[PATCH v4 0/3] Kinetic ExpressWire library and KTD2801 backlight driver

[PATCH v4 0/3] Kinetic ExpressWire library and KTD2801 backlight driver

[Duje Mihanović]

Hello,

This series adds support for the Kinetic KTD2801 LED backlight driver
IC found in samsung,coreprimevelte.

Support is already upstream for the somewhat similar KTD2692 flash
driver, and this series since v3 also moves its ExpressWire code into a
separate library and converts the KTD2692 driver to use that library.

Signed-off-by: Duje Mihanović <duje.mihanovic@skole.hr>
---
Changes in v4:
- Drop 'extern' keywords in leds-expresswire.h
- Add 'expresswire_write_u8' to leds-expresswire.c and use it in the two
  drivers
- Move GPIOLIB dependency to LEDS_EXPRESSWIRE instead of letting clients
  handle it
- Drop time constant macros
- Drop delay.h include in ktd2692
- Drop bits.h and delay.h includes in ktd2801
- Link to v3: https://lore.kernel.org/r/20240120-ktd2801-v3-0-fe2cbafffb21@skole.hr

Changes in v3:
- Split ExpressWire code into library (and convert KTD2692 to use this
  library)
- Rewrite commit messages
- Add link to datasheet
- Drop of.h include in ktd2801
- Use _cansleep and usleep_range when powering off
- Clean up bitwise operation in update_status
- Link to v2: https://lore.kernel.org/r/20240118-ktd2801-v2-0-425cf32e0769@skole.hr

Changes in v2:
- Address maintainer comments:
  - Drop MODULE_ALIAS
  - Rename enable-gpios to ctrl-gpios
  - Rename ktd2801_backlight->desc to ktd2801_backlight->gpiod
  - Give time constants more descriptive names and note their origins in
    Samsung driver
  - Convert to GPIO_ACTIVE_HIGH
- Update trailers
- Link to v1: https://lore.kernel.org/r/20231005-ktd2801-v1-0-43cd85b0629a@skole.hr

---
Duje Mihanović (3):
      leds: ktd2692: move ExpressWire code to library
      dt-bindings: backlight: add Kinetic KTD2801 binding
      backlight: Add Kinetic KTD2801 backlight support

 .../bindings/leds/backlight/kinetic,ktd2801.yaml   |  46 ++++++++
 MAINTAINERS                                        |  13 +++
 drivers/leds/Kconfig                               |   4 +
 drivers/leds/Makefile                              |   3 +
 drivers/leds/flash/Kconfig                         |   2 +-
 drivers/leds/flash/leds-ktd2692.c                  | 116 +++++--------------
 drivers/leds/leds-expresswire.c                    |  68 +++++++++++
 drivers/video/backlight/Kconfig                    |   7 ++
 drivers/video/backlight/Makefile                   |   1 +
 drivers/video/backlight/ktd2801-backlight.c        | 128 +++++++++++++++++++++
 include/linux/leds-expresswire.h                   |  36 ++++++
 11 files changed, 334 insertions(+), 90 deletions(-)
---
base-commit: 0dd3ee31125508cd67f7e7172247f05b7fd1753a
change-id: 20231004-ktd2801-0f3883cb59d0

Best regards,
-- 
Duje Mihanović <duje.mihanovic@skole.hr>

[PATCH v4 1/3] leds: ktd2692: move ExpressWire code to library

[Duje Mihanović]

The ExpressWire protocol is shared between at least KTD2692 and KTD2801
with slight differences such as timings and the former not having a
defined set of pulses for enabling the protocol (possibly because it
does not support PWM unlike KTD2801). Despite these differences the
ExpressWire handling code can be shared between the two, so move it into
a library in preparation for adding KTD2801 support.

Suggested-by: Daniel Thompson <daniel.thompson@linaro.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Duje Mihanović <duje.mihanovic@skole.hr>
---
 MAINTAINERS                       |   7 +++
 drivers/leds/Kconfig              |   4 ++
 drivers/leds/Makefile             |   3 +
 drivers/leds/flash/Kconfig        |   2 +-
 drivers/leds/flash/leds-ktd2692.c | 116 +++++++++-----------------------------
 drivers/leds/leds-expresswire.c   |  68 ++++++++++++++++++++++
 include/linux/leds-expresswire.h  |  36 ++++++++++++
 7 files changed, 146 insertions(+), 90 deletions(-)

diff --git a/MAINTAINERS b/MAINTAINERS
index a7c4cf8201e0..87b12d2448a0 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -7902,6 +7902,13 @@ S:	Maintained
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/linkinjeon/exfat.git
 F:	fs/exfat/
 
