[PATCH 1/3 v3] dt-bindings: backlight: Add some common backlight properties

[PATCH 1/3 v3] dt-bindings: backlight: Add some common backlight properties

[Linus Walleij]

Let's use a common.yaml include for the backlight like we do with
the LEDs. The LEDs are inherently incompatible so their bindings
cannot be reused for backlight.

Cc: devicetree@vger.kernel.org
Suggested-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
---
ChangeLog v2->v3:
- Drop the | for the description
- Drop the "default-on" property, we're not using it.
- Drop the minimum 0 for unsigned u32:s
ChangeLog v1->v2:
- New patch as suggested by Sam.
---
 .../bindings/leds/backlight/common.yaml       | 34 +++++++++++++++++++
 1 file changed, 34 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/leds/backlight/common.yaml

diff --git a/Documentation/devicetree/bindings/leds/backlight/common.yaml b/Documentation/devicetree/bindings/leds/backlight/common.yaml
new file mode 100644
index 000000000000..4e7e95e331a5
--- /dev/null
+++ b/Documentation/devicetree/bindings/leds/backlight/common.yaml
@@ -0,0 +1,34 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/leds/backlight/common.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Common backlight properties
+
+maintainers:
+  - Lee Jones <lee.jones@linaro.org>
+  - Daniel Thompson <daniel.thompson@linaro.org>
+  - Jingoo Han <jingoohan1@gmail.com>
+
+description:
+  Backlight devices provide backlight for different types of graphical
+  displays. They are typically but not necessarily implemented using a white
+  LED powered by a boost converter.
+
+properties:
+  default-brightness:
+    description:
+      The default brightness that should be applied to the LED by the operating
+      system on start-up. The brightness should not exceed the brightness the
+      LED can provide.
+    $ref: /schemas/types.yaml#definitions/uint32
+
+  max-brightness:
+    description:
+      Normally the maximum brightness is determined by the hardware and this
+      property is not required. This property is used to put a software limit
+      on the brightness apart from what the driver says, as it could happen
+      that a LED can be made so bright that it gets damaged or causes damage
+      due to restrictions in a specific system, such as mounting conditions.
+    $ref: /schemas/types.yaml#definitions/uint32
-- 
2.26.2

[PATCH 1/3 v3] dt-bindings: backlight: Add some common backlight properties

[Linus Walleij]

Let's use a common.yaml include for the backlight like we do with
the LEDs. The LEDs are inherently incompatible so their bindings
cannot be reused for backlight.

Cc: devicetree@vger.kernel.org
Suggested-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
---
ChangeLog v2->v3:
- Drop the | for the description
- Drop the "default-on" property, we're not using it.
- Drop the minimum 0 for unsigned u32:s
ChangeLog v1->v2:
- New patch as suggested by Sam.
---
 .../bindings/leds/backlight/common.yaml       | 34 +++++++++++++++++++
 1 file changed, 34 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/leds/backlight/common.yaml

diff --git a/Documentation/devicetree/bindings/leds/backlight/common.yaml b/Documentation/devicetree/bindings/leds/backlight/common.yaml
new file mode 100644
index 000000000000..4e7e95e331a5
--- /dev/null
+++ b/Documentation/devicetree/bindings/leds/backlight/common.yaml
@@ -0,0 +1,34 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/leds/backlight/common.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Common backlight properties
+
+maintainers:
+  - Lee Jones <lee.jones@linaro.org>
+  - Daniel Thompson <daniel.thompson@linaro.org>
+  - Jingoo Han <jingoohan1@gmail.com>
+
+description:
+  Backlight devices provide backlight for different types of graphical
+  displays. They are typically but not necessarily implemented using a white
+  LED powered by a boost converter.
+
+properties:
+  default-brightness:
+    description:
+      The default brightness that should be applied to the LED by the operating
+      system on start-up. The brightness should not exceed the brightness the
+      LED can provide.
+    $ref: /schemas/types.yaml#definitions/uint32
+
+  max-brightness:
+    description:
+      Normally the maximum brightness is determined by the hardware and this
+      property is not required. This property is used to put a software limit
+      on the brightness apart from what the driver says, as it could happen
+      that a LED can be made so bright that it gets damaged or causes damage
+      due to restrictions in a specific system, such as mounting conditions.
+    $ref: /schemas/types.yaml#definitions/uint32
-- 
2.26.2

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[PATCH 2/3 v3] dt-bindings: backlight: Add Kinetic KTD253 bindings

[Linus Walleij]

This adds device tree bindings for the Kinetic KTD253
white LED backlight driver.

