1// SPDX-License-Identifier: GPL-2.0+
2/*
3 * HD44780 Character LCD driver for Linux
4 *
5 * Copyright (C) 2000-2008, Willy Tarreau <w@1wt.eu>
6 * Copyright (C) 2016-2017 Glider bvba
7 */
8
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>
16
17#include "charlcd.h"
18#include "hd44780_common.h"
19
20enum hd44780_pin {
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 */
26 PIN_DATA4,
27 PIN_DATA5,
28 PIN_DATA6,
29 PIN_DATA7,
30 PIN_CTRL_RS,
31 PIN_CTRL_RW, /* Optional */
32 PIN_CTRL_E,
33 PIN_CTRL_BL, /* Optional */
34 PIN_NUM
35};
36
37struct hd44780 {
38 struct gpio_desc *pins[PIN_NUM];
39};
40
41static void hd44780_backlight(struct charlcd *lcd, enum charlcd_onoff on)
42{
43 struct hd44780_common *hdc = lcd->drvdata;
44 struct hd44780 *hd = hdc->hd44780;
45
46 if (hd->pins[PIN_CTRL_BL])
47 gpiod_set_value_cansleep(desc: hd->pins[PIN_CTRL_BL], value: on);
48}
49
50static void hd44780_strobe_gpio(struct hd44780 *hd)
51{
52 /* Maintain the data during 20 us before the strobe */
53 udelay(20);
54
55 gpiod_set_value_cansleep(desc: hd->pins[PIN_CTRL_E], value: 1);
56
57 /* Maintain the strobe during 40 us */
58 udelay(40);
59
60 gpiod_set_value_cansleep(desc: hd->pins[PIN_CTRL_E], value: 0);
61}
62
63/* write to an LCD panel register in 8 bit GPIO mode */
64static void hd44780_write_gpio8(struct hd44780 *hd, u8 val, unsigned int rs)
65{
66 DECLARE_BITMAP(values, 10); /* for DATA[0-7], RS, RW */
67 unsigned int n;
68
69 values[0] = val;
70 __assign_bit(nr: 8, addr: values, value: rs);
71 n = hd->pins[PIN_CTRL_RW] ? 10 : 9;
72
73 /* Present the data to the port */
74 gpiod_set_array_value_cansleep(array_size: n, desc_array: &hd->pins[PIN_DATA0], NULL, value_bitmap: values);
75
76 hd44780_strobe_gpio(hd);
77}
78
79/* write to an LCD panel register in 4 bit GPIO mode */
80static void hd44780_write_gpio4(struct hd44780 *hd, u8 val, unsigned int rs)
81{
82 DECLARE_BITMAP(values, 6); /* for DATA[4-7], RS, RW */
83 unsigned int n;
84
85 /* High nibble + RS, RW */
86 values[0] = val >> 4;
87 __assign_bit(nr: 4, addr: values, value: rs);
88 n = hd->pins[PIN_CTRL_RW] ? 6 : 5;
89
90 /* Present the data to the port */
91 gpiod_set_array_value_cansleep(array_size: n, desc_array: &hd->pins[PIN_DATA4], NULL, value_bitmap: values);
92
93 hd44780_strobe_gpio(hd);
94
95 /* Low nibble */
96 values[0] &= ~0x0fUL;
97 values[0] |= val & 0x0f;
98
99 /* Present the data to the port */
100 gpiod_set_array_value_cansleep(array_size: n, desc_array: &hd->pins[PIN_DATA4], NULL, value_bitmap: values);
101
102 hd44780_strobe_gpio(hd);
103}
104
105/* Send a command to the LCD panel in 8 bit GPIO mode */
106static void hd44780_write_cmd_gpio8(struct hd44780_common *hdc, int cmd)
107{
108 struct hd44780 *hd = hdc->hd44780;
109
110 hd44780_write_gpio8(hd, val: cmd, rs: 0);
111
112 /* The shortest command takes at least 120 us */
113 udelay(120);
114}
115
116/* Send data to the LCD panel in 8 bit GPIO mode */
117static void hd44780_write_data_gpio8(struct hd44780_common *hdc, int data)
118{
119 struct hd44780 *hd = hdc->hd44780;
120
121 hd44780_write_gpio8(hd, val: data, rs: 1);
122
123 /* The shortest data takes at least 45 us */
124 udelay(45);
125}
126
