  		ath79_spi_cleanup_cs(spi);
  
  	return status;
  }
  
  static void ath79_spi_cleanup(struct spi_device *spi)
  {
  	ath79_spi_cleanup_cs(spi);
  	spi_bitbang_cleanup(spi);
  }

  static u32 ath79_spi_txrx_mode0(struct spi_device *spi, unsigned int nsecs,

  			       u32 word, u8 bits)
  {
  	struct ath79_spi *sp = ath79_spidev_to_sp(spi);
  	u32 ioc = sp->ioc_base;
  
  	/* clock starts at inactive polarity */
  	for (word <<= (32 - bits); likely(bits); bits--) {
  		u32 out;
  
  		if (word & (1 << 31))
  			out = ioc | AR71XX_SPI_IOC_DO;
  		else
  			out = ioc & ~AR71XX_SPI_IOC_DO;
  
  		/* setup MSB (to slave) on trailing edge */
  		ath79_spi_wr(sp, AR71XX_SPI_REG_IOC, out);

  		ath79_spi_delay(sp, nsecs);

  		ath79_spi_wr(sp, AR71XX_SPI_REG_IOC, out | AR71XX_SPI_IOC_CLK);

  		ath79_spi_delay(sp, nsecs);

  		if (bits == 1)
  			ath79_spi_wr(sp, AR71XX_SPI_REG_IOC, out);

  
  		word <<= 1;
  	}
  
  	return ath79_spi_rr(sp, AR71XX_SPI_REG_RDS);
  }

  static int ath79_spi_probe(struct platform_device *pdev)

  {
  	struct spi_master *master;
  	struct ath79_spi *sp;
  	struct ath79_spi_platform_data *pdata;
  	struct resource	*r;

  	unsigned long rate;

  	int ret;
  
  	master = spi_alloc_master(&pdev->dev, sizeof(*sp));
  	if (master == NULL) {
  		dev_err(&pdev->dev, "failed to allocate spi master
  ");
  		return -ENOMEM;
  	}
  
  	sp = spi_master_get_devdata(master);

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

  	platform_set_drvdata(pdev, sp);

  	pdata = dev_get_platdata(&pdev->dev);

  	master->bits_per_word_mask = SPI_BPW_RANGE_MASK(1, 32);

  	master->setup = ath79_spi_setup;
  	master->cleanup = ath79_spi_cleanup;
  	if (pdata) {
  		master->bus_num = pdata->bus_num;
  		master->num_chipselect = pdata->num_chipselect;

  	}

  	sp->bitbang.master = master;

  	sp->bitbang.chipselect = ath79_spi_chipselect;
  	sp->bitbang.txrx_word[SPI_MODE_0] = ath79_spi_txrx_mode0;
  	sp->bitbang.setup_transfer = spi_bitbang_setup_transfer;
  	sp->bitbang.flags = SPI_CS_HIGH;
  
  	r = platform_get_resource(pdev, IORESOURCE_MEM, 0);

  	sp->base = devm_ioremap_resource(&pdev->dev, r);
  	if (IS_ERR(sp->base)) {
  		ret = PTR_ERR(sp->base);

  		goto err_put_master;
  	}

  	sp->clk = devm_clk_get(&pdev->dev, "ahb");

  	if (IS_ERR(sp->clk)) {
  		ret = PTR_ERR(sp->clk);

  		goto err_put_master;

  	}

  	ret = clk_prepare_enable(sp->clk);

  	if (ret)

  		goto err_put_master;

  
  	rate = DIV_ROUND_UP(clk_get_rate(sp->clk), MHZ);
  	if (!rate) {
  		ret = -EINVAL;
  		goto err_clk_disable;
  	}
  
  	sp->rrw_delay = ATH79_SPI_RRW_DELAY_FACTOR / rate;
  	dev_dbg(&pdev->dev, "register read/write delay is %u nsecs
  ",
  		sp->rrw_delay);

  	ath79_spi_enable(sp);

  	ret = spi_bitbang_start(&sp->bitbang);
  	if (ret)

  		goto err_disable;

  
  	return 0;

  err_disable:
  	ath79_spi_disable(sp);

  err_clk_disable:

  	clk_disable_unprepare(sp->clk);

  err_put_master:

  	spi_master_put(sp->bitbang.master);
  
  	return ret;
  }

  static int ath79_spi_remove(struct platform_device *pdev)

  {
  	struct ath79_spi *sp = platform_get_drvdata(pdev);
  
  	spi_bitbang_stop(&sp->bitbang);

  	ath79_spi_disable(sp);

  	clk_disable_unprepare(sp->clk);

  	spi_master_put(sp->bitbang.master);
  
  	return 0;
  }

  static void ath79_spi_shutdown(struct platform_device *pdev)
  {
  	ath79_spi_remove(pdev);
  }

  static const struct of_device_id ath79_spi_of_match[] = {
  	{ .compatible = "qca,ar7100-spi", },
  	{ },
  };

  MODULE_DEVICE_TABLE(of, ath79_spi_of_match);

  static struct platform_driver ath79_spi_driver = {
  	.probe		= ath79_spi_probe,

  	.remove		= ath79_spi_remove,

  	.shutdown	= ath79_spi_shutdown,

  	.driver		= {
  		.name	= DRV_NAME,

  		.of_match_table = ath79_spi_of_match,

  	},
  };

  module_platform_driver(ath79_spi_driver);

  
  MODULE_DESCRIPTION("SPI controller driver for Atheros AR71XX/AR724X/AR913X");
  MODULE_AUTHOR("Gabor Juhos <juhosg@openwrt.org>");
  MODULE_LICENSE("GPL v2");
  MODULE_ALIAS("platform:" DRV_NAME);