diff options
Diffstat (limited to 'drivers/auxdisplay/hd44780.c')
| -rw-r--r-- | drivers/auxdisplay/hd44780.c | 325 |
1 files changed, 325 insertions, 0 deletions
diff --git a/drivers/auxdisplay/hd44780.c b/drivers/auxdisplay/hd44780.c new file mode 100644 index 000000000..df3da49ff --- /dev/null +++ b/drivers/auxdisplay/hd44780.c @@ -0,0 +1,325 @@ +// SPDX-License-Identifier: GPL-2.0+ +/* + * HD44780 Character LCD driver for Linux + * + * Copyright (C) 2000-2008, Willy Tarreau <w@1wt.eu> + * Copyright (C) 2016-2017 Glider bvba + */ + +#include <linux/delay.h> +#include <linux/gpio/consumer.h> +#include <linux/module.h> +#include <linux/mod_devicetable.h> +#include <linux/platform_device.h> +#include <linux/property.h> +#include <linux/slab.h> + +#include <misc/charlcd.h> + + +enum hd44780_pin { + /* Order does matter due to writing to GPIO array subsets! */ + PIN_DATA0, /* Optional */ + PIN_DATA1, /* Optional */ + PIN_DATA2, /* Optional */ + PIN_DATA3, /* Optional */ + PIN_DATA4, + PIN_DATA5, + PIN_DATA6, + PIN_DATA7, + PIN_CTRL_RS, + PIN_CTRL_RW, /* Optional */ + PIN_CTRL_E, + PIN_CTRL_BL, /* Optional */ + PIN_NUM +}; + +struct hd44780 { + struct gpio_desc *pins[PIN_NUM]; +}; + +static void hd44780_backlight(struct charlcd *lcd, int on) +{ + struct hd44780 *hd = lcd->drvdata; + + if (hd->pins[PIN_CTRL_BL]) + gpiod_set_value_cansleep(hd->pins[PIN_CTRL_BL], on); +} + +static void hd44780_strobe_gpio(struct hd44780 *hd) +{ + /* Maintain the data during 20 us before the strobe */ + udelay(20); + + gpiod_set_value_cansleep(hd->pins[PIN_CTRL_E], 1); + + /* Maintain the strobe during 40 us */ + udelay(40); + + gpiod_set_value_cansleep(hd->pins[PIN_CTRL_E], 0); +} + +/* write to an LCD panel register in 8 bit GPIO mode */ +static void hd44780_write_gpio8(struct hd44780 *hd, u8 val, unsigned int rs) +{ + int values[10]; /* for DATA[0-7], RS, RW */ + unsigned int i, n; + + for (i = 0; i < 8; i++) + values[PIN_DATA0 + i] = !!(val & BIT(i)); + values[PIN_CTRL_RS] = rs; + n = 9; + if (hd->pins[PIN_CTRL_RW]) { + values[PIN_CTRL_RW] = 0; + n++; + } + + /* Present the data to the port */ + gpiod_set_array_value_cansleep(n, &hd->pins[PIN_DATA0], values); + + hd44780_strobe_gpio(hd); +} + +/* write to an LCD panel register in 4 bit GPIO mode */ +static void hd44780_write_gpio4(struct hd44780 *hd, u8 val, unsigned int rs) +{ + int values[10]; /* for DATA[0-7], RS, RW, but DATA[0-3] is unused */ + unsigned int i, n; + + /* High nibble + RS, RW */ + for (i = 4; i < 8; i++) + values[PIN_DATA0 + i] = !!(val & BIT(i)); + values[PIN_CTRL_RS] = rs; + n = 5; + if (hd->pins[PIN_CTRL_RW]) { + values[PIN_CTRL_RW] = 0; + n++; + } + + /* Present the data to the port */ + gpiod_set_array_value_cansleep(n, &hd->pins[PIN_DATA4], + &values[PIN_DATA4]); + + hd44780_strobe_gpio(hd); + + /* Low nibble */ + for (i = 0; i < 4; i++) + values[PIN_DATA4 + i] = !!(val & BIT(i)); + + /* Present the data to the port */ + gpiod_set_array_value_cansleep(n, &hd->pins[PIN_DATA4], + &values[PIN_DATA4]); + + hd44780_strobe_gpio(hd); +} + +/* Send a command to the LCD panel in 8 bit GPIO mode */ +static void hd44780_write_cmd_gpio8(struct charlcd *lcd, int cmd) +{ + struct hd44780 *hd = lcd->drvdata; + + hd44780_write_gpio8(hd, cmd, 0); + + /* The shortest command takes at least 120 us */ + udelay(120); +} + +/* Send data to the LCD panel in 8 bit GPIO mode */ +static void hd44780_write_data_gpio8(struct charlcd *lcd, int data) +{ + struct hd44780 *hd = lcd->drvdata; + + hd44780_write_gpio8(hd, data, 1); + + /* The shortest data takes at least 45 us */ + udelay(45); +} + +static const struct charlcd_ops hd44780_ops_gpio8 = { + .write_cmd = hd44780_write_cmd_gpio8, + .write_data = hd44780_write_data_gpio8, + .backlight = hd44780_backlight, +}; + +/* Send a command to the LCD panel in 4 bit GPIO mode */ +static void hd44780_write_cmd_gpio4(struct charlcd *lcd, int cmd) +{ + struct hd44780 *hd = lcd->drvdata; + + hd44780_write_gpio4(hd, cmd, 0); + + /* The shortest command takes at least 120 us */ + udelay(120); +} + +/* Send 4-bits of a command to the LCD panel in raw 4 bit GPIO mode */ +static void hd44780_write_cmd_raw_gpio4(struct charlcd *lcd, int cmd) +{ + int values[10]; /* for DATA[0-7], RS, RW, but DATA[0-3] is unused */ + struct hd44780 *hd = lcd->drvdata; + unsigned int i, n; + + /* Command nibble + RS, RW */ + for (i = 0; i < 4; i++) + values[PIN_DATA4 + i] = !!