[Letux-kernel] LetuxOS Kernel v5.0-rc1 - BeaglBone backlight issues

H. Nikolaus Schaller hns at goldelico.com
Tue Mar 19 18:26:59 CET 2019


> Am 19.03.2019 um 16:18 schrieb H. Nikolaus Schaller <hns at goldelico.com>:
> 
> 
>> Am 18.03.2019 um 21:04 schrieb H. Nikolaus Schaller <hns at goldelico.com>:
>> 
>> * BBB+LCDC:	display ok, backlight is always on (but does not respond to "xset dpms")
> 
> This seems to have a threefold reason:
> 1. there is no DT node for connecting the backlight to the panel driver
> 2. the CONFIG_PWM_TIEHRPWM driver is not configured
> 3. after proerly configuring, pwmss_probe() or ehrpwm_pwm_probe() is never called...
>   and the pwm_bl finally fails with EPROBE_DEFER and no /sys/class/backlight is
>   registered.

Ah,
I found it. Seems to be

	https://elixir.bootlin.com/linux/v5.1-rc1/source/arch/arm/boot/dts/am33xx-l4.dtsi#L1953

	status = "disabled";

for the epwmss at 0 parent node. Therefore it does not probe it and look for the ehrpwm1 child node
(which I already have enabled in the specific DTS).

So now I can focus on experimenting with the SGX drivers and user space on this device...

BR,
Nikolaus


> The result is that the PWM driver does not run and therefore no backlight pwm driver.
> 
> I now wonder if it ever did work... Probably not...
> 
> BR,
> Nikolaus
> 
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