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

Ville Syrjälä ville.syrjala at linux.intel.com
Tue Dec 19 19:48:37 UTC 2017

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).


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

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