(cmd & BIT(i)); + values[PIN_CTRL_RS] = 0; + n = 5; + if (hd->pins[PIN_CTRL_RW]) { + values[PIN_CTRL_RW] = 0; + n++; + } + + /* Present the data to the port */ + gpiod_set_array_value_cansleep(n, &hd->pins[PIN_DATA4], + &values[PIN_DATA4]); + + hd44780_strobe_gpio(hd); +} + +/* Send data to the LCD panel in 4 bit GPIO mode */ +static void hd44780_write_data_gpio4(struct charlcd *lcd, int data) +{ + struct hd44780 *hd = lcd->drvdata; + + hd44780_write_gpio4(hd, data, 1); + + /* The shortest data takes at least 45 us */ + udelay(45); +} + +static const struct charlcd_ops hd44780_ops_gpio4 = { + .write_cmd = hd44780_write_cmd_gpio4, + .write_cmd_raw4 = hd44780_write_cmd_raw_gpio4, + .write_data = hd44780_write_data_gpio4, + .backlight = hd44780_backlight, +}; + +static int hd44780_probe(struct platform_device *pdev) +{ + struct device *dev = &pdev->dev; + unsigned int i, base; + struct charlcd *lcd; + struct hd44780 *hd; + int ifwidth, ret; + + /* Required pins */ + ifwidth = gpiod_count(dev, "data"); + if (ifwidth < 0) + return ifwidth; + + switch (ifwidth) { + case 4: + base = PIN_DATA4; + break; + case 8: + base = PIN_DATA0; + break; + default: + return -EINVAL; + } + + lcd = charlcd_alloc(sizeof(struct hd44780)); + if (!lcd) + return -ENOMEM; + + hd = lcd->drvdata; + + for (i = 0; i < ifwidth; i++) { + hd->pins[base + i] = devm_gpiod_get_index(dev, "data", i, + GPIOD_OUT_LOW); + if (IS_ERR(hd->pins[base + i])) { + ret = PTR_ERR(hd->pins[base + i]); + goto fail; + } + } + + hd->pins[PIN_CTRL_E] = devm_gpiod_get(dev, "enable", GPIOD_OUT_LOW); + if (IS_ERR(hd->pins[PIN_CTRL_E])) { + ret = PTR_ERR(hd->pins[PIN_CTRL_E]); + goto fail; + } + + hd->pins[PIN_CTRL_RS] = devm_gpiod_get(dev, "rs", GPIOD_OUT_HIGH); + if (IS_ERR(hd->pins[PIN_CTRL_RS])) { + ret = PTR_ERR(hd->pins[PIN_CTRL_RS]); + goto fail; + } + + /* Optional pins */ + hd->pins[PIN_CTRL_RW] = devm_gpiod_get_optional(dev, "rw", + GPIOD_OUT_LOW); + if (IS_ERR(hd->pins[PIN_CTRL_RW])) { + ret = PTR_ERR(hd->pins[PIN_CTRL_RW]); + goto fail; + } + + hd->pins[PIN_CTRL_BL] = devm_gpiod_get_optional(dev, "backlight", + GPIOD_OUT_LOW); + if (IS_ERR(hd->pins[PIN_CTRL_BL])) { + ret = PTR_ERR(hd->pins[PIN_CTRL_BL]); + goto fail; + } + + /* Required properties */ + ret = device_property_read_u32(dev, "display-height-chars", + &lcd->height); + if (ret) + goto fail; + ret = device_property_read_u32(dev, "display-width-chars", &lcd->width); + if (ret) + goto fail; + + /* + * On displays with more than two rows, the internal buffer width is + * usually equal to the display width + */ + if (lcd->height > 2) + lcd->bwidth = lcd->width; + + /* Optional properties */ + device_property_read_u32(dev, "internal-buffer-width", &lcd->bwidth); + + lcd->ifwidth = ifwidth; + lcd->ops = ifwidth == 8 ? &hd44780_ops_gpio8 : &hd44780_ops_gpio4; + + ret = charlcd_register(lcd); + if (ret) + goto fail; + + platform_set_drvdata(pdev, lcd); + return 0; + +fail: + kfree(lcd); + return ret; +} + +static int hd44780_remove(struct platform_device *pdev) +{ + struct charlcd *lcd = platform_get_drvdata(pdev); + + charlcd_unregister(lcd); + + kfree(lcd); + return 0; +} + +static const struct of_device_id hd44780_of_match[] = { + { .compatible = "hit,hd44780" }, + { /* sentinel */ } +}; +MODULE_DEVICE_TABLE(of, hd44780_of_match); + +static struct platform_driver hd44780_driver = { + .probe = hd44780_probe, + .remove = hd44780_remove, + .driver = { + .name = "hd44780", + .of_match_table = hd44780_of_match, + }, +}; + +module_platform_driver(hd44780_driver); +MODULE_DESCRIPTION("HD44780 Character LCD driver"); +MODULE_AUTHOR("Geert Uytterhoeven <geert@linux-m68k.org>"); +MODULE_LICENSE("GPL"); |