path: root/Documentation/kernel-parameters.txt
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authorDaniel Vetter <daniel.vetter@ffwll.ch>2015-08-26 21:49:42 +0200
committerDaniel Vetter <daniel.vetter@ffwll.ch>2015-09-08 13:45:51 +0200
commitf8aeb41c4b7e9de0a4df4ed1ba78cd6ee5c87281 (patch)
treedcb44b375c102ac180a000b94cad46b94a4f8a24 /Documentation/kernel-parameters.txt
parentf64c5573d253ab3f9c01b4056c5f75a889d18502 (diff)
drm/atomic: refuse changing CRTC for planes directly
Very strictly speaking this is possible if you have special hw and genlocked CRTCs. In general switching a plane between two active CRTC just won't work so well and is probably not tested at all. Just forbid it. I've put this into the core since right now no helper or driver copes with it, no userspace has code for it and no one asks for it. Yes there's piles of corner-cases where this would be possible to do this like: - switch from inactive crtc to active crtc - switch from active crtc to inactive crtc - genlocked display - invisible plane (to do whatever) - idle plane hw due to dsi cmd mode/psr - whatever but looking at details it's not that easy to implement this correctly. Hence just put it into the core and add a comment, since the only userspace we have right now for atomic (weston) doesn't want to use direct plane switching either. v2: don't bother with complexity and just outright disallow plane switching without the intermediate OFF state. Simplifies drivers, we don't have any hw that could do it anyway and current atomic userspace (weston) works like this already anyway. v3: Bikeshed function name (Ville) and add comment (Rob). v4: Also bikeshed commit message (Rob). v5: Fix compile warnings reported by 0-day. Cc: Thierry Reding <thierry.reding@gmail.com> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> Cc: Daniel Stone <daniels@collabora.com> Acked-by: Daniel Stone <daniels@collabora.com> Reviewed-by: Rob Clark <robdclark@gmail.com> Acked-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
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