drivers/auxdisplay/hd44780.c

   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/platform_device.h>
  13 #include <linux/property.h>
  14 #include <linux/slab.h>
  15
  16 #include <misc/charlcd.h>
  17
  18
  19 enum hd44780_pin {
  20         /* Order does matter due to writing to GPIO array subsets! */
  21         PIN_DATA0,      /* Optional */
  22         PIN_DATA1,      /* Optional */
  23         PIN_DATA2,      /* Optional */
  24         PIN_DATA3,      /* Optional */
  25         PIN_DATA4,
  26         PIN_DATA5,
  27         PIN_DATA6,
  28         PIN_DATA7,
  29         PIN_CTRL_RS,
  30         PIN_CTRL_RW,    /* Optional */
  31         PIN_CTRL_E,
  32         PIN_CTRL_BL,   /* Optional */
  33         PIN_NUM
  34 };
  35
  36 struct hd44780 {
  37         struct gpio_desc *pins[PIN_NUM];
  38 };
  39
  40 static void hd44780_backlight(struct charlcd *lcd, int on)
  41 {
  42         struct hd44780 *hd = lcd->drvdata;
  43
  44         if (hd->pins[PIN_CTRL_BL])
  45                 gpiod_set_value_cansleep(hd->pins[PIN_CTRL_BL], on);
  46 }
  47
  48 static void hd44780_strobe_gpio(struct hd44780 *hd)
  49 {
  50         /* Maintain the data during 20 us before the strobe */
  51         udelay(20);
  52
  53         gpiod_set_value_cansleep(hd->pins[PIN_CTRL_E], 1);
  54
  55         /* Maintain the strobe during 40 us */
  56         udelay(40);
  57
  58         gpiod_set_value_cansleep(hd->pins[PIN_CTRL_E], 0);
  59 }
  60
  61 /* write to an LCD panel register in 8 bit GPIO mode */
  62 static void hd44780_write_gpio8(struct hd44780 *hd, u8 val, unsigned int rs)
  63 {
  64         int values[10]; /* for DATA[0-7], RS, RW */
  65         unsigned int i, n;
  66
  67         for (i = 0; i < 8; i++)
  68                 values[PIN_DATA0 + i] = !!(val & BIT(i));
  69         values[PIN_CTRL_RS] = rs;
  70         n = 9;
  71         if (hd->pins[PIN_CTRL_RW]) {
  72                 values[PIN_CTRL_RW] = 0;
  73                 n++;
  74         }
  75
  76         /* Present the data to the port */
  77         gpiod_set_array_value_cansleep(n, &hd->pins[PIN_DATA0], values);
  78
  79         hd44780_strobe_gpio(hd);
  80 }
  81
  82 /* write to an LCD panel register in 4 bit GPIO mode */
  83 static void hd44780_write_gpio4(struct hd44780 *hd, u8 val, unsigned int rs)
  84 {
  85         int values[10]; /* for DATA[0-7], RS, RW, but DATA[0-3] is unused */
  86         unsigned int i, n;
  87
  88         /* High nibble + RS, RW */
  89         for (i = 4; i < 8; i++)
  90                 values[PIN_DATA0 + i] = !!(val & BIT(i));
  91         values[PIN_CTRL_RS] = rs;
  92         n = 5;
  93         if (hd->pins[PIN_CTRL_RW]) {
  94                 values[PIN_CTRL_RW] = 0;
  95                 n++;
  96         }
  97
  98         /* Present the data to the port */
  99         gpiod_set_array_value_cansleep(n, &hd->pins[PIN_DATA4],
 100                                        &values[PIN_DATA4]);
 101
 102         hd44780_strobe_gpio(hd);
 103
 104         /* Low nibble */
 105         for (i = 0; i < 4; i++)
 106                 values[PIN_DATA4 + i] = !!(val & BIT(i));
 107
 108         /* Present the data to the port */
 109         gpiod_set_array_value_cansleep(n, &hd->pins[PIN_DATA4],
 110                                        &values[PIN_DATA4]);
 111
 112         hd44780_strobe_gpio(hd);
 113 }
 114
 115 /* Send a command to the LCD panel in 8 bit GPIO mode */
 116 static void hd44780_write_cmd_gpio8(struct charlcd *lcd, int cmd)
