There is single LED that can be turned on and off by the user, or set to
be controlled by the charger in 2 different modes.

The driver initializes the LED to be controlled by the charger, but
allows to switch it to user control, and change the mode of charging
indication via a sysfs.

The driver was developed on AXP813, but should work on other PMICs like
that without changes.

Signed-off-by: Ondrej Jirman <redacted>
---
  drivers/leds/Kconfig       |   7 ++
  drivers/leds/Makefile      |   1 +
  drivers/leds/leds-axp20x.c | 240 +++++++++++++++++++++++++++++++++++++
  drivers/mfd/axp20x.c       |   3 +
  4 files changed, 251 insertions(+)
  create mode 100644 drivers/leds/leds-axp20x.c

diff --git a/drivers/leds/Kconfig b/drivers/leds/Kconfig
index d82f1dea37111..80a3f31f6f4c3 100644
--- a/drivers/leds/Kconfig
+++ b/drivers/leds/Kconfig

@@ -846,6 +846,13 @@ config LEDS_TPS6105X
  	  It is a single boost converter primarily for white LEDs and
  	  audio amplifiers.
  
+config LEDS_AXP20X
+	tristate "Charger LED support for AXP20X-like PMICs (AXP813, ...)"
+	depends on LEDS_CLASS && MFD_AXP20X
+	help
+	  This option enables support for on-chip LED driver on
+	  AXP20X-like PMICs.
+
  comment "LED Triggers"
  source "drivers/leds/trigger/Kconfig"
  

diff --git a/drivers/leds/Makefile b/drivers/leds/Makefile
index d7e1107753fb1..80ea1bc4744b0 100644
--- a/drivers/leds/Makefile
+++ b/drivers/leds/Makefile

@@ -86,6 +86,7 @@ obj-$(CONFIG_LEDS_TI_LMU_COMMON)	+= leds-ti-lmu-common.o
  obj-$(CONFIG_LEDS_LM3697)		+= leds-lm3697.o
  obj-$(CONFIG_LEDS_LM36274)		+= leds-lm36274.o
  obj-$(CONFIG_LEDS_TPS6105X)		+= leds-tps6105x.o
+obj-$(CONFIG_LEDS_AXP20X)		+= leds-axp20x.o
  
  # LED SPI Drivers
  obj-$(CONFIG_LEDS_CR0014114)		+= leds-cr0014114.o

diff --git a/drivers/leds/leds-axp20x.c b/drivers/leds/leds-axp20x.c
new file mode 100644
index 0000000000000..e6c9853b84d52
--- /dev/null
+++ b/drivers/leds/leds-axp20x.c

