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path: root/drivers/auxdisplay/hd44780.c
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-rw-r--r--drivers/auxdisplay/hd44780.c305
1 files changed, 305 insertions, 0 deletions
diff --git a/drivers/auxdisplay/hd44780.c b/drivers/auxdisplay/hd44780.c
new file mode 100644
index 000000000..bcbe13092
--- /dev/null
+++ b/drivers/auxdisplay/hd44780.c
@@ -0,0 +1,305 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * HD44780 Character LCD driver for Linux
+ *
+ * Copyright (C) 2000-2008, Willy Tarreau <w@1wt.eu>
+ * Copyright (C) 2016-2017 Glider bvba
+ */
+
+#include <linux/delay.h>
+#include <linux/gpio/consumer.h>
+#include <linux/module.h>
+#include <linux/mod_devicetable.h>
+#include <linux/platform_device.h>
+#include <linux/property.h>
+#include <linux/slab.h>
+
+#include "charlcd.h"
+
+enum hd44780_pin {
+ /* Order does matter due to writing to GPIO array subsets! */
+ PIN_DATA0, /* Optional */
+ PIN_DATA1, /* Optional */
+ PIN_DATA2, /* Optional */
+ PIN_DATA3, /* Optional */
+ PIN_DATA4,
+ PIN_DATA5,
+ PIN_DATA6,
+ PIN_DATA7,
+ PIN_CTRL_RS,
+ PIN_CTRL_RW, /* Optional */
+ PIN_CTRL_E,
+ PIN_CTRL_BL, /* Optional */
+ PIN_NUM
+};
+
+struct hd44780 {
+ struct gpio_desc *pins[PIN_NUM];
+};
+
+static void hd44780_backlight(struct charlcd *lcd, int on)
+{
+ struct hd44780 *hd = lcd->drvdata;
+
+ if (hd->pins[PIN_CTRL_BL])
+ gpiod_set_value_cansleep(hd->pins[PIN_CTRL_BL], on);
+}
+
+static void hd44780_strobe_gpio(struct hd44780 *hd)
+{
+ /* Maintain the data during 20 us before the strobe */
+ udelay(20);
+
+ gpiod_set_value_cansleep(hd->pins[PIN_CTRL_E], 1);
+
+ /* Maintain the strobe during 40 us */
+ udelay(40);
+
+ gpiod_set_value_cansleep(hd->pins[PIN_CTRL_E], 0);
+}
+
+/* write to an LCD panel register in 8 bit GPIO mode */
+static void hd44780_write_gpio8(struct hd44780 *hd, u8 val, unsigned int rs)
+{
+ DECLARE_BITMAP(values, 10); /* for DATA[0-7], RS, RW */
+ unsigned int n;
+
+ values[0] = val;
+ __assign_bit(8, values, rs);
+ n = hd->pins[PIN_CTRL_RW] ? 10 : 9;
+
+ /* Present the data to the port */
+ gpiod_set_array_value_cansleep(n, &hd->pins[PIN_DATA0], NULL, values);
+
+ hd44780_strobe_gpio(hd);
+}
+
+/* write to an LCD panel register in 4 bit GPIO mode */
+static void hd44780_write_gpio4(struct hd44780 *hd, u8 val, unsigned int rs)
+{
+ DECLARE_BITMAP(values, 6); /* for DATA[4-7], RS, RW */
+ unsigned int n;
+
+ /* High nibble + RS, RW */
+ values[0] = val >> 4;
+ __assign_bit(4, values, rs);
+ n = hd->pins[PIN_CTRL_RW] ? 6 : 5;
+
+ /* Present the data to the port */
+ gpiod_set_array_value_cansleep(n, &hd->pins[PIN_DATA4], NULL, values);
+
+ hd44780_strobe_gpio(hd);
+
+ /* Low nibble */
+ values[0] &= ~0x0fUL;
+ values[0] |= val & 0x0f;
+
+ /* Present the data to the port */
+ gpiod_set_array_value_cansleep(n, &hd->pins[PIN_DATA4], NULL, values);
+
+ hd44780_strobe_gpio(hd);
+}
+
+/* Send a command to the LCD panel in 8 bit GPIO mode */
+static void hd44780_write_cmd_gpio8(struct charlcd *lcd, int cmd)
+{
+ struct hd44780 *hd = lcd->drvdata;
+
+ hd44780_write_gpio8(hd, cmd, 0);
+
+ /* The shortest command takes at least 120 us */
+ udelay(120);
+}
+
+/* Send data to the LCD panel in 8 bit GPIO mode */
+static void hd44780_write_data_gpio8(struct charlcd *lcd, int data)
+{
+ struct hd44780 *hd = lcd->drvdata;
+
+ hd44780_write_gpio8(hd, data, 1);
+
+ /* The shortest data takes at least 45 us */
+ udelay(45);
+}
+
+static const struct charlcd_ops hd44780_ops_gpio8 = {
+ .write_cmd = hd44780_write_cmd_gpio8,
+ .write_data = hd44780_write_data_gpio8,
+ .backlight = hd44780_backlight,
+};
+
+/* Send a command to the LCD panel in 4 bit GPIO mode */
+static void hd44780_write_cmd_gpio4(struct charlcd *lcd, int cmd)
+{
+ struct hd44780 *hd = lcd->drvdata;
+
+ hd44780_write_gpio4(hd, cmd, 0);
+
+ /* The shortest command takes at least 120 us */
+ udelay(120);
+}
+
+/* Send 4-bits of a command to the LCD panel in raw 4 bit GPIO mode */