Cc: devicetree@vger.kernel.org
Cc: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
---
ChangeLog v2->v3:
- Drop the pointless cargo-culted "default-on" property that
  we were not using
- Correct the brightness in the example to something legal (13)
ChangeLog v1->v2:
- Create common.yaml for backlight as suggested by Sam and
  use that.
- Rename the GPIO line "enable-gpios"
---
 .../leds/backlight/kinetic,ktd253.yaml        | 46 +++++++++++++++++++
 1 file changed, 46 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/leds/backlight/kinetic,ktd253.yaml

diff --git a/Documentation/devicetree/bindings/leds/backlight/kinetic,ktd253.yaml b/Documentation/devicetree/bindings/leds/backlight/kinetic,ktd253.yaml
new file mode 100644
index 000000000000..7a6ec1f8c0f3
--- /dev/null
+++ b/Documentation/devicetree/bindings/leds/backlight/kinetic,ktd253.yaml
@@ -0,0 +1,46 @@
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/leds/backlight/kinetic,ktd253.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Kinetic Technologies KTD253 one-wire backlight
+
+maintainers:
+  - Linus Walleij <linus.walleij@linaro.org>
+
+description: |
+  The Kinetic Technologies KTD253 is a white LED backlight that is
+  controlled by a single GPIO line. If you just turn on the backlight
+  it goes to maximum backlight then you can set the level of backlight
+  using pulses on the enable wire. This is sometimes referred to as
+  "expresswire".
+
+allOf:
+  - $ref: common.yaml#
+
+properties:
+  compatible:
+    const: kinetic,ktd253
+
+  enable-gpios:
+    description: GPIO to use to enable/disable and dim the backlight.
+    maxItems: 1
+
+  default-brightness: true
+  max-brightness: true
+
+required:
+  - compatible
+  - enable-gpios
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/gpio/gpio.h>
+    backlight {
+        compatible = "kinetic,ktd253";
+        enable-gpios = <&gpio2 5 GPIO_ACTIVE_HIGH>;
+        default-brightness = <13>;
+    };
-- 
2.26.2

[PATCH 2/3 v3] dt-bindings: backlight: Add Kinetic KTD253 bindings

[Linus Walleij]

This adds device tree bindings for the Kinetic KTD253
white LED backlight driver.

Cc: devicetree@vger.kernel.org
Cc: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
---
ChangeLog v2->v3:
- Drop the pointless cargo-culted "default-on" property that
  we were not using
- Correct the brightness in the example to something legal (13)
ChangeLog v1->v2:
- Create common.yaml for backlight as suggested by Sam and
  use that.
- Rename the GPIO line "enable-gpios"
---
 .../leds/backlight/kinetic,ktd253.yaml        | 46 +++++++++++++++++++
 1 file changed, 46 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/leds/backlight/kinetic,ktd253.yaml

diff --git a/Documentation/devicetree/bindings/leds/backlight/kinetic,ktd253.yaml b/Documentation/devicetree/bindings/leds/backlight/kinetic,ktd253.yaml
new file mode 100644
index 000000000000..7a6ec1f8c0f3
--- /dev/null
+++ b/Documentation/devicetree/bindings/leds/backlight/kinetic,ktd253.yaml
@@ -0,0 +1,46 @@
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/leds/backlight/kinetic,ktd253.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Kinetic Technologies KTD253 one-wire backlight
+
+maintainers:
+  - Linus Walleij <linus.walleij@linaro.org>
+
+description: |
+  The Kinetic Technologies KTD253 is a white LED backlight that is
+  controlled by a single GPIO line. If you just turn on the backlight
+  it goes to maximum backlight then you can set the level of backlight
+  using pulses on the enable wire. This is sometimes referred to as
+  "expresswire".
+
+allOf:
+  - $ref: common.yaml#
+
+properties:
+  compatible:
+    const: kinetic,ktd253
+
+  enable-gpios:
+    description: GPIO to use to enable/disable and dim the backlight.
+    maxItems: 1
+
+  default-brightness: true
+  max-brightness: true
+
+required:
+  - compatible
+  - enable-gpios
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/gpio/gpio.h>
+    backlight {
+        compatible = "kinetic,ktd253";
+        enable-gpios = <&gpio2 5 GPIO_ACTIVE_HIGH>;
+        default-brightness = <13>;
+    };
-- 
2.26.2

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[PATCH 3/3 v3] backlight: Add Kinetic KTD253 backlight driver

[Linus Walleij]

The Kinetic KTD253 backlight driver is controlled with a
single GPIO line, but still supports a range of brightness
settings by sending fast pulses on the line.

This is based off the source code release for the Samsung
GT-S7710 mobile phone.

Cc: Sam Ravnborg <sam@ravnborg.org>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
---
ChangeLog v2->v3:
- Collect Daniel's review tag.
ChangeLog v1->v2:
- Expose the 32 actual hardware levels of brightness directly
  instead of using an interpolated "brightness" table.
- Use the new backlight_get_brightness() helper.
- Call backlight_update_status() in probe instead of calling
  local functions to sync brightness.
- Sort includes alphabetically.
- Name the GPIO line "enable" and grab that in accordance
  with the change to the DT bindings.
---
 MAINTAINERS                                |   6 +
 drivers/video/backlight/Kconfig            |   8 +
 drivers/video/backlight/Makefile           |   1 +
 drivers/video/backlight/ktd253-backlight.c | 198 +++++++++++++++++++++
 4 files changed, 213 insertions(+)
 create mode 100644 drivers/video/backlight/ktd253-backlight.c

diff --git a/MAINTAINERS b/MAINTAINERS
index deaafb617361..ef6b4a279d25 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -9722,6 +9722,12 @@ F:	Documentation/admin-guide/auxdisplay/ks0108.rst
 F:	drivers/auxdisplay/ks0108.c
 F:	include/linux/ks0108.h
 
