[Bug 49402] [snb dp dongle] DP-to-dual-HDMI (link_train issue?)

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=49402

--- Comment #18 from Jesse Barnes <jbarnes at virtuousgeek.org> ---
On Tue, 16 Apr 2013 09:50:53 +0000
bugzilla-daemon at freedesktop.org wrote:

> https://bugs.freedesktop.org/show_bug.cgi?id=49402
> 
> --- Comment #17 from Ville Syrjala <ville.syrjala at linux.intel.com> ---
> I tried a few random things for this on IVB.
> 
> - tried to send the training pattern and training lane set with one aux write
> instead of two.
> - tried to disable enhanced framing
> - tried to force some voltage swing/pre-emphasis values
> - tried with 6 bpc so that we'd get 1.62 links speed instead of 2.7
> - tried to send post cursor2 traning values in case that would trick the sink
> into cooperation
> 
> Unfortunately none of that helped.
> 
> The BIOS produces a picture with the dongle, so I tried to compare some of the
> register values. The main differences I saw were that the BIOS uses auto
> training for FDI, some of the M/N values were different, and of course the BIOS
> also has panel fitter active since it's using a 720x400 resolution.

The m/n values could definitely be a factor.  Maybe our DP values are
slightly off and causing some skew in the dongle?

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