[PATCH v5 2/2] backlight: ktz8866: Add support for Kinetic KTZ8866 backlight

Jianhua Lu
2023-01-17T15:47:18Z

Add support for Kinetic KTZ8866 backlight, which is used in
Xiaomi tablet, Mi Pad 5 series. This driver lightly based on
downstream implementation [1].
[1] https://github.com/MiCode/Xiaomi_Kernel_OpenSource/blob/elish-r-oss/drivers/video/backlight/ktz8866.c

Signed-off-by: Jianhua Lu <lujianhua000@gmail.com>
---
Changes in v2:
- Add missing staitc modifier to ktz8866_write function.

Changes in v3:
- Add 2022 to Copyright line.
- Sort headers.
- Remove meaningless comment.
- Use definitions instead of hardcoding.
- Add missing maintainer info.

Changes in v4:
- Change 2022 to 2023.
- Remove useless macro and enum.
- Describe settings by devicetree.
- Move header file to C file.
Changes in v5:
- Change "2023" to "2022, 2023" in Copyright line.
- Set scale property for backlight.

MAINTAINERS | 6 +
drivers/video/backlight/Kconfig | 8 ++
drivers/video/backlight/Makefile | 1 +
drivers/video/backlight/ktz8866.c | 201 ++++++++++++++++++++++++++++++
4 files changed, 216 insertions(+)
create mode 100644 drivers/video/backlight/ktz8866.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 42fc47c6edfd..2084e74e1b58 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -11674,6 +11674,12 @@ M: John Hawley <warthog9@eaglescrag.net>
S: Maintained
F: tools/testing/ktest

+KTZ8866 BACKLIGHT DRIVER
+M: Jianhua Lu <lujianhua000@gmail.com>
+S: Maintained
+F: Documentation/devicetree/bindings/leds/backlight/kinetic,ktz8866.yaml
+F: drivers/video/backlight/ktz8866.c
+
L3MDEV
M: David Ahern <dsahern@kernel.org>
L: netdev@vger.kernel.org
diff --git a/drivers/video/backlight/Kconfig b/drivers/video/backlight/Kconfig
index 936ba1e4d35e..2845fd7e33ad 100644
--- a/drivers/video/backlight/Kconfig
+++ b/drivers/video/backlight/Kconfig
@@ -190,6 +190,14 @@ config BACKLIGHT_KTD253
which is a 1-wire GPIO-controlled backlight found in some mobile
phones.

+config BACKLIGHT_KTZ8866
+ tristate "Backlight Driver for Kinetic KTZ8866"
+ depends on I2C
+ select REGMAP_I2C
+ help
+ Say Y to enabled the backlight driver for the Kinetic KTZ8866
+ found in Xiaomi Mi Pad 5 series.
+
config BACKLIGHT_LM3533
tristate "Backlight Driver for LM3533"
depends on MFD_LM3533
diff --git a/drivers/video/backlight/Makefile b/drivers/video/backlight/Makefile
index e815f3f1deff..f70a819c304c 100644
--- a/drivers/video/backlight/Makefile
+++ b/drivers/video/backlight/Makefile
@@ -36,6 +36,7 @@ obj-$(CONFIG_BACKLIGHT_HP680) += hp680_bl.o
obj-$(CONFIG_BACKLIGHT_HP700) += jornada720_bl.o
obj-$(CONFIG_BACKLIGHT_IPAQ_MICRO) += ipaq_micro_bl.o
obj-$(CONFIG_BACKLIGHT_KTD253) += ktd253-backlight.o
+obj-$(CONFIG_BACKLIGHT_KTZ8866) += ktz8866.o
obj-$(CONFIG_BACKLIGHT_LM3533) += lm3533_bl.o
obj-$(CONFIG_BACKLIGHT_LM3630A) += lm3630a_bl.o
obj-$(CONFIG_BACKLIGHT_LM3639) += lm3639_bl.o
diff --git a/drivers/video/backlight/ktz8866.c b/drivers/video/backlight/ktz8866.c
new file mode 100644
index 000000000000..02d9be6e9df2
--- /dev/null
+++ b/drivers/video/backlight/ktz8866.c
@@ -0,0 +1,201 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Backlight driver for the Kinetic KTZ8866
+ *
+ * Copyright (C) 2022, 2023 Jianhua Lu <lujianhua000@gmail.com>
+ */
+
+#include <linux/backlight.h>
+#include <linux/delay.h>
+#include <linux/err.h>
+#include <linux/i2c.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/regmap.h>
+
+#define DEFAULT_BRIGHTNESS 1500
+#define MAX_BRIGHTNESS 2047
+#define REG_MAX 0x15
+
+/* reg */
+#define DEVICE_ID 0x01
+#define BL_CFG1 0x02
+#define BL_CFG2 0x03
+#define BL_BRT_LSB 0x04
+#define BL_BRT_MSB 0x05
+#define BL_EN 0x08
+#define LCD_BIAS_CFG1 0x09
+#define LCD_BIAS_CFG2 0x0A
+#define LCD_BIAS_CFG3 0x0B
+#define LCD_BOOST_CFG 0x0C
+#define OUTP_CFG 0x0D
+#define OUTN_CFG 0x0E
+#define FLAG 0x0F
+#define BL_OPTION1 0x10
+#define BL_OPTION2 0x11
+#define PWM2DIG_LSBs 0x12
+#define PWM2DIG_MSBs 0x13
+#define BL_DIMMING 0x14
+#define PWM_RAMP_TIME 0x15
+
+/* definition */
+#define BL_EN_BIT BIT(6)
+#define LCD_BIAS_EN 0x9F
+#define PWM_HYST 0x5
+
+struct ktz8866 {
+ struct i2c_client *client;
+ struct regmap *regmap;
+ bool led_on;
+};
+
+static const struct regmap_config ktz8866_regmap_config = {
+ .reg_bits = 8,
+ .val_bits = 8,
+ .max_register = REG_MAX,
+};
+
+static int ktz8866_write(struct ktz8866 *ktz, unsigned int reg,
+ unsigned int val)
+{
+ return regmap_write(ktz->regmap, reg, val);
+}
+
+static int ktz8866_update_bits(struct ktz8866 *ktz, unsigned int reg,
+ unsigned int mask, unsigned int val)
+{
+ return regmap_update_bits(ktz->regmap, reg, mask, val);
+}
+
+static int ktz8866_backlight_update_status(struct backlight_device *backlight_dev)
+{
+ struct ktz8866 *ktz = bl_get_data(backlight_dev);
+ unsigned int brightness = backlight_get_brightness(backlight_dev);
+
+ if (!ktz->led_on && brightness > 0) {
+ ktz8866_update_bits(ktz, BL_EN, BL_EN_BIT, BL_EN_BIT);
+ ktz->led_on = true;
+ } else if (brightness == 0) {
+ ktz8866_update_bits(ktz, BL_EN, BL_EN_BIT, 0);
+ ktz->led_on = false;
+ msleep(10);
+ }
+
+ /* Set brightness */
+ ktz8866_write(ktz, BL_BRT_LSB, brightness & 0x7);
+ ktz8866_write(ktz, BL_BRT_MSB, (brightness >> 3) & 0xFF);
+
+ return 0;
+}
+
+static const struct backlight_ops ktz8866_backlight_ops = {
+ .options = BL_CORE_SUSPENDRESUME,
+ .update_status = ktz8866_backlight_update_status,
+};
+
+static void ktz8866_init(struct ktz8866 *ktz)
+{
+ unsigned int val;
+
+ if(of_property_read_u32(ktz->client->dev.of_node, "current-num-sinks", &val))
+ ktz8866_write(ktz, BL_EN, BIT(val) - 1);
+ else
+ /* Enable all 6 current sinks if the number of current sinks isn't specifed. */
+ ktz8866_write(ktz, BL_EN, BIT(6) - 1);
+
+ if(of_property_read_u32(ktz->client->dev.of_node, "current-ramping-time-us", &val)) {
+ if(val <= 128) {
+ ktz8866_write(ktz, BL_CFG2, BIT(7) | (ilog2(val) << 3) | PWM_HYST);
+ } else {
+ ktz8866_write(ktz, BL_CFG2, BIT(7) | ((5 + val / 64) << 3) | PWM_HYST);
+ }
+ }
+
+ if(of_property_read_u32(ktz->client->dev.of_node, "led-ramping-time-us", &val)) {
+ unsigned int ramp_off_time = ilog2(val) + 1;
+ unsigned int ramp_on_time = ramp_off_time << 4;
+ ktz8866_write(ktz, BL_DIMMING, ramp_on_time | ramp_off_time);
+ }
+
+ if(of_property_read_bool(ktz->client->dev.of_node, "enable-lcd-bias"))
+ ktz8866_write(ktz, LCD_BIAS_CFG1, LCD_BIAS_EN);
+}
+
+static int ktz8866_probe(struct i2c_client *client,
+ const struct i2c_device_id *id)
+{
+ struct backlight_device *backlight_dev;
+ struct backlight_properties props;
+ struct ktz8866 *ktz;
+
+ ktz = devm_kzalloc(&client->dev, sizeof(*ktz), GFP_KERNEL);
+ if (!ktz)
+ return -ENOMEM;
+
+ ktz->client = client;
+ ktz->regmap = devm_regmap_init_i2c(client, &ktz8866_regmap_config);
+
+ if (IS_ERR(ktz->regmap)) {
+ dev_err(&client->dev, "failed to init regmap\n");
+ return PTR_ERR(ktz->regmap);
+ }
+
+ memset(&props, 0, sizeof(props));
+ props.type = BACKLIGHT_RAW;
+ props.max_brightness = MAX_BRIGHTNESS;
+ props.brightness = DEFAULT_BRIGHTNESS;
+ props.scale = BACKLIGHT_SCALE_LINEAR;
+
+ backlight_dev = devm_backlight_device_register(
+ &client->dev, "ktz8866-backlight", &client->dev, ktz,
+ &ktz8866_backlight_ops, &props);
+
+ if (IS_ERR(backlight_dev)) {
+ dev_err(&client->dev, "failed to register backlight device\n");
+ return PTR_ERR(backlight_dev);
+ }
+
+ ktz8866_init(ktz);
+
+ i2c_set_clientdata(client, backlight_dev);
+ backlight_update_status(backlight_dev);
+
+ return 0;
+}
+
+static void ktz8866_remove(struct i2c_client *client)
+{
+ struct backlight_device *backlight_dev = i2c_get_clientdata(client);
+
+ backlight_dev->props.brightness = 0;
+ backlight_update_status(backlight_dev);
+}
+
+static const struct i2c_device_id ktz8866_ids[] = {
+ { "ktz8866", 0 },
+ {},
+};
+MODULE_DEVICE_TABLE(i2c, ktz8866_ids);
+
+static const struct of_device_id ktz8866_match_table[] = {
+ {
+ .compatible = "kinetic,ktz8866",
+ },
+ {},
+};
+
+static struct i2c_driver ktz8866_driver = {
+ .driver = {
+ .name = "ktz8866",
+ .of_match_table = ktz8866_match_table,
+ },
+ .probe = ktz8866_probe,
+ .remove = ktz8866_remove,
+ .id_table = ktz8866_ids,
+};
+
+module_i2c_driver(ktz8866_driver);
+
+MODULE_DESCRIPTION("Kinetic KTZ8866 Backlight Driver");
+MODULE_AUTHOR("Jianhua Lu <lujianhua000@gmail.com>");
+MODULE_LICENSE("GPL");
--
2.38.2