+KTD253 BACKLIGHT DRIVER
+M:	Linus Walleij <linus.walleij@linaro.org>
+S:	Maintained
+F:	Documentation/devicetree/bindings/leds/backlight/kinetic,ktd253.yaml
+F:	drivers/video/backlight/ktd253-backlight.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 87f9fc238d28..d83c87b902c1 100644
--- a/drivers/video/backlight/Kconfig
+++ b/drivers/video/backlight/Kconfig
@@ -182,6 +182,14 @@ config BACKLIGHT_IPAQ_MICRO
 	  computers. Say yes if you have one of the h3100/h3600/h3700
 	  machines.
 
+config BACKLIGHT_KTD253
+	tristate "Backlight Driver for Kinetic KTD253"
+	depends on GPIOLIB || COMPILE_TEST
+	help
+	  Say y to enabled the backlight driver for the Kinetic KTD253
+	  which is a 1-wire GPIO-controlled backlight found in some mobile
+	  phones.
+
 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 13463b99f1f9..685f3f1ca4df 100644
--- a/drivers/video/backlight/Makefile
+++ b/drivers/video/backlight/Makefile
@@ -35,6 +35,7 @@ obj-$(CONFIG_BACKLIGHT_GPIO)		+= gpio_backlight.o
 obj-$(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_LM3533)		+= lm3533_bl.o
 obj-$(CONFIG_BACKLIGHT_LM3630A)		+= lm3630a_bl.o
 obj-$(CONFIG_BACKLIGHT_LM3639)		+= lm3639_bl.o
diff --git a/drivers/video/backlight/ktd253-backlight.c b/drivers/video/backlight/ktd253-backlight.c
new file mode 100644
index 000000000000..e3fee3f1f582
--- /dev/null
+++ b/drivers/video/backlight/ktd253-backlight.c
@@ -0,0 +1,198 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Backlight driver for the Kinetic KTD253
+ * Based on code and know-how from the Samsung GT-S7710
+ * Gareth Phillips <gareth.phillips@samsung.com>
+ */
+#include <linux/backlight.h>
+#include <linux/delay.h>
+#include <linux/err.h>
+#include <linux/fb.h>
+#include <linux/gpio/consumer.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/limits.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/property.h>
+#include <linux/slab.h>
+
+/* Current ratio is n/32 from 1/32 to 32/32 */
+#define KTD253_MIN_RATIO 1
+#define KTD253_MAX_RATIO 32
+#define KTD253_DEFAULT_RATIO 13
+
+#define KTD253_T_LOW_NS (200 + 10) /* Additional 10ns as safety factor */
+#define KTD253_T_HIGH_NS (200 + 10) /* Additional 10ns as safety factor */
+#define KTD253_T_OFF_MS 3
+
+struct ktd253_backlight {
+	struct device *dev;
+	struct backlight_device *bl;
+	struct gpio_desc *gpiod;
+	u16 ratio;
+};
+
+static int ktd253_backlight_update_status(struct backlight_device *bl)
+{
+	struct ktd253_backlight *ktd253 = bl_get_data(bl);
+	int brightness = backlight_get_brightness(bl);
+	u16 target_ratio;
+	u16 current_ratio = ktd253->ratio;
+	unsigned long flags;
+
+	dev_dbg(ktd253->dev, "new brightness/ratio: %d/32\n", brightness);
+
+	target_ratio = brightness;
+
+	if (target_ratio == current_ratio)
+		/* This is already right */
+		return 0;
+
+	if (target_ratio == 0) {
+		gpiod_set_value_cansleep(ktd253->gpiod, 0);
+		/*
+		 * We need to keep the GPIO low for at least this long
+		 * to actually switch the KTD253 off.
+		 */
+		msleep(KTD253_T_OFF_MS);
+		ktd253->ratio = 0;
+		return 0;
+	}
+
+	if (current_ratio == 0) {
+		gpiod_set_value_cansleep(ktd253->gpiod, 1);
+		ndelay(KTD253_T_HIGH_NS);
+		/* We always fall back to this when we power on */
+		current_ratio = KTD253_MAX_RATIO;
+	}
+
+	/*
+	 * WARNING:
+	 * The loop to set the correct current level is performed
+	 * with interrupts disabled as it is timing critical.
+	 * The maximum number of cycles of the loop is 32
+	 * so the time taken will be (T_LOW_NS + T_HIGH_NS + loop_time) * 32,
+	 */
+	local_irq_save(flags);
+	while (current_ratio != target_ratio) {
+		/*
+		 * These GPIO operations absolutely can NOT sleep so no
+		 * _cansleep suffixes, and no using GPIO expanders on
+		 * slow buses for this!
+		 */
+		gpiod_set_value(ktd253->gpiod, 0);
