1 // SPDX-License-Identifier: GPL-2.0+
3 * HD44780 Character LCD driver for Linux
5 * Copyright (C) 2000-2008, Willy Tarreau <w@1wt.eu>
6 * Copyright (C) 2016-2017 Glider bvba
9 #include <linux/delay.h>
10 #include <linux/gpio/consumer.h>
11 #include <linux/module.h>
12 #include <linux/mod_devicetable.h>
13 #include <linux/platform_device.h>
14 #include <linux/property.h>
15 #include <linux/slab.h>
18 #include "hd44780_common.h"
21 /* Order does matter due to writing to GPIO array subsets! */
22 PIN_DATA0, /* Optional */
23 PIN_DATA1, /* Optional */
24 PIN_DATA2, /* Optional */
25 PIN_DATA3, /* Optional */
31 PIN_CTRL_RW, /* Optional */
33 PIN_CTRL_BL, /* Optional */
38 struct gpio_desc *pins[PIN_NUM];
41 static void hd44780_backlight(struct charlcd *lcd, enum charlcd_onoff on)
43 struct hd44780_common *hdc = lcd->drvdata;
44 struct hd44780 *hd = hdc->hd44780;
46 if (hd->pins[PIN_CTRL_BL])
47 gpiod_set_value_cansleep(hd->pins[PIN_CTRL_BL], on);
50 static void hd44780_strobe_gpio(struct hd44780 *hd)
52 /* Maintain the data during 20 us before the strobe */
55 gpiod_set_value_cansleep(hd->pins[PIN_CTRL_E], 1);
57 /* Maintain the strobe during 40 us */
60 gpiod_set_value_cansleep(hd->pins[PIN_CTRL_E], 0);
63 /* write to an LCD panel register in 8 bit GPIO mode */
64 static void hd44780_write_gpio8(struct hd44780 *hd, u8 val, unsigned int rs)
66 DECLARE_BITMAP(values, 10); /* for DATA[0-7], RS, RW */
70 __assign_bit(8, values, rs);
71 n = hd->pins[PIN_CTRL_RW] ? 10 : 9;
73 /* Present the data to the port */
74 gpiod_set_array_value_cansleep(n, &hd->pins[PIN_DATA0], NULL, values);
76 hd44780_strobe_gpio(hd);
79 /* write to an LCD panel register in 4 bit GPIO mode */
80 static void hd44780_write_gpio4(struct hd44780 *hd, u8 val, unsigned int rs)
82 DECLARE_BITMAP(values, 6); /* for DATA[4-7], RS, RW */
85 /* High nibble + RS, RW */
87 __assign_bit(4, values, rs);
88 n = hd->pins[PIN_CTRL_RW] ? 6 : 5;
90 /* Present the data to the port */
91 gpiod_set_array_value_cansleep(n, &hd->pins[PIN_DATA4], NULL, values);
93 hd44780_strobe_gpio(hd);
97 values[0] |= val & 0x0f;
99 /* Present the data to the port */
100 gpiod_set_array_value_cansleep(n, &hd->pins[PIN_DATA4], NULL, values);
102 hd44780_strobe_gpio(hd);
105 /* Send a command to the LCD panel in 8 bit GPIO mode */
106 static void hd44780_write_cmd_gpio8(struct hd44780_common *hdc, int cmd)
108 struct hd44780 *hd = hdc->hd44780;
110 hd44780_write_gpio8(hd, cmd, 0);
112 /* The shortest command takes at least 120 us */
116 /* Send data to the LCD panel in 8 bit GPIO mode */
117 static void hd44780_write_data_gpio8(struct hd44780_common *hdc, int data)
119 struct hd44780 *hd = hdc->hd44780;
121 hd44780_write_gpio8(hd, data, 1);
123 /* The shortest data takes at least 45 us */
127 static const struct charlcd_ops hd44780_ops_gpio8 = {
128 .backlight = hd44780_backlight,
129 .print = hd44780_common_print,
130 .gotoxy = hd44780_common_gotoxy,
131 .home = hd44780_common_home,
134 /* Send a command to the LCD panel in 4 bit GPIO mode */
135 static void hd44780_write_cmd_gpio4(struct hd44780_common *hdc, int cmd)
137 struct hd44780 *hd = hdc->hd44780;
139 hd44780_write_gpio4(hd, cmd, 0);
141 /* The shortest command takes at least 120 us */
145 /* Send 4-bits of a command to the LCD panel in raw 4 bit GPIO mode */
146 static void hd44780_write_cmd_raw_gpio4(struct hd44780_common *hdc, int cmd)
