platform/x86: portwell-ec: Add GPIO and WDT driver for Portwell EC

Adds a driver for the ITE Embedded Controller (EC) on Portwell boards.
It integrates with the Linux GPIO and watchdog subsystems to provide:

- Control/monitoring of up to 8 EC GPIO pins.
- Hardware watchdog timer with 1-255 second timeouts.

The driver communicates with the EC via I/O port 0xe300 and identifies
the hardware by the "PWG" firmware signature. This enables enhanced
system management for Portwell embedded/industrial platforms.

Signed-off-by: Yen-Chi Huang <jesse.huang@portwell.com.tw>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/a04be962-b207-4085-af5b-523f59bffcbc@portwell.com.tw
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

MAINTAINERS

@@ -19216,6 +19216,12 @@ S:	Maintained
 F:	drivers/pnp/
 F:	include/linux/pnp.h
 
+PORTWELL EC DRIVER
+M:	Yen-Chi Huang <jesse.huang@portwell.com.tw>
+L:	platform-driver-x86@vger.kernel.org
+S:	Maintained
+F:	drivers/platform/x86/portwell-ec.c
+
 POSIX CLOCKS and TIMERS
 M:	Anna-Maria Behnsen <anna-maria@linutronix.de>
 M:	Frederic Weisbecker <frederic@kernel.org>

drivers/platform/x86/Kconfig

@@ -779,6 +779,21 @@ config PCENGINES_APU2
 	  To compile this driver as a module, choose M here: the module
 	  will be called pcengines-apuv2.
 
+config PORTWELL_EC
+	tristate "Portwell Embedded Controller driver"
+	depends on X86 && HAS_IOPORT && WATCHDOG && GPIOLIB
+	select WATCHDOG_CORE
+	help
+	  This driver provides support for the GPIO pins and watchdog timer
+	  embedded in Portwell's EC.
+
+	  Theoretically, this driver should work on multiple Portwell platforms,
+	  but it has only been tested on the Portwell NANO-6064 board.
+	  If you encounter any issues on other boards, please report them.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called portwell-ec.
+
 config BARCO_P50_GPIO
 	tristate "Barco P50 GPIO driver for identify LED/button"
 	depends on GPIOLIB

drivers/platform/x86/Makefile

@@ -92,6 +92,9 @@ obj-$(CONFIG_XO1_RFKILL)	+= xo1-rfkill.o
 # PC Engines
 obj-$(CONFIG_PCENGINES_APU2)	+= pcengines-apuv2.o
 
+# Portwell
+obj-$(CONFIG_PORTWELL_EC)	+= portwell-ec.o
+
 # Barco
 obj-$(CONFIG_BARCO_P50_GPIO)	+= barco-p50-gpio.o
 