+		ndelay(KTD253_T_LOW_NS);
+		gpiod_set_value(ktd253->gpiod, 1);
+		ndelay(KTD253_T_HIGH_NS);
+		/* After 1/32 we loop back to 32/32 */
+		if (current_ratio == KTD253_MIN_RATIO)
+			current_ratio = KTD253_MAX_RATIO;
+		else
+			current_ratio--;
+	}
+	local_irq_restore(flags);
+	ktd253->ratio = current_ratio;
+
+	dev_dbg(ktd253->dev, "new ratio set to %d/32\n", target_ratio);
+
+	return 0;
+}
+
+static const struct backlight_ops ktd253_backlight_ops = {
+	.options	= BL_CORE_SUSPENDRESUME,
+	.update_status	= ktd253_backlight_update_status,
+};
+
+static int ktd253_backlight_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct backlight_device *bl;
+	struct ktd253_backlight *ktd253;
+	u32 max_brightness;
+	u32 brightness;
+	int ret;
+
+	ktd253 = devm_kzalloc(dev, sizeof(*ktd253), GFP_KERNEL);
+	if (!ktd253)
+		return -ENOMEM;
+	ktd253->dev = dev;
+
+	ret = device_property_read_u32(dev, "max-brightness", &max_brightness);
+	if (ret)
+		max_brightness = KTD253_MAX_RATIO;
+	if (max_brightness > KTD253_MAX_RATIO) {
+		/* Clamp brightness to hardware max */
+		dev_err(dev, "illegal max brightness specified\n");
+		max_brightness = KTD253_MAX_RATIO;
+	}
+
+	ret = device_property_read_u32(dev, "default-brightness", &brightness);
+	if (ret)
+		brightness = KTD253_DEFAULT_RATIO;
+	if (brightness > max_brightness) {
+		/* Clamp default brightness to max brightness */
+		dev_err(dev, "default brightness exceeds max brightness\n");
+		brightness = max_brightness;
+	}
+
+	if (brightness)
+		/* This will be the default ratio when the KTD253 is enabled */
+		ktd253->ratio = KTD253_MAX_RATIO;
+	else
+		ktd253->ratio = 0;
+
+	ktd253->gpiod = devm_gpiod_get(dev, "enable",
+				       brightness ? GPIOD_OUT_HIGH :
+				       GPIOD_OUT_LOW);
+	if (IS_ERR(ktd253->gpiod)) {
+		ret = PTR_ERR(ktd253->gpiod);
+		if (ret != -EPROBE_DEFER)
+			dev_err(dev, "gpio line missing or invalid.\n");
+		return ret;
+	}
+	gpiod_set_consumer_name(ktd253->gpiod, dev_name(dev));
+
+	bl = devm_backlight_device_register(dev, dev_name(dev), dev, ktd253,
+					    &ktd253_backlight_ops, NULL);
+	if (IS_ERR(bl)) {
+		dev_err(dev, "failed to register backlight\n");
+		return PTR_ERR(bl);
+	}
+	bl->props.max_brightness = max_brightness;
+	/* When we just enable the GPIO line we set max brightness */
+	if (brightness) {
+		bl->props.brightness = brightness;
+		bl->props.power = FB_BLANK_UNBLANK;
+	} else {
+		bl->props.brightness = 0;
+		bl->props.power = FB_BLANK_POWERDOWN;
+	}
+
+	ktd253->bl = bl;
+	platform_set_drvdata(pdev, bl);
+	backlight_update_status(bl);
+
+	return 0;
+}
+
+static const struct of_device_id ktd253_backlight_of_match[] = {
+	{ .compatible = "kinetic,ktd253" },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, ktd253_backlight_of_match);
+
+static struct platform_driver ktd253_backlight_driver = {
+	.driver = {
+		.name = "ktd253-backlight",
+		.of_match_table = ktd253_backlight_of_match,
+	},
+	.probe		= ktd253_backlight_probe,
+};
+module_platform_driver(ktd253_backlight_driver);
+
+MODULE_AUTHOR("Linus Walleij <linus.walleij@linaro.org>");
+MODULE_DESCRIPTION("Kinetic KTD253 Backlight Driver");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:ktd253-backlight");
-- 
2.26.2

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Re: [PATCH 1/3 v3] dt-bindings: backlight: Add some common backlight properties

[Daniel Thompson]

On Wed, Aug 19, 2020 at 10:51:48PM +0200, Linus Walleij wrote:
> Let's use a common.yaml include for the backlight like we do with
> the LEDs. The LEDs are inherently incompatible so their bindings
> cannot be reused for backlight.
> 
> Cc: devicetree@vger.kernel.org
> Suggested-by: Sam Ravnborg <sam@ravnborg.org>
> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