@@ -0,0 +1,240 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * LED Driver for X-Powers AXP813 PMIC and similar.
+ *
+ * Copyright(c) 2020 Ondrej Jirman <megous@megous.com>
+ */
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/platform_device.h>
+#include <linux/leds.h>
+#include <linux/slab.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/mfd/axp20x.h>
+
+#define AXP20X_CHGLED_CTRL_MASK		BIT(3)
+#define AXP20X_CHGLED_CTRL_CHARGER	BIT(3)
+#define AXP20X_CHGLED_CTRL_USER		0
+
+#define AXP20X_CHRG_CTRL2_MODE		BIT(4)
+
+#define AXP20X_CHGLED_USER_STATE_MASK		GENMASK(5, 4)
+#define AXP20X_CHGLED_USER_STATE_OFF		(0 << 4)
+#define AXP20X_CHGLED_USER_STATE_BLINK_SLOW	(1 << 4)
+#define AXP20X_CHGLED_USER_STATE_BLINK_FAST	(2 << 4)
+#define AXP20X_CHGLED_USER_STATE_ON		(3 << 4)
+
+struct axp20x_led {
+	struct led_classdev cdev;
+	struct regmap *regmap;
+};
+
+static int axp20x_led_set(struct led_classdev *led_cdev,
+			   enum led_brightness value)
+{
+	struct axp20x_led *led =
+			container_of(led_cdev, struct axp20x_led, cdev);
+	unsigned int val;
+
+	val = value == LED_OFF ? AXP20X_CHGLED_USER_STATE_OFF :
+		AXP20X_CHGLED_USER_STATE_ON;
+
+	return regmap_update_bits(led->regmap, AXP20X_OFF_CTRL,
+				  AXP20X_CHGLED_USER_STATE_MASK, val);
+
+}
+
+static ssize_t charger_control_show(struct device *dev,
+				    struct device_attribute *attr, char *buf)
+{
+	struct led_classdev *led_cdev = dev_get_drvdata(dev);
+	struct axp20x_led *led =
+		container_of(led_cdev, struct axp20x_led, cdev);
+	unsigned int val;
+	int ret;
+
+	ret = regmap_read(led->regmap, AXP20X_OFF_CTRL, &val);
+	if (ret)
+		return ret;
+
+	return scnprintf(buf, PAGE_SIZE, "%u\n",
+			 val & AXP20X_CHGLED_CTRL_MASK ? 1 : 0);
+}
+
+static ssize_t charger_control_store(struct device *dev,
+				     struct device_attribute *attr,
+				     const char *buf, size_t len)
+{
+	struct led_classdev *led_cdev = dev_get_drvdata(dev);
+	struct axp20x_led *led =
+			container_of(led_cdev, struct axp20x_led, cdev);
+	bool status;
+	int ret;
+
+	ret = kstrtobool(buf, &status);
+	if (ret)
+		return ret;
+
+	ret = regmap_update_bits(led->regmap, AXP20X_OFF_CTRL,
+				 AXP20X_CHGLED_CTRL_MASK,
+				 status ? AXP20X_CHGLED_CTRL_CHARGER :
+				 AXP20X_CHGLED_CTRL_USER);
+	if (ret)
+		return ret;
+
+	return len;
+}
+
+static ssize_t charger_mode_show(struct device *dev,
+				 struct device_attribute *attr, char *buf)
+{
+	struct led_classdev *led_cdev = dev_get_drvdata(dev);
+	struct axp20x_led *led =
+		container_of(led_cdev, struct axp20x_led, cdev);
+	unsigned int val;
+	int ret;
+
+	ret = regmap_read(led->regmap, AXP20X_CHRG_CTRL2, &val);
+	if (ret)
+		return ret;
+
+	return scnprintf(buf, PAGE_SIZE, "%u\n",
+			 val & AXP20X_CHRG_CTRL2_MODE ? 1 : 0);
+}
+
+static ssize_t charger_mode_store(struct device *dev,
+				  struct device_attribute *attr,
+				  const char *buf, size_t len)
+{
+	struct led_classdev *led_cdev = dev_get_drvdata(dev);
+	struct axp20x_led *led =
+		container_of(led_cdev, struct axp20x_led, cdev);
+	unsigned int mode;
+	int ret;
+
+	ret = kstrtouint(buf, 0, &mode);
+	if (ret)
+		return ret;
+
+	if (mode > 1)
+		return -ERANGE;
+
+	ret = regmap_update_bits(led->regmap, AXP20X_CHRG_CTRL2,
+				 AXP20X_CHRG_CTRL2_MODE,
+				 mode ? AXP20X_CHRG_CTRL2_MODE : 0);
+	if (ret)
+		return ret;
+
+	return len;
+}
+
+static DEVICE_ATTR_RW(charger_control);
+static DEVICE_ATTR_RW(charger_mode);
+
+static struct attribute *axp20x_led_attrs[] = {
+	&dev_attr_charger_control.attr,
+	&dev_attr_charger_mode.attr,
+	NULL,
+};
+
+ATTRIBUTE_GROUPS(axp20x_led);
+
+static int axp20x_led_probe(struct platform_device *pdev)
+{
+	struct axp20x_dev *axp20x;
+	struct axp20x_led *led;
+	int ret;
+
+	if (!of_device_is_available(pdev->dev.of_node))
+		return -ENODEV;
+
+	axp20x = dev_get_drvdata(pdev->dev.parent);
+	if (!axp20x)
+		return -EINVAL;
+
+	led = devm_kzalloc(&pdev->dev,
+			   sizeof(struct axp20x_led),
+			   GFP_KERNEL);
+	if (!led)
+		return -ENOMEM;
+
+	platform_set_drvdata(pdev, led);
+
+	led->regmap = axp20x->regmap;
+
+	led->cdev.name = "axp20x-chgarger-led";