/*
   * 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/workqueue.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		rrw_delay;
  };
  
  static inline u32 ath79_spi_rr(struct ath79_spi *sp, unsigned reg)
  {
  	return ioread32(sp->base + reg);
  }
  
  static inline void ath79_spi_wr(struct ath79_spi *sp, unsigned 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 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 (spi->chip_select) {
  		struct ath79_spi_controller_data *cdata = spi->controller_data;
  
  		/* SPI is normally active-low */
  		gpio_set_value(cdata->gpio, cs_high);
  	} else {
  		if (cs_high)
  			sp->ioc_base |= AR71XX_SPI_IOC_CS0;
  		else
  			sp->ioc_base &= ~AR71XX_SPI_IOC_CS0;
  
  		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_controller_data *cdata;
  	int status;
  
  	cdata = spi->controller_data;
  	if (spi->chip_select && !cdata)
  		return -EINVAL;
  
  	status = 0;
  	if (spi->chip_select) {
  		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(cdata->gpio, flags,
  					  dev_name(&spi->dev));
  	}
  
  	return status;
  }
  
  static void ath79_spi_cleanup_cs(struct spi_device *spi)
  {
  	if (spi->chip_select) {
  		struct ath79_spi_controller_data *cdata = spi->controller_data;
  		gpio_free(cdata->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 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);
  	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);
  	if (r == NULL) {
  		ret = -ENOENT;
  		goto err_put_master;
  	}
  
  	sp->base = devm_ioremap(&pdev->dev, r->start, resource_size(r));
  	if (!sp->base) {
  		ret = -ENXIO;
  		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_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(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(sp->clk);
  	spi_master_put(sp->bitbang.master);
  
  	return 0;
  }
  
  static void ath79_spi_shutdown(struct platform_device *pdev)
  {
  	ath79_spi_remove(pdev);
  }
  
  static struct platform_driver ath79_spi_driver = {
  	.probe		= ath79_spi_probe,
  	.remove		= ath79_spi_remove,
  	.shutdown	= ath79_spi_shutdown,
  	.driver		= {
  		.name	= DRV_NAME,
  		.owner	= THIS_MODULE,
  	},
  };
  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);