Take Dell XPS 13 (2015) as an example. The vbt min 10 out of [0..255].
The PWM max is 937 so the corresponding PWM min is 37 (10*937/256).
This commit makes the sysfs brightness 1 map to the PWM brightness 37
and 100 map to the PWM brightness 937.
Signed-off-by: Shih-Yuan Lee (FourDollars) <sy...@canonical.com>
---
drivers/gpu/drm/i915/intel_panel.c | 30 ++++++++++++++++++++++++------
1 file changed, 24 insertions(+), 6 deletions(-)
diff --git a/drivers/gpu/drm/i915/intel_panel.c
b/drivers/gpu/drm/i915/intel_panel.c
index a24df35..8652ce2 100644
--- a/drivers/gpu/drm/i915/intel_panel.c
+++ b/drivers/gpu/drm/i915/intel_panel.c
@@ -1207,11 +1207,12 @@ static int intel_backlight_device_register(struct
intel_connector *connector)
memset(&props, 0, sizeof(props));
props.type = BACKLIGHT_RAW;
- /*
- * Note: Everything should work even if the backlight device max
- * presented to the userspace is arbitrarily chosen.
- */
- props.max_brightness = panel->backlight.max;
+ /* Setting max to fixed 100 if the range is large enough. */
+ if (panel->backlight.max > panel->backlight.min + 99)
+ props.max_brightness = 100;
+ else
+ props.max_brightness = panel->backlight.max -
panel->backlight.min;
+
props.brightness = scale_hw_to_user(connector,
panel->backlight.level,
props.max_brightness);
@@ -1414,6 +1415,8 @@ static u32 get_backlight_min_vbt(struct intel_connector
*connector)
struct drm_device *dev = connector->base.dev;
struct drm_i915_private *dev_priv = dev->dev_private;
struct intel_panel *panel = &connector->panel;
+ u32 pwm_min;
+ u32 pwm_step;
int min;
WARN_ON(panel->backlight.max == 0);
@@ -1432,7 +1435,22 @@ static u32 get_backlight_min_vbt(struct intel_connector
*connector)
}
/* vbt value is a coefficient in range [0..255] */
- return scale(min, 0, 255, 0, panel->backlight.max);
+ pwm_min = scale(min, 0, 255, 0, panel->backlight.max);
+
+ /* Calculate the PWM step */
+ if (panel->backlight.max > pwm_min + 99)
+ pwm_step = scale(1, 0, 99, 0, panel->backlight.max - pwm_min);
+ else
+ pwm_step = 1;
+
+ /*
+ * Because sysfs brightness 0 is used to turn off the backlight, we
need step
+ * down a little bit to make sysfs brightness 1 match the lowest
brightness.
+ */
+ if (pwm_min >= pwm_step)
+ pwm_min -= pwm_step;
+
+ return pwm_min;
}
static int lpt_setup_backlight(struct intel_connector *connector, enum pipe
unused)
--
1.9.1
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