 117 {
 118         struct hd44780 *hd = lcd->drvdata;
 119
 120         hd44780_write_gpio8(hd, cmd, 0);
 121
 122         /* The shortest command takes at least 120 us */
 123         udelay(120);
 124 }
 125
 126 /* Send data to the LCD panel in 8 bit GPIO mode */
 127 static void hd44780_write_data_gpio8(struct charlcd *lcd, int data)
 128 {
 129         struct hd44780 *hd = lcd->drvdata;
 130
 131         hd44780_write_gpio8(hd, data, 1);
 132
 133         /* The shortest data takes at least 45 us */
 134         udelay(45);
 135 }
 136
 137 static const struct charlcd_ops hd44780_ops_gpio8 = {
 138         .write_cmd      = hd44780_write_cmd_gpio8,
 139         .write_data     = hd44780_write_data_gpio8,
 140         .backlight      = hd44780_backlight,
 141 };
 142
 143 /* Send a command to the LCD panel in 4 bit GPIO mode */
 144 static void hd44780_write_cmd_gpio4(struct charlcd *lcd, int cmd)
 145 {
 146         struct hd44780 *hd = lcd->drvdata;
 147
 148         hd44780_write_gpio4(hd, cmd, 0);
 149
 150         /* The shortest command takes at least 120 us */
 151         udelay(120);
 152 }
 153
 154 /* Send 4-bits of a command to the LCD panel in raw 4 bit GPIO mode */
 155 static void hd44780_write_cmd_raw_gpio4(struct charlcd *lcd, int cmd)
 156 {
 157         int values[10]; /* for DATA[0-7], RS, RW, but DATA[0-3] is unused */
 158         struct hd44780 *hd = lcd->drvdata;
 159         unsigned int i, n;
 160
 161         /* Command nibble + RS, RW */
 162         for (i = 0; i < 4; i++)
 163                 values[PIN_DATA4 + i] = !!(cmd & BIT(i));
 164         values[PIN_CTRL_RS] = 0;
 165         n = 5;
 166         if (hd->pins[PIN_CTRL_RW]) {
 167                 values[PIN_CTRL_RW] = 0;
 168                 n++;
 169         }
 170
 171         /* Present the data to the port */
 172         gpiod_set_array_value_cansleep(n, &hd->pins[PIN_DATA4],
 173                                        &values[PIN_DATA4]);
 174
 175         hd44780_strobe_gpio(hd);
 176 }
 177
 178 /* Send data to the LCD panel in 4 bit GPIO mode */
 179 static void hd44780_write_data_gpio4(struct charlcd *lcd, int data)
 180 {
 181         struct hd44780 *hd = lcd->drvdata;
 182
 183         hd44780_write_gpio4(hd, data, 1);
 184
 185         /* The shortest data takes at least 45 us */
 186         udelay(45);
 187 }
 188
 189 static const struct charlcd_ops hd44780_ops_gpio4 = {
 190         .write_cmd      = hd44780_write_cmd_gpio4,
 191         .write_cmd_raw4 = hd44780_write_cmd_raw_gpio4,
 192         .write_data     = hd44780_write_data_gpio4,
 193         .backlight      = hd44780_backlight,
 194 };
 195
 196 static int hd44780_probe(struct platform_device *pdev)
 197 {
 198         struct device *dev = &pdev->dev;
 199         unsigned int i, base;
 200         struct charlcd *lcd;
 201         struct hd44780 *hd;
 202         int ifwidth, ret;
 203
 204         /* Required pins */
 205         ifwidth = gpiod_count(dev, "data");
 206         if (ifwidth < 0)
 207                 return ifwidth;
 208
 209         switch (ifwidth) {
 210         case 4:
 211                 base = PIN_DATA4;
 212                 break;
 213         case 8:
 214                 base = PIN_DATA0;
 215                 break;
 216         default:
 217                 return -EINVAL;
 218         }
 219
 220         lcd = charlcd_alloc(sizeof(struct hd44780));
 221         if (!lcd)
 222                 return -ENOMEM;
 223
 224         hd = lcd->drvdata;
 225
 226         for (i = 0; i < ifwidth; i++) {