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


> ---
> ChangeLog v2->v3:
> - Drop the | for the description
> - Drop the "default-on" property, we're not using it.
> - Drop the minimum 0 for unsigned u32:s
> ChangeLog v1->v2:
> - New patch as suggested by Sam.
> ---
>  .../bindings/leds/backlight/common.yaml       | 34 +++++++++++++++++++
>  1 file changed, 34 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/leds/backlight/common.yaml
> 
> diff --git a/Documentation/devicetree/bindings/leds/backlight/common.yaml b/Documentation/devicetree/bindings/leds/backlight/common.yaml
> new file mode 100644
> index 000000000000..4e7e95e331a5
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/leds/backlight/common.yaml
> @@ -0,0 +1,34 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/leds/backlight/common.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Common backlight properties
> +
> +maintainers:
> +  - Lee Jones <lee.jones@linaro.org>
> +  - Daniel Thompson <daniel.thompson@linaro.org>
> +  - Jingoo Han <jingoohan1@gmail.com>
> +
> +description:
> +  Backlight devices provide backlight for different types of graphical
> +  displays. They are typically but not necessarily implemented using a white
> +  LED powered by a boost converter.
> +
> +properties:
> +  default-brightness:
> +    description:
> +      The default brightness that should be applied to the LED by the operating
> +      system on start-up. The brightness should not exceed the brightness the
> +      LED can provide.
> +    $ref: /schemas/types.yaml#definitions/uint32
> +
> +  max-brightness:
> +    description:
> +      Normally the maximum brightness is determined by the hardware and this
> +      property is not required. This property is used to put a software limit
> +      on the brightness apart from what the driver says, as it could happen
> +      that a LED can be made so bright that it gets damaged or causes damage
> +      due to restrictions in a specific system, such as mounting conditions.
> +    $ref: /schemas/types.yaml#definitions/uint32
> -- 
> 2.26.2
> 

Re: [PATCH 1/3 v3] dt-bindings: backlight: Add some common backlight properties

[Daniel Thompson]

On Wed, Aug 19, 2020 at 10:51:48PM +0200, Linus Walleij wrote:
> Let's use a common.yaml include for the backlight like we do with
> the LEDs. The LEDs are inherently incompatible so their bindings
> cannot be reused for backlight.
> 
> Cc: devicetree@vger.kernel.org
> Suggested-by: Sam Ravnborg <sam@ravnborg.org>
> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

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


> ---
> ChangeLog v2->v3:
> - Drop the | for the description
> - Drop the "default-on" property, we're not using it.
> - Drop the minimum 0 for unsigned u32:s
> ChangeLog v1->v2:
> - New patch as suggested by Sam.
> ---
>  .../bindings/leds/backlight/common.yaml       | 34 +++++++++++++++++++
>  1 file changed, 34 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/leds/backlight/common.yaml
> 
> diff --git a/Documentation/devicetree/bindings/leds/backlight/common.yaml b/Documentation/devicetree/bindings/leds/backlight/common.yaml
> new file mode 100644
> index 000000000000..4e7e95e331a5
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/leds/backlight/common.yaml
> @@ -0,0 +1,34 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/leds/backlight/common.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Common backlight properties
> +
> +maintainers:
> +  - Lee Jones <lee.jones@linaro.org>
> +  - Daniel Thompson <daniel.thompson@linaro.org>
> +  - Jingoo Han <jingoohan1@gmail.com>
> +
> +description:
> +  Backlight devices provide backlight for different types of graphical
> +  displays. They are typically but not necessarily implemented using a white
> +  LED powered by a boost converter.
> +
> +properties:
> +  default-brightness:
> +    description:
> +      The default brightness that should be applied to the LED by the operating
> +      system on start-up. The brightness should not exceed the brightness the
> +      LED can provide.
> +    $ref: /schemas/types.yaml#definitions/uint32
> +
> +  max-brightness:
> +    description:
> +      Normally the maximum brightness is determined by the hardware and this
> +      property is not required. This property is used to put a software limit
> +      on the brightness apart from what the driver says, as it could happen
> +      that a LED can be made so bright that it gets damaged or causes damage
> +      due to restrictions in a specific system, such as mounting conditions.
> +    $ref: /schemas/types.yaml#definitions/uint32
> -- 
> 2.26.2
> 
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Re: [PATCH 2/3 v3] dt-bindings: backlight: Add Kinetic KTD253 bindings

[Daniel Thompson]

On Wed, Aug 19, 2020 at 10:51:49PM +0200, Linus Walleij wrote:
> This adds device tree bindings for the Kinetic KTD253
> white LED backlight driver.
> 
> Cc: devicetree@vger.kernel.org
> Cc: Sam Ravnborg <sam@ravnborg.org>
> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

