leds: Add AAEON UP board LED driver

Add support for LEDs on AAEON UP boards. These leds are managed by the
onboard FPGA:
- UP boards: yellow, green, red
- UP Squared boards: blue, yellow, green, red

Based on the work done by Gary Wang <garywang@aaeon.com.tw>, largely
rewritten.

Signed-off-by: Thomas Richard <thomas.richard@bootlin.com>
Link: https://lore.kernel.org/r/20241211-aaeon-up-board-pinctrl-support-v1-2-24719be27631@bootlin.com
Signed-off-by: Lee Jones <lee@kernel.org>

drivers/leds/Kconfig

@@ -817,6 +817,15 @@ config LEDS_SC27XX_BLTC
 	  This driver can also be built as a module. If so the module will be
 	  called leds-sc27xx-bltc.
 
+config LEDS_UPBOARD
+	tristate "LED support for the UP board"
+	depends on LEDS_CLASS && MFD_UPBOARD_FPGA
+	help
+	  This option enables support for the UP board LEDs.
+
+	  This driver can also be built as a module. If so the module will be
+	  called leds-upboard.
+
 comment "LED driver for blink(1) USB RGB LED is under Special HID drivers (HID_THINGM)"
 
 config LEDS_BLINKM

drivers/leds/Makefile

@@ -89,6 +89,7 @@ obj-$(CONFIG_LEDS_TI_LMU_COMMON)	+= leds-ti-lmu-common.o
 obj-$(CONFIG_LEDS_TLC591XX)		+= leds-tlc591xx.o
 obj-$(CONFIG_LEDS_TPS6105X)		+= leds-tps6105x.o
 obj-$(CONFIG_LEDS_TURRIS_OMNIA)		+= leds-turris-omnia.o
+obj-$(CONFIG_LEDS_UPBOARD)		+= leds-upboard.o
 obj-$(CONFIG_LEDS_WM831X_STATUS)	+= leds-wm831x-status.o
 obj-$(CONFIG_LEDS_WM8350)		+= leds-wm8350.o
 obj-$(CONFIG_LEDS_WRAP)			+= leds-wrap.o

drivers/leds/leds-upboard.c

@@ -0,0 +1,126 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * UP board LED driver.
+ *
+ * Copyright (c) AAEON. All rights reserved.
+ * Copyright (C) 2024 Bootlin
+ *
+ * Author: Gary Wang <garywang@aaeon.com.tw>
+ * Author: Thomas Richard <thomas.richard@bootlin.com>
+ */
+
+#include <linux/device.h>
+#include <linux/container_of.h>
+#include <linux/leds.h>
+#include <linux/mfd/upboard-fpga.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+
+#define led_cdev_to_led_upboard(c)	container_of(c, struct upboard_led, cdev)
+
+struct upboard_led {
+	struct regmap_field *field;
+	struct led_classdev cdev;
+};
+
+struct upboard_led_profile {
+	const char *name;
+	unsigned int bit;
+};
+
+static struct upboard_led_profile upboard_up_led_profile[] = {
+	{ "upboard:yellow:" LED_FUNCTION_STATUS, 0 },
+	{ "upboard:green:" LED_FUNCTION_STATUS, 1 },
+	{ "upboard:red:" LED_FUNCTION_STATUS, 2 },
+};
+
+static struct upboard_led_profile upboard_up2_led_profile[] = {
+	{ "upboard:blue:" LED_FUNCTION_STATUS, 0 },
+	{ "upboard:yellow:" LED_FUNCTION_STATUS, 1 },
+	{ "upboard:green:" LED_FUNCTION_STATUS, 2 },
+	{ "upboard:red:" LED_FUNCTION_STATUS, 3 },
+};
+
+static enum led_brightness upboard_led_brightness_get(struct led_classdev *cdev)
+{
+	struct upboard_led *led = led_cdev_to_led_upboard(cdev);
+	int brightness, ret;
+
+	ret = regmap_field_read(led->field, &brightness);
+
+	return ret ? LED_OFF : brightness;
+};
+
+static int upboard_led_brightness_set(struct led_classdev *cdev, enum led_brightness brightness)
+{
+	struct upboard_led *led = led_cdev_to_led_upboard(cdev);
+
+	return regmap_field_write(led->field, brightness != LED_OFF);
+};
+
+static int upboard_led_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct upboard_fpga *fpga = dev_get_drvdata(dev->parent);
+	struct upboard_led_profile *led_profile;
+	struct upboard_led *led;
+	int led_instances, ret, i;
+
+	switch (fpga->fpga_data->type) {
+	case UPBOARD_UP_FPGA:
+		led_profile = upboard_up_led_profile;
+		led_instances = ARRAY_SIZE(upboard_up_led_profile);
+		break;
+	case UPBOARD_UP2_FPGA:
+		led_profile = upboard_up2_led_profile;
+		led_instances = ARRAY_SIZE(upboard_up2_led_profile);
+		break;
+	default:
+		return dev_err_probe(dev, -EINVAL, "Unknown device type %d\n",
+				     fpga->fpga_data->type);
+	}
+
+	for (i = 0; i < led_instances; i++) {
+		const struct reg_field fldconf = {
+			.reg = UPBOARD_REG_FUNC_EN0,
+			.lsb = led_profile[i].bit,
+			.msb = led_profile[i].bit,
+		};
+
+		led = devm_kzalloc(dev, sizeof(*led), GFP_KERNEL);
+		if (!led)
+			return -ENOMEM;
+
+		led->field = devm_regmap_field_alloc(&pdev->dev, fpga->regmap, fldconf);
+		if (IS_ERR(led->field))
+			return PTR_ERR(led->field);
+
+		led->cdev.brightness_get = upboard_led_brightness_get;
+		led->cdev.brightness_set_blocking = upboard_led_brightness_set;
+		led->cdev.max_brightness = LED_ON;
+
+		led->cdev.name = led_profile[i].name;
+
+		ret = devm_led_classdev_register(dev, &led->cdev);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+
+static struct platform_driver upboard_led_driver = {
+	.driver = {
+		.name = "upboard-leds",
+	},
+	.probe = upboard_led_probe,
+};
+
+module_platform_driver(upboard_led_driver);
+
+MODULE_AUTHOR("Gary Wang <garywang@aaeon.com.tw>");
+MODULE_AUTHOR("Thomas Richard <thomas.richard@bootlin.com>");
+MODULE_DESCRIPTION("UP Board LED driver");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:upboard-led");