drm/i915: Use I915_READ_FW for plane updates
Optimize the plane register accesses a little bit by grabbing the uncore lock manually across the entire pile of accesses and using I915_READ_FW(). This helps keep the pipe update vblank evade critical section below our 100 usec deadline, particularly with lockdep enabled. And in general we want to keep that critical section as short as possible as it's executed with interrupts disabled. Not all plane updates currently happen from within the vblank evade critical section, so we must use the irqsave/irqrestore variants of the spinlock functions in the plane hooks. Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com> Link: http://patchwork.freedesktop.org/patch/msgid/20170309154434.29303-5-ville.syrjala@linux.intel.comReviewed-by: NMaarten Lankhorst <maarten.lankhorst@linux.intel.com>
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