/*
   * Driver for the on-board character LCD found on some ARM reference boards
   * This is basically an Hitachi HD44780 LCD with a custom IP block to drive it
   * http://en.wikipedia.org/wiki/HD44780_Character_LCD
   * Currently it will just display the text "ARM Linux" and the linux version
   *
   * License terms: GNU General Public License (GPL) version 2
   * Author: Linus Walleij <triad@df.lth.se>
   */
  #include <linux/init.h>
  #include <linux/module.h>
  #include <linux/interrupt.h>
  #include <linux/platform_device.h>
  #include <linux/completion.h>
  #include <linux/delay.h>
  #include <linux/io.h>
  #include <linux/slab.h>
  #include <linux/workqueue.h>
  #include <generated/utsrelease.h>
  
  #define DRIVERNAME "arm-charlcd"
  #define CHARLCD_TIMEOUT (msecs_to_jiffies(1000))
  
  /* Offsets to registers */
  #define CHAR_COM	0x00U
  #define CHAR_DAT	0x04U
  #define CHAR_RD		0x08U
  #define CHAR_RAW	0x0CU
  #define CHAR_MASK	0x10U
  #define CHAR_STAT	0x14U
  
  #define CHAR_RAW_CLEAR	0x00000000U
  #define CHAR_RAW_VALID	0x00000100U
  
  /* Hitachi HD44780 display commands */
  #define HD_CLEAR			0x01U
  #define HD_HOME				0x02U
  #define HD_ENTRYMODE			0x04U
  #define HD_ENTRYMODE_INCREMENT		0x02U
  #define HD_ENTRYMODE_SHIFT		0x01U
  #define HD_DISPCTRL			0x08U
  #define HD_DISPCTRL_ON			0x04U
  #define HD_DISPCTRL_CURSOR_ON		0x02U
  #define HD_DISPCTRL_CURSOR_BLINK	0x01U
  #define HD_CRSR_SHIFT			0x10U
  #define HD_CRSR_SHIFT_DISPLAY		0x08U
  #define HD_CRSR_SHIFT_DISPLAY_RIGHT	0x04U
  #define HD_FUNCSET			0x20U
  #define HD_FUNCSET_8BIT			0x10U
  #define HD_FUNCSET_2_LINES		0x08U
  #define HD_FUNCSET_FONT_5X10		0x04U
  #define HD_SET_CGRAM			0x40U
  #define HD_SET_DDRAM			0x80U
  #define HD_BUSY_FLAG			0x80U
  
  /**
   * @dev: a pointer back to containing device
   * @phybase: the offset to the controller in physical memory
   * @physize: the size of the physical page
   * @virtbase: the offset to the controller in virtual memory
   * @irq: reserved interrupt number
   * @complete: completion structure for the last LCD command
   */
  struct charlcd {
  	struct device *dev;
  	u32 phybase;
  	u32 physize;
  	void __iomem *virtbase;
  	int irq;
  	struct completion complete;
  	struct delayed_work init_work;
  };
  
  static irqreturn_t charlcd_interrupt(int irq, void *data)
  {
  	struct charlcd *lcd = data;
  	u8 status;
  
  	status = readl(lcd->virtbase + CHAR_STAT) & 0x01;
  	/* Clear IRQ */
  	writel(CHAR_RAW_CLEAR, lcd->virtbase + CHAR_RAW);
  	if (status)
  		complete(&lcd->complete);
  	else
  		dev_info(lcd->dev, "Spurious IRQ (%02x)
  ", status);
  	return IRQ_HANDLED;
  }
  
  
  static void charlcd_wait_complete_irq(struct charlcd *lcd)
  {
  	int ret;
  
  	ret = wait_for_completion_interruptible_timeout(&lcd->complete,
  							CHARLCD_TIMEOUT);
  	/* Disable IRQ after completion */
  	writel(0x00, lcd->virtbase + CHAR_MASK);
  
  	if (ret < 0) {
  		dev_err(lcd->dev,
  			"wait_for_completion_interruptible_timeout() "
  			"returned %d waiting for ready
  ", ret);
  		return;
  	}
  
  	if (ret == 0) {
  		dev_err(lcd->dev, "charlcd controller timed out "
  			"waiting for ready
  ");
  		return;
  	}
  }
  
  static u8 charlcd_4bit_read_char(struct charlcd *lcd)
  {
  	u8 data;
  	u32 val;
  	int i;
  