127static 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,
132 .clear_display = hd44780_common_clear_display,
133 .init_display = hd44780_common_init_display,
134 .shift_cursor = hd44780_common_shift_cursor,
135 .shift_display = hd44780_common_shift_display,
136 .display = hd44780_common_display,
137 .cursor = hd44780_common_cursor,
138 .blink = hd44780_common_blink,
139 .fontsize = hd44780_common_fontsize,
140 .lines = hd44780_common_lines,
141 .redefine_char = hd44780_common_redefine_char,
142};
143
144/* Send a command to the LCD panel in 4 bit GPIO mode */
145static void hd44780_write_cmd_gpio4(struct hd44780_common *hdc, int cmd)
146{
147 struct hd44780 *hd = hdc->hd44780;
148
149 hd44780_write_gpio4(hd, val: cmd, rs: 0);
150
151 /* The shortest command takes at least 120 us */
152 udelay(120);
153}
154
155/* Send 4-bits of a command to the LCD panel in raw 4 bit GPIO mode */
156static void hd44780_write_cmd_raw_gpio4(struct hd44780_common *hdc, int cmd)
157{
158 DECLARE_BITMAP(values, 6); /* for DATA[4-7], RS, RW */
159 struct hd44780 *hd = hdc->hd44780;
160 unsigned int n;
161
162 /* Command nibble + RS, RW */
163 values[0] = cmd & 0x0f;
164 n = hd->pins[PIN_CTRL_RW] ? 6 : 5;
165
166 /* Present the data to the port */
167 gpiod_set_array_value_cansleep(array_size: n, desc_array: &hd->pins[PIN_DATA4], NULL, value_bitmap: values);
168
169 hd44780_strobe_gpio(hd);
170}
171
172/* Send data to the LCD panel in 4 bit GPIO mode */
173static void hd44780_write_data_gpio4(struct hd44780_common *hdc, int data)
174{
175 struct hd44780 *hd = hdc->hd44780;
176
177 hd44780_write_gpio4(hd, val: data, rs: 1);
178
179 /* The shortest data takes at least 45 us */
180 udelay(45);
181}
182
183static const struct charlcd_ops hd44780_ops_gpio4 = {
184 .backlight = hd44780_backlight,
185 .print = hd44780_common_print,
186 .gotoxy = hd44780_common_gotoxy,
187 .home = hd44780_common_home,
188 .clear_display = hd44780_common_clear_display,
189 .init_display = hd44780_common_init_display,
190 .shift_cursor = hd44780_common_shift_cursor,
191 .shift_display = hd44780_common_shift_display,
192 .display = hd44780_common_display,
193 .cursor = hd44780_common_cursor,
194 .blink = hd44780_common_blink,
195 .fontsize = hd44780_common_fontsize,
196 .lines = hd44780_common_lines,
197 .redefine_char = hd44780_common_redefine_char,
198};
199
200static int hd44780_probe(struct platform_device *pdev)
201{
202 struct device *dev = &pdev->dev;
203 unsigned int i, base;
204 struct charlcd *lcd;
205 struct hd44780_common *hdc;
206 struct hd44780 *hd;
207 int ifwidth, ret = -ENOMEM;
208
209 /* Required pins */
210 ifwidth = gpiod_count(dev, con_id: "data");
211 if (ifwidth < 0)
212 return ifwidth;
213
214 switch (ifwidth) {
215 case 4:
216 base = PIN_DATA4;
217 break;
218 case 8:
219 base = PIN_DATA0;
220 break;
221 default:
222 return -EINVAL;
223 }
224
225 hdc = hd44780_common_alloc();
226 if (!hdc)
227 return -ENOMEM;
228
229 lcd = charlcd_alloc();
230 if (!lcd)
231 goto fail1;
232
233 hd = kzalloc(size: sizeof(struct hd44780), GFP_KERNEL);
234 if (!hd)
235 goto fail2;
236
237 hdc->hd44780 = hd;
238 lcd->drvdata = hdc;
239 for (i = 0; i < ifwidth; i++) {
240 hd->pins[base + i] = devm_gpiod_get_index(dev, con_id: "data", idx: i,
