[Intel-gfx] [PATCH] properly enable the blc controller on the right pipe

Carsten Emde C.Emde at osadl.org
Tue Jul 24 09:30:26 CEST 2012

On 07/20/2012 10:10 AM, Daniel Vetter wrote:
> On Fri, Jul 20, 2012 at 12:51:41AM +0200, Carsten Emde wrote:
>> On 07/19/2012 04:40 PM, Daniel Vetter wrote:
>>> Well, the backlight-confusion branch had a bug and outright disabled
>>> the intel backlight :( drm-intel-next-queued should have fixes for all
>>> the backlight goofus I've accidentally created, so testing feedback on
>>> that branch would be highly appreciated.
>> This branch is now broken again. The original drm-intel-next-queued
>> branch works well (it still has the quirk), but after I reverted the
>> Acer quirk, the screen remains dark.
>> I double-checked it and used exactly the same patch to revert the
>> quirk in the two trees: The backlight-confusion branch works, and
>> the drm-intel-next-queued branch does not.
>> I then used drivers/gpu/drm/i915/intel_panel.c from
>> backlight-confusion in drm-intel-next-queued and - it worked again.
>> When testing the two differences separately it turned out this patch
>> did the magic:
> Yeah, I guess your system only worked whith the old code because it
> accidentally disabled the entire backlight stuff. Now that that doesn't
> happen any more, it's as broken as ever.
> I'll look into creating another patch, afaict from digging through git
> history, this backlight combination mode is totally bogus. But if we kill
> it, a few machines will resume with dimmed backlight, because we don't
> restore the lbpc register properly.
After all that hassle and bearing in mind that we found only two 
notebooks so far, Acer Aspire 5732Z and 5734Z, that suffer from this 
backlight inversion problem, shouldn't we simply return to the quirk 
solution? I would quickly add the data of the other Acer to the 
backlight quirks, send a rebased patch, and we are all set.


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