[Intel-gfx] [PATCH] drm/i915: fix up readout of the lvds dither bit on gen2/3

[Knut Petersen]

On 11.07.2013 19:22, Daniel Vetter wrote:
> On Thu, Jul 11, 2013 at 06:29:15PM +0200, Knut Petersen wrote:
>> On 11.07.2013 13:49, Chris Wilson wrote:
>>> On Thu, Jul 11, 2013 at 01:35:40PM +0200, Daniel Vetter wrote:
>>>> It's in the PFIT_CONTROL register, but very much associated with the
>>>> lvds encoder. So move the readout for it (in the case of an otherwise
>>>> disabled pfit) from the pipe to the lvds encoder's get_config
>>>> function.
>>>>
>>>> Otherwise we get a pipe state mismatch if we use pipe B for a non-lvds
>>>> output and we've left the dither bit enabled behind us. This can
>>>> happen if the BIOS has set the bit (some seem to unconditionally do
>>>> that, even in the complete absence of an lvds port), but not enabled
>>>> pipe B at boot-up. Then we won't clear the pfit control register since
>>>> we can only touch that if the pfit is associated with our pipe in the
>>>> crtc configuration - we could trample over the pfit state of the other
>>>> pipe otherwise since it's shared. Once pipe B is enabled we notice
>>>> that the 6to8 dither bit is set and complain about the mismatch.
>>>>
>>>> Note that testing indicates that we don't actually need to set this
>>>> bit when the pfit is disabled, dithering on 18bpp panels seems to work
>>>> regardless. But ripping that code out is not something for a bugfix
>>>> meant for -rc kernels.
>>>>
>>>> v2: While at it clarify the logic in i9xx_get_pfit_config, spurred by
>>>> comments from Chris on irc.
>>>>
>>>> v3: Use Chris suggestion to make the control flow in
>>>> i9xx_get_pfit_config easier to understand.
>>>>
>>>> v4: Kill the extra line, spotted by Chris.
>>>>
>>>> Reported-by: Knut Petersen <Knut_Petersen at t-online.de>
>>>> Cc: Knut Petersen <Knut_Petersen at t-online.de>
>>>> Cc: Chris Wilson <chris at chris-wilson.co.uk>
>>>> References: http://lists.freedesktop.org/archives/intel-gfx/2013-July/030092.html
>>>> Signed-off-by: Daniel Vetter <daniel.vetter at ffwll.ch>
>>> Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
>>> -Chris
>>>
>> Tested-by: Knut Petersen <Knut_Petersen at t-online.de>
>>
>> Thanks, that patch cures both inital boot and suspend/resume problems.
>> Attached find dmesg (inital boot) and dmesg2 (suspend/resume cycle).
> Thanks for testing and reporting this issue, patch is merged into my
> -fixes queue now.
>
> Thanks, Daniel
We have -rc2, but this patch is still missing ...

cu,
  Knut