+EXPRESSWIRE PROTOCOL LIBRARY
+M:	Duje Mihanović <duje.mihanovic@skole.hr>
+L:	linux-leds@vger.kernel.org
+S:	Maintained
+F:	drivers/leds/leds-expresswire.c
+F:	include/linux/leds-expresswire.h
+
 EXT2 FILE SYSTEM
 M:	Jan Kara <jack@suse.com>
 L:	linux-ext4@vger.kernel.org
diff --git a/drivers/leds/Kconfig b/drivers/leds/Kconfig
index 6292fddcc55c..15e1c3c238ab 100644
--- a/drivers/leds/Kconfig
+++ b/drivers/leds/Kconfig
@@ -181,6 +181,10 @@ config LEDS_EL15203000
 	  To compile this driver as a module, choose M here: the module
 	  will be called leds-el15203000.
 
+config LEDS_EXPRESSWIRE
+	bool
+	depends on GPIOLIB
+
 config LEDS_TURRIS_OMNIA
 	tristate "LED support for CZ.NIC's Turris Omnia"
 	depends on LEDS_CLASS_MULTICOLOR
diff --git a/drivers/leds/Makefile b/drivers/leds/Makefile
index d7348e8bc019..a63a07d01c6f 100644
--- a/drivers/leds/Makefile
+++ b/drivers/leds/Makefile
@@ -89,6 +89,9 @@ obj-$(CONFIG_LEDS_WM831X_STATUS)	+= leds-wm831x-status.o
 obj-$(CONFIG_LEDS_WM8350)		+= leds-wm8350.o
 obj-$(CONFIG_LEDS_WRAP)			+= leds-wrap.o
 
+# Kinetic ExpressWire Protocol
+obj-$(CONFIG_LEDS_EXPRESSWIRE)		+= leds-expresswire.o
+
 # LED SPI Drivers
 obj-$(CONFIG_LEDS_CR0014114)		+= leds-cr0014114.o
 obj-$(CONFIG_LEDS_DAC124S085)		+= leds-dac124s085.o
diff --git a/drivers/leds/flash/Kconfig b/drivers/leds/flash/Kconfig
index 4e08dbc05709..a0fb755b58dc 100644
--- a/drivers/leds/flash/Kconfig
+++ b/drivers/leds/flash/Kconfig
@@ -23,7 +23,7 @@ config LEDS_AS3645A
 config LEDS_KTD2692
 	tristate "LED support for Kinetic KTD2692 flash LED controller"
 	depends on OF
-	depends on GPIOLIB || COMPILE_TEST
+	select LEDS_EXPRESSWIRE
 	help
 	  This option enables support for Kinetic KTD2692 LED flash connected
 	  through ExpressWire interface.
diff --git a/drivers/leds/flash/leds-ktd2692.c b/drivers/leds/flash/leds-ktd2692.c
index 598eee5daa52..7bb0aa2753e3 100644
--- a/drivers/leds/flash/leds-ktd2692.c
+++ b/drivers/leds/flash/leds-ktd2692.c
@@ -6,9 +6,9 @@
  * Ingi Kim <ingi2.kim@samsung.com>
  */
 
-#include <linux/delay.h>
 #include <linux/err.h>
 #include <linux/gpio/consumer.h>
+#include <linux/leds-expresswire.h>
 #include <linux/led-class-flash.h>
 #include <linux/module.h>
 #include <linux/mutex.h>
@@ -37,22 +37,9 @@
 #define KTD2692_REG_FLASH_CURRENT_BASE		0x80
 #define KTD2692_REG_MODE_BASE			0xA0
 
-/* Set bit coding time for expresswire interface */
-#define KTD2692_TIME_RESET_US			700
-#define KTD2692_TIME_DATA_START_TIME_US		10
-#define KTD2692_TIME_HIGH_END_OF_DATA_US	350
-#define KTD2692_TIME_LOW_END_OF_DATA_US		10
-#define KTD2692_TIME_SHORT_BITSET_US		4
-#define KTD2692_TIME_LONG_BITSET_US		12
-
 /* KTD2692 default length of name */
 #define KTD2692_NAME_LENGTH			20
 
-enum ktd2692_bitset {
-	KTD2692_LOW = 0,
-	KTD2692_HIGH,
-};
-
 /* Movie / Flash Mode Control */
 enum ktd2692_led_mode {
 	KTD2692_MODE_DISABLE = 0,	/* default */
@@ -71,7 +58,19 @@ struct ktd2692_led_config_data {
 	enum led_brightness max_brightness;
 };
 