241 flags: GPIOD_OUT_LOW);
242 if (IS_ERR(ptr: hd->pins[base + i])) {
243 ret = PTR_ERR(ptr: hd->pins[base + i]);
244 goto fail3;
245 }
246 }
247
248 hd->pins[PIN_CTRL_E] = devm_gpiod_get(dev, con_id: "enable", flags: GPIOD_OUT_LOW);
249 if (IS_ERR(ptr: hd->pins[PIN_CTRL_E])) {
250 ret = PTR_ERR(ptr: hd->pins[PIN_CTRL_E]);
251 goto fail3;
252 }
253
254 hd->pins[PIN_CTRL_RS] = devm_gpiod_get(dev, con_id: "rs", flags: GPIOD_OUT_HIGH);
255 if (IS_ERR(ptr: hd->pins[PIN_CTRL_RS])) {
256 ret = PTR_ERR(ptr: hd->pins[PIN_CTRL_RS]);
257 goto fail3;
258 }
259
260 /* Optional pins */
261 hd->pins[PIN_CTRL_RW] = devm_gpiod_get_optional(dev, con_id: "rw",
262 flags: GPIOD_OUT_LOW);
263 if (IS_ERR(ptr: hd->pins[PIN_CTRL_RW])) {
264 ret = PTR_ERR(ptr: hd->pins[PIN_CTRL_RW]);
265 goto fail3;
266 }
267
268 hd->pins[PIN_CTRL_BL] = devm_gpiod_get_optional(dev, con_id: "backlight",
269 flags: GPIOD_OUT_LOW);
270 if (IS_ERR(ptr: hd->pins[PIN_CTRL_BL])) {
271 ret = PTR_ERR(ptr: hd->pins[PIN_CTRL_BL]);
272 goto fail3;
273 }
274
275 /* Required properties */
276 ret = device_property_read_u32(dev, propname: "display-height-chars",
277 val: &lcd->height);
278 if (ret)
279 goto fail3;
280 ret = device_property_read_u32(dev, propname: "display-width-chars", val: &lcd->width);
281 if (ret)
282 goto fail3;
283
284 /*
285 * On displays with more than two rows, the internal buffer width is
286 * usually equal to the display width
287 */
288 if (lcd->height > 2)
289 hdc->bwidth = lcd->width;
290
291 /* Optional properties */
292 device_property_read_u32(dev, propname: "internal-buffer-width", val: &hdc->bwidth);
293
294 hdc->ifwidth = ifwidth;
295 if (ifwidth == 8) {
296 lcd->ops = &hd44780_ops_gpio8;
297 hdc->write_data = hd44780_write_data_gpio8;
298 hdc->write_cmd = hd44780_write_cmd_gpio8;
299 } else {
300 lcd->ops = &hd44780_ops_gpio4;
301 hdc->write_data = hd44780_write_data_gpio4;
302 hdc->write_cmd = hd44780_write_cmd_gpio4;
303 hdc->write_cmd_raw4 = hd44780_write_cmd_raw_gpio4;
304 }
305
306 ret = charlcd_register(lcd);
307 if (ret)
308 goto fail3;
309
310 platform_set_drvdata(pdev, data: lcd);
311 return 0;
312
313fail3:
314 kfree(objp: hd);
315fail2:
316 kfree(objp: lcd);
317fail1:
318 kfree(objp: hdc);
319 return ret;
320}
321
322static void hd44780_remove(struct platform_device *pdev)
323{
324 struct charlcd *lcd = platform_get_drvdata(pdev);
325 struct hd44780_common *hdc = lcd->drvdata;
326
327 charlcd_unregister(lcd);
328 kfree(objp: hdc->hd44780);
329 kfree(objp: lcd->drvdata);
330
331 kfree(objp: lcd);
332}
333
334static const struct of_device_id hd44780_of_match[] = {
335 { .compatible = "hit,hd44780" },
336 { /* sentinel */ }
337};
338MODULE_DEVICE_TABLE(of, hd44780_of_match);
339
340static struct platform_driver hd44780_driver = {
341 .probe = hd44780_probe,
342 .remove_new = hd44780_remove,
343 .driver = {
344 .name = "hd44780",
345 .of_match_table = hd44780_of_match,
346 },
347};
348
349module_platform_driver(hd44780_driver);
350MODULE_DESCRIPTION("HD44780 Character LCD driver");
351MODULE_AUTHOR("Geert Uytterhoeven <geert@linux-m68k.org>");
352MODULE_LICENSE("GPL");
353

source code of linux/drivers/auxdisplay/hd44780.c