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 "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
  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
  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 */
  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 */
  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 */
 106 static void hd44780_write_cmd_gpio8(struct charlcd *lcd, int cmd)
 107 {
 108         struct hd44780_common *hdc = lcd->drvdata;
 109         struct hd44780 *hd = hdc->hd44780;
 110
 111         hd44780_write_gpio8(hd, cmd, 0);
 112
 113         /* The shortest command takes at least 120 us */
 114         udelay(120);
 115 }
 116
 117 /* Send data to the LCD panel in 8 bit GPIO mode */
 118 static void hd44780_write_data_gpio8(struct hd44780_common *hdc, int data)
 119 {
 120         struct hd44780 *hd = hdc->hd44780;
 121
 122         hd44780_write_gpio8(hd, data, 1);
 123
 124         /* The shortest data takes at least 45 us */
 125         udelay(45);
 126 }
 127
 128 static const struct charlcd_ops hd44780_ops_gpio8 = {
 129         .write_cmd      = hd44780_write_cmd_gpio8,
 130         .backlight      = hd44780_backlight,
 131 };
 132
 133 /* Send a command to the LCD panel in 4 bit GPIO mode */
 134 static void hd44780_write_cmd_gpio4(struct charlcd *lcd, int cmd)
 135 {
 136         struct hd44780_common *hdc = lcd->drvdata;
 137         struct hd44780 *hd = hdc->hd44780;
 138
 139         hd44780_write_gpio4(hd, cmd, 0);
 140
 141         /* The shortest command takes at least 120 us */
 142         udelay(120);
 143 }
 144
 145 /* Send 4-bits of a command to the LCD panel in raw 4 bit GPIO mode */
 146 static void hd44780_write_cmd_raw_gpio4(struct charlcd *lcd, int cmd)
 147 {
 148         DECLARE_BITMAP(values, 6); /* for DATA[4-7], RS, RW */
 149         struct hd44780_common *hdc = lcd->drvdata;
 150         struct hd44780 *hd = hdc->hd44780;
 151         unsigned int n;
 152
 153         /* Command nibble + RS, RW */
 154         values[0] = cmd & 0x0f;
 155         n = hd->pins[PIN_CTRL_RW] ? 6 : 5;
 156
 157         /* Present the data to the port */
 158         gpiod_set_array_value_cansleep(n, &hd->pins[PIN_DATA4], NULL, values);
 159
 160         hd44780_strobe_gpio(hd);
 161 }
 162
 163 /* Send data to the LCD panel in 4 bit GPIO mode */
 164 static void hd44780_write_data_gpio4(struct hd44780_common *hdc, int data)
 165 {
 166         struct hd44780 *hd = hdc->hd44780;
 167
 168         hd44780_write_gpio4(hd, data, 1);
 169
 170         /* The shortest data takes at least 45 us */
 171         udelay(45);
 172 }
 173
 174 static const struct charlcd_ops hd44780_ops_gpio4 = {
 175         .write_cmd      = hd44780_write_cmd_gpio4,
 176         .write_cmd_raw4 = hd44780_write_cmd_raw_gpio4,
 177         .backlight      = hd44780_backlight,
 178 };
 179
 180 static int hd44780_probe(struct platform_device *pdev)
 181 {
 182         struct device *dev = &pdev->dev;
 183         unsigned int i, base;
 184         struct charlcd *lcd;
 185         struct hd44780_common *hdc;
 186         struct hd44780 *hd;
 187         int ifwidth, ret = -ENOMEM;
 188
 189         /* Required pins */
 190         ifwidth = gpiod_count(dev, "data");
 191         if (ifwidth < 0)
 192                 return ifwidth;
 193
 194         switch (ifwidth) {
 195         case 4:
 196                 base = PIN_DATA4;
 197                 break;
 198         case 8:
 199                 base = PIN_DATA0;
 200                 break;
 201         default:
 202                 return -EINVAL;
 203         }
 204
 205         hdc = hd44780_common_alloc();
 206         if (!hdc)
 207                 return -ENOMEM;
 208
 209         lcd = charlcd_alloc();
 210         if (!lcd)
 211                 goto fail1;
 212
 213         hd = kzalloc(sizeof(struct hd44780), GFP_KERNEL);
 214         if (!hd)
 215                 goto fail2;
 216
 217         hdc->hd44780 = hd;