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


> ---
> ChangeLog v2->v3:
> - Drop the pointless cargo-culted "default-on" property that
>   we were not using
> - Correct the brightness in the example to something legal (13)
> ChangeLog v1->v2:
> - Create common.yaml for backlight as suggested by Sam and
>   use that.
> - Rename the GPIO line "enable-gpios"
> ---
>  .../leds/backlight/kinetic,ktd253.yaml        | 46 +++++++++++++++++++
>  1 file changed, 46 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/leds/backlight/kinetic,ktd253.yaml
> 
> diff --git a/Documentation/devicetree/bindings/leds/backlight/kinetic,ktd253.yaml b/Documentation/devicetree/bindings/leds/backlight/kinetic,ktd253.yaml
> new file mode 100644
> index 000000000000..7a6ec1f8c0f3
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/leds/backlight/kinetic,ktd253.yaml
> @@ -0,0 +1,46 @@
> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/leds/backlight/kinetic,ktd253.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Kinetic Technologies KTD253 one-wire backlight
> +
> +maintainers:
> +  - Linus Walleij <linus.walleij@linaro.org>
> +
> +description: |
> +  The Kinetic Technologies KTD253 is a white LED backlight that is
> +  controlled by a single GPIO line. If you just turn on the backlight
> +  it goes to maximum backlight then you can set the level of backlight
> +  using pulses on the enable wire. This is sometimes referred to as
> +  "expresswire".
> +
> +allOf:
> +  - $ref: common.yaml#
> +
> +properties:
> +  compatible:
> +    const: kinetic,ktd253
> +
> +  enable-gpios:
> +    description: GPIO to use to enable/disable and dim the backlight.
> +    maxItems: 1
> +
> +  default-brightness: true
> +  max-brightness: true
> +
> +required:
> +  - compatible
> +  - enable-gpios
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    #include <dt-bindings/gpio/gpio.h>
> +    backlight {
> +        compatible = "kinetic,ktd253";
> +        enable-gpios = <&gpio2 5 GPIO_ACTIVE_HIGH>;
> +        default-brightness = <13>;
> +    };
> -- 
> 2.26.2
> 

Re: [PATCH 2/3 v3] dt-bindings: backlight: Add Kinetic KTD253 bindings

[Daniel Thompson]

On Wed, Aug 19, 2020 at 10:51:49PM +0200, Linus Walleij wrote:
> This adds device tree bindings for the Kinetic KTD253
> white LED backlight driver.
> 
> Cc: devicetree@vger.kernel.org
> Cc: Sam Ravnborg <sam@ravnborg.org>
> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

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


> ---
> ChangeLog v2->v3:
> - Drop the pointless cargo-culted "default-on" property that
>   we were not using
> - Correct the brightness in the example to something legal (13)
> ChangeLog v1->v2:
> - Create common.yaml for backlight as suggested by Sam and
>   use that.
> - Rename the GPIO line "enable-gpios"
> ---
>  .../leds/backlight/kinetic,ktd253.yaml        | 46 +++++++++++++++++++
>  1 file changed, 46 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/leds/backlight/kinetic,ktd253.yaml
> 
> diff --git a/Documentation/devicetree/bindings/leds/backlight/kinetic,ktd253.yaml b/Documentation/devicetree/bindings/leds/backlight/kinetic,ktd253.yaml
> new file mode 100644
> index 000000000000..7a6ec1f8c0f3
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/leds/backlight/kinetic,ktd253.yaml
> @@ -0,0 +1,46 @@
> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/leds/backlight/kinetic,ktd253.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Kinetic Technologies KTD253 one-wire backlight
> +
> +maintainers:
> +  - Linus Walleij <linus.walleij@linaro.org>
> +
> +description: |
> +  The Kinetic Technologies KTD253 is a white LED backlight that is
> +  controlled by a single GPIO line. If you just turn on the backlight
> +  it goes to maximum backlight then you can set the level of backlight
> +  using pulses on the enable wire. This is sometimes referred to as
> +  "expresswire".
> +
> +allOf:
> +  - $ref: common.yaml#
> +
> +properties:
> +  compatible:
> +    const: kinetic,ktd253
> +
> +  enable-gpios:
> +    description: GPIO to use to enable/disable and dim the backlight.
> +    maxItems: 1
> +
> +  default-brightness: true
> +  max-brightness: true
> +
> +required:
> +  - compatible
> +  - enable-gpios
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    #include <dt-bindings/gpio/gpio.h>
> +    backlight {
> +        compatible = "kinetic,ktd253";
> +        enable-gpios = <&gpio2 5 GPIO_ACTIVE_HIGH>;
> +        default-brightness = <13>;
> +    };
> -- 
> 2.26.2
> 
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Re: [PATCH 1/3 v3] dt-bindings: backlight: Add some common backlight properties

[Rob Herring]

On Wed, Aug 19, 2020 at 10:51:48PM +0200, Linus Walleij wrote:
> Let's use a common.yaml include for the backlight like we do with
> the LEDs. The LEDs are inherently incompatible so their bindings
> cannot be reused for backlight.
> 
> Cc: devicetree@vger.kernel.org
> Suggested-by: Sam Ravnborg <sam@ravnborg.org>
> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
> ---
> ChangeLog v2->v3:
> - Drop the | for the description
> - Drop the "default-on" property, we're not using it.
> - Drop the minimum 0 for unsigned u32:s
> ChangeLog v1->v2:
> - New patch as suggested by Sam.
> ---
>  .../bindings/leds/backlight/common.yaml       | 34 +++++++++++++++++++
>  1 file changed, 34 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/leds/backlight/common.yaml

