Re: [PATCH 5/8] Add Advantech EIO Backlight driver

---
 MAINTAINERS                      |   1 +
 drivers/video/backlight/Kconfig  |   6 +
 drivers/video/backlight/Makefile |   1 +
 drivers/video/backlight/eio_bl.c | 268 +++++++++++++++++++++++++++++++++++++++
 4 files changed, 276 insertions(+)

diff --git a/MAINTAINERS b/MAINTAINERS
index be9d3c4e1ce1..df4b4cc31257 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS

@@ -623,6 +623,7 @@ F:	drivers/gpio/gpio-eio.c
 F:	drivers/hwmon/eio-hwmon.c
 F:	drivers/i2c/busses/i2c-eio.c
 F:	drivers/mfd/eio_core.c
+F:	drivers/video/backlight/eio_bl.c
 F:	include/linux/mfd/eio.h

 ADXL313 THREE-AXIS DIGITAL ACCELEROMETER DRIVER

diff --git a/drivers/video/backlight/Kconfig b/drivers/video/backlight/Kconfig
index a1422ddd1c22..ddd3d6922553 100644
--- a/drivers/video/backlight/Kconfig
+++ b/drivers/video/backlight/Kconfig

@@ -496,6 +496,12 @@ config BACKLIGHT_RAVE_SP
 	help
 	  Support for backlight control on RAVE SP device.

+config BACKLIGHT_EIO
+	tristate "Advantech EIO Backlight"
+	depends on MFD_EIO && BACKLIGHT_CLASS_DEVICE
+	help
+	  Backlight driver for Advantech EIO.
+
 config BACKLIGHT_LED
 	tristate "Generic LED based Backlight Driver"
 	depends on LEDS_CLASS && OF

diff --git a/drivers/video/backlight/Makefile b/drivers/video/backlight/Makefile
index a5d62b018102..4601b644b6d4 100644
--- a/drivers/video/backlight/Makefile
+++ b/drivers/video/backlight/Makefile

@@ -30,6 +30,7 @@ obj-$(CONFIG_BACKLIGHT_BD6107)		+= bd6107.o
 obj-$(CONFIG_BACKLIGHT_CLASS_DEVICE)	+= backlight.o
 obj-$(CONFIG_BACKLIGHT_DA903X)		+= da903x_bl.o
 obj-$(CONFIG_BACKLIGHT_DA9052)		+= da9052_bl.o
+obj-$(CONFIG_BACKLIGHT_EIO)		+= eio_bl.o
 obj-$(CONFIG_BACKLIGHT_EP93XX)		+= ep93xx_bl.o
 obj-$(CONFIG_BACKLIGHT_GPIO)		+= gpio_backlight.o
 obj-$(CONFIG_BACKLIGHT_HP680)		+= hp680_bl.o

diff --git a/drivers/video/backlight/eio_bl.c b/drivers/video/backlight/eio_bl.c
new file mode 100644
index 000000000000..2b9fd4d48d30
--- /dev/null
+++ b/drivers/video/backlight/eio_bl.c

@@ -0,0 +1,268 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Backlight driver for Advantech EIO Embedded controller.
+ *
+ * Copyright (C) 2025 Advantech Corporation. All rights reserved.
+ */
+
+#include <linux/backlight.h>
+#include <linux/errno.h>
+#include <linux/mfd/core.h>
+#include <linux/mfd/eio.h>
+#include <linux/module.h>
+#include <linux/uaccess.h>
+
+#define PMC_BL_WRITE		0x20
+#define PMC_BL_READ		0x21
+
+#define BL_CTRL_STATUS		0x00
+#define BL_CTRL_ENABLE		0x12
+#define BL_CTRL_ENABLE_INVERT	0x13
+#define BL_CTRL_DUTY		0x14
+#define BL_CTRL_INVERT		0x15
+#define BL_CTRL_FREQ		0x16
+
+#define BL_MAX			2
+
+#define BL_STATUS_AVAIL		0x01
+#define BL_ENABLE_OFF		0x00
+#define BL_ENABLE_ON		0x01
+#define BL_ENABLE_AUTO		BIT(1)
+
+#define USE_DEFAULT		-1
+#define THERMAL_MAX		100
+
+#define BL_AVAIL		BIT(0)
+#define BL_PWM_DC		BIT(1)
+#define BL_PWM_SRC		BIT(2)
+#define BL_BRI_INVERT		BIT(3)
+#define BL_ENABLE_PIN_SUPP	BIT(4)
+#define BL_POWER_INVERT		BIT(5)
+#define BL_ENABLE_PIN_EN	BIT(6)
+#define BL_FIRMWARE_ERROR	BIT(7)