 227                 hd->pins[base + i] = devm_gpiod_get_index(dev, "data", i,
 228                                                           GPIOD_OUT_LOW);
 229                 if (IS_ERR(hd->pins[base + i])) {
 230                         ret = PTR_ERR(hd->pins[base + i]);
 231                         goto fail;
 232                 }
 233         }
 234
 235         hd->pins[PIN_CTRL_E] = devm_gpiod_get(dev, "enable", GPIOD_OUT_LOW);
 236         if (IS_ERR(hd->pins[PIN_CTRL_E])) {
 237                 ret = PTR_ERR(hd->pins[PIN_CTRL_E]);
 238                 goto fail;
 239         }
 240
 241         hd->pins[PIN_CTRL_RS] = devm_gpiod_get(dev, "rs", GPIOD_OUT_HIGH);
 242         if (IS_ERR(hd->pins[PIN_CTRL_RS])) {
 243                 ret = PTR_ERR(hd->pins[PIN_CTRL_RS]);
 244                 goto fail;
 245         }
 246
 247         /* Optional pins */
 248         hd->pins[PIN_CTRL_RW] = devm_gpiod_get_optional(dev, "rw",
 249                                                         GPIOD_OUT_LOW);
 250         if (IS_ERR(hd->pins[PIN_CTRL_RW])) {
 251                 ret = PTR_ERR(hd->pins[PIN_CTRL_RW]);
 252                 goto fail;
 253         }
 254
 255         hd->pins[PIN_CTRL_BL] = devm_gpiod_get_optional(dev, "backlight",
 256                                                         GPIOD_OUT_LOW);
 257         if (IS_ERR(hd->pins[PIN_CTRL_BL])) {
 258                 ret = PTR_ERR(hd->pins[PIN_CTRL_BL]);
 259                 goto fail;
 260         }
 261
 262         /* Required properties */
 263         ret = device_property_read_u32(dev, "display-height-chars",
 264                                        &lcd->height);
 265         if (ret)
 266                 goto fail;
 267         ret = device_property_read_u32(dev, "display-width-chars", &lcd->width);
 268         if (ret)
 269                 goto fail;
 270
 271         /*
 272          * On displays with more than two rows, the internal buffer width is
 273          * usually equal to the display width
 274          */
 275         if (lcd->height > 2)
 276                 lcd->bwidth = lcd->width;
 277
 278         /* Optional properties */
 279         device_property_read_u32(dev, "internal-buffer-width", &lcd->bwidth);
 280
 281         lcd->ifwidth = ifwidth;
 282         lcd->ops = ifwidth == 8 ? &hd44780_ops_gpio8 : &hd44780_ops_gpio4;
 283
 284         ret = charlcd_register(lcd);
 285         if (ret)
 286                 goto fail;
 287
 288         platform_set_drvdata(pdev, lcd);
 289         return 0;
 290
 291 fail:
 292         kfree(lcd);
 293         return ret;
 294 }
 295
 296 static int hd44780_remove(struct platform_device *pdev)
 297 {
 298         struct charlcd *lcd = platform_get_drvdata(pdev);
 299
 300         charlcd_unregister(lcd);
 301         return 0;
 302 }
 303
 304 static const struct of_device_id hd44780_of_match[] = {
 305         { .compatible = "hit,hd44780" },
 306         { /* sentinel */ }
 307 };
 308 MODULE_DEVICE_TABLE(of, hd44780_of_match);
 309
 310 static struct platform_driver hd44780_driver = {
 311         .probe = hd44780_probe,
 312         .remove = hd44780_remove,
 313         .driver         = {
 314                 .name   = "hd44780",
 315                 .of_match_table = hd44780_of_match,
 316         },
 317 };
 318
 319 module_platform_driver(hd44780_driver);
 320 MODULE_DESCRIPTION("HD44780 Character LCD driver");
 321 MODULE_AUTHOR("Geert Uytterhoeven <geert@linux-m68k.org>");
 322 MODULE_LICENSE("GPL");