Reviewed-by: Rob Herring <robh@kernel.org>

Re: [PATCH 1/3 v3] dt-bindings: backlight: Add some common backlight properties

[Rob Herring]

On Wed, Aug 19, 2020 at 10:51:48PM +0200, Linus Walleij wrote:
> Let's use a common.yaml include for the backlight like we do with
> the LEDs. The LEDs are inherently incompatible so their bindings
> cannot be reused for backlight.
> 
> Cc: devicetree@vger.kernel.org
> Suggested-by: Sam Ravnborg <sam@ravnborg.org>
> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
> ---
> ChangeLog v2->v3:
> - Drop the | for the description
> - Drop the "default-on" property, we're not using it.
> - Drop the minimum 0 for unsigned u32:s
> ChangeLog v1->v2:
> - New patch as suggested by Sam.
> ---
>  .../bindings/leds/backlight/common.yaml       | 34 +++++++++++++++++++
>  1 file changed, 34 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/leds/backlight/common.yaml

Reviewed-by: Rob Herring <robh@kernel.org>
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Re: [PATCH 2/3 v3] dt-bindings: backlight: Add Kinetic KTD253 bindings

[Rob Herring]

On Wed, 19 Aug 2020 22:51:49 +0200, Linus Walleij wrote:
> This adds device tree bindings for the Kinetic KTD253
> white LED backlight driver.
> 
> Cc: devicetree@vger.kernel.org
> Cc: Sam Ravnborg <sam@ravnborg.org>
> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
> ---
> ChangeLog v2->v3:
> - Drop the pointless cargo-culted "default-on" property that
>   we were not using
> - Correct the brightness in the example to something legal (13)
> ChangeLog v1->v2:
> - Create common.yaml for backlight as suggested by Sam and
>   use that.
> - Rename the GPIO line "enable-gpios"
> ---
>  .../leds/backlight/kinetic,ktd253.yaml        | 46 +++++++++++++++++++
>  1 file changed, 46 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/leds/backlight/kinetic,ktd253.yaml
> 

Reviewed-by: Rob Herring <robh@kernel.org>

Re: [PATCH 2/3 v3] dt-bindings: backlight: Add Kinetic KTD253 bindings

[Rob Herring]

On Wed, 19 Aug 2020 22:51:49 +0200, Linus Walleij wrote:
> This adds device tree bindings for the Kinetic KTD253
> white LED backlight driver.
> 
> Cc: devicetree@vger.kernel.org
> Cc: Sam Ravnborg <sam@ravnborg.org>
> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
> ---
> ChangeLog v2->v3:
> - Drop the pointless cargo-culted "default-on" property that
>   we were not using
> - Correct the brightness in the example to something legal (13)
> ChangeLog v1->v2:
> - Create common.yaml for backlight as suggested by Sam and
>   use that.
> - Rename the GPIO line "enable-gpios"
> ---
>  .../leds/backlight/kinetic,ktd253.yaml        | 46 +++++++++++++++++++
>  1 file changed, 46 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/leds/backlight/kinetic,ktd253.yaml
> 

Reviewed-by: Rob Herring <robh@kernel.org>
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Re: [PATCH 1/3 v3] dt-bindings: backlight: Add some common backlight properties

[Lee Jones]

On Wed, 19 Aug 2020, Linus Walleij wrote:

> Let's use a common.yaml include for the backlight like we do with
> the LEDs. The LEDs are inherently incompatible so their bindings
> cannot be reused for backlight.
> 
> Cc: devicetree@vger.kernel.org
> Suggested-by: Sam Ravnborg <sam@ravnborg.org>
> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
> ---
> ChangeLog v2->v3:
> - Drop the | for the description
> - Drop the "default-on" property, we're not using it.
> - Drop the minimum 0 for unsigned u32:s
> ChangeLog v1->v2:
> - New patch as suggested by Sam.
> ---
>  .../bindings/leds/backlight/common.yaml       | 34 +++++++++++++++++++
>  1 file changed, 34 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/leds/backlight/common.yaml

Applied, thanks.

-- 
Lee Jones [李琼斯]
Senior Technical Lead - Developer Services
Linaro.org │ Open source software for Arm SoCs
Follow Linaro: Facebook | Twitter | Blog

Re: [PATCH 1/3 v3] dt-bindings: backlight: Add some common backlight properties

[Lee Jones]

On Wed, 19 Aug 2020, Linus Walleij wrote:

> Let's use a common.yaml include for the backlight like we do with
> the LEDs. The LEDs are inherently incompatible so their bindings
> cannot be reused for backlight.
> 
> Cc: devicetree@vger.kernel.org
> Suggested-by: Sam Ravnborg <sam@ravnborg.org>
> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
> ---
> ChangeLog v2->v3:
> - Drop the | for the description
> - Drop the "default-on" property, we're not using it.
> - Drop the minimum 0 for unsigned u32:s
> ChangeLog v1->v2:
> - New patch as suggested by Sam.
> ---
>  .../bindings/leds/backlight/common.yaml       | 34 +++++++++++++++++++
>  1 file changed, 34 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/leds/backlight/common.yaml

Applied, thanks.

