On Thu, Apr 29, 2021 at 11:31:20AM +0000, pgeiem wrote:
On Thursday, April 29, 2021 1:00 PM, Daniel Thompson daniel.thompson@linaro.org wrote:
On Fri, Apr 23, 2021 at 01:04:23PM +0000, pgeiem wrote:
Dear all, On a custom board I have a simple DPI panel. Panel's backlight is drive with an I2C led driver (PCA9632). led-backlight driver is sued to manage this as a backlight. When using brightness-levels and default-brightness-level the backlight stay turned-off even if manually trying to set a different index value to brightness through sysfs. I traced this issue as follow: When led_bl_update_status() is called the brightness value is returned from backlight_get_brightness() which call backlight_is_blank(). In my case backlight_is_blank() return true due to props.power = FB_BLANK_POWERDOWN which is != FB_BLANK_UNBLANK. I traced why at startup props.power is FB_BLANK_POWERDOWN and found that in led_bl_probe() when a default brightness is set (>0) props.power is set to FB_BLANK_POWERDOWN which seems incorrect to me. I made the small change below and default brightness is correctly used at startup. I am not really sure this is an issue and if my change is correct or if I am doing something incorrect somewhere else. So I first would like to get your opinion on this and if correct will send a patch.
Makes sense. Please send this as a patch.
Daniel.
I finally believe this was correct.
A link between the panel and the backlight was missing in dts. With this link the backlight is turned on (props.power = FB_BLANK_UNBLANK) from drm_panel_enable function after enabling the panel.
Let me know if you disagree and still believe I should send the patch.
The original logic is definitely wrong.
However that doesn't mean the driver will be fully correct after fixing since it does look like is missing the logic found in other similar drivers (pwm-bl.c and gpio_backlight.c) to handle the various different cases w.r.t. handover from active backlight by the bootloader.
Daniel.