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Ville Syrjälä 977d22b6df drm/i915: Do a dummy DPCD read before the actual read ... commit f6a1906674 upstream. Sometimes we seem to get utter garbage from DPCD reads. The resulting buffer is filled with the same byte, and the operation completed without errors. My HP ZR24w monitor seems particularly susceptible to this problem once it's gone into a sleep mode. The issue seems to happen only for the first AUX message that wakes the sink up. But as the first AUX read we often do is the DPCD receiver cap it does wreak a bit of havoc with subsequent link training etc. when the receiver cap bw/lane/etc. information is garbage. A sufficient workaround seems to be to perform a single byte dummy read before reading the actual data. I suppose that just wakes up the sink sufficiently and we can just throw away the returned data in case it's crap. DP_DPCD_REV seems like a sufficiently safe location to read here. Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com> Reviewed-by: Todd Previte <tprevite@gmail.com> Signed-off-by: Jani Nikula <jani.nikula@intel.com> Signed-off-by: Luis Henriques <luis.henriques@canonical.com>		History 2014-11-13 11:48:47 +00:00
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drm	drm/i915: Do a dummy DPCD read before the actual read	2014-11-13 11:48:47 +00:00
host1x	gpu: host1x: Rename internal functions for clarity	2014-06-05 23:10:30 +02:00
ipu-v3	Merge branch 'drm-next' of git://people.freedesktop.org/~airlied/linux	2014-06-12 11:32:30 -07:00
vga	vgaarb: Don't default exclusively to first video device with mem+io	2014-10-09 12:23:49 -07:00
Makefile	gpu: ipu-v3: Move i.MX IPUv3 core driver out of staging	2014-06-04 11:06:52 +02:00