+const struct expresswire_timing ktd2692_timing = {
+	.poweroff_us = 700,
+	.data_start_us = 10,
+	.end_of_data_low_us = 10,
+	.end_of_data_high_us = 350,
+	.short_bitset_us = 4,
+	.long_bitset_us = 12
+};
+
 struct ktd2692_context {
+	/* Common ExpressWire properties (ctrl GPIO and timing) */
+	struct expresswire_common_props props;
+
 	/* Related LED Flash class device */
 	struct led_classdev_flash fled_cdev;
 
@@ -80,7 +79,6 @@ struct ktd2692_context {
 	struct regulator *regulator;
 
 	struct gpio_desc *aux_gpio;
-	struct gpio_desc *ctrl_gpio;
 
 	enum ktd2692_led_mode mode;
 	enum led_brightness torch_brightness;
@@ -92,67 +90,6 @@ static struct ktd2692_context *fled_cdev_to_led(
 	return container_of(fled_cdev, struct ktd2692_context, fled_cdev);
 }
 
-static void ktd2692_expresswire_start(struct ktd2692_context *led)
-{
-	gpiod_direction_output(led->ctrl_gpio, KTD2692_HIGH);
-	udelay(KTD2692_TIME_DATA_START_TIME_US);
-}
-
-static void ktd2692_expresswire_reset(struct ktd2692_context *led)
-{
-	gpiod_direction_output(led->ctrl_gpio, KTD2692_LOW);
-	udelay(KTD2692_TIME_RESET_US);
-}
-
-static void ktd2692_expresswire_end(struct ktd2692_context *led)
-{
-	gpiod_direction_output(led->ctrl_gpio, KTD2692_LOW);
-	udelay(KTD2692_TIME_LOW_END_OF_DATA_US);
-	gpiod_direction_output(led->ctrl_gpio, KTD2692_HIGH);
-	udelay(KTD2692_TIME_HIGH_END_OF_DATA_US);
-}
-
-static void ktd2692_expresswire_set_bit(struct ktd2692_context *led, bool bit)
-{
-	/*
-	 * The Low Bit(0) and High Bit(1) is based on a time detection
-	 * algorithm between time low and time high
-	 * Time_(L_LB) : Low time of the Low Bit(0)
-	 * Time_(H_LB) : High time of the LOW Bit(0)
-	 * Time_(L_HB) : Low time of the High Bit(1)
-	 * Time_(H_HB) : High time of the High Bit(1)
-	 *
-	 * It can be simplified to:
-	 * Low Bit(0) : 2 * Time_(H_LB) < Time_(L_LB)
-	 * High Bit(1) : 2 * Time_(L_HB) < Time_(H_HB)
-	 * HIGH  ___           ____    _..     _________    ___
-	 *          |_________|    |_..  |____|         |__|
-	 * LOW        <L_LB>  <H_LB>     <L_HB>  <H_HB>
-	 *          [  Low Bit (0) ]     [  High Bit(1) ]
-	 */
-	if (bit) {
-		gpiod_direction_output(led->ctrl_gpio, KTD2692_LOW);
-		udelay(KTD2692_TIME_SHORT_BITSET_US);
-		gpiod_direction_output(led->ctrl_gpio, KTD2692_HIGH);
-		udelay(KTD2692_TIME_LONG_BITSET_US);
-	} else {
-		gpiod_direction_output(led->ctrl_gpio, KTD2692_LOW);
-		udelay(KTD2692_TIME_LONG_BITSET_US);
-		gpiod_direction_output(led->ctrl_gpio, KTD2692_HIGH);
-		udelay(KTD2692_TIME_SHORT_BITSET_US);
-	}
-}
-
-static void ktd2692_expresswire_write(struct ktd2692_context *led, u8 value)
-{
-	int i;
-
-	ktd2692_expresswire_start(led);
-	for (i = 7; i >= 0; i--)
-		ktd2692_expresswire_set_bit(led, value & BIT(i));
-	ktd2692_expresswire_end(led);
-}
-
 static int ktd2692_led_brightness_set(struct led_classdev *led_cdev,
 				       enum led_brightness brightness)
 {
@@ -163,14 +100,14 @@ static int ktd2692_led_brightness_set(struct led_classdev *led_cdev,
 
 	if (brightness == LED_OFF) {
 		led->mode = KTD2692_MODE_DISABLE;
-		gpiod_direction_output(led->aux_gpio, KTD2692_LOW);
+		gpiod_direction_output(led->aux_gpio, 0);
 	} else {
-		ktd2692_expresswire_write(led, brightness |
+		expresswire_write_u8(&led->props, brightness |
 					KTD2692_REG_MOVIE_CURRENT_BASE);
 		led->mode = KTD2692_MODE_MOVIE;
 	}
 
