summaryrefslogtreecommitdiffstats
diff options
context:
space:
mode:
authorEnric Balletbo i Serra <enric.balletbo@collabora.com>2018-04-09 10:33:31 +0200
committerLee Jones <lee.jones@linaro.org>2018-07-04 11:31:18 +0200
commit1e5e7cc794b5a332c23216dade0a2e937d694b7f (patch)
treecc70709be606271643554a68d33af26324b22433
parentbacklight: pwm_bl: Linear interpolation between brightness-levels (diff)
downloadlinux-1e5e7cc794b5a332c23216dade0a2e937d694b7f.tar.xz
linux-1e5e7cc794b5a332c23216dade0a2e937d694b7f.zip
dt-bindings: pwm-backlight: Add a num-interpolation-steps property
The num-interpolated-steps property specifies the number of interpolated steps between each value of brightness-level table. This is useful for high resolution PWMs to not have to list out every possible value in the brightness-level array. Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com> Acked-by: Daniel Thompson <daniel.thompson@linaro.org> Reviewed-by: Rob Herring <robh@kernel.org> Signed-off-by: Lee Jones <lee.jones@linaro.org>
-rw-r--r--Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt19
1 files changed, 19 insertions, 0 deletions
diff --git a/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt b/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt
index 310810906613..ce9b5746b774 100644
--- a/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt
+++ b/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt
@@ -21,6 +21,11 @@ Optional properties:
and enabling the backlight using GPIO.
- pwm-off-delay-ms: Delay in ms between disabling the backlight using GPIO
and setting PWM value to 0.
+ - num-interpolated-steps: Number of interpolated steps between each value
+ of brightness-levels table. This way a high
+ resolution pwm duty cycle can be used without
+ having to list out every possible value in the
+ brightness-level array.
[0]: Documentation/devicetree/bindings/pwm/pwm.txt
[1]: Documentation/devicetree/bindings/gpio/gpio.txt
@@ -39,3 +44,17 @@ Example:
post-pwm-on-delay-ms = <10>;
pwm-off-delay-ms = <10>;
};
+
+Example using num-interpolation-steps:
+
+ backlight {
+ compatible = "pwm-backlight";
+ pwms = <&pwm 0 5000000>;
+
+ brightness-levels = <0 2048 4096 8192 16384 65535>;
+ num-interpolated-steps = <2048>;
+ default-brightness-level = <4096>;
+
+ power-supply = <&vdd_bl_reg>;
+ enable-gpios = <&gpio 58 0>;
+ };