[PATCH v2 21/21] gpio: add GPIO controller found on Waveshare DSI TOUCH panels

Dmitry Baryshkov
2026-04-11T12:11:35Z

The Waveshare DSI TOUCH family of panels has separate on-board GPIO
controller, which controls power supplies to the panel and the touch
screen and provides reset pins for both the panel and the touchscreen.
Also it provides a simple PWM controller for panel backlight. Add
support for this GPIO controller.

Tested-by: Riccardo Mereu <r.mereu@arduino.cc>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
---
drivers/gpio/Kconfig | 10 ++
drivers/gpio/Makefile | 1 +
drivers/gpio/gpio-waveshare-dsi.c | 208 ++++++++++++++++++++++++++++++++++++++
3 files changed, 219 insertions(+)

diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index dbe7c6e63eab..1b210c451151 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -805,6 +805,16 @@ config GPIO_VISCONTI
help
Say yes here to support GPIO on Tohisba Visconti.

+config GPIO_WAVESHARE_DSI_TOUCH
+ tristate "Waveshare GPIO controller for DSI panels"
+ depends on BACKLIGHT_CLASS_DEVICE
+ depends on I2C
+ select REGMAP_I2C
+ help
+ Enable support for the GPIO and PWM controller found on Waveshare DSI
+ TOUCH panel kits. It provides GPIOs (used for regulator control and
+ resets) and backlight support.
+
config GPIO_WCD934X
tristate "Qualcomm Technologies Inc WCD9340/WCD9341 GPIO controller driver"
depends on MFD_WCD934X
diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
index 20d4a57afdaa..75ce89fc3b93 100644
--- a/drivers/gpio/Makefile
+++ b/drivers/gpio/Makefile
@@ -207,6 +207,7 @@ obj-$(CONFIG_GPIO_VIRTUSER) += gpio-virtuser.o
obj-$(CONFIG_GPIO_VIRTIO) += gpio-virtio.o
obj-$(CONFIG_GPIO_VISCONTI) += gpio-visconti.o
obj-$(CONFIG_GPIO_VX855) += gpio-vx855.o
+obj-$(CONFIG_GPIO_WAVESHARE_DSI_TOUCH) += gpio-waveshare-dsi.o
obj-$(CONFIG_GPIO_WCD934X) += gpio-wcd934x.o
obj-$(CONFIG_GPIO_WHISKEY_COVE) += gpio-wcove.o
obj-$(CONFIG_GPIO_WINBOND) += gpio-winbond.o
diff --git a/drivers/gpio/gpio-waveshare-dsi.c b/drivers/gpio/gpio-waveshare-dsi.c
new file mode 100644
index 000000000000..f4a1d4d3b872
--- /dev/null
+++ b/drivers/gpio/gpio-waveshare-dsi.c
@@ -0,0 +1,208 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2024 Waveshare International Limited
+ * Copyright (c) Qualcomm Technologies, Inc. and/or its subsidiaries.
+ */
+
+#include <linux/backlight.h>
+#include <linux/err.h>
+#include <linux/fb.h>
+#include <linux/gpio/driver.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/regmap.h>
+
+/* I2C registers of the microcontroller. */
+#define REG_TP 0x94
+#define REG_LCD 0x95
+#define REG_PWM 0x96
+#define REG_SIZE 0x97
+#define REG_ID 0x98
+#define REG_VERSION 0x99
+
+enum {
+ GPIO_AVDD = 0,
+ GPIO_PANEL_RESET = 1,
+ GPIO_BL_ENABLE = 2,
+ GPIO_IOVCC = 4,
+ GPIO_VCC = 8,
+ GPIO_TS_RESET = 9,
+};
+
+#define NUM_GPIO 16
+
+struct waveshare_gpio {
+ struct mutex dir_lock;
+ struct mutex pwr_lock;
+ struct regmap *regmap;
+ u16 poweron_state;
+
+ struct gpio_chip gc;
+};
+
+static const struct regmap_config waveshare_gpio_regmap_config = {
+ .reg_bits = 8,
+ .val_bits = 8,
+ .max_register = REG_PWM,
+};
+
+static int waveshare_gpio_get(struct waveshare_gpio *state, unsigned int offset)
+{
+ u16 pwr_state;
+
+ guard(mutex)(&state->pwr_lock);
+ pwr_state = state->poweron_state & BIT(offset);
+
+ return !!pwr_state;
+}
+
+static int waveshare_gpio_set(struct waveshare_gpio *state, unsigned int offset, int value)
+{
+ u16 last_val;
+ int err;
+
+ guard(mutex)(&state->pwr_lock);
+
+ last_val = state->poweron_state;
+ if (value)
+ last_val |= BIT(offset);
+ else
+ last_val &= ~BIT(offset);
+
+ state->poweron_state = last_val;
+
+ err = regmap_write(state->regmap, REG_TP, last_val >> 8);
+ if (!err)
