[Intel-gfx] [PATCH] drm/i915/vlv: Add cdclk workaround for DSI

[Ville Syrjälä]

On Tue, Dec 19, 2017 at 08:31:07PM +0100, Hans de Goede wrote:
> Hi,
> 
> I forgot to add a coverletter, anyways what I wanted to put in the
> coverletter and not in the commit message is a link to a picture of the
> problem this fixes:
> 
> https://fedorapeople.org/~jwrdegoede/IMG_20171217_195637.jpg
> 
> Note the screen is actually a portrait screen, so the picture is the
> right way up. Beside the obvious left shift with wrap-around of the
> picture, also all the green in there is supposed to be blue.
> 
> Another less clear picture is this one:
> 
> https://fedorapeople.org/~jwrdegoede/IMG_20171217_195507.jpg
> 
> Again with wrong colors.
> 
> ###
> 
> While working on this I also noticed that the pixelclock as
> the driver gets it from the VBT is not the same as the one the
> GOP uses, on the tablet in question the VBT says 77000 KHz
> and the GOP uses (according to the initial readback) 78125 KHz,
> on another tablet I noticed the VBT saying 78125 KHz, where
> as the GOP was using 68xxx KHz which came to a refresh-rate
> of around 60 Hz, where as the VBT value is 69 Hz IIRC.
> 
> Neither of these cause any actual issue (fixing the pixelclock
> to match the GOP programmed value does not fix the issue, where
> as using the GOP cdclk of 333333KHz does).

https://patchwork.freedesktop.org/patch/127189/

I suppose it's unlike that would help here since it's just about the 
overlap in dual link mode, but there could be other fail in the DSI
clock code.


-- 
Ville Syrjälä
Intel OTC