-	ktd2692_expresswire_write(led, led->mode | KTD2692_REG_MODE_BASE);
+	expresswire_write_u8(&led->props, led->mode | KTD2692_REG_MODE_BASE);
 	mutex_unlock(&led->lock);
 
 	return 0;
@@ -187,17 +124,17 @@ static int ktd2692_led_flash_strobe_set(struct led_classdev_flash *fled_cdev,
 
 	if (state) {
 		flash_tm_reg = GET_TIMEOUT_OFFSET(timeout->val, timeout->step);
-		ktd2692_expresswire_write(led, flash_tm_reg
+		expresswire_write_u8(&led->props, flash_tm_reg
 				| KTD2692_REG_FLASH_TIMEOUT_BASE);
 
 		led->mode = KTD2692_MODE_FLASH;
-		gpiod_direction_output(led->aux_gpio, KTD2692_HIGH);
+		gpiod_direction_output(led->aux_gpio, 1);
 	} else {
 		led->mode = KTD2692_MODE_DISABLE;
-		gpiod_direction_output(led->aux_gpio, KTD2692_LOW);
+		gpiod_direction_output(led->aux_gpio, 0);
 	}
 
-	ktd2692_expresswire_write(led, led->mode | KTD2692_REG_MODE_BASE);
+	expresswire_write_u8(&led->props, led->mode | KTD2692_REG_MODE_BASE);
 
 	fled_cdev->led_cdev.brightness = LED_OFF;
 	led->mode = KTD2692_MODE_DISABLE;
@@ -247,12 +184,12 @@ static void ktd2692_init_flash_timeout(struct led_classdev_flash *fled_cdev,
 static void ktd2692_setup(struct ktd2692_context *led)
 {
 	led->mode = KTD2692_MODE_DISABLE;
-	ktd2692_expresswire_reset(led);
-	gpiod_direction_output(led->aux_gpio, KTD2692_LOW);
+	expresswire_power_off(&led->props);
+	gpiod_direction_output(led->aux_gpio, 0);
 
-	ktd2692_expresswire_write(led, (KTD2692_MM_MIN_CURR_THRESHOLD_SCALE - 1)
+	expresswire_write_u8(&led->props, (KTD2692_MM_MIN_CURR_THRESHOLD_SCALE - 1)
 				 | KTD2692_REG_MM_MIN_CURR_THRESHOLD_BASE);
-	ktd2692_expresswire_write(led, KTD2692_FLASH_MODE_CURR_PERCENT(45)
+	expresswire_write_u8(&led->props, KTD2692_FLASH_MODE_CURR_PERCENT(45)
 				 | KTD2692_REG_FLASH_CURRENT_BASE);
 }
 
@@ -277,8 +214,8 @@ static int ktd2692_parse_dt(struct ktd2692_context *led, struct device *dev,
 	if (!np)
 		return -ENXIO;
 
-	led->ctrl_gpio = devm_gpiod_get(dev, "ctrl", GPIOD_ASIS);
-	ret = PTR_ERR_OR_ZERO(led->ctrl_gpio);
+	led->props.ctrl_gpio = devm_gpiod_get(dev, "ctrl", GPIOD_ASIS);
+	ret = PTR_ERR_OR_ZERO(led->props.ctrl_gpio);
 	if (ret)
 		return dev_err_probe(dev, ret, "cannot get ctrl-gpios\n");
 
@@ -412,6 +349,7 @@ static struct platform_driver ktd2692_driver = {
 
 module_platform_driver(ktd2692_driver);
 