+ err = regmap_write(state->regmap, REG_LCD, last_val & 0xff);
+
+ return err;
+}
+
+static int waveshare_gpio_gpio_get_direction(struct gpio_chip *gc, unsigned int offset)
+{
+ return GPIO_LINE_DIRECTION_OUT;
+}
+
+static int waveshare_gpio_gpio_get(struct gpio_chip *gc, unsigned int offset)
+{
+ struct waveshare_gpio *state = gpiochip_get_data(gc);
+
+ return waveshare_gpio_get(state, offset);
+}
+
+static int waveshare_gpio_gpio_set(struct gpio_chip *gc, unsigned int offset, int value)
+{
+ struct waveshare_gpio *state = gpiochip_get_data(gc);
+
+ return waveshare_gpio_set(state, offset, value);
+}
+
+static int waveshare_gpio_update_status(struct backlight_device *bl)
+{
+ struct waveshare_gpio *state = bl_get_data(bl);
+ int brightness = backlight_get_brightness(bl);
+
+ waveshare_gpio_set(state, GPIO_BL_ENABLE, brightness);
+
+ return regmap_write(state->regmap, REG_PWM, brightness);
+}
+
+static const struct backlight_ops waveshare_gpio_bl = {
+ .update_status = waveshare_gpio_update_status,
+};
+
+static int waveshare_gpio_probe(struct i2c_client *i2c)
+{
+ struct backlight_properties props = {};
+ struct waveshare_gpio *state;
+ struct device *dev = &i2c->dev;
+ struct backlight_device *bl;
+ struct regmap *regmap;
+ unsigned int data;
+ int ret;
+
+ state = devm_kzalloc(dev, sizeof(*state), GFP_KERNEL);
+ if (!state)
+ return -ENOMEM;
+
+ ret = devm_mutex_init(dev, &state->dir_lock);
+ if (ret)
+ return ret;
+
+ ret = devm_mutex_init(dev, &state->pwr_lock);
+ if (ret)
+ return ret;
+
+ regmap = devm_regmap_init_i2c(i2c, &waveshare_gpio_regmap_config);
+ if (IS_ERR(regmap))
+ return dev_err_probe(dev, PTR_ERR(regmap), "Failed to allocate register map\n");
+
+ state->regmap = regmap;
+ i2c_set_clientdata(i2c, state);
+
+ ret = regmap_read(regmap, REG_ID, &data);
+ if (ret < 0)
+ return dev_err_probe(dev, ret, "Failed to read register\n");
+
+ dev_dbg(dev, "waveshare panel hw id = 0x%x\n", data);
+
+ ret = regmap_read(regmap, REG_SIZE, &data);
+ if (ret < 0)
+ return dev_err_probe(dev, ret, "Failed to read register\n");
+
+ dev_dbg(dev, "waveshare panel size = %d\n", data);
+
+ ret = regmap_read(regmap, REG_VERSION, &data);
+ if (ret < 0)
+ return dev_err_probe(dev, ret, "Failed to read register\n");
+
+ dev_dbg(dev, "waveshare panel mcu version = 0x%x\n", data);
+
+ ret = waveshare_gpio_set(state, GPIO_TS_RESET, 1);
+ if (ret)
+ return dev_err_probe(dev, ret, "Failed to program GPIOs\n");
+
+ msleep(20);
+
+ state->gc.parent = dev;
+ state->gc.label = i2c->name;
+ state->gc.owner = THIS_MODULE;
+ state->gc.base = -1;
+ state->gc.ngpio = NUM_GPIO;
+
+ /* it is output only */
+ state->gc.get = waveshare_gpio_gpio_get;
+ state->gc.set = waveshare_gpio_gpio_set;
+ state->gc.get_direction = waveshare_gpio_gpio_get_direction;
+ state->gc.can_sleep = true;
+
+ ret = devm_gpiochip_add_data(dev, &state->gc, state);
+ if (ret)
+ return dev_err_probe(dev, ret, "Failed to create gpiochip\n");
+
+ props.type = BACKLIGHT_RAW;
+ props.max_brightness = 255;
+ props.brightness = 255;
+ bl = devm_backlight_device_register(dev, dev_name(dev), dev, state,
+ &waveshare_gpio_bl, &props);
+ return PTR_ERR_OR_ZERO(bl);
+}
+
+static const struct of_device_id waveshare_gpio_dt_ids[] = {
+ { .compatible = "waveshare,dsi-touch-gpio" },
+ {},
+};
+MODULE_DEVICE_TABLE(of, waveshare_gpio_dt_ids);
+
+static struct i2c_driver waveshare_gpio_regulator_driver = {
+ .driver = {
+ .name = "waveshare-regulator",
+ .of_match_table = of_match_ptr(waveshare_gpio_dt_ids),
+ },
+ .probe = waveshare_gpio_probe,
+};
+
+module_i2c_driver(waveshare_gpio_regulator_driver);
+
+MODULE_DESCRIPTION("GPIO controller driver for Waveshare DSI touch panels");
+MODULE_LICENSE("GPL");

--
2.47.3