Low Threshold Brightness should be configured to have a linear relation
in brightness scale. This patch adds device tree support for low
threshold brightness as optional one for pwm_backlight.
Signed-off-by: Philip, Avinash <avinashphilip@xxxxxx>
---
:100644 100644 1e4fc72... 5c54380... M Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt
:100644 100644 995f016... 4965408... M drivers/video/backlight/pwm_bl.c
.../bindings/video/backlight/pwm-backlight.txt | 21 ++++++++++++++++++++
drivers/video/backlight/pwm_bl.c | 5 ++++
2 files changed, 26 insertions(+), 0 deletions(-)
diff --git a/Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt b/Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt
index 1e4fc72..5c54380 100644
--- a/Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt
+++ b/Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt
@@ -14,6 +14,8 @@ Required properties:
Optional properties:
- pwm-names: a list of names for the PWM devices specified in the
"pwms" property (see PWM binding[0])
+ - low_threshold_brightness: brightness threshold low level. (get linear
+ scales in brightness in low end of brightness levels)
[0]: Documentation/devicetree/bindings/pwm/pwm.txt
@@ -26,3 +28,22 @@ Example:
brightness-levels = <0 4 8 16 32 64 128 255>;
default-brightness-level = <6>;
};
+
+Example for brightness_threshold_level:
+
+ backlight {
+ compatible = "pwm-backlight";
+ pwms = <&pwm 0 50000>;
+
+ brightness-levels = <0 4 8 16 32 64 128 255>;
+ default-brightness-level = <6>;
+ low_threshold_brightness = <50>;
+ };
+};
+Note:
+Low threshold support is required to have linear brightness scale from
+0 to max. For some panels, backlight absent on low end of brightness
+scale. So support for Low Threshold been required. So that the scale of
+brightness changed from Low Threshold to Max in scales defined in
+brightness-levels. In this example 20% maximum brightness scale should
+be required to turn on panel backlight.
diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
index 995f016..4965408 100644
--- a/drivers/video/backlight/pwm_bl.c
+++ b/drivers/video/backlight/pwm_bl.c
@@ -143,6 +143,11 @@ static int pwm_backlight_parse_dt(struct device *dev,
data->dft_brightness = value;
data->max_brightness--;
+
+ ret = of_property_read_u32(node, "low_threshold_brightness",
+ &value);
+ if (!ret)
+ data->lth_brightness = value;
}
/*
--
1.7.1
--
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