  	/* If we can, use an IRQ to wait for the data, else poll */
  	if (lcd->irq >= 0)
  		charlcd_wait_complete_irq(lcd);
  	else {
  		i = 0;
  		val = 0;
  		while (!(val & CHAR_RAW_VALID) && i < 10) {
  			udelay(100);
  			val = readl(lcd->virtbase + CHAR_RAW);
  			i++;
  		}
  
  		writel(CHAR_RAW_CLEAR, lcd->virtbase + CHAR_RAW);
  	}
  	msleep(1);
  
  	/* Read the 4 high bits of the data */
  	data = readl(lcd->virtbase + CHAR_RD) & 0xf0;
  
  	/*
  	 * The second read for the low bits does not trigger an IRQ
  	 * so in this case we have to poll for the 4 lower bits
  	 */
  	i = 0;
  	val = 0;
  	while (!(val & CHAR_RAW_VALID) && i < 10) {
  		udelay(100);
  		val = readl(lcd->virtbase + CHAR_RAW);
  		i++;
  	}
  	writel(CHAR_RAW_CLEAR, lcd->virtbase + CHAR_RAW);
  	msleep(1);
  
  	/* Read the 4 low bits of the data */
  	data |= (readl(lcd->virtbase + CHAR_RD) >> 4) & 0x0f;
  
  	return data;
  }
  
  static bool charlcd_4bit_read_bf(struct charlcd *lcd)
  {
  	if (lcd->irq >= 0) {
  		/*
  		 * If we'll use IRQs to wait for the busyflag, clear any
  		 * pending flag and enable IRQ
  		 */
  		writel(CHAR_RAW_CLEAR, lcd->virtbase + CHAR_RAW);
  		init_completion(&lcd->complete);
  		writel(0x01, lcd->virtbase + CHAR_MASK);
  	}
  	readl(lcd->virtbase + CHAR_COM);
  	return charlcd_4bit_read_char(lcd) & HD_BUSY_FLAG ? true : false;
  }
  
  static void charlcd_4bit_wait_busy(struct charlcd *lcd)
  {
  	int retries = 50;
  
  	udelay(100);
  	while (charlcd_4bit_read_bf(lcd) && retries)
  		retries--;
  	if (!retries)
  		dev_err(lcd->dev, "timeout waiting for busyflag
  ");
  }
  
  static void charlcd_4bit_command(struct charlcd *lcd, u8 cmd)
  {
  	u32 cmdlo = (cmd << 4) & 0xf0;
  	u32 cmdhi = (cmd & 0xf0);
  
  	writel(cmdhi, lcd->virtbase + CHAR_COM);
  	udelay(10);
  	writel(cmdlo, lcd->virtbase + CHAR_COM);
  	charlcd_4bit_wait_busy(lcd);
  }
  
  static void charlcd_4bit_char(struct charlcd *lcd, u8 ch)
  {
  	u32 chlo = (ch << 4) & 0xf0;
  	u32 chhi = (ch & 0xf0);
  
  	writel(chhi, lcd->virtbase + CHAR_DAT);
  	udelay(10);
  	writel(chlo, lcd->virtbase + CHAR_DAT);
  	charlcd_4bit_wait_busy(lcd);
  }
  
  static void charlcd_4bit_print(struct charlcd *lcd, int line, const char *str)
  {
  	u8 offset;
  	int i;
  
  	/*
  	 * We support line 0, 1
  	 * Line 1 runs from 0x00..0x27
  	 * Line 2 runs from 0x28..0x4f
  	 */
  	if (line == 0)
  		offset = 0;
  	else if (line == 1)
  		offset = 0x28;
  	else
  		return;
  
  	/* Set offset */
  	charlcd_4bit_command(lcd, HD_SET_DDRAM | offset);
  
  	/* Send string */
  	for (i = 0; i < strlen(str) && i < 0x28; i++)
  		charlcd_4bit_char(lcd, str[i]);
  }
  
  static void charlcd_4bit_init(struct charlcd *lcd)
  {
  	/* These commands cannot be checked with the busy flag */
  	writel(HD_FUNCSET | HD_FUNCSET_8BIT, lcd->virtbase + CHAR_COM);
  	msleep(5);
  	writel(HD_FUNCSET | HD_FUNCSET_8BIT, lcd->virtbase + CHAR_COM);
  	udelay(100);
  	writel(HD_FUNCSET | HD_FUNCSET_8BIT, lcd->virtbase + CHAR_COM);
  	udelay(100);
  	/* Go to 4bit mode */
  	writel(HD_FUNCSET, lcd->virtbase + CHAR_COM);
  	udelay(100);
  	/*
  	 * 4bit mode, 2 lines, 5x8 font, after this the number of lines
  	 * and the font cannot be changed until the next initialization sequence
  	 */
  	charlcd_4bit_command(lcd, HD_FUNCSET | HD_FUNCSET_2_LINES);
  	charlcd_4bit_command(lcd, HD_DISPCTRL | HD_DISPCTRL_ON);
  	charlcd_4bit_command(lcd, HD_ENTRYMODE | HD_ENTRYMODE_INCREMENT);
  	charlcd_4bit_command(lcd, HD_CLEAR);
  	charlcd_4bit_command(lcd, HD_HOME);
  	/* Put something useful in the display */
  	charlcd_4bit_print(lcd, 0, "ARM Linux");
  	charlcd_4bit_print(lcd, 1, UTS_RELEASE);
  }
  
