[PATCH v6 1/5] pwm-backlight: enable/disable the PWM before/after LCD enable toggle.

Enric Balletbo Serra eballetbo at gmail.com
Mon Mar 26 07:40:21 PDT 2018

Hi Pavel,

2018-03-26 12:42 GMT+02:00 Pavel Machek <pavel at ucw.cz>:
> On Mon 2018-03-26 11:52:09, Enric Balletbo i Serra wrote:
>> Before this patch the enable signal was set before the PWM signal and
>> vice-versa on power off. This sequence is wrong, at least, it is on
>> the different panels datasheets that I checked, so I inverted the sequence
>> to follow the specs.
>> For reference the following panels have the mentioned sequence:
>>   - N133HSE-EA1 (Innolux)
>>   - N116BGE (Innolux)
>>   - N156BGE-L21 (Innolux)
>>   - B101EAN0 (Auo)
>>   - B101AW03 (Auo)
>>   - LTN101NT05 (Samsung)
>>   - CLAA101WA01A (Chunghwa)
> Ok, but this changes behaviour for other panels, too. Are you sure you
> are not breaking one of those?

I can't say that I am 100% sure because I didn't find all the
datasheets of all the panels supported in the kernel. But all the
datasheets I checked specifies this sequence as valid. In general I
think that doesn't really matter, but I know that at least the
B116XTN02 panel requires enable first the PWM, wait 10ms and then
enable BL_EN to avoid garbage. So the other way around is not valid
for this panel. That's the reason for this patchset.

If anyone knows a panel that says the contrary, please let me know and
I'll try to rework the patches to satisfy both requirements.


>                                                                 Pavel
> --
> (english) http://www.livejournal.com/~pavelmachek
> (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

More information about the Linux-rockchip mailing list