drivers/auxdisplay/hd44780.c

   1 /*
   2  * HD44780 Character LCD driver for Linux
   3  *
   4  * Copyright (C) 2000-2008, Willy Tarreau <w@1wt.eu>
   5  * Copyright (C) 2016-2017 Glider bvba
   6  *
   7  * This program is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU General Public License
   9  * as published by the Free Software Foundation; either version
  10  * 2 of the License, or (at your option) any later version.
  11  */
  12
  13 #include <linux/delay.h>
  14 #include <linux/gpio/consumer.h>
  15 #include <linux/module.h>
  16 #include <linux/platform_device.h>
  17 #include <linux/property.h>
  18 #include <linux/slab.h>
  19
  20 #include <misc/charlcd.h>
  21
  22
  23 enum hd44780_pin {
  24         /* Order does matter due to writing to GPIO array subsets! */
  25         PIN_DATA0,      /* Optional */
  26         PIN_DATA1,      /* Optional */
  27         PIN_DATA2,      /* Optional */
  28         PIN_DATA3,      /* Optional */
  29         PIN_DATA4,
  30         PIN_DATA5,
  31         PIN_DATA6,
  32         PIN_DATA7,
  33         PIN_CTRL_RS,
  34         PIN_CTRL_RW,    /* Optional */
  35         PIN_CTRL_E,
  36         PIN_CTRL_BL,   /* Optional */
  37         PIN_NUM
  38 };
  39
  40 struct hd44780 {
  41         struct gpio_desc *pins[PIN_NUM];
  42 };
  43
  44 static void hd44780_backlight(struct charlcd *lcd, int on)
  45 {
  46         struct hd44780 *hd = lcd->drvdata;
  47
  48         if (hd->pins[PIN_CTRL_BL])
  49                 gpiod_set_value_cansleep(hd->pins[PIN_CTRL_BL], on);
  50 }
  51
  52 static void hd44780_strobe_gpio(struct hd44780 *hd)
  53 {
  54         /* Maintain the data during 20 us before the strobe */
  55         udelay(20);
  56
  57         gpiod_set_value_cansleep(hd->pins[PIN_CTRL_E], 1);
  58
  59         /* Maintain the strobe during 40 us */
  60         udelay(40);
  61
  62         gpiod_set_value_cansleep(hd->pins[PIN_CTRL_E], 0);
  63 }
  64
  65 /* write to an LCD panel register in 8 bit GPIO mode */
  66 static void hd44780_write_gpio8(struct hd44780 *hd, u8 val, unsigned int rs)
  67 {
  68         int values[10]; /* for DATA[0-7], RS, RW */
  69         unsigned int i, n;
  70
  71         for (i = 0; i < 8; i++)
  72                 values[PIN_DATA0 + i] = !!(val & BIT(i));
  73         values[PIN_CTRL_RS] = rs;
  74         n = 9;
  75         if (hd->pins[PIN_CTRL_RW]) {
  76                 values[PIN_CTRL_RW] = 0;
  77                 n++;
  78         }
  79
  80         /* Present the data to the port */
  81         gpiod_set_array_value_cansleep(n, &hd->pins[PIN_DATA0], values);
  82
  83         hd44780_strobe_gpio(hd);
  84 }
  85
  86 /* write to an LCD panel register in 4 bit GPIO mode */
  87 static void hd44780_write_gpio4(struct hd44780 *hd, u8 val, unsigned int rs)
  88 {
  89         int values[10]; /* for DATA[0-7], RS, RW, but DATA[0-3] is unused */
  90         unsigned int i, n;
  91
  92         /* High nibble + RS, RW */
  93         for (i = 4; i < 8; i++)
  94                 values[PIN_DATA0 + i] = !!(val & BIT(i));
  95         values[PIN_CTRL_RS] = rs;
  96         n = 5;
  97         if (hd->pins[PIN_CTRL_RW]) {
  98                 values[PIN_CTRL_RW] = 0;
  99                 n++;
 100         }
 101
 102         /* Present the data to the port */
 103         gpiod_set_array_value_cansleep(n, &hd->pins[PIN_DATA4],
 104                                        &values[PIN_DATA4]);
 105
 106         hd44780_strobe_gpio(hd);
 107
 108         /* Low nibble */
 109         for (i = 0; i < 4; i++)
 110                 values[PIN_DATA4 + i] = !!(val & BIT(i));
