[Bug 48772] Signal unstable over Display Port on 2560x1440 monitor

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=48772

--- Comment #11 from Alex Deucher <agd5f at yahoo.com> 2012-04-20 08:19:54 PDT ---
(In reply to comment #9)
> 
> I never really understood this problem, not since the days of sdr. Single
> channel ddr3-1066 provides roughly 8 times the raw bandwidth of what a
> 2560x1440 resolution (at 32bpp, 60hz) needs so that should be plenty to serve
> other MC clients as well (with lesser priority). So what's the problem there,
> too small buffer size for scanout?

I'm just speculating.  I suspect it's more of a latency/timing thing than
bandwidth.  If the request is not there when the LB needs it, it'll run dry.

(In reply to comment #10)
> Does the driver know it's memory bandwidth so it could remove modes it cannot
> drive from the list?

It could and does in some cases and there's even code to check it in the
watermark setup although it probably needs a bit of tweaking for APUs. 
Unfortunately the way the drm is structured makes it hard to do a good job
since modesetting is per crtc so you only get a partial picture.  I'll talk to
the display team and see what they have to say.

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