 218         lcd->drvdata = hdc;
 219         for (i = 0; i < ifwidth; i++) {
 220                 hd->pins[base + i] = devm_gpiod_get_index(dev, "data", i,
 221                                                           GPIOD_OUT_LOW);
 222                 if (IS_ERR(hd->pins[base + i])) {
 223                         ret = PTR_ERR(hd->pins[base + i]);
 224                         goto fail3;
 225                 }
 226         }
 227
 228         hd->pins[PIN_CTRL_E] = devm_gpiod_get(dev, "enable", GPIOD_OUT_LOW);
 229         if (IS_ERR(hd->pins[PIN_CTRL_E])) {
 230                 ret = PTR_ERR(hd->pins[PIN_CTRL_E]);
 231                 goto fail3;
 232         }
 233
 234         hd->pins[PIN_CTRL_RS] = devm_gpiod_get(dev, "rs", GPIOD_OUT_HIGH);
 235         if (IS_ERR(hd->pins[PIN_CTRL_RS])) {
 236                 ret = PTR_ERR(hd->pins[PIN_CTRL_RS]);
 237                 goto fail3;
 238         }
 239
 240         /* Optional pins */
 241         hd->pins[PIN_CTRL_RW] = devm_gpiod_get_optional(dev, "rw",
 242                                                         GPIOD_OUT_LOW);
 243         if (IS_ERR(hd->pins[PIN_CTRL_RW])) {
 244                 ret = PTR_ERR(hd->pins[PIN_CTRL_RW]);
 245                 goto fail3;
 246         }
 247
 248         hd->pins[PIN_CTRL_BL] = devm_gpiod_get_optional(dev, "backlight",
 249                                                         GPIOD_OUT_LOW);
 250         if (IS_ERR(hd->pins[PIN_CTRL_BL])) {
 251                 ret = PTR_ERR(hd->pins[PIN_CTRL_BL]);
 252                 goto fail3;
 253         }
 254
 255         /* Required properties */
 256         ret = device_property_read_u32(dev, "display-height-chars",
 257                                        &lcd->height);
 258         if (ret)
 259                 goto fail3;
 260         ret = device_property_read_u32(dev, "display-width-chars", &lcd->width);
 261         if (ret)
 262                 goto fail3;
 263
 264         /*
 265          * On displays with more than two rows, the internal buffer width is
 266          * usually equal to the display width
 267          */
 268         if (lcd->height > 2)
 269                 hdc->bwidth = lcd->width;
 270
 271         /* Optional properties */
 272         device_property_read_u32(dev, "internal-buffer-width", &hdc->bwidth);
 273
 274         hdc->ifwidth = ifwidth;
 275         if (ifwidth == 8) {
 276                 lcd->ops = &hd44780_ops_gpio8;
 277                 hdc->write_data = hd44780_write_data_gpio8;
 278         } else {
 279                 lcd->ops = &hd44780_ops_gpio4;
 280                 hdc->write_data = hd44780_write_data_gpio4;
 281         }
 282
 283         ret = charlcd_register(lcd);
 284         if (ret)
 285                 goto fail3;
 286
 287         platform_set_drvdata(pdev, lcd);
 288         return 0;
 289
 290 fail3:
 291         kfree(hd);
 292 fail2:
 293         kfree(lcd);
 294 fail1:
 295         kfree(hdc);
 296         return ret;
 297 }
 298
 299 static int hd44780_remove(struct platform_device *pdev)
 300 {
 301         struct charlcd *lcd = platform_get_drvdata(pdev);
 302
 303         kfree(lcd->drvdata);
 304         charlcd_unregister(lcd);
 305
 306         kfree(lcd);
 307         return 0;
 308 }
 309
 310 static const struct of_device_id hd44780_of_match[] = {
 311         { .compatible = "hit,hd44780" },
 312         { /* sentinel */ }
 313 };
 314 MODULE_DEVICE_TABLE(of, hd44780_of_match);
 315
 316 static struct platform_driver hd44780_driver = {
 317         .probe = hd44780_probe,
 318         .remove = hd44780_remove,
 319         .driver         = {
 320                 .name   = "hd44780",
 321                 .of_match_table = hd44780_of_match,
 322         },
 323 };
 324
 325 module_platform_driver(hd44780_driver);
 326 MODULE_DESCRIPTION("HD44780 Character LCD driver");
 327 MODULE_AUTHOR("Geert Uytterhoeven <geert@linux-m68k.org>");
 328 MODULE_LICENSE("GPL");