+
+static uint bri_freq = USE_DEFAULT;
+module_param(bri_freq, uint, 0444);
+MODULE_PARM_DESC(bri_freq, "Setup backlight PWM frequency.\n");
+
+static int bri_invert = USE_DEFAULT;
+module_param(bri_invert, int, 0444);
+MODULE_PARM_DESC(bri_invert, "Setup backlight PWM polarity.\n");
+
+static int bl_power_invert = USE_DEFAULT;
+module_param(bl_power_invert, int, 0444);
+MODULE_PARM_DESC(bl_power_invert, "Setup backlight enable pin polarity.\n");
+
+static int timeout;
+module_param(timeout, int, 0444);
+MODULE_PARM_DESC(timeout, "Set PMC command timeout value.\n");

+
+struct eio_bl_dev {
+	struct device *mfd;
+	u8 id;
+	u8 max;

+};
+
+static int pmc_write(struct device *mfd, u8 ctrl, u8 dev_id, void *data)
+{
+	struct pmc_op op = {
+		.cmd       = PMC_BL_WRITE,
+		.control   = ctrl,
+		.device_id = dev_id,
+		.payload   = (u8 *)data,
+		.size      = (ctrl == BL_CTRL_FREQ) ? 4 : 1,
+		.timeout   = timeout,
+	};
+
+	return eio_core_pmc_operation(mfd, &op);
+}
+
+static int pmc_read(struct device *mfd, u8 ctrl, u8 dev_id, void *data)
+{
+	struct pmc_op op = {
+		.cmd       = PMC_BL_READ,
+		.control   = ctrl,
+		.device_id = dev_id,
+		.payload   = (u8 *)data,
+		.size      = (ctrl == BL_CTRL_FREQ) ? 4 : 1,
+		.timeout   = timeout,
+	};
+
+	return eio_core_pmc_operation(mfd, &op);
+}
+
+static int bl_update_status(struct backlight_device *bl)
+{
+	struct eio_bl_dev *eio_bl = bl_get_data(bl);
+	u32 max  = bl->props.max_brightness;
+	u8 duty = clamp_val(bl->props.brightness, 0, max);
+	u8 sw = bl->props.power == BACKLIGHT_POWER_OFF;

+	int ret;
+
+	/* Setup PWM duty */
+	ret = pmc_write(eio_bl->mfd, BL_CTRL_DUTY, eio_bl->id, &duty);
+	if (ret)
+		return ret;
+
+	/* Setup backlight enable pin */
+	return pmc_write(eio_bl->mfd, BL_CTRL_ENABLE, eio_bl->id, &sw);
+}
+
+static int bl_get_brightness(struct backlight_device *bl)
+{
+	struct eio_bl_dev *eio_bl = bl_get_data(bl);
+	u8 duty = 0;
+	int ret;
+
+	ret = pmc_read(eio_bl->mfd, BL_CTRL_DUTY, eio_bl->id, &duty);
+
+	if (ret)
+		return ret;
+
+	return duty;
+}
+
+static const struct backlight_ops bl_ops = {
+	.get_brightness = bl_get_brightness,
+	.update_status	= bl_update_status,
+	.options	= BL_CORE_SUSPENDRESUME,
+};
+
+static int bl_init(struct device *dev, int id,
+		   struct backlight_properties *props)
+{
+	int ret;
+	u8 enabled = 0;
+	u8 status = 0;
+
+	/* Check EC-supported backlight */
+	ret = pmc_read(dev, BL_CTRL_STATUS, id, &status);
+	if (ret)
+		return ret;
+
+	if (!(status & BL_STATUS_AVAIL)) {
+		dev_dbg(dev, "eio_bl%d hardware report disabled.\n", id);
+		return -ENXIO;

