[PATCH v5 4/5] gpio: aaeon: Add GPIO driver for SRG-IMX8P MCU

["Thomas Perrot (Schneider Electric)" <thomas.perrot@bootlin.com>]

Add GPIO driver for the Aaeon SRG-IMX8P embedded controller. This
driver supports 7 GPO (General Purpose Output) pins and 12 GPIO pins
that can be configured as inputs or outputs.

The driver implements proper state management for GPO pins (which are
output-only) and full direction control for GPIO pins. During probe,
all pins are reset to a known state (GPOs low, GPIOs as inputs) to
prevent undefined behavior across system reboots, as the MCU does not
reset GPIO states on soft reboot.

Co-developed-by: Jérémie Dautheribes (Schneider Electric) <jeremie.dautheribes@bootlin.com>
Signed-off-by: Jérémie Dautheribes (Schneider Electric) <jeremie.dautheribes@bootlin.com>
Acked-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>
Reviewed-by: Linus Walleij <linusw@kernel.org>
Signed-off-by: Thomas Perrot (Schneider Electric) <thomas.perrot@bootlin.com>
---
 MAINTAINERS                   |   1 +
 drivers/gpio/Kconfig          |   9 ++
 drivers/gpio/Makefile         |   1 +
 drivers/gpio/gpio-aaeon-mcu.c | 229 ++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 240 insertions(+)

diff --git a/MAINTAINERS b/MAINTAINERS
index f91b6a1826d0..2538f8c4bc14 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -191,6 +191,7 @@ M:	Thomas Perrot <thomas.perrot@bootlin.com>
 R:	Jérémie Dautheribes <jeremie.dautheribes@bootlin.com>
 S:	Maintained
 F:	Documentation/devicetree/bindings/mfd/aaeon,srg-imx8p-mcu.yaml
+F:	drivers/gpio/gpio-aaeon-mcu.c
 F:	drivers/mfd/aaeon-mcu.c
 F:	include/linux/mfd/aaeon-mcu.h
 
diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index c74da29253e8..4b37b5a15958 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -157,6 +157,15 @@ config GPIO_74XX_MMIO
 	    8 bits:	74244 (Input), 74273 (Output)
 	    16 bits:	741624 (Input), 7416374 (Output)
 
