https://bugs.freedesktop.org/show_bug.cgi?id=48772
--- Comment #11 from Alex Deucher agd5f@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.