1d7aaa0cfe
Some early bios versions seem to ship with the wrong tuning values for the MCH, possible resulting in pipe underruns under load. Especially on DP outputs this can lead to black screen, since DP really doesn't like an occasional whack from an underrun. Unfortunately the registers seem to be locked after boot, so the only thing we can do is politely point out issues and suggest a BIOS upgrade. Arthur Runyan pointed us at this issue while discussion DP bugs - thus far no confirmation from a bug report yet that it helps. But at least some of my machines here have wrong values, so this might be useful in understanding bug reports. v2: After a bit more discussion with Art and Ben we've decided to only the check the watermark values, since the OREF ones could be be a notch more aggressive on certain machines. Cc: Ben Widawsky <ben@bwidawsk.net> Cc: Runyan, Arthur J <arthur.j.runyan@intel.com> Reviewed-by: Ben Widawsky <ben@bwidawsk.net> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch> |
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