148 DECLARE_BITMAP(values, 6); /* for DATA[4-7], RS, RW */
149 struct hd44780 *hd = hdc->hd44780;
152 /* Command nibble + RS, RW */
153 values[0] = cmd & 0x0f;
154 n = hd->pins[PIN_CTRL_RW] ? 6 : 5;
156 /* Present the data to the port */
157 gpiod_set_array_value_cansleep(n, &hd->pins[PIN_DATA4], NULL, values);
159 hd44780_strobe_gpio(hd);
162 /* Send data to the LCD panel in 4 bit GPIO mode */
163 static void hd44780_write_data_gpio4(struct hd44780_common *hdc, int data)
165 struct hd44780 *hd = hdc->hd44780;
167 hd44780_write_gpio4(hd, data, 1);
169 /* The shortest data takes at least 45 us */
173 static const struct charlcd_ops hd44780_ops_gpio4 = {
174 .backlight = hd44780_backlight,
175 .print = hd44780_common_print,
176 .gotoxy = hd44780_common_gotoxy,
177 .home = hd44780_common_home,
180 static int hd44780_probe(struct platform_device *pdev)
182 struct device *dev = &pdev->dev;
183 unsigned int i, base;
185 struct hd44780_common *hdc;
187 int ifwidth, ret = -ENOMEM;
190 ifwidth = gpiod_count(dev, "data");
205 hdc = hd44780_common_alloc();
209 lcd = charlcd_alloc();
213 hd = kzalloc(sizeof(struct hd44780), GFP_KERNEL);
219 for (i = 0; i < ifwidth; i++) {
220 hd->pins[base + i] = devm_gpiod_get_index(dev, "data", i,
222 if (IS_ERR(hd->pins[base + i])) {
223 ret = PTR_ERR(hd->pins[base + i]);
228 hd->pins[PIN_CTRL_E] = devm_gpiod_get(dev, "enable", GPIOD_OUT_LOW);
229 if (IS_ERR(hd->pins[PIN_CTRL_E])) {
230 ret = PTR_ERR(hd->pins[PIN_CTRL_E]);
234 hd->pins[PIN_CTRL_RS] = devm_gpiod_get(dev, "rs", GPIOD_OUT_HIGH);
235 if (IS_ERR(hd->pins[PIN_CTRL_RS])) {
236 ret = PTR_ERR(hd->pins[PIN_CTRL_RS]);
241 hd->pins[PIN_CTRL_RW] = devm_gpiod_get_optional(dev, "rw",
243 if (IS_ERR(hd->pins[PIN_CTRL_RW])) {
244 ret = PTR_ERR(hd->pins[PIN_CTRL_RW]);
248 hd->pins[PIN_CTRL_BL] = devm_gpiod_get_optional(dev, "backlight",
250 if (IS_ERR(hd->pins[PIN_CTRL_BL])) {
251 ret = PTR_ERR(hd->pins[PIN_CTRL_BL]);
255 /* Required properties */
256 ret = device_property_read_u32(dev, "display-height-chars",
260 ret = device_property_read_u32(dev, "display-width-chars", &lcd->width);
265 * On displays with more than two rows, the internal buffer width is
266 * usually equal to the display width
269 hdc->bwidth = lcd->width;
271 /* Optional properties */
272 device_property_read_u32(dev, "internal-buffer-width", &hdc->bwidth);
274 hdc->ifwidth = ifwidth;
276 lcd->ops = &hd44780_ops_gpio8;
277 hdc->write_data = hd44780_write_data_gpio8;
278 hdc->write_cmd = hd44780_write_cmd_gpio8;
280 lcd->ops = &hd44780_ops_gpio4;
281 hdc->write_data = hd44780_write_data_gpio4;
282 hdc->write_cmd = hd44780_write_cmd_gpio4;
283 hdc->write_cmd_raw4 = hd44780_write_cmd_raw_gpio4;
286 ret = charlcd_register(lcd);
290 platform_set_drvdata(pdev, lcd);
302 static int hd44780_remove(struct platform_device *pdev)
304 struct charlcd *lcd = platform_get_drvdata(pdev);
307 charlcd_unregister(lcd);
313 static const struct of_device_id hd44780_of_match[] = {
314 { .compatible = "hit,hd44780" },
317 MODULE_DEVICE_TABLE(of, hd44780_of_match);
319 static struct platform_driver hd44780_driver = {
320 .probe = hd44780_probe,
321 .remove = hd44780_remove,
324 .of_match_table = hd44780_of_match,
328 module_platform_driver(hd44780_driver);
329 MODULE_DESCRIPTION("HD44780 Character LCD driver");
330 MODULE_AUTHOR("Geert Uytterhoeven <geert@linux-m68k.org>");
331 MODULE_LICENSE("GPL");