[PATCH v7 13/13] video: backlight: mt6370: Add MediaTek MT6370 support

[ChiaEn Wu <peterwu.pub@gmail.com>]

From: ChiaEn Wu <chiaen_wu@richtek.com>

MediaTek MT6370 is a SubPMIC consisting of a single cell battery charger
with ADC monitoring, RGB LEDs, dual channel flashlight, WLED backlight
driver, display bias voltage supply, one general purpose LDO, and the
USB Type-C & PD controller complies with the latest USB Type-C and PD
standards.

Add a support for the MediaTek MT6370 backlight driver.
It controls 4 channels of 8 series WLEDs in
2048 (only for MT6370/MT6371) / 16384 (only for MT6372)
current steps (30 mA) in exponential or linear mapping curves.

Signed-off-by: ChiaEn Wu <chiaen_wu@richtek.com>
---

v7
- Add support 'exponential mode' property parsing
- Add 'return dev_err_probe()' after 'if (IS_ERR(priv->enable_gpio))'
- Add 'mt6372' compatible string
- Revise Kconfig help text
- Revise update()/get() for supporting 16384 steps (MT6372)
- Revise all shift usages form using 'ffs() and fls()' to defining the
  _SHIFT macros.
- Revise 'brightness ? 1 : 0' to '!!brightness' in gpiod_set_value()
---
 drivers/video/backlight/Kconfig            |  13 ++
 drivers/video/backlight/Makefile           |   1 +
 drivers/video/backlight/mt6370-backlight.c | 351 +++++++++++++++++++++++++++++
 3 files changed, 365 insertions(+)
 create mode 100644 drivers/video/backlight/mt6370-backlight.c

diff --git a/drivers/video/backlight/Kconfig b/drivers/video/backlight/Kconfig
index a003e02..936ba1e 100644
--- a/drivers/video/backlight/Kconfig
+++ b/drivers/video/backlight/Kconfig
@@ -268,6 +268,19 @@ config BACKLIGHT_MAX8925
 	  If you have a LCD backlight connected to the WLED output of MAX8925
 	  WLED output, say Y here to enable this driver.
 