  static void charlcd_init_work(struct work_struct *work)
  {
  	struct charlcd *lcd =
  		container_of(work, struct charlcd, init_work.work);
  
  	charlcd_4bit_init(lcd);
  }
  
  static int __init charlcd_probe(struct platform_device *pdev)
  {
  	int ret;
  	struct charlcd *lcd;
  	struct resource *res;
  
  	lcd = kzalloc(sizeof(struct charlcd), GFP_KERNEL);
  	if (!lcd)
  		return -ENOMEM;
  
  	lcd->dev = &pdev->dev;
  
  	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
  	if (!res) {
  		ret = -ENOENT;
  		goto out_no_resource;
  	}
  	lcd->phybase = res->start;
  	lcd->physize = resource_size(res);
  
  	if (request_mem_region(lcd->phybase, lcd->physize,
  			       DRIVERNAME) == NULL) {
  		ret = -EBUSY;
  		goto out_no_memregion;
  	}
  
  	lcd->virtbase = ioremap(lcd->phybase, lcd->physize);
  	if (!lcd->virtbase) {
  		ret = -ENOMEM;
  		goto out_no_memregion;
  	}
  
  	lcd->irq = platform_get_irq(pdev, 0);
  	/* If no IRQ is supplied, we'll survive without it */
  	if (lcd->irq >= 0) {
  		if (request_irq(lcd->irq, charlcd_interrupt, 0,
  				DRIVERNAME, lcd)) {
  			ret = -EIO;
  			goto out_no_irq;
  		}
  	}
  
  	platform_set_drvdata(pdev, lcd);
  
  	/*
  	 * Initialize the display in a delayed work, because
  	 * it is VERY slow and would slow down the boot of the system.
  	 */
  	INIT_DELAYED_WORK(&lcd->init_work, charlcd_init_work);
  	schedule_delayed_work(&lcd->init_work, 0);
  
  	dev_info(&pdev->dev, "initialized ARM character LCD at %08x
  ",
  		lcd->phybase);
  
  	return 0;
  
  out_no_irq:
  	iounmap(lcd->virtbase);
  out_no_memregion:
  	release_mem_region(lcd->phybase, SZ_4K);
  out_no_resource:
  	kfree(lcd);
  	return ret;
  }
  
  static int __exit charlcd_remove(struct platform_device *pdev)
  {
  	struct charlcd *lcd = platform_get_drvdata(pdev);
  
  	if (lcd) {
  		free_irq(lcd->irq, lcd);
  		iounmap(lcd->virtbase);
  		release_mem_region(lcd->phybase, lcd->physize);
  		kfree(lcd);
  	}
  
  	return 0;
  }
  
  static int charlcd_suspend(struct device *dev)
  {
  	struct platform_device *pdev = to_platform_device(dev);
  	struct charlcd *lcd = platform_get_drvdata(pdev);
  
  	/* Power the display off */
  	charlcd_4bit_command(lcd, HD_DISPCTRL);
  	return 0;
  }
  
  static int charlcd_resume(struct device *dev)
  {
  	struct platform_device *pdev = to_platform_device(dev);
  	struct charlcd *lcd = platform_get_drvdata(pdev);
  
  	/* Turn the display back on */
  	charlcd_4bit_command(lcd, HD_DISPCTRL | HD_DISPCTRL_ON);
  	return 0;
  }
  
  static const struct dev_pm_ops charlcd_pm_ops = {
  	.suspend = charlcd_suspend,
  	.resume = charlcd_resume,
  };
  
  static struct platform_driver charlcd_driver = {
  	.driver = {
  		.name = DRIVERNAME,
  		.owner = THIS_MODULE,
  		.pm = &charlcd_pm_ops,
  	},
  	.remove = __exit_p(charlcd_remove),
  };
  
  module_platform_driver_probe(charlcd_driver, charlcd_probe);
  
  MODULE_AUTHOR("Linus Walleij <triad@df.lth.se>");
  MODULE_DESCRIPTION("ARM Character LCD Driver");
  MODULE_LICENSE("GPL v2");