drm/i915: Fix cursor updates on some platforms
Turns out that just writing CURPOS isn't sufficient to move the cursor on some platforms. My 830 works just fine, but eg. 945 and PNV don't. On those platforms we need to arm even the CURPOS update with a CURBASE write. Even worse, a write to any of the cursor register apart from CURBASE will cancel an already pending cursor update. So if we have armed a CURCNTR/CURBASE update, a subsequent CURPOS write prior to vblank would cancel that armed update. Thus we're left with a cursor that doesn't appear to move, or even change shape. Fix the problem by always performing the CURBASE write after a CURPOS write. Bspec is somewhat unclear which platforms actually require this CURBASE write and which don't. So to keep it simple and to make sure we really fix the problem across all supported devices, let's just perform the CURBASE write unconditionally. Cc: Paul Menzel <pmenzel@molgen.mpg.de> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=101790 Fixes: 75343a44 ("drm/i915: Drop useless posting reads from cursor commit") Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com> Tested-by: NPaul Menzel <paulepanter@users.sourceforge.net> Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch> Link: https://patchwork.freedesktop.org/patch/msgid/20170714155227.6089-1-ville.syrjala@linux.intel.com
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