Re: [PATCH 6/6] drm/i915: set the backlight panel delays registers to 1

[Jani Nikula <jani.nikula@linux.intel.com>]

On Tue, 28 Jan 2014, Daniel Vetter <daniel@ffwll.ch> wrote:
> On Tue, Jan 28, 2014 at 09:57:57AM +0200, Jani Nikula wrote:
>> On Thu, 19 Dec 2013, Paulo Zanoni <przanoni@gmail.com> wrote:
>> > From: Paulo Zanoni <paulo.r.zanoni@intel.com>
>> >
>> > Because we already do the wait in software: see
>> > ironlake_wait_backlight_on and ironlake_edp_wait_backlight_off.
>> >
>> > For the "backlight on" delay, even BSpec says we need to program 0x1
>> > to PP_ON_DELAYS 12:0.
>> >
>> > For the "backlight off" delay, if we don't do the same thing, when we
>> > call ironlake_wait_panel_off we'll end up waiting for the it again.
>> >
>> > On my machine the off delay is 200ms, so we save this amount of time
>> > whenever we disable the panel (e.g, suspend).
>> 
>> Whoa. This appears to fix an eDP black screen with 24->18 bpp dithering:
>> 
>> https://bugs.freedesktop.org/show_bug.cgi?id=73567#c21
>
> I dunno whether I should cry or laugh ... Problem is that I don't really
> see a way to port just this patch to 3.14. So we need the entire series,
> which is a bit much imo. At least until we have more users scaling our
> walls.

I also dunno whether I should cry or laugh... but for me it's because
the report has two devices of the same model, and one gets fixed by this
and the other not...

BR,
Jani.


-- 
Jani Nikula, Intel Open Source Technology Center