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/mod_devicetable.h>
  13 #include <linux/platform_device.h>
  14 #include <linux/property.h>
  15 #include <linux/slab.h>
  16
  17 #include <misc/charlcd.h>
  18
  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
  41 static void hd44780_backlight(struct charlcd *lcd, int on)
  42 {
  43         struct hd44780 *hd = lcd->drvdata;
  44
  45         if (hd->pins[PIN_CTRL_BL])
  46                 gpiod_set_value_cansleep(hd->pins[PIN_CTRL_BL], on);
  47 }
  48
  49 static void hd44780_strobe_gpio(struct hd44780 *hd)
  50 {
  51         /* Maintain the data during 20 us before the strobe */
  52         udelay(20);
  53
  54         gpiod_set_value_cansleep(hd->pins[PIN_CTRL_E], 1);
  55
  56         /* Maintain the strobe during 40 us */
  57         udelay(40);
  58
  59         gpiod_set_value_cansleep(hd->pins[PIN_CTRL_E], 0);
  60 }
  61
  62 /* write to an LCD panel register in 8 bit GPIO mode */
  63 static void hd44780_write_gpio8(struct hd44780 *hd, u8 val, unsigned int rs)
  64 {
  65         DECLARE_BITMAP(values, 10); /* for DATA[0-7], RS, RW */
  66         unsigned int n;
  67
  68         values[0] = val;
  69         __assign_bit(8, values, rs);
  70         n = hd->pins[PIN_CTRL_RW] ? 10 : 9;
  71
  72         /* Present the data to the port */
  73         gpiod_set_array_value_cansleep(n, &hd->pins[PIN_DATA0], NULL, values);
  74
  75         hd44780_strobe_gpio(hd);
  76 }
  77
  78 /* write to an LCD panel register in 4 bit GPIO mode */
  79 static void hd44780_write_gpio4(struct hd44780 *hd, u8 val, unsigned int rs)
  80 {
  81         DECLARE_BITMAP(values, 6); /* for DATA[4-7], RS, RW */
  82         unsigned int n;
  83
  84         /* High nibble + RS, RW */
  85         values[0] = val >> 4;
  86         __assign_bit(4, values, rs);
  87         n = hd->pins[PIN_CTRL_RW] ? 6 : 5;
  88
  89         /* Present the data to the port */
  90         gpiod_set_array_value_cansleep(n, &hd->pins[PIN_DATA4], NULL, values);
  91
  92         hd44780_strobe_gpio(hd);
  93
  94         /* Low nibble */
  95         values[0] &= ~0x0fUL;
  96         values[0] |= val & 0x0f;
  97
  98         /* Present the data to the port */
  99         gpiod_set_array_value_cansleep(n, &hd->pins[PIN_DATA4], NULL, values);
 100
 101         hd44780_strobe_gpio(hd);
 102 }
 103
 104 /* Send a command to the LCD panel in 8 bit GPIO mode */
 105 static void hd44780_write_cmd_gpio8(struct charlcd *lcd, int cmd)
 106 {
 107         struct hd44780 *hd = lcd->drvdata;
 108
 109         hd44780_write_gpio8(hd, cmd, 0);
 110
 111         /* The shortest command takes at least 120 us */
 112         udelay(120);
 113 }
 114
 115 /* Send data to the LCD panel in 8 bit GPIO mode */
 116 static void hd44780_write_data_gpio8(struct charlcd *lcd, int data)
 117 {
 118         struct hd44780 *hd = lcd->drvdata;
 119
 120         hd44780_write_gpio8(hd, data, 1);
 121
 122         /* The shortest data takes at least 45 us */
 123         udelay(45);
 124 }
 125
 126 static const struct charlcd_ops hd44780_ops_gpio8 = {
 127         .write_cmd      = hd44780_write_cmd_gpio8,
 128         .write_data     = hd44780_write_data_gpio8,
 129         .backlight      = hd44780_backlight,
 130 };
 131
 132 /* Send a command to the LCD panel in 4 bit GPIO mode */
 133 static void hd44780_write_cmd_gpio4(struct charlcd *lcd, int cmd)
 134 {
 135         struct hd44780 *hd = lcd->drvdata;
 136
 137         hd44780_write_gpio4(hd, cmd, 0);
 138
 139         /* The shortest command takes at least 120 us */
 140         udelay(120);
 141 }
 142
 143 /* Send 4-bits of a command to the LCD panel in raw 4 bit GPIO mode */
 144 static void hd44780_write_cmd_raw_gpio4(struct charlcd *lcd, int cmd)
 145 {
 146         DECLARE_BITMAP(values, 6); /* for DATA[4-7], RS, RW */
 147         struct hd44780 *hd = lcd->drvdata;
 148         unsigned int n;
 149
 150         /* Command nibble + RS, RW */
 151         values[0] = cmd & 0x0f;
 152         n = hd->pins[PIN_CTRL_RW] ? 6 : 5;
 153
 154         /* Present the data to the port */
 155         gpiod_set_array_value_cansleep(n, &hd->pins[PIN_DATA4], NULL, values);
 156
 157         hd44780_strobe_gpio(hd);
 158 }
 159
 160 /* Send data to the LCD panel in 4 bit GPIO mode */
 161 static void hd44780_write_data_gpio4(struct charlcd *lcd, int data)
 162 {
 163         struct hd44780 *hd = lcd->drvdata;
 164
 165         hd44780_write_gpio4(hd, data, 1);
 166
 167         /* The shortest data takes at least 45 us */
 168         udelay(45);
 169 }
 170
 171 static const struct charlcd_ops hd44780_ops_gpio4 = {