+MODULE_IMPORT_NS(EXPRESSWIRE);
 MODULE_AUTHOR("Ingi Kim <ingi2.kim@samsung.com>");
 MODULE_DESCRIPTION("Kinetic KTD2692 LED driver");
 MODULE_LICENSE("GPL v2");
diff --git a/drivers/leds/leds-expresswire.c b/drivers/leds/leds-expresswire.c
new file mode 100644
index 000000000000..89e147b0e019
--- /dev/null
+++ b/drivers/leds/leds-expresswire.c
@@ -0,0 +1,68 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Shared library for Kinetic's ExpressWire protocol.
+ * This protocol works by pulsing the ExpressWire IC's control GPIO.
+ * ktd2692 and ktd2801 are known to use this protocol.
+ */
+
+#include <linux/delay.h>
+#include <linux/gpio/consumer.h>
+#include <linux/leds-expresswire.h>
+
+void expresswire_power_off(struct expresswire_common_props *props)
+{
+	gpiod_set_value_cansleep(props->ctrl_gpio, 0);
+	usleep_range(props->timing.poweroff_us, props->timing.poweroff_us * 2);
+}
+EXPORT_SYMBOL_NS_GPL(expresswire_power_off, EXPRESSWIRE);
+
+void expresswire_enable(struct expresswire_common_props *props)
+{
+	gpiod_set_value(props->ctrl_gpio, 1);
+	udelay(props->timing.detect_delay_us);
+	gpiod_set_value(props->ctrl_gpio, 0);
+	udelay(props->timing.detect_us);
+	gpiod_set_value(props->ctrl_gpio, 1);
+}
+EXPORT_SYMBOL_NS_GPL(expresswire_enable, EXPRESSWIRE);
+
+void expresswire_start(struct expresswire_common_props *props)
+{
+	gpiod_set_value(props->ctrl_gpio, 1);
+	udelay(props->timing.data_start_us);
+}
+EXPORT_SYMBOL_NS_GPL(expresswire_start, EXPRESSWIRE);
+
+void expresswire_end(struct expresswire_common_props *props)
+{
+	gpiod_set_value(props->ctrl_gpio, 0);
+	udelay(props->timing.end_of_data_low_us);
+	gpiod_set_value(props->ctrl_gpio, 1);
+	udelay(props->timing.end_of_data_high_us);
+}
+EXPORT_SYMBOL_NS_GPL(expresswire_end, EXPRESSWIRE);
+
+void expresswire_set_bit(struct expresswire_common_props *props, bool bit)
+{
+	if (bit) {
+		gpiod_set_value(props->ctrl_gpio, 0);
+		udelay(props->timing.short_bitset_us);
+		gpiod_set_value(props->ctrl_gpio, 1);
+		udelay(props->timing.long_bitset_us);
+	} else {
+		gpiod_set_value(props->ctrl_gpio, 0);
+		udelay(props->timing.long_bitset_us);
+		gpiod_set_value(props->ctrl_gpio, 1);
+		udelay(props->timing.short_bitset_us);
+	}
+}
+EXPORT_SYMBOL_NS_GPL(expresswire_set_bit, EXPRESSWIRE);
+
+void expresswire_write_u8(struct expresswire_common_props *props, u8 val)
+{
+	expresswire_start(props);
+	for (int i = 7; i >= 0; i--)
+		expresswire_set_bit(props, val & BIT(i));
+	expresswire_end(props);
+}
+EXPORT_SYMBOL_NS_GPL(expresswire_write_u8, EXPRESSWIRE);
diff --git a/include/linux/leds-expresswire.h b/include/linux/leds-expresswire.h
new file mode 100644
index 000000000000..3c61902ccac8
--- /dev/null
+++ b/include/linux/leds-expresswire.h
@@ -0,0 +1,36 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Shared library for Kinetic's ExpressWire protocol.
+ * This protocol works by pulsing the ExpressWire IC's control GPIO.
+ * ktd2692 and ktd2801 are known to use this protocol.
+ */
+
+#ifndef _LEDS_EXPRESSWIRE_H
+#define _LEDS_EXPRESSWIRE_H
+
+#include <linux/gpio/consumer.h>
+
+struct expresswire_timing {
+	unsigned long poweroff_us;
+	unsigned long detect_delay_us;
+	unsigned long detect_us;
+	unsigned long data_start_us;
+	unsigned long end_of_data_low_us;
+	unsigned long end_of_data_high_us;
+	unsigned long short_bitset_us;
+	unsigned long long_bitset_us;
+};
+
+struct expresswire_common_props {
+	struct gpio_desc *ctrl_gpio;
+	struct expresswire_timing timing;
+};
+
+void expresswire_power_off(struct expresswire_common_props *props);
+void expresswire_enable(struct expresswire_common_props *props);
+void expresswire_start(struct expresswire_common_props *props);
+void expresswire_end(struct expresswire_common_props *props);
+void expresswire_set_bit(struct expresswire_common_props *props, bool bit);
+void expresswire_write_u8(struct expresswire_common_props *props, u8 val);
+
+#endif /* _LEDS_EXPRESSWIRE_H */

-- 
2.43.0

[PATCH v4 2/3] dt-bindings: backlight: add Kinetic KTD2801 binding

[Duje Mihanović]

KTD2801 is a LED backlight driver IC found in samsung,coreprimevelte.
The brightness can be set using PWM or the ExpressWire protocol. Add
a DT binding for the KTD2801.