drivers/platform/x86/portwell-ec.c

@@ -0,0 +1,291 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * portwell-ec.c: Portwell embedded controller driver.
+ *
+ * Tested on:
+ *  - Portwell NANO-6064
+ *
+ * This driver provides support for GPIO and Watchdog Timer
+ * functionalities of the Portwell boards with ITE embedded controller (EC).
+ * The EC is accessed through I/O ports and provides:
+ *  - 8 GPIO pins for control and monitoring
+ *  - Hardware watchdog with 1-15300 second timeout range
+ *
+ * It integrates with the Linux GPIO and Watchdog subsystems, allowing
+ * userspace interaction with EC GPIO pins and watchdog control,
+ * ensuring system stability and configurability.
+ *
+ * (C) Copyright 2025 Portwell, Inc.
+ * Author: Yen-Chi Huang (jesse.huang@portwell.com.tw)
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/acpi.h>
+#include <linux/bitfield.h>
+#include <linux/dmi.h>
+#include <linux/gpio/driver.h>
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/ioport.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/sizes.h>
+#include <linux/string.h>
+#include <linux/watchdog.h>
+
+#define PORTWELL_EC_IOSPACE              0xe300
+#define PORTWELL_EC_IOSPACE_LEN          SZ_256
+
+#define PORTWELL_GPIO_PINS               8
+#define PORTWELL_GPIO_DIR_REG            0x2b
+#define PORTWELL_GPIO_VAL_REG            0x2c
+
+#define PORTWELL_WDT_EC_CONFIG_ADDR      0x06
+#define PORTWELL_WDT_CONFIG_ENABLE       0x1
+#define PORTWELL_WDT_CONFIG_DISABLE      0x0
+#define PORTWELL_WDT_EC_COUNT_MIN_ADDR   0x07
+#define PORTWELL_WDT_EC_COUNT_SEC_ADDR   0x08
+#define PORTWELL_WDT_EC_MAX_COUNT_SECOND (255 * 60)
+
+#define PORTWELL_EC_FW_VENDOR_ADDRESS    0x4d
+#define PORTWELL_EC_FW_VENDOR_LENGTH     3
+#define PORTWELL_EC_FW_VENDOR_NAME       "PWG"
+
+static bool force;
+module_param(force, bool, 0444);
+MODULE_PARM_DESC(force, "Force loading EC driver without checking DMI boardname");
+
+static const struct dmi_system_id pwec_dmi_table[] = {
+	{
+		.ident = "NANO-6064 series",
+		.matches = {
+			DMI_MATCH(DMI_BOARD_NAME, "NANO-6064"),
+		},
+	},
+	{ }
+};
+MODULE_DEVICE_TABLE(dmi, pwec_dmi_table);
+
+/* Functions for access EC via IOSPACE */
+
+static void pwec_write(u8 index, u8 data)
+{
+	outb(data, PORTWELL_EC_IOSPACE + index);
+}
+
+static u8 pwec_read(u8 address)
+{
+	return inb(PORTWELL_EC_IOSPACE + address);
+}
+
+/* GPIO functions */
+
+static int pwec_gpio_get(struct gpio_chip *chip, unsigned int offset)
+{
+	return pwec_read(PORTWELL_GPIO_VAL_REG) & BIT(offset) ? 1 : 0;
+}
+
+static int pwec_gpio_set_rv(struct gpio_chip *chip, unsigned int offset, int val)
+{
+	u8 tmp = pwec_read(PORTWELL_GPIO_VAL_REG);
+
+	if (val)
+		tmp |= BIT(offset);
+	else
+		tmp &= ~BIT(offset);
+	pwec_write(PORTWELL_GPIO_VAL_REG, tmp);
+
+	return 0;
+}
+
+static int pwec_gpio_get_direction(struct gpio_chip *chip, unsigned int offset)
+{
+	u8 direction = pwec_read(PORTWELL_GPIO_DIR_REG) & BIT(offset);
+
+	if (direction)
+		return GPIO_LINE_DIRECTION_IN;
+
+	return GPIO_LINE_DIRECTION_OUT;
+}
+
+/*
+ * Changing direction causes issues on some boards,
+ * so direction_input and direction_output are disabled for now.
+ */
+
+static int pwec_gpio_direction_input(struct gpio_chip *gc, unsigned int offset)
+{
+	return -EOPNOTSUPP;
+}
+
+static int pwec_gpio_direction_output(struct gpio_chip *gc, unsigned int offset, int value)
+{
+	return -EOPNOTSUPP;
+}
+
+static struct gpio_chip pwec_gpio_chip = {
+	.label = "portwell-ec-gpio",
+	.get_direction = pwec_gpio_get_direction,
+	.direction_input = pwec_gpio_direction_input,
+	.direction_output = pwec_gpio_direction_output,
+	.get = pwec_gpio_get,
+	.set_rv = pwec_gpio_set_rv,
+	.base = -1,
+	.ngpio = PORTWELL_GPIO_PINS,