+config BACKLIGHT_MT6370
+	tristate "MediaTek MT6370 Backlight Driver"
+	depends on MFD_MT6370
+	help
+	  This enables support for Mediatek MT6370 Backlight driver.
+	  It's commonly used to drive the display WLED. There are 4 channels
+	  inside, and each channel supports up to 30mA of current capability
+	  with 2048 current steps (only for MT6370/MT6371) or 16384 current
+	  steps (only for MT6372) in exponential or linear mapping curves.
+
+	  This driver can also be built as a module. If so, the module
+	  will be called "mt6370-backlight".
+
 config BACKLIGHT_APPLE
 	tristate "Apple Backlight Driver"
 	depends on X86 && ACPI
diff --git a/drivers/video/backlight/Makefile b/drivers/video/backlight/Makefile
index cae2c83..e815f3f 100644
--- a/drivers/video/backlight/Makefile
+++ b/drivers/video/backlight/Makefile
@@ -44,6 +44,7 @@ obj-$(CONFIG_BACKLIGHT_LP855X)		+= lp855x_bl.o
 obj-$(CONFIG_BACKLIGHT_LP8788)		+= lp8788_bl.o
 obj-$(CONFIG_BACKLIGHT_LV5207LP)	+= lv5207lp.o
 obj-$(CONFIG_BACKLIGHT_MAX8925)		+= max8925_bl.o
+obj-$(CONFIG_BACKLIGHT_MT6370)		+= mt6370-backlight.o
 obj-$(CONFIG_BACKLIGHT_OMAP1)		+= omap1_bl.o
 obj-$(CONFIG_BACKLIGHT_PANDORA)		+= pandora_bl.o
 obj-$(CONFIG_BACKLIGHT_PCF50633)	+= pcf50633-backlight.o
diff --git a/drivers/video/backlight/mt6370-backlight.c b/drivers/video/backlight/mt6370-backlight.c
new file mode 100644
index 0000000..4c889b4
--- /dev/null
+++ b/drivers/video/backlight/mt6370-backlight.c
@@ -0,0 +1,351 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2022 Richtek Technology Corp.
+ *
+ * Author: ChiaEn Wu <chiaen_wu@richtek.com>
+ */
+
+#include <linux/backlight.h>
+#include <linux/bitfield.h>
+#include <linux/bits.h>
+#include <linux/gpio/consumer.h>
+#include <linux/kernel.h>
+#include <linux/minmax.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+
+#define MT6370_REG_DEV_INFO		0x100
+#define MT6370_REG_BL_EN		0x1A0
+#define MT6370_REG_BL_BSTCTRL		0x1A1
+#define MT6370_REG_BL_PWM		0x1A2
+#define MT6370_REG_BL_DIM2		0x1A4
+
+#define MT6370_VENID_MASK		GENMASK(7, 4)
+#define MT6370_BL_EXT_EN_MASK		BIT(7)
+#define MT6370_BL_EN_MASK		BIT(6)
+#define MT6370_BL_CODE_MASK		BIT(0)
+#define MT6370_BL_CH_MASK		GENMASK(5, 2)
+#define MT6370_BL_CH_SHIFT		2
+#define MT6370_BL_DIM2_COMMON_MASK	GENMASK(2, 0)
+#define MT6370_BL_DIM2_COMMON_SHIFT	3
+#define MT6370_BL_DIM2_6372_MASK	GENMASK(5, 0)
+#define MT6370_BL_DIM2_6372_SHIFT	6
+#define MT6370_BL_PWM_EN_MASK		BIT(7)
+#define MT6370_BL_PWM_HYS_EN_MASK	BIT(2)
+#define MT6370_BL_PWM_HYS_SEL_MASK	GENMASK(1, 0)
+#define MT6370_BL_OVP_EN_MASK		BIT(7)
+#define MT6370_BL_OVP_SEL_MASK		GENMASK(6, 5)
+#define MT6370_BL_OVP_SEL_SHIFT		5
+#define MT6370_BL_OC_EN_MASK		BIT(3)
+#define MT6370_BL_OC_SEL_MASK		GENMASK(2, 1)
+#define MT6370_BL_OC_SEL_SHIFT		1
+
+#define MT6370_BL_PWM_HYS_TH_MIN_STEP	1
+#define MT6370_BL_PWM_HYS_TH_MAX_STEP	64
+#define MT6370_BL_OVP_MIN_UV		17000000
+#define MT6370_BL_OVP_MAX_UV		29000000
+#define MT6370_BL_OVP_STEP_UV		4000000
+#define MT6370_BL_OCP_MIN_UA		900000
+#define MT6370_BL_OCP_MAX_UA		1800000
+#define MT6370_BL_OCP_STEP_UA		300000
+#define MT6370_BL_MAX_COMMON_BRIGHTNESS	2048
+#define MT6370_BL_MAX_6372_BRIGHTNESS	16384
+#define MT6370_BL_MAX_CH		15
+
+enum {
+	MT6370_VID_COMMON = 1,
+	MT6370_VID_6372,
+};
+
+struct mt6370_priv {
+	u8 dim2_mask;
+	u8 dim2_shift;
+	int def_max_brightness;
+	struct backlight_device *bl;
+	struct device *dev;
+	struct gpio_desc *enable_gpio;
+	struct regmap *regmap;
+};
+
+static int mt6370_bl_update_status(struct backlight_device *bl_dev)
+{
+	struct mt6370_priv *priv = bl_get_data(bl_dev);
+	int brightness = backlight_get_brightness(bl_dev);
+	unsigned int enable_val;
+	u8 brightness_val[2];
+	int ret;
+
+	if (brightness) {
+		brightness_val[0] = (brightness - 1) & priv->dim2_mask;
+		brightness_val[1] = (brightness - 1) >> priv->dim2_shift;
