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Commit 694e409d authored by Ville Syrjälä's avatar Ville Syrjälä