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Duje Mihanović <duje.mihanovic@skole.hr>
---
 .../bindings/leds/backlight/kinetic,ktd2801.yaml   | 46 ++++++++++++++++++++++
 1 file changed, 46 insertions(+)

diff --git a/Documentation/devicetree/bindings/leds/backlight/kinetic,ktd2801.yaml b/Documentation/devicetree/bindings/leds/backlight/kinetic,ktd2801.yaml
new file mode 100644
index 000000000000..b005065e0f48
--- /dev/null
+++ b/Documentation/devicetree/bindings/leds/backlight/kinetic,ktd2801.yaml
@@ -0,0 +1,46 @@
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/leds/backlight/kinetic,ktd2801.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Kinetic Technologies KTD2801 one-wire backlight
+
+maintainers:
+  - Duje Mihanović <duje.mihanovic@skole.hr>
+
+description: |
+  The Kinetic Technologies KTD2801 is a LED backlight driver controlled
+  by a single GPIO line. The driver can be controlled with a PWM signal
+  or by pulsing the GPIO line to set the backlight level. This is called
+  "ExpressWire".
+
+allOf:
+  - $ref: common.yaml#
+
+properties:
+  compatible:
+    const: kinetic,ktd2801
+
+  ctrl-gpios:
+    maxItems: 1
+
+  default-brightness: true
+  max-brightness: true
+
+required:
+  - compatible
+  - ctrl-gpios
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/gpio/gpio.h>
+
+    backlight {
+        compatible = "kinetic,ktd2801";
+        ctrl-gpios = <&gpio 97 GPIO_ACTIVE_HIGH>;
+        max-brightness = <210>;
+        default-brightness = <100>;
+    };

-- 
2.43.0

[PATCH v4 3/3] backlight: Add Kinetic KTD2801 backlight support

[Duje Mihanović]

KTD2801 is a LED backlight driver IC found in samsung,coreprimevelte.
The brightness can be set using PWM or the ExpressWire protocol. Add
support for the KTD2801.

Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Duje Mihanović <duje.mihanovic@skole.hr>
---
 MAINTAINERS                                 |   6 ++
 drivers/video/backlight/Kconfig             |   7 ++
 drivers/video/backlight/Makefile            |   1 +
 drivers/video/backlight/ktd2801-backlight.c | 128 ++++++++++++++++++++++++++++
 4 files changed, 142 insertions(+)

diff --git a/MAINTAINERS b/MAINTAINERS
index 87b12d2448a0..dddffbd8d2a0 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -11891,6 +11891,12 @@ S:	Maintained
 F:	Documentation/devicetree/bindings/leds/backlight/kinetic,ktd253.yaml
 F:	drivers/video/backlight/ktd253-backlight.c
 
+KTD2801 BACKLIGHT DRIVER
+M:	Duje Mihanović <duje.mihanovic@skole.hr>
+S:	Maintained
+F:	Documentation/devicetree/bindings/leds/backlight/kinetic,ktd2801.yaml
+F:	drivers/video/backlight/ktd2801-backlight.c
+
 KTEST
 M:	Steven Rostedt <rostedt@goodmis.org>
 M:	John Hawley <warthog9@eaglescrag.net>
diff --git a/drivers/video/backlight/Kconfig b/drivers/video/backlight/Kconfig
index 51387b1ef012..bba9d8ffccff 100644
--- a/drivers/video/backlight/Kconfig
+++ b/drivers/video/backlight/Kconfig
@@ -183,6 +183,13 @@ config BACKLIGHT_KTD253
 	  which is a 1-wire GPIO-controlled backlight found in some mobile
 	  phones.
 