+	}
+
+	ret = pmc_read(dev, BL_CTRL_DUTY, id, &props->brightness);
+	if (ret)
+		return ret;
+
+	/* Invert PWM */
+	dev_dbg(dev, "bri_invert=%d\n", bri_invert);

+	if (bri_invert > USE_DEFAULT) {
+		ret = pmc_write(dev, BL_CTRL_INVERT, id, &bri_invert);
+		if (ret)
+			return ret;
+	}
+
+	bri_invert = 0;
+	ret = pmc_read(dev, BL_CTRL_INVERT, id, &bri_invert);
+	if (ret)
+		return ret;

+
+	dev_dbg(dev, "bri_freq=%u\n", bri_freq);
+	if (bri_freq != USE_DEFAULT) {
+		ret = pmc_write(dev, BL_CTRL_FREQ, id, &bri_freq);
+		if (ret)
+			return ret;
+	}
+
+	ret = pmc_read(dev, BL_CTRL_FREQ, id, &bri_freq);
+	if (ret)
+		return ret;
+
+	dev_dbg(dev, "bl_power_invert=%d\n", bl_power_invert);
+	if (bl_power_invert >= USE_DEFAULT) {
+		ret = pmc_write(dev, BL_CTRL_ENABLE_INVERT, id, &bl_power_invert);
+		if (ret)
+			return ret;
+	}
+
+	bl_power_invert = 0;
+	ret = pmc_read(dev, BL_CTRL_ENABLE_INVERT, id, &bl_power_invert);
+	if (ret)
+		return ret;
+
+	/* Read power state */
+	ret = pmc_read(dev, BL_CTRL_ENABLE, id, &enabled);
+	if (ret)
+		return ret;
+
+	props->power = enabled ? BACKLIGHT_POWER_OFF : BACKLIGHT_POWER_ON;
+
+	return 0;
+}
+
+static int bl_probe(struct platform_device *pdev)
+{
+	u8 id;
+	struct device *dev = &pdev->dev;
+	struct eio_dev *eio_dev = dev_get_drvdata(dev->parent);
+
+	if (!eio_dev) {
+		dev_err(dev, "eio_core not present\n");
+		return -ENODEV;
+	}
+
+	for (id = 0; id < BL_MAX; id++) {
+		char name[32];
+		struct backlight_properties props;
+		struct eio_bl_dev *eio_bl;
+		struct backlight_device *bl;
+		int ret;
+
+		memset(&props, 0, sizeof(props));
+		props.type           = BACKLIGHT_RAW;
+		props.max_brightness = THERMAL_MAX;
+		props.power          = BACKLIGHT_POWER_OFF;
+		props.brightness     = props.max_brightness;

+
+		eio_bl = devm_kzalloc(dev, sizeof(*eio_bl), GFP_KERNEL);
+		if (!eio_bl)
+			return -ENOMEM;
+
+		eio_bl->mfd = dev->parent;
+		eio_bl->id  = id;
+		eio_bl->max = props.max_brightness;
+
+		ret = bl_init(eio_bl->mfd, id, &props);
+		if (ret) {
+			dev_info(dev, "%d No Backlight %u enabled!\n", ret, id);
+			continue;
+		}

+
+		snprintf(name, sizeof(name), "%s%u", pdev->name, id);
+
+		bl = devm_backlight_device_register(dev, name, dev, eio_bl,
+						    &bl_ops, &props);
+
+		if (IS_ERR(bl)) {
+			ret = PTR_ERR(bl);
+			if (ret == -EPROBE_DEFER)
+				return ret;
+
+			dev_err(dev, "register %s failed: %d\n", name, ret);
+			continue;
+		}
+
+		dev_info(dev, "%s registered (max=%u)\n", name, props.max_brightness);

+	}
+
+	return 0;
+}
+
+static struct platform_driver bl_driver = {
+	.probe  = bl_probe,
+	.driver = {
+		.name = "eio_bl",
+	},
+};
+
+module_platform_driver(bl_driver);
+
+MODULE_AUTHOR("Wenkai Chung <wenkai.chung@advantech.com.tw>");
+MODULE_AUTHOR("Ramiro Oliveira <ramiro.oliveira@advantech.com>");
+MODULE_DESCRIPTION("Backlight driver for Advantech EIO embedded controller");
+MODULE_LICENSE("GPL");