 172         .write_cmd      = hd44780_write_cmd_gpio4,
 173         .write_cmd_raw4 = hd44780_write_cmd_raw_gpio4,
 174         .write_data     = hd44780_write_data_gpio4,
 175         .backlight      = hd44780_backlight,
 176 };
 177
 178 static int hd44780_probe(struct platform_device *pdev)
 179 {
 180         struct device *dev = &pdev->dev;
 181         unsigned int i, base;
 182         struct charlcd *lcd;
 183         struct hd44780 *hd;
 184         int ifwidth, ret;
 185
 186         /* Required pins */
 187         ifwidth = gpiod_count(dev, "data");
 188         if (ifwidth < 0)
 189                 return ifwidth;
 190
 191         switch (ifwidth) {
 192         case 4:
 193                 base = PIN_DATA4;
 194                 break;
 195         case 8:
 196                 base = PIN_DATA0;
 197                 break;
 198         default:
 199                 return -EINVAL;
 200         }
 201
 202         lcd = charlcd_alloc(sizeof(struct hd44780));
 203         if (!lcd)
 204                 return -ENOMEM;
 205
 206         hd = lcd->drvdata;
 207
 208         for (i = 0; i < ifwidth; i++) {
 209                 hd->pins[base + i] = devm_gpiod_get_index(dev, "data", i,
 210                                                           GPIOD_OUT_LOW);
 211                 if (IS_ERR(hd->pins[base + i])) {
 212                         ret = PTR_ERR(hd->pins[base + i]);
 213                         goto fail;
 214                 }
 215         }
 216
 217         hd->pins[PIN_CTRL_E] = devm_gpiod_get(dev, "enable", GPIOD_OUT_LOW);
 218         if (IS_ERR(hd->pins[PIN_CTRL_E])) {
 219                 ret = PTR_ERR(hd->pins[PIN_CTRL_E]);
 220                 goto fail;
 221         }
 222
 223         hd->pins[PIN_CTRL_RS] = devm_gpiod_get(dev, "rs", GPIOD_OUT_HIGH);
 224         if (IS_ERR(hd->pins[PIN_CTRL_RS])) {
 225                 ret = PTR_ERR(hd->pins[PIN_CTRL_RS]);
 226                 goto fail;
 227         }
 228
 229         /* Optional pins */
 230         hd->pins[PIN_CTRL_RW] = devm_gpiod_get_optional(dev, "rw",
 231                                                         GPIOD_OUT_LOW);
 232         if (IS_ERR(hd->pins[PIN_CTRL_RW])) {
 233                 ret = PTR_ERR(hd->pins[PIN_CTRL_RW]);
 234                 goto fail;
 235         }
 236
 237         hd->pins[PIN_CTRL_BL] = devm_gpiod_get_optional(dev, "backlight",
 238                                                         GPIOD_OUT_LOW);
 239         if (IS_ERR(hd->pins[PIN_CTRL_BL])) {
 240                 ret = PTR_ERR(hd->pins[PIN_CTRL_BL]);
 241                 goto fail;
 242         }
 243
 244         /* Required properties */
 245         ret = device_property_read_u32(dev, "display-height-chars",
 246                                        &lcd->height);
 247         if (ret)
 248                 goto fail;
 249         ret = device_property_read_u32(dev, "display-width-chars", &lcd->width);
 250         if (ret)
 251                 goto fail;
 252
 253         /*
 254          * On displays with more than two rows, the internal buffer width is
 255          * usually equal to the display width
 256          */
 257         if (lcd->height > 2)
 258                 lcd->bwidth = lcd->width;
 259
 260         /* Optional properties */
 261         device_property_read_u32(dev, "internal-buffer-width", &lcd->bwidth);
 262
 263         lcd->ifwidth = ifwidth;
 264         lcd->ops = ifwidth == 8 ? &hd44780_ops_gpio8 : &hd44780_ops_gpio4;
 265
 266         ret = charlcd_register(lcd);
 267         if (ret)
 268                 goto fail;
 269
 270         platform_set_drvdata(pdev, lcd);
 271         return 0;
 272
 273 fail:
 274         kfree(lcd);
 275         return ret;
 276 }
 277
 278 static int hd44780_remove(struct platform_device *pdev)
 279 {
 280         struct charlcd *lcd = platform_get_drvdata(pdev);
 281
 282         charlcd_unregister(lcd);
 283         return 0;
 284 }
 285
 286 static const struct of_device_id hd44780_of_match[] = {
 287         { .compatible = "hit,hd44780" },
 288         { /* sentinel */ }
 289 };
 290 MODULE_DEVICE_TABLE(of, hd44780_of_match);
 291
 292 static struct platform_driver hd44780_driver = {
 293         .probe = hd44780_probe,
 294         .remove = hd44780_remove,
 295         .driver         = {
 296                 .name   = "hd44780",
 297                 .of_match_table = hd44780_of_match,
 298         },
 299 };
 300
 301 module_platform_driver(hd44780_driver);
 302 MODULE_DESCRIPTION("HD44780 Character LCD driver");
 303 MODULE_AUTHOR("Geert Uytterhoeven <geert@linux-m68k.org>");
 304 MODULE_LICENSE("GPL");