Commits
Chris Wilson committed f22f4cf524e
drm/i915: Limit the number of loops for reading a split 64bit register commit acd29f7b22262d9e848393b9b6ae13eb42d22514 upstream. In I915_READ64_2x32 we attempt to read a 64bit register using 2 32bit reads. Due to the nature of the registers we try to read in this manner, they may increment between the two instruction (e.g. a timestamp counter). To keep the result accurate, we repeat the read if we detect an overflow (i.e. the upper value varies). However, some hardware is just plain flaky and may endless loop as the the upper 32bits are not stable. Just give up after a couple of tries and report whatever we read last. v2: Use the most recent values when erring out on an unstable register. Reported-by: russianneuromancer@ya.ru Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=91906 Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Cc: Michał Winiarski <michal.winiarski@intel.com> Cc: Daniel Vetter <daniel.vetter@ffwll.ch> Cc: Jani Nikula <jani.nikula@linux.intel.com> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch> Signed-off-by: Jani Nikula <jani.nikula@intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>