+config GPIO_AAEON_MCU
+	tristate "Aaeon MCU GPIO support"
+	depends on MFD_AAEON_MCU
+	help
+	  Select this option to enable GPIO support for the Aaeon SRG-IMX8P
+	  onboard MCU. This driver provides access to GPIO pins and GPO
+	  (General Purpose Output) pins controlled by the microcontroller.
+	  The driver handles both input and output configuration.
+
 config GPIO_ALTERA
 	tristate "Altera GPIO"
 	select GPIOLIB_IRQCHIP
diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
index 2421a8fd3733..1ba6318bc558 100644
--- a/drivers/gpio/Makefile
+++ b/drivers/gpio/Makefile
@@ -29,6 +29,7 @@ obj-$(CONFIG_GPIO_104_IDI_48)		+= gpio-104-idi-48.o
 obj-$(CONFIG_GPIO_104_IDIO_16)		+= gpio-104-idio-16.o
 obj-$(CONFIG_GPIO_74X164)		+= gpio-74x164.o
 obj-$(CONFIG_GPIO_74XX_MMIO)		+= gpio-74xx-mmio.o
+obj-$(CONFIG_GPIO_AAEON_MCU)		+= gpio-aaeon-mcu.o
 obj-$(CONFIG_GPIO_ADNP)			+= gpio-adnp.o
 obj-$(CONFIG_GPIO_ADP5520)		+= gpio-adp5520.o
 obj-$(CONFIG_GPIO_ADP5585)		+= gpio-adp5585.o
diff --git a/drivers/gpio/gpio-aaeon-mcu.c b/drivers/gpio/gpio-aaeon-mcu.c
new file mode 100644
index 000000000000..a37d3dc83795
--- /dev/null
+++ b/drivers/gpio/gpio-aaeon-mcu.c
@@ -0,0 +1,229 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Aaeon MCU GPIO driver
+ *
+ * Copyright (C) 2026 Bootlin
+ * Author: Jérémie Dautheribes <jeremie.dautheribes@bootlin.com>
+ * Author: Thomas Perrot <thomas.perrot@bootlin.com>
+ */
+
+#include <linux/bitops.h>
+#include <linux/gpio/driver.h>
+#include <linux/mfd/aaeon-mcu.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+
+#define AAEON_MCU_CONFIG_GPIO_INPUT	0x69
+#define AAEON_MCU_CONFIG_GPIO_OUTPUT	0x6F
+#define AAEON_MCU_READ_GPIO		0x72
+#define AAEON_MCU_WRITE_GPIO		0x77
+
+#define AAEON_MCU_CONTROL_GPO		0x6C
+
+#define MAX_GPIOS	12
+#define MAX_GPOS	7
+
+struct aaeon_mcu_gpio {
+	struct gpio_chip gc;
+	struct regmap *regmap;
+	DECLARE_BITMAP(dir_in, MAX_GPOS + MAX_GPIOS);
+	DECLARE_BITMAP(gpo_state, MAX_GPOS);
+};
+
+static int aaeon_mcu_gpio_config_input_cmd(struct aaeon_mcu_gpio *data,
+					   unsigned int offset)
+{
+	return regmap_write(data->regmap,
+			    AAEON_MCU_REG(AAEON_MCU_CONFIG_GPIO_INPUT, offset - 7),
+			    0);
+}
+
+static int aaeon_mcu_gpo_set_cmd(struct aaeon_mcu_gpio *data, unsigned int offset, int value)
+{
+	return regmap_write(data->regmap,
+			    AAEON_MCU_REG(AAEON_MCU_CONTROL_GPO, offset + 1),
+			    !!value);
+}
+
+static int aaeon_mcu_gpio_direction_input(struct gpio_chip *gc, unsigned int offset)
+{
+	struct aaeon_mcu_gpio *data = gpiochip_get_data(gc);
+	int ret;
+
+	if (offset < MAX_GPOS) {
+		dev_err(gc->parent,
+			"offset %d is a GPO (output-only) pin, cannot be configured as input\n",
+			offset);
+		return -EOPNOTSUPP;
+	}
+
+	ret = aaeon_mcu_gpio_config_input_cmd(data, offset);
+	if (ret < 0)
+		return ret;
+
+	__set_bit(offset, data->dir_in);
+
+	return 0;
+}
+
+static int aaeon_mcu_gpio_config_output_cmd(struct aaeon_mcu_gpio *data,
+					    unsigned int offset,
+					    int value)
+{
+	int ret;
+
+	ret = regmap_write(data->regmap,
+			   AAEON_MCU_REG(AAEON_MCU_CONFIG_GPIO_OUTPUT, offset - 7),
+			   0);
+	if (ret < 0)
+		return ret;
+
+	return regmap_write(data->regmap,
+			    AAEON_MCU_REG(AAEON_MCU_WRITE_GPIO, offset - 7),
+			    !!value);
+}
+
+static int aaeon_mcu_gpio_direction_output(struct gpio_chip *gc, unsigned int offset, int value)
+{
+	struct aaeon_mcu_gpio *data = gpiochip_get_data(gc);
+	int ret;
+
+	if (offset < MAX_GPOS) {
+		ret = aaeon_mcu_gpo_set_cmd(data, offset, value);
+		if (ret)
+			return ret;
+		__assign_bit(offset, data->gpo_state, value);
+		return 0;
+	}
+
+	ret = aaeon_mcu_gpio_config_output_cmd(data, offset, value);
+	if (ret < 0)
+		return ret;
+
+	__clear_bit(offset, data->dir_in);
+
+	return 0;
+}
+
+static int aaeon_mcu_gpio_get_direction(struct gpio_chip *gc, unsigned int offset)
+{
+	struct aaeon_mcu_gpio *data = gpiochip_get_data(gc);
+
+	return test_bit(offset, data->dir_in) ?
+		GPIO_LINE_DIRECTION_IN : GPIO_LINE_DIRECTION_OUT;
+}
+
+static int aaeon_mcu_gpio_get(struct gpio_chip *gc, unsigned int offset)
+{
+	struct aaeon_mcu_gpio *data = gpiochip_get_data(gc);
+	unsigned int rsp;
+	int ret;
+
+	if (offset < MAX_GPOS)
+		return test_bit(offset, data->gpo_state);
+
+	ret = regmap_read(data->regmap,
+			  AAEON_MCU_REG(AAEON_MCU_READ_GPIO, offset - 7),
+			  &rsp);
+	if (ret < 0)
+		return ret;
+
+	return rsp;
+}
+
+static int aaeon_mcu_gpio_set_cmd(struct aaeon_mcu_gpio *data, unsigned int offset, int value)
+{
+	return regmap_write(data->regmap,
+			    AAEON_MCU_REG(AAEON_MCU_WRITE_GPIO, offset - 7),
+			    !!value);
+}
+
+static int aaeon_mcu_gpio_set(struct gpio_chip *gc, unsigned int offset,
+			      int value)
+{
+	struct aaeon_mcu_gpio *data = gpiochip_get_data(gc);
+	int ret;
+
+	if (offset >= MAX_GPOS)
+		return aaeon_mcu_gpio_set_cmd(data, offset, value);
+
+	ret = aaeon_mcu_gpo_set_cmd(data, offset, value);
+	if (ret)
+		return ret;
+	__assign_bit(offset, data->gpo_state, value);
+	return 0;
+}
+
+static const struct gpio_chip aaeon_mcu_chip = {
+	.label			= "gpio-aaeon-mcu",
+	.owner			= THIS_MODULE,
+	.get_direction		= aaeon_mcu_gpio_get_direction,
+	.direction_input	= aaeon_mcu_gpio_direction_input,
+	.direction_output	= aaeon_mcu_gpio_direction_output,
+	.get			= aaeon_mcu_gpio_get,
+	.set			= aaeon_mcu_gpio_set,
+	.base			= -1,
+	.ngpio			= MAX_GPOS + MAX_GPIOS,
+	.can_sleep		= true,
+};
+
+static void aaeon_mcu_gpio_reset(struct aaeon_mcu_gpio *data, struct device *dev)
+{
+	unsigned int i;
+	int ret;
+
+	/* Reset all GPOs */
+	for (i = 0; i < MAX_GPOS; i++) {
+		ret = aaeon_mcu_gpo_set_cmd(data, i, 0);
+		if (ret < 0)
+			dev_warn(dev, "Failed to reset GPO %u state: %d\n", i, ret);
+		__clear_bit(i, data->dir_in);
+	}
+
+	/* Reset all GPIOs */
+	for (i = MAX_GPOS; i < MAX_GPOS + MAX_GPIOS; i++) {
+		ret = aaeon_mcu_gpio_config_input_cmd(data, i);
+		if (ret < 0)
+			dev_warn(dev, "Failed to reset GPIO %u state: %d\n", i, ret);
+		__set_bit(i, data->dir_in);
+	}
+}
+
+static int aaeon_mcu_gpio_probe(struct platform_device *pdev)
+{
+	struct aaeon_mcu_gpio *data;
+
+	data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	data->regmap = dev_get_regmap(pdev->dev.parent, NULL);
+	if (!data->regmap)
+		return -ENODEV;
+
+	data->gc = aaeon_mcu_chip;
+	data->gc.parent = pdev->dev.parent;
+
+	/*
+	 * Reset all GPIO states to a known configuration. The MCU does not
+	 * reset GPIO state on soft reboot, only on power cycle (hard reboot).
+	 * Without this reset, GPIOs would retain their previous state across
+	 * reboots, which could lead to unexpected behavior.
+	 */
+	aaeon_mcu_gpio_reset(data, &pdev->dev);
+
+	return devm_gpiochip_add_data(&pdev->dev, &data->gc, data);
+}
+
+static struct platform_driver aaeon_mcu_gpio_driver = {
+	.driver = {
+		.name = "aaeon-mcu-gpio",
+	},
+	.probe = aaeon_mcu_gpio_probe,
+};
+module_platform_driver(aaeon_mcu_gpio_driver);
+
+MODULE_DESCRIPTION("GPIO interface for Aaeon MCU");
+MODULE_AUTHOR("Jérémie Dautheribes <jeremie.dautheribes@bootlin.com>");
+MODULE_LICENSE("GPL");

-- 
2.53.0