When booting with DT make it possible to use the whole range of the PWM when
controlling the backlight in a same way it is possible when the kernel is
booted in non DT mode.
A new property "max-brightness-level" can be used to specify the maximum
value the PWM can handle (time slots).
DTS files can use either the "brightness-levels" or the "max-brightness-level"
to configure the PWM.
In case both of these properties exist the driver will prefer the
"brightness-levels" over the "max-brightness-level".
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@xxxxxx>
---
.../bindings/video/backlight/pwm-backlight.txt | 12 +++++++++--
drivers/video/backlight/pwm_bl.c | 24 ++++++++++++++--------
2 files changed, 25 insertions(+), 11 deletions(-)
diff --git a/Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt b/Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt
index 1e4fc72..517924b 100644
--- a/Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt
+++ b/Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt
@@ -3,13 +3,21 @@ pwm-backlight bindings
Required properties:
- compatible: "pwm-backlight"
- pwms: OF device-tree PWM specification (see PWM binding[0])
+
+ Brightness range can be configured with either "brightness-levels" or with
+ "max-brightness-level".
- brightness-levels: Array of distinct brightness levels. Typically these
are in the range from 0 to 255, but any range starting at 0 will do.
The actual brightness level (PWM duty cycle) will be interpolated
from these values. 0 means a 0% duty cycle (darkest/off), while the
last value in the array represents a 100% duty cycle (brightest).
- - default-brightness-level: the default brightness level (index into the
- array defined by the "brightness-levels" property)
+ - max-brightness-level: The maximum brightness level the PWM supports. When
+ the brightness is specified using this property the whole range from 0 to
+ "max-brightness-level" will be available to configure.
+ - default-brightness-level: the default brightness level. With
+ "brightness-levels" it is an index into the array defined by the
+ "brightness-levels" property. When it is used with "max-brightness-level"
+ it is the value in the range from 0 to "max-brightness-level"
Optional properties:
- pwm-names: a list of names for the PWM devices specified in the
diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
index df2d115..c0e4bc7 100644
--- a/drivers/video/backlight/pwm_bl.c
+++ b/drivers/video/backlight/pwm_bl.c
@@ -111,10 +111,17 @@ static int pwm_backlight_parse_dt(struct device *dev,
/* determine the number of brightness levels */
prop = of_find_property(node, "brightness-levels", &num_levels);
- if (!prop)
- return -EINVAL;
+ if (!prop) {
+ /* Levels not provided, look for the maximum property */
+ ret = of_property_read_u32(node, "max-brightness-level",
+ &value);
+ if (ret < 0)
+ return ret;
- num_levels /= sizeof(u32);
+ data->max_brightness = value;
+ } else {
+ num_levels /= sizeof(u32);
+ }
/* read brightness levels from DT property */
if (num_levels > 0) {
@@ -130,14 +137,13 @@ static int pwm_backlight_parse_dt(struct device *dev,
return ret;
data->max_brightness = num_levels;
+ }
- ret = of_property_read_u32(node, "default-brightness-level",
- &value);
- if (ret < 0)
- return ret;
+ ret = of_property_read_u32(node, "default-brightness-level", &value);
+ if (ret < 0)
+ return ret;
- data->dft_brightness = value;
- }
+ data->dft_brightness = value;
/*
* TODO: Most users of this driver use a number of GPIOs to control
--
1.8.1.1
--
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