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
20 enum 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
37 struct hd44780 {
38 struct gpio_desc *pins[PIN_NUM];
39 };
40
hd44780_backlight(struct charlcd * lcd,enum charlcd_onoff on)41 static 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(hd->pins[PIN_CTRL_BL], on);
48 }
49
hd44780_strobe_gpio(struct hd44780 * hd)50 static 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(hd->pins[PIN_CTRL_E], 1);
56
57 /* Maintain the strobe during 40 us */
58 udelay(40);
59
60 gpiod_set_value_cansleep(hd->pins[PIN_CTRL_E], 0);
61 }
62
63 /* write to an LCD panel register in 8 bit GPIO mode */
hd44780_write_gpio8(struct hd44780 * hd,u8 val,unsigned int rs)64 static 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(8, values, rs);
71 n = hd->pins[PIN_CTRL_RW] ? 10 : 9;
72
73 /* Present the data to the port */
74 gpiod_set_array_value_cansleep(n, &hd->pins[PIN_DATA0], NULL, values);
75
76 hd44780_strobe_gpio(hd);
77 }
78
79 /* write to an LCD panel register in 4 bit GPIO mode */
hd44780_write_gpio4(struct hd44780 * hd,u8 val,unsigned int rs)80 static 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(4, values, rs);
88 n = hd->pins[PIN_CTRL_RW] ? 6 : 5;
89
90 /* Present the data to the port */
91 gpiod_set_array_value_cansleep(n, &hd->pins[PIN_DATA4], NULL, 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(n, &hd->pins[PIN_DATA4], NULL, values);
101
102 hd44780_strobe_gpio(hd);
103 }
104
105 /* Send a command to the LCD panel in 8 bit GPIO mode */
hd44780_write_cmd_gpio8(struct hd44780_common * hdc,int cmd)106 static void hd44780_write_cmd_gpio8(struct hd44780_common *hdc, int cmd)
107 {
108 struct hd44780 *hd = hdc->hd44780;
109
110 hd44780_write_gpio8(hd, cmd, 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 */
hd44780_write_data_gpio8(struct hd44780_common * hdc,int data)117 static void hd44780_write_data_gpio8(struct hd44780_common *hdc, int data)
118 {
119 struct hd44780 *hd = hdc->hd44780;
120
121 hd44780_write_gpio8(hd, data, 1);
122
123 /* The shortest data takes at least 45 us */
124 udelay(45);
125 }
126
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,
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 */
hd44780_write_cmd_gpio4(struct hd44780_common * hdc,int cmd)145 static void hd44780_write_cmd_gpio4(struct hd44780_common *hdc, int cmd)
146 {
147 struct hd44780 *hd = hdc->hd44780;
148
149 hd44780_write_gpio4(hd, cmd, 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 */
hd44780_write_cmd_raw_gpio4(struct hd44780_common * hdc,int cmd)156 static 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(n, &hd->pins[PIN_DATA4], NULL, values);
168
169 hd44780_strobe_gpio(hd);
170 }
171
172 /* Send data to the LCD panel in 4 bit GPIO mode */
hd44780_write_data_gpio4(struct hd44780_common * hdc,int data)173 static void hd44780_write_data_gpio4(struct hd44780_common *hdc, int data)
174 {
175 struct hd44780 *hd = hdc->hd44780;
176
177 hd44780_write_gpio4(hd, data, 1);
178
179 /* The shortest data takes at least 45 us */
180 udelay(45);
181 }
182
183 static 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
hd44780_probe(struct platform_device * pdev)200 static 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, "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(sizeof(*hd), 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, "data", i,
241 GPIOD_OUT_LOW);
242 if (IS_ERR(hd->pins[base + i])) {
243 ret = PTR_ERR(hd->pins[base + i]);
244 goto fail3;
245 }
246 }
247
248 hd->pins[PIN_CTRL_E] = devm_gpiod_get(dev, "enable", GPIOD_OUT_LOW);
249 if (IS_ERR(hd->pins[PIN_CTRL_E])) {
250 ret = PTR_ERR(hd->pins[PIN_CTRL_E]);
251 goto fail3;
252 }
253
254 hd->pins[PIN_CTRL_RS] = devm_gpiod_get(dev, "rs", GPIOD_OUT_HIGH);
255 if (IS_ERR(hd->pins[PIN_CTRL_RS])) {
256 ret = PTR_ERR(hd->pins[PIN_CTRL_RS]);
257 goto fail3;
258 }
259
260 /* Optional pins */
261 hd->pins[PIN_CTRL_RW] = devm_gpiod_get_optional(dev, "rw",
262 GPIOD_OUT_LOW);
263 if (IS_ERR(hd->pins[PIN_CTRL_RW])) {
264 ret = PTR_ERR(hd->pins[PIN_CTRL_RW]);
265 goto fail3;
266 }
267
268 hd->pins[PIN_CTRL_BL] = devm_gpiod_get_optional(dev, "backlight",
269 GPIOD_OUT_LOW);
270 if (IS_ERR(hd->pins[PIN_CTRL_BL])) {
271 ret = PTR_ERR(hd->pins[PIN_CTRL_BL]);
272 goto fail3;
273 }
274
275 /* Required properties */
276 ret = device_property_read_u32(dev, "display-height-chars",
277 &lcd->height);
278 if (ret)
279 goto fail3;
280 ret = device_property_read_u32(dev, "display-width-chars", &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, "internal-buffer-width", &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, lcd);
311 return 0;
312
313 fail3:
314 kfree(hd);
315 fail2:
316 kfree(lcd);
317 fail1:
318 kfree(hdc);
319 return ret;
320 }
321
hd44780_remove(struct platform_device * pdev)322 static 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(hdc->hd44780);
329 kfree(lcd->drvdata);
330
331 kfree(lcd);
332 }
333
334 static const struct of_device_id hd44780_of_match[] = {
335 { .compatible = "hit,hd44780" },
336 { /* sentinel */ }
337 };
338 MODULE_DEVICE_TABLE(of, hd44780_of_match);
339
340 static struct platform_driver hd44780_driver = {
341 .probe = hd44780_probe,
342 .remove = hd44780_remove,
343 .driver = {
344 .name = "hd44780",
345 .of_match_table = hd44780_of_match,
346 },
347 };
348
349 module_platform_driver(hd44780_driver);
350 MODULE_DESCRIPTION("HD44780 Character LCD driver");
351 MODULE_AUTHOR("Geert Uytterhoeven <geert@linux-m68k.org>");
352 MODULE_LICENSE("GPL");
353