+
+		ret = regmap_raw_write(priv->regmap, MT6370_REG_BL_DIM2,
+				       brightness_val, sizeof(brightness_val));
+		if (ret)
+			return ret;
+	}
+
+	gpiod_set_value(priv->enable_gpio, !!brightness);
+
+	enable_val = brightness ? MT6370_BL_EN_MASK : 0;
+	return regmap_update_bits(priv->regmap, MT6370_REG_BL_EN,
+				  MT6370_BL_EN_MASK, enable_val);
+}
+
+static int mt6370_bl_get_brightness(struct backlight_device *bl_dev)
+{
+	struct mt6370_priv *priv = bl_get_data(bl_dev);
+	unsigned int enable;
+	u8 brightness_val[2];
+	int brightness, ret;
+
+	ret = regmap_read(priv->regmap, MT6370_REG_BL_EN, &enable);
+	if (ret)
+		return ret;
+
+	if (!(enable & MT6370_BL_EN_MASK))
+		return 0;
+
+	ret = regmap_raw_read(priv->regmap, MT6370_REG_BL_DIM2,
+			      brightness_val, sizeof(brightness_val));
+	if (ret)
+		return ret;
+
+	brightness = brightness_val[1] << priv->dim2_shift;
+	brightness += brightness_val[0] & priv->dim2_mask;
+
+	return brightness + 1;
+}
+
+static const struct backlight_ops mt6370_bl_ops = {
+	.options = BL_CORE_SUSPENDRESUME,
+	.update_status = mt6370_bl_update_status,
+	.get_brightness = mt6370_bl_get_brightness,
+};
+
+static int mt6370_init_backlight_properties(struct mt6370_priv *priv,
+					    struct backlight_properties *props)
+{
+	struct device *dev = priv->dev;
+	u8 prop_val;
+	u32 brightness, ovp_uV, ocp_uA;
+	unsigned int mask, val;
+	int ret;
+
+	/* Vendor optional properties */
+	val = 0;
+	if (device_property_read_bool(dev, "mediatek,bled-pwm-enable"))
+		val |= MT6370_BL_PWM_EN_MASK;
+
+	if (device_property_read_bool(dev, "mediatek,bled-pwm-hys-enable"))
+		val |= MT6370_BL_PWM_HYS_EN_MASK;
+
+	ret = device_property_read_u8(dev,
+				      "mediatek,bled-pwm-hys-input-th-steps",
+				      &prop_val);
+	if (!ret) {
+		prop_val = clamp_val(prop_val,
+				     MT6370_BL_PWM_HYS_TH_MIN_STEP,
+				     MT6370_BL_PWM_HYS_TH_MAX_STEP);
+		prop_val = prop_val <= 1 ? 0 :
+			   prop_val <= 4 ? 1 :
+			   prop_val <= 16 ? 2 : 3;
+		val |= prop_val;
+	}
+
+	ret = regmap_update_bits(priv->regmap, MT6370_REG_BL_PWM,
+				 val, val);
+	if (ret)
+		return ret;
+
+	val = 0;
+	if (device_property_read_bool(dev, "mediatek,bled-ovp-shutdown"))
+		val |= MT6370_BL_OVP_EN_MASK;
+
+	ret = device_property_read_u32(dev, "mediatek,bled-ovp-microvolt",
+				       &ovp_uV);
+	if (!ret) {
+		ovp_uV = clamp_val(ovp_uV, MT6370_BL_OVP_MIN_UV,
+				   MT6370_BL_OVP_MAX_UV);
+		ovp_uV = DIV_ROUND_UP(ovp_uV - MT6370_BL_OVP_MIN_UV,
+				      MT6370_BL_OVP_STEP_UV);
+		val |= ovp_uV << MT6370_BL_OVP_SEL_SHIFT;
+	}
+
+	if (device_property_read_bool(dev, "mediatek,bled-ocp-shutdown"))
+		val |= MT6370_BL_OC_EN_MASK;
+
+	ret = device_property_read_u32(dev, "mediatek,bled-ocp-microamp",
+				       &ocp_uA);
+	if (!ret) {
+		ocp_uA = clamp_val(ocp_uA, MT6370_BL_OCP_MIN_UA,
+				   MT6370_BL_OCP_MAX_UA);
+		ocp_uA = DIV_ROUND_UP(ocp_uA - MT6370_BL_OCP_MIN_UA,
+				      MT6370_BL_OCP_STEP_UA);
+		val |= ocp_uA << MT6370_BL_OC_SEL_SHIFT;
+	}
+
+	ret = regmap_update_bits(priv->regmap, MT6370_REG_BL_BSTCTRL,
+				 val, val);
+	if (ret)
+		return ret;
+
+	/* Common properties */
+	ret = device_property_read_u32(dev, "max-brightness", &brightness);
+	if (ret)
+		brightness = priv->def_max_brightness;
+
+	props->max_brightness = min_t(u32, brightness, priv->def_max_brightness);
+
+	ret = device_property_read_u32(dev, "default-brightness", &brightness);
+	if (ret)
+		brightness = props->max_brightness;
+
+	props->brightness = min_t(u32, brightness, props->max_brightness);
+
+	val = 0;
+	if (device_property_read_bool(dev, "mediatek,bled-exponential-mode-enable")) {
+		val |= MT6370_BL_CODE_MASK;
+		props->scale = BACKLIGHT_SCALE_NON_LINEAR;
+	} else
+		props->scale = BACKLIGHT_SCALE_LINEAR;
+
+	ret = device_property_read_u8(dev, "mediatek,bled-channel-use",
+				      &prop_val);
