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

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Hi,

On 19-12-17 20:48, Ville Syrjälä wrote:
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.

Yes that is is not applicable to the Vi8 where I'm seeing the
77000 KHz used by GOP vs 78125 KHz used by i915.

Looking at intel_dsi_vbt_init the pclk on the boards where I'm
seeing an inconsistency is just taken directly from mode->clock,
which in turn is simply dvo_timing->clock * 10.

Again: these different pixel-clocks do not seem to be an issue,
I just noticed this too while looking at the problem best seen
here:

https://fedorapeople.org/~jwrdegoede/IMG_20171217_195637.jpg

Regards,

Hans
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