[PATCH v9 10/10] video: backlight: mt6370: Add MediaTek MT6370 support

ChiaEn Wu
2022-08-30T03:44:00Z

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 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.

Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: ChiaEn Wu <chiaen_wu@richtek.com>
---

v9
- Revise the format of the comments.
---
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..623d4f2
--- /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/platform_device.h>
+#include <linux/property.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)
+{
+ /*
+ * Because MT6372 uses 14 bits to control the brightness,
+ * MT6370 and MT6371 use 11 bits. This function is used
+ * to check the vendor's ID and set the relative hardware
+ * mask, shift and default maximum brightness value that
+ * should be used.
+ */
+ 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)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)
+ return dev_err_probe(priv->dev, -EINVAL,
+ "Buggy DT, wrong compatible string\n");
+
+ 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 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