 111
 112         /* Present the data to the port */
 113         gpiod_set_array_value_cansleep(n, &hd->pins[PIN_DATA4],
 114                                        &values[PIN_DATA4]);
 115
 116         hd44780_strobe_gpio(hd);
 117 }
 118
 119 /* Send a command to the LCD panel in 8 bit GPIO mode */
 120 static void hd44780_write_cmd_gpio8(struct charlcd *lcd, int cmd)
 121 {
 122         struct hd44780 *hd = lcd->drvdata;
 123
 124         hd44780_write_gpio8(hd, cmd, 0);
 125
 126         /* The shortest command takes at least 120 us */
 127         udelay(120);
 128 }
 129
 130 /* Send data to the LCD panel in 8 bit GPIO mode */
 131 static void hd44780_write_data_gpio8(struct charlcd *lcd, int data)
 132 {
 133         struct hd44780 *hd = lcd->drvdata;
 134
 135         hd44780_write_gpio8(hd, data, 1);
 136
 137         /* The shortest data takes at least 45 us */
 138         udelay(45);
 139 }
 140
 141 static const struct charlcd_ops hd44780_ops_gpio8 = {
 142         .write_cmd      = hd44780_write_cmd_gpio8,
 143         .write_data     = hd44780_write_data_gpio8,
 144         .backlight      = hd44780_backlight,
 145 };
 146
 147 /* Send a command to the LCD panel in 4 bit GPIO mode */
 148 static void hd44780_write_cmd_gpio4(struct charlcd *lcd, int cmd)
 149 {
 150         struct hd44780 *hd = lcd->drvdata;
 151
 152         hd44780_write_gpio4(hd, cmd, 0);
 153
 154         /* The shortest command takes at least 120 us */
 155         udelay(120);
 156 }
 157
 158 /* Send 4-bits of a command to the LCD panel in raw 4 bit GPIO mode */
 159 static void hd44780_write_cmd_raw_gpio4(struct charlcd *lcd, int cmd)
 160 {
 161         int values[10]; /* for DATA[0-7], RS, RW, but DATA[0-3] is unused */
 162         struct hd44780 *hd = lcd->drvdata;
 163         unsigned int i, n;
 164
 165         /* Command nibble + RS, RW */
 166         for (i = 0; i < 4; i++)
 167                 values[PIN_DATA4 + i] = !!(cmd & BIT(i));
 168         values[PIN_CTRL_RS] = 0;
 169         n = 5;
 170         if (hd->pins[PIN_CTRL_RW]) {
 171                 values[PIN_CTRL_RW] = 0;
 172                 n++;
 173         }
 174
 175         /* Present the data to the port */
 176         gpiod_set_array_value_cansleep(n, &hd->pins[PIN_DATA4],
 177                                        &values[PIN_DATA4]);
 178
 179         hd44780_strobe_gpio(hd);
 180 }
 181
 182 /* Send data to the LCD panel in 4 bit GPIO mode */
 183 static void hd44780_write_data_gpio4(struct charlcd *lcd, int data)
 184 {
 185         struct hd44780 *hd = lcd->drvdata;
 186
 187         hd44780_write_gpio4(hd, data, 1);
 188
 189         /* The shortest data takes at least 45 us */
 190         udelay(45);
 191 }
 192
 193 static const struct charlcd_ops hd44780_ops_gpio4 = {
 194         .write_cmd      = hd44780_write_cmd_gpio4,
 195         .write_cmd_raw4 = hd44780_write_cmd_raw_gpio4,
 196         .write_data     = hd44780_write_data_gpio4,
 197         .backlight      = hd44780_backlight,
 198 };
 199
 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 *hd;
 206         int ifwidth, ret;
 207
 208         /* Required pins */
 209         ifwidth = gpiod_count(dev, "data");
 210         if (ifwidth < 0)
 211                 return ifwidth;
 212
 213         switch (ifwidth) {
 214         case 4:
 215                 base = PIN_DATA4;
 216                 break;
 217         case 8:
 218                 base = PIN_DATA0;
 219                 break;
 220         default:
 221                 return -EINVAL;
 222         }
 223
 224         lcd = charlcd_alloc(sizeof(struct hd44780));
 225         if (!lcd)