+static void hd44780_write_cmd_raw_gpio4(struct charlcd *lcd, int cmd)
+{
+ DECLARE_BITMAP(values, 6); /* for DATA[4-7], RS, RW */
+ struct hd44780 *hd = lcd->drvdata;
+ unsigned int n;
+
+ /* Command nibble + RS, RW */
+ values[0] = cmd & 0x0f;
+ n = hd->pins[PIN_CTRL_RW] ? 6 : 5;
+
+ /* Present the data to the port */
+ gpiod_set_array_value_cansleep(n, &hd->pins[PIN_DATA4], NULL, values);
+
+ hd44780_strobe_gpio(hd);
+}
+
+/* Send data to the LCD panel in 4 bit GPIO mode */
+static void hd44780_write_data_gpio4(struct charlcd *lcd, int data)
+{
+ struct hd44780 *hd = lcd->drvdata;
+
+ hd44780_write_gpio4(hd, data, 1);
+
+ /* The shortest data takes at least 45 us */
+ udelay(45);
+}
+
+static const struct charlcd_ops hd44780_ops_gpio4 = {
+ .write_cmd = hd44780_write_cmd_gpio4,
+ .write_cmd_raw4 = hd44780_write_cmd_raw_gpio4,
+ .write_data = hd44780_write_data_gpio4,
+ .backlight = hd44780_backlight,
+};
+
+static int hd44780_probe(struct platform_device *pdev)
+{
+ struct device *dev = &pdev->dev;
+ unsigned int i, base;
+ struct charlcd *lcd;
+ struct hd44780 *hd;
+ int ifwidth, ret;
+
+ /* Required pins */
+ ifwidth = gpiod_count(dev, "data");
+ if (ifwidth < 0)
+ return ifwidth;
+
+ switch (ifwidth) {
+ case 4:
+ base = PIN_DATA4;
+ break;
+ case 8:
+ base = PIN_DATA0;
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ lcd = charlcd_alloc(sizeof(struct hd44780));
+ if (!lcd)
+ return -ENOMEM;
+
+ hd = lcd->drvdata;
+
+ for (i = 0; i < ifwidth; i++) {
+ hd->pins[base + i] = devm_gpiod_get_index(dev, "data", i,
+ GPIOD_OUT_LOW);
+ if (IS_ERR(hd->pins[base + i])) {
+ ret = PTR_ERR(hd->pins[base + i]);
+ goto fail;
+ }
+ }
+
+ hd->pins[PIN_CTRL_E] = devm_gpiod_get(dev, "enable", GPIOD_OUT_LOW);
+ if (IS_ERR(hd->pins[PIN_CTRL_E])) {
+ ret = PTR_ERR(hd->pins[PIN_CTRL_E]);
+ goto fail;
+ }
+
+ hd->pins[PIN_CTRL_RS] = devm_gpiod_get(dev, "rs", GPIOD_OUT_HIGH);
+ if (IS_ERR(hd->pins[PIN_CTRL_RS])) {
+ ret = PTR_ERR(hd->pins[PIN_CTRL_RS]);
+ goto fail;
+ }
+
+ /* Optional pins */
+ hd->pins[PIN_CTRL_RW] = devm_gpiod_get_optional(dev, "rw",
+ GPIOD_OUT_LOW);
+ if (IS_ERR(hd->pins[PIN_CTRL_RW])) {
+ ret = PTR_ERR(hd->pins[PIN_CTRL_RW]);
+ goto fail;
+ }
+
+ hd->pins[PIN_CTRL_BL] = devm_gpiod_get_optional(dev, "backlight",
+ GPIOD_OUT_LOW);
+ if (IS_ERR(hd->pins[PIN_CTRL_BL])) {
+ ret = PTR_ERR(hd->pins[PIN_CTRL_BL]);
+ goto fail;
+ }
+
+ /* Required properties */
+ ret = device_property_read_u32(dev, "display-height-chars",
+ &lcd->height);
+ if (ret)
+ goto fail;
+ ret = device_property_read_u32(dev, "display-width-chars", &lcd->width);
+ if (ret)
+ goto fail;
+
+ /*
+ * On displays with more than two rows, the internal buffer width is
+ * usually equal to the display width
+ */
+ if (lcd->height > 2)
+ lcd->bwidth = lcd->width;
+
+ /* Optional properties */
+ device_property_read_u32(dev, "internal-buffer-width", &lcd->bwidth);
+
+ lcd->ifwidth = ifwidth;
+ lcd->ops = ifwidth == 8 ? &hd44780_ops_gpio8 : &hd44780_ops_gpio4;
+
+ ret = charlcd_register(lcd);
+ if (ret)
+ goto fail;
+
+ platform_set_drvdata(pdev, lcd);
+ return 0;
+
+fail:
+ charlcd_free(lcd);
+ return ret;
+}
+
+static int hd44780_remove(struct platform_device *pdev)
+{
+ struct charlcd *lcd = platform_get_drvdata(pdev);
+
+ charlcd_unregister(lcd);
+
+ charlcd_free(lcd);
+ return 0;
+}
+
+static const struct of_device_id hd44780_of_match[] = {
+ { .compatible = "hit,hd44780" },
+ { /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, hd44780_of_match);
+
+static struct platform_driver hd44780_driver = {
+ .probe = hd44780_probe,
+ .remove = hd44780_remove,
+ .driver = {
+ .name = "hd44780",
+ .of_match_table = hd44780_of_match,
+ },
+};
+
+module_platform_driver(hd44780_driver);
+MODULE_DESCRIPTION("HD44780 Character LCD driver");
+MODULE_AUTHOR("Geert Uytterhoeven <geert@linux-m68k.org>");
+MODULE_LICENSE("GPL");
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-01 00:56:35 +0000