+	if (ret) {
+		dev_err(dev, "mediatek,bled-channel-use DT property missing\n");
+		return ret;
+	}
+
+	if (!prop_val || prop_val > MT6370_BL_MAX_CH) {
+		dev_err(dev,
+			"No channel specified or over than upper bound (%d)\n",
+			prop_val);
+		return -EINVAL;
+	}
+
+	mask = MT6370_BL_EXT_EN_MASK | MT6370_BL_CH_MASK;
+	val |= prop_val << MT6370_BL_CH_SHIFT;
+
+	if (priv->enable_gpio)
+		val |= MT6370_BL_EXT_EN_MASK;
+
+	return regmap_update_bits(priv->regmap, MT6370_REG_BL_EN, mask, val);
+}
+
+static int mt6370_check_vendor_info(struct mt6370_priv *priv)
+{
+	/*
+	 * MT6372 uses 14 bits to control the brightness but MT6370 and MT6371
+	 * use 11 bits. They are different so we have to use this function to
+	 * check the vendor ID and use different mask, shift and default
+	 * maxiimum brightness value.
+	 */
+	unsigned int dev_info, hw_vid, of_vid;
+	int ret;
+
+	ret = regmap_read(priv->regmap, MT6370_REG_DEV_INFO, &dev_info);
+	if (ret)
+		return ret;
+
+	of_vid = (uintptr_t)of_device_get_match_data(priv->dev);
+	hw_vid = FIELD_GET(MT6370_VENID_MASK, dev_info);
+	hw_vid = hw_vid == 0x9 || hw_vid == 0xb ? MT6370_VID_6372 : MT6370_VID_COMMON;
+	if (hw_vid != of_vid) {
+		dev_err(priv->dev, "Buggy DT, wrong compatible string\n");
+		return -EINVAL;
+	}
+
+	if (hw_vid == MT6370_VID_6372) {
+		priv->dim2_mask = MT6370_BL_DIM2_6372_MASK;
+		priv->dim2_shift = MT6370_BL_DIM2_6372_SHIFT;
+		priv->def_max_brightness = MT6370_BL_MAX_6372_BRIGHTNESS;
+	} else {
+		priv->dim2_mask = MT6370_BL_DIM2_COMMON_MASK;
+		priv->dim2_shift = MT6370_BL_DIM2_COMMON_SHIFT;
+		priv->def_max_brightness = MT6370_BL_MAX_COMMON_BRIGHTNESS;
+	}
+
+	return 0;
+}
+
+static int mt6370_bl_probe(struct platform_device *pdev)
+{
+	struct backlight_properties props = {
+		.type = BACKLIGHT_RAW,
+	};
+	struct device *dev = &pdev->dev;
+	struct mt6370_priv *priv;
+	int ret;
+
+	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	priv->dev = dev;
+
+	priv->regmap = dev_get_regmap(dev->parent, NULL);
+	if (!priv->regmap)
+		return dev_err_probe(dev, -ENODEV, "Failed to get regmap\n");
+
+	ret = mt6370_check_vendor_info(priv);
+	if (ret)
+		return dev_err_probe(dev, ret, "Failed to check vendor info\n");
+
+	priv->enable_gpio = devm_gpiod_get_optional(dev, "enable",
+						    GPIOD_OUT_HIGH);
+	if (IS_ERR(priv->enable_gpio))
+		return dev_err_probe(dev, PTR_ERR(priv->enable_gpio),
+				     "Failed to get 'enable' gpio\n");
+
+	ret = mt6370_init_backlight_properties(priv, &props);
+	if (ret)
+		return dev_err_probe(dev, ret,
+				     "Failed to init backlight properties\n");
+
+	priv->bl = devm_backlight_device_register(dev, pdev->name, dev, priv,
+						  &mt6370_bl_ops, &props);
+	if (IS_ERR(priv->bl))
+		return dev_err_probe(dev, PTR_ERR(priv->bl),
+				     "Failed to register backlight\n");
+
+	backlight_update_status(priv->bl);
+	platform_set_drvdata(pdev, priv);
+
+	return 0;
+}
+
+static int mt6370_bl_remove(struct platform_device *pdev)
+{
+	struct mt6370_priv *priv = platform_get_drvdata(pdev);
+	struct backlight_device *bl_dev = priv->bl;
+
+	bl_dev->props.brightness = 0;
+	backlight_update_status(priv->bl);
+
+	return 0;
+}
+
+static const struct of_device_id __maybe_unused mt6370_bl_of_match[] = {
+	{ .compatible = "mediatek,mt6370-backlight", .data = (void *)MT6370_VID_COMMON },
+	{ .compatible = "mediatek,mt6372-backlight", .data = (void *)MT6370_VID_6372 },
+	{}
+};
+MODULE_DEVICE_TABLE(of, mt6370_bl_of_match);
+
+static struct platform_driver mt6370_bl_driver = {
+	.driver = {
+		.name = "mt6370-backlight",
+		.of_match_table = mt6370_bl_of_match,
+	},
+	.probe = mt6370_bl_probe,
+	.remove = mt6370_bl_remove,
+};
+module_platform_driver(mt6370_bl_driver);
+
+MODULE_AUTHOR("ChiaEn Wu <chiaen_wu@richtek.com>");
+MODULE_DESCRIPTION("MediaTek MT6370 Backlight Driver");
+MODULE_LICENSE("GPL v2");
-- 
2.7.4