+config BACKLIGHT_KTD2801
+	tristate "Backlight Driver for Kinetic KTD2801"
+	select LEDS_EXPRESSWIRE
+	help
+	  Say Y to enable the backlight driver for the Kinetic KTD2801 1-wire
+	  GPIO-controlled backlight found in Samsung Galaxy Core Prime VE LTE.
+
 config BACKLIGHT_KTZ8866
 	tristate "Backlight Driver for Kinetic KTZ8866"
 	depends on I2C
diff --git a/drivers/video/backlight/Makefile b/drivers/video/backlight/Makefile
index f72e1c3c59e9..b33b647f31ca 100644
--- a/drivers/video/backlight/Makefile
+++ b/drivers/video/backlight/Makefile
@@ -35,6 +35,7 @@ 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-$(CONFIG_BACKLIGHT_KTD2801)		+= ktd2801-backlight.o
 obj-$(CONFIG_BACKLIGHT_KTZ8866)		+= ktz8866.o
 obj-$(CONFIG_BACKLIGHT_LM3533)		+= lm3533_bl.o
 obj-$(CONFIG_BACKLIGHT_LM3630A)		+= lm3630a_bl.o
diff --git a/drivers/video/backlight/ktd2801-backlight.c b/drivers/video/backlight/ktd2801-backlight.c
new file mode 100644
index 000000000000..c020acff40f1
--- /dev/null
+++ b/drivers/video/backlight/ktd2801-backlight.c
@@ -0,0 +1,128 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Datasheet:
+ * https://www.kinet-ic.com/uploads/web/KTD2801/KTD2801-04b.pdf
+ */
+#include <linux/backlight.h>
+#include <linux/gpio/consumer.h>
+#include <linux/leds-expresswire.h>
+#include <linux/platform_device.h>
+#include <linux/property.h>
+
+#define KTD2801_DEFAULT_BRIGHTNESS	100
+#define KTD2801_MAX_BRIGHTNESS		255
+
+/* These values have been extracted from Samsung's driver. */
+const struct expresswire_timing ktd2801_timing = {
+	.poweroff_us = 2600,
+	.detect_delay_us = 150,
+	.detect_us = 270,
+	.data_start_us = 5,
+	.short_bitset_us = 5,
+	.long_bitset_us = 15,
+	.end_of_data_low_us = 10,
+	.end_of_data_high_us = 350
+};
+
+struct ktd2801_backlight {
+	struct expresswire_common_props props;
+	struct backlight_device *bd;
+	bool was_on;
+};
+
+static int ktd2801_update_status(struct backlight_device *bd)
+{
+	struct ktd2801_backlight *ktd2801 = bl_get_data(bd);
+	u8 brightness = (u8) backlight_get_brightness(bd);
+
+	if (backlight_is_blank(bd)) {
+		expresswire_power_off(&ktd2801->props);
+		ktd2801->was_on = false;
+		return 0;
+	}
+
+	if (!ktd2801->was_on) {
+		expresswire_enable(&ktd2801->props);
+		ktd2801->was_on = true;
+	}
+
+	expresswire_write_u8(&ktd2801->props, brightness);
+
+	return 0;
+}
+
+static const struct backlight_ops ktd2801_backlight_ops = {
+	.update_status = ktd2801_update_status,
+};
+
+static int ktd2801_backlight_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct backlight_device *bd;
+	struct ktd2801_backlight *ktd2801;
+	u32 brightness, max_brightness;
+	int ret;
+
+	ktd2801 = devm_kzalloc(dev, sizeof(*ktd2801), GFP_KERNEL);
+	if (!ktd2801)
+		return -ENOMEM;
+	ktd2801->was_on = true;
+	ktd2801->props.timing = ktd2801_timing;
+
+	ret = device_property_read_u32(dev, "max-brightness", &max_brightness);
+	if (ret)
+		max_brightness = KTD2801_MAX_BRIGHTNESS;
+	if (max_brightness > KTD2801_MAX_BRIGHTNESS) {
+		dev_err(dev, "illegal max brightness specified\n");
+		max_brightness = KTD2801_MAX_BRIGHTNESS;
+	}
+
+	ret = device_property_read_u32(dev, "default-brightness", &brightness);
+	if (ret)
+		brightness = KTD2801_DEFAULT_BRIGHTNESS;
+	if (brightness > max_brightness) {
+		dev_err(dev, "default brightness exceeds max\n");
+		brightness = max_brightness;
+	}
+
+	ktd2801->props.ctrl_gpio = devm_gpiod_get(dev, "ctrl", GPIOD_OUT_HIGH);
+	if (IS_ERR(ktd2801->props.ctrl_gpio))
+		return dev_err_probe(dev, PTR_ERR(ktd2801->props.ctrl_gpio),
+				"failed to get backlight GPIO");
+	gpiod_set_consumer_name(ktd2801->props.ctrl_gpio, dev_name(dev));
+
+	bd = devm_backlight_device_register(dev, dev_name(dev), dev, ktd2801,
+			&ktd2801_backlight_ops, NULL);
+	if (IS_ERR(bd))
+		return dev_err_probe(dev, PTR_ERR(bd),
+				"failed to register backlight");
+
+	bd->props.max_brightness = max_brightness;
+	bd->props.brightness = brightness;
+
+	ktd2801->bd = bd;
+	platform_set_drvdata(pdev, bd);
+	backlight_update_status(bd);
+
+	return 0;
+}
+
+static const struct of_device_id ktd2801_of_match[] = {
+	{ .compatible = "kinetic,ktd2801" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, ktd2801_of_match);
+
+static struct platform_driver ktd2801_backlight_driver = {
+	.driver = {
+		.name = "ktd2801-backlight",
+		.of_match_table = ktd2801_of_match,
+	},
+	.probe = ktd2801_backlight_probe,
+};
+module_platform_driver(ktd2801_backlight_driver);
+
+MODULE_IMPORT_NS(EXPRESSWIRE);
+MODULE_AUTHOR("Duje Mihanović <duje.mihanovic@skole.hr>");
+MODULE_DESCRIPTION("Kinetic KTD2801 Backlight Driver");
+MODULE_LICENSE("GPL");