-- 
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Senior Technical Lead - Developer Services
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Re: [PATCH 2/3 v3] dt-bindings: backlight: Add Kinetic KTD253 bindings

[Lee Jones]

On Wed, 19 Aug 2020, Linus Walleij wrote:

> This adds device tree bindings for the Kinetic KTD253
> white LED backlight driver.
> 
> Cc: devicetree@vger.kernel.org
> Cc: Sam Ravnborg <sam@ravnborg.org>
> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
> ---
> ChangeLog v2->v3:
> - Drop the pointless cargo-culted "default-on" property that
>   we were not using
> - Correct the brightness in the example to something legal (13)
> ChangeLog v1->v2:
> - Create common.yaml for backlight as suggested by Sam and
>   use that.
> - Rename the GPIO line "enable-gpios"
> ---
>  .../leds/backlight/kinetic,ktd253.yaml        | 46 +++++++++++++++++++
>  1 file changed, 46 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/leds/backlight/kinetic,ktd253.yaml

Applied, thanks.

-- 
Lee Jones [李琼斯]
Senior Technical Lead - Developer Services
Linaro.org │ Open source software for Arm SoCs
Follow Linaro: Facebook | Twitter | Blog

Re: [PATCH 2/3 v3] dt-bindings: backlight: Add Kinetic KTD253 bindings

[Lee Jones]

On Wed, 19 Aug 2020, Linus Walleij wrote:

> This adds device tree bindings for the Kinetic KTD253
> white LED backlight driver.
> 
> Cc: devicetree@vger.kernel.org
> Cc: Sam Ravnborg <sam@ravnborg.org>
> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
> ---
> ChangeLog v2->v3:
> - Drop the pointless cargo-culted "default-on" property that
>   we were not using
> - Correct the brightness in the example to something legal (13)
> ChangeLog v1->v2:
> - Create common.yaml for backlight as suggested by Sam and
>   use that.
> - Rename the GPIO line "enable-gpios"
> ---
>  .../leds/backlight/kinetic,ktd253.yaml        | 46 +++++++++++++++++++
>  1 file changed, 46 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/leds/backlight/kinetic,ktd253.yaml

Applied, thanks.

-- 
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Senior Technical Lead - Developer Services
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Re: [PATCH 3/3 v3] backlight: Add Kinetic KTD253 backlight driver

[Lee Jones]

On Wed, 19 Aug 2020, Linus Walleij wrote:

> The Kinetic KTD253 backlight driver is controlled with a
> single GPIO line, but still supports a range of brightness
> settings by sending fast pulses on the line.
> 
> This is based off the source code release for the Samsung
> GT-S7710 mobile phone.
> 
> Cc: Sam Ravnborg <sam@ravnborg.org>
> Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
> ---
> ChangeLog v2->v3:
> - Collect Daniel's review tag.
> ChangeLog v1->v2:
> - Expose the 32 actual hardware levels of brightness directly
>   instead of using an interpolated "brightness" table.
> - Use the new backlight_get_brightness() helper.
> - Call backlight_update_status() in probe instead of calling
>   local functions to sync brightness.
> - Sort includes alphabetically.
> - Name the GPIO line "enable" and grab that in accordance
>   with the change to the DT bindings.
> ---
>  MAINTAINERS                                |   6 +
>  drivers/video/backlight/Kconfig            |   8 +
>  drivers/video/backlight/Makefile           |   1 +
>  drivers/video/backlight/ktd253-backlight.c | 198 +++++++++++++++++++++
>  4 files changed, 213 insertions(+)
>  create mode 100644 drivers/video/backlight/ktd253-backlight.c

Applied, thanks.

-- 
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Senior Technical Lead - Developer Services
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Re: [PATCH 3/3 v3] backlight: Add Kinetic KTD253 backlight driver

[Linus Walleij]

On Fri, Aug 28, 2020 at 12:47 PM Lee Jones <lee.jones@linaro.org> wrote:

> >  create mode 100644 drivers/video/backlight/ktd253-backlight.c
>
> Applied, thanks.

Not to unnecessarily nag but I can't see this in linux-next and since we
are at -rc7 it makes me a bit nervous, is it still gonna be in v5.10?

Yours,
Linus Walleij
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Re: [PATCH 3/3 v3] backlight: Add Kinetic KTD253 backlight driver

[Lee Jones]

On Wed, 30 Sep 2020, Linus Walleij wrote:

> On Fri, Aug 28, 2020 at 12:47 PM Lee Jones <lee.jones@linaro.org> wrote:
> 
> > >  create mode 100644 drivers/video/backlight/ktd253-backlight.c
> >
> > Applied, thanks.
> 
> Not to unnecessarily nag but I can't see this in linux-next and since we
> are at -rc7 it makes me a bit nervous, is it still gonna be in v5.10?

Heh, you're right.  Apologies, tested and pushed now.

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