 226                 return -ENOMEM;
 227
 228         hd = lcd->drvdata;
 229
 230         for (i = 0; i < ifwidth; i++) {
 231                 hd->pins[base + i] = devm_gpiod_get_index(dev, "data", i,
 232                                                           GPIOD_OUT_LOW);
 233                 if (IS_ERR(hd->pins[base + i])) {
 234                         ret = PTR_ERR(hd->pins[base + i]);
 235                         goto fail;
 236                 }
 237         }
 238
 239         hd->pins[PIN_CTRL_E] = devm_gpiod_get(dev, "enable", GPIOD_OUT_LOW);
 240         if (IS_ERR(hd->pins[PIN_CTRL_E])) {
 241                 ret = PTR_ERR(hd->pins[PIN_CTRL_E]);
 242                 goto fail;
 243         }
 244
 245         hd->pins[PIN_CTRL_RS] = devm_gpiod_get(dev, "rs", GPIOD_OUT_HIGH);
 246         if (IS_ERR(hd->pins[PIN_CTRL_RS])) {
 247                 ret = PTR_ERR(hd->pins[PIN_CTRL_RS]);
 248                 goto fail;
 249         }
 250
 251         /* Optional pins */
 252         hd->pins[PIN_CTRL_RW] = devm_gpiod_get_optional(dev, "rw",
 253                                                         GPIOD_OUT_LOW);
 254         if (IS_ERR(hd->pins[PIN_CTRL_RW])) {
 255                 ret = PTR_ERR(hd->pins[PIN_CTRL_RW]);
 256                 goto fail;
 257         }
 258
 259         hd->pins[PIN_CTRL_BL] = devm_gpiod_get_optional(dev, "backlight",
 260                                                         GPIOD_OUT_LOW);
 261         if (IS_ERR(hd->pins[PIN_CTRL_BL])) {
 262                 ret = PTR_ERR(hd->pins[PIN_CTRL_BL]);
 263                 goto fail;
 264         }
 265
 266         /* Required properties */
 267         ret = device_property_read_u32(dev, "display-height-chars",
 268                                        &lcd->height);
 269         if (ret)
 270                 goto fail;
 271         ret = device_property_read_u32(dev, "display-width-chars", &lcd->width);
 272         if (ret)
 273                 goto fail;
 274
 275         /*
 276          * On displays with more than two rows, the internal buffer width is
 277          * usually equal to the display width
 278          */
 279         if (lcd->height > 2)
 280                 lcd->bwidth = lcd->width;
 281
 282         /* Optional properties */
 283         device_property_read_u32(dev, "internal-buffer-width", &lcd->bwidth);
 284
 285         lcd->ifwidth = ifwidth;
 286         lcd->ops = ifwidth == 8 ? &hd44780_ops_gpio8 : &hd44780_ops_gpio4;
 287
 288         ret = charlcd_register(lcd);
 289         if (ret)
 290                 goto fail;
 291
 292         platform_set_drvdata(pdev, lcd);
 293         return 0;
 294
 295 fail:
 296         kfree(lcd);
 297         return ret;
 298 }
 299
 300 static int hd44780_remove(struct platform_device *pdev)
 301 {
 302         struct charlcd *lcd = platform_get_drvdata(pdev);
 303
 304         charlcd_unregister(lcd);
 305         return 0;
 306 }
 307
 308 static const struct of_device_id hd44780_of_match[] = {
 309         { .compatible = "hit,hd44780" },
 310         { /* sentinel */ }
 311 };
 312 MODULE_DEVICE_TABLE(of, hd44780_of_match);
 313
 314 static struct platform_driver hd44780_driver = {
 315         .probe = hd44780_probe,
 316         .remove = hd44780_remove,
 317         .driver         = {
 318                 .name   = "hd44780",
 319                 .of_match_table = hd44780_of_match,
 320         },
 321 };
 322
 323 module_platform_driver(hd44780_driver);
 324 MODULE_DESCRIPTION("HD44780 Character LCD driver");
 325 MODULE_AUTHOR("Geert Uytterhoeven <geert@linux-m68k.org>");
 326 MODULE_LICENSE("GPL");