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// 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/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);
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");
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