--- /dev/null
+/*
+ * 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/of.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_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\n",
+ 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 const struct of_device_id charlcd_match[] = {
+ { .compatible = "arm,versatile-lcd", },
+ {}
+};
+
+static struct platform_driver charlcd_driver = {
+ .driver = {
+ .name = DRIVERNAME,
+ .pm = &charlcd_pm_ops,
+ .of_match_table = of_match_ptr(charlcd_match),
+ },
+ .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");
Code Review / kvmfornfv.git / blobdiff