+};
+
+/* Watchdog functions */
+
+static void pwec_wdt_write_timeout(unsigned int timeout)
+{
+	pwec_write(PORTWELL_WDT_EC_COUNT_MIN_ADDR, timeout / 60);
+	pwec_write(PORTWELL_WDT_EC_COUNT_SEC_ADDR, timeout % 60);
+}
+
+static int pwec_wdt_trigger(struct watchdog_device *wdd)
+{
+	pwec_wdt_write_timeout(wdd->timeout);
+	pwec_write(PORTWELL_WDT_EC_CONFIG_ADDR, PORTWELL_WDT_CONFIG_ENABLE);
+
+	return 0;
+}
+
+static int pwec_wdt_start(struct watchdog_device *wdd)
+{
+	return pwec_wdt_trigger(wdd);
+}
+
+static int pwec_wdt_stop(struct watchdog_device *wdd)
+{
+	pwec_write(PORTWELL_WDT_EC_CONFIG_ADDR, PORTWELL_WDT_CONFIG_DISABLE);
+	return 0;
+}
+
+static int pwec_wdt_set_timeout(struct watchdog_device *wdd, unsigned int timeout)
+{
+	wdd->timeout = timeout;
+	pwec_wdt_write_timeout(wdd->timeout);
+
+	return 0;
+}
+
+/* Ensure consistent min/sec read in case of second rollover. */
+static unsigned int pwec_wdt_get_timeleft(struct watchdog_device *wdd)
+{
+	u8 sec, min, old_min;
+
+	do {
+		old_min = pwec_read(PORTWELL_WDT_EC_COUNT_MIN_ADDR);
+		sec = pwec_read(PORTWELL_WDT_EC_COUNT_SEC_ADDR);
+		min = pwec_read(PORTWELL_WDT_EC_COUNT_MIN_ADDR);
+	} while (min != old_min);
+
+	return min * 60 + sec;
+}
+
+static const struct watchdog_ops pwec_wdt_ops = {
+	.owner = THIS_MODULE,
+	.start = pwec_wdt_start,
+	.stop = pwec_wdt_stop,
+	.ping = pwec_wdt_trigger,
+	.set_timeout = pwec_wdt_set_timeout,
+	.get_timeleft = pwec_wdt_get_timeleft,
+};
+
+static struct watchdog_device ec_wdt_dev = {
+	.info = &(struct watchdog_info){
+		.options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
+		.identity = "Portwell EC watchdog",
+	},
+	.ops = &pwec_wdt_ops,
+	.timeout = 60,
+	.min_timeout = 1,
+	.max_timeout = PORTWELL_WDT_EC_MAX_COUNT_SECOND,
+};
+
+static int pwec_firmware_vendor_check(void)
+{
+	u8 buf[PORTWELL_EC_FW_VENDOR_LENGTH + 1];
+	u8 i;
+
+	for (i = 0; i < PORTWELL_EC_FW_VENDOR_LENGTH; i++)
+		buf[i] = pwec_read(PORTWELL_EC_FW_VENDOR_ADDRESS + i);
+	buf[PORTWELL_EC_FW_VENDOR_LENGTH] = '\0';
+
+	return !strcmp(PORTWELL_EC_FW_VENDOR_NAME, buf) ? 0 : -ENODEV;
+}
+
+static int pwec_probe(struct platform_device *pdev)
+{
+	int ret;
+
+	if (!devm_request_region(&pdev->dev, PORTWELL_EC_IOSPACE,
+				PORTWELL_EC_IOSPACE_LEN, dev_name(&pdev->dev))) {
+		dev_err(&pdev->dev, "failed to get IO region\n");
+		return -EBUSY;
+	}
+
+	ret = pwec_firmware_vendor_check();
+	if (ret < 0)
+		return ret;
+
+	ret = devm_gpiochip_add_data(&pdev->dev, &pwec_gpio_chip, NULL);
+	if (ret < 0) {
+		dev_err(&pdev->dev, "failed to register Portwell EC GPIO\n");
+		return ret;
+	}
+
+	ret = devm_watchdog_register_device(&pdev->dev, &ec_wdt_dev);
+	if (ret < 0) {
+		dev_err(&pdev->dev, "failed to register Portwell EC Watchdog\n");
+		return ret;
+	}
+
+	return 0;
+}
+
+static struct platform_driver pwec_driver = {
+	.driver = {
+		.name = "portwell-ec",
+	},
+	.probe = pwec_probe,
+};
+
+static struct platform_device *pwec_dev;
+
+static int __init pwec_init(void)
+{
+	int ret;
+
+	if (!dmi_check_system(pwec_dmi_table)) {
+		if (!force)
+			return -ENODEV;
+		pr_warn("force load portwell-ec without DMI check\n");
+	}
+
+	ret = platform_driver_register(&pwec_driver);
+	if (ret)
+		return ret;
+
+	pwec_dev = platform_device_register_simple("portwell-ec", -1, NULL, 0);
+	if (IS_ERR(pwec_dev)) {
+		platform_driver_unregister(&pwec_driver);
+		return PTR_ERR(pwec_dev);
+	}
+
+	return 0;
+}
+
+static void __exit pwec_exit(void)
+{
+	platform_device_unregister(pwec_dev);
+	platform_driver_unregister(&pwec_driver);
+}
+
+module_init(pwec_init);
+module_exit(pwec_exit);
+
+MODULE_AUTHOR("Yen-Chi Huang <jesse.huang@portwell.com.tw>");
+MODULE_DESCRIPTION("Portwell EC Driver");
+MODULE_LICENSE("GPL");