-- 
2.43.0

Re: [PATCH v4 1/3] leds: ktd2692: move ExpressWire code to library

[Daniel Thompson]

On Mon, Jan 22, 2024 at 08:50:57PM +0100, Duje Mihanović wrote:
> The ExpressWire protocol is shared between at least KTD2692 and KTD2801
> with slight differences such as timings and the former not having a
> defined set of pulses for enabling the protocol (possibly because it
> does not support PWM unlike KTD2801). Despite these differences the
> ExpressWire handling code can be shared between the two, so move it into
> a library in preparation for adding KTD2801 support.
>
> Suggested-by: Daniel Thompson <daniel.thompson@linaro.org>
> Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
> Signed-off-by: Duje Mihanović <duje.mihanovic@skole.hr>

Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>


Daniel.

Re: [PATCH v4 2/3] dt-bindings: backlight: add Kinetic KTD2801 binding

[Daniel Thompson]

On Mon, Jan 22, 2024 at 08:50:58PM +0100, Duje Mihanović wrote:
> KTD2801 is a LED backlight driver IC found in samsung,coreprimevelte.
> The brightness can be set using PWM or the ExpressWire protocol. Add
> a DT binding for the KTD2801.
>
> Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
> Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
> Signed-off-by: Duje Mihanović <duje.mihanovic@skole.hr>

Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>


Daniel.

Re: [PATCH v4 3/3] backlight: Add Kinetic KTD2801 backlight support

[Daniel Thompson]

On Mon, Jan 22, 2024 at 08:50:59PM +0100, Duje Mihanović wrote:
> KTD2801 is a LED backlight driver IC found in samsung,coreprimevelte.
> The brightness can be set using PWM or the ExpressWire protocol. Add
> support for the KTD2801.
>
> Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
> Signed-off-by: Duje Mihanović <duje.mihanovic@skole.hr>

Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>


Daniel.

Re: [PATCH v4 1/3] leds: ktd2692: move ExpressWire code to library

[Lee Jones]

On Mon, 22 Jan 2024, Duje Mihanović wrote:

> The ExpressWire protocol is shared between at least KTD2692 and KTD2801
> with slight differences such as timings and the former not having a
> defined set of pulses for enabling the protocol (possibly because it
> does not support PWM unlike KTD2801). Despite these differences the
> ExpressWire handling code can be shared between the two, so move it into
> a library in preparation for adding KTD2801 support.
> 
> Suggested-by: Daniel Thompson <daniel.thompson@linaro.org>
> Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
> Signed-off-by: Duje Mihanović <duje.mihanovic@skole.hr>
> ---
>  MAINTAINERS                       |   7 +++
>  drivers/leds/Kconfig              |   4 ++
>  drivers/leds/Makefile             |   3 +
>  drivers/leds/flash/Kconfig        |   2 +-
>  drivers/leds/flash/leds-ktd2692.c | 116 +++++++++-----------------------------

>  drivers/leds/leds-expresswire.c   |  68 ++++++++++++++++++++++
>  include/linux/leds-expresswire.h  |  36 ++++++++++++

Please can you separate the Expresswire addition into its own patch?

>  7 files changed, 146 insertions(+), 90 deletions(-)

-- 
Lee Jones [李琼斯]