[PATCH 1/3] ARM: driver for the character LCD found in ARM refdesigns

* [PATCH 1/3] ARM: driver for the character LCD found in ARM refdesigns
@ 2010-07-06 15:21 Linus Walleij
  2010-07-07  8:47 ` Colin Tuckley
  2010-07-15 10:22 ` Russell King - ARM Linux
  0 siblings, 2 replies; 9+ messages in thread
From: Linus Walleij @ 2010-07-06 15:21 UTC (permalink / raw)
  To: linux-arm-kernel

This adds a driver for the character LCD found on the ARM Versatile
and RealView Platform Baseboards. It doesn't do very much more than
display the text "ARM Linux" on the first line and the linux banner
on the second line, but that's still useful.

Signed-off-by: Linus Walleij <triad@df.lth.se>
---
Submission notes:

This hardware does not have PrimeCell IDs so it has to be a platform
driver.

The 4bit mode is the only one that seems to work. I tried putting
the display into 8bit mode and failed miserably.

The IRQ is stated in the reference manual as "don't use" because it
is "reserved for future use" but I implemented it anyway. I
interpret future use as "future reference boards" and the driver
is written in such a way that it will fall back on polling if no
IRQ is supplied, so just don't supply the IRQ for platforms that
don't have it and the driver will poll instead.
---
 arch/arm/common/Kconfig    |    3 +
 arch/arm/common/Makefile   |    1 +
 arch/arm/common/char-lcd.c |  396 ++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 400 insertions(+), 0 deletions(-)
 create mode 100644 arch/arm/common/char-lcd.c

diff --git a/arch/arm/common/Kconfig b/arch/arm/common/Kconfig
index 0a34c81..f6b4837 100644
--- a/arch/arm/common/Kconfig
+++ b/arch/arm/common/Kconfig
@@ -12,6 +12,9 @@ config ARM_VIC_NR
 	  The maximum number of VICs available in the system, for
 	  power management.
 
+config ARM_CHAR_LCD
+	bool
+
 config ICST
 	bool
 
diff --git a/arch/arm/common/Makefile b/arch/arm/common/Makefile
index e6e8664..89ff2ee 100644
--- a/arch/arm/common/Makefile
+++ b/arch/arm/common/Makefile
@@ -4,6 +4,7 @@
 
 obj-$(CONFIG_ARM_GIC)		+= gic.o
 obj-$(CONFIG_ARM_VIC)		+= vic.o
+obj-$(CONFIG_ARM_CHAR_LCD)	+= char-lcd.o
 obj-$(CONFIG_ICST)		+= icst.o
 obj-$(CONFIG_PL330)		+= pl330.o
 obj-$(CONFIG_SA1111)		+= sa1111.o
diff --git a/arch/arm/common/char-lcd.c b/arch/arm/common/char-lcd.c
new file mode 100644
index 0000000..9e3879e
--- /dev/null
+++ b/arch/arm/common/char-lcd.c
@@ -0,0 +1,396 @@
+/*
+ * 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)\n", 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\n", ret);
+		return;
+	}
+
+	if (ret == 0) {
+		dev_err(lcd->dev, "charlcd controller timed out "
+			"waiting for ready\n");
+		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\n");
+}
+
+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_remap;
+	}
+
+	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, IRQF_DISABLED,
+				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, "initalized ARM character LCD at %08x\n",
+		lcd->phybase);
+
+	return 0;
+
+out_no_irq:
+	iounmap(lcd->virtbase);
+out_no_remap:
+	platform_set_drvdata(pdev, NULL);
+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);
+		platform_set_drvdata(pdev, NULL);
+		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),
+};
+
+static int __init charlcd_init(void)
+{
+	return platform_driver_probe(&charlcd_driver, charlcd_probe);
+}
+
+static void __exit charlcd_exit(void)
+{
+	platform_driver_unregister(&charlcd_driver);
+}
+
+module_init(charlcd_init);
+module_exit(charlcd_exit);
+
+MODULE_AUTHOR("Linus Walleij <triad@df.lth.se>");
+MODULE_DESCRIPTION("ARM Character LCD Driver");
+MODULE_LICENSE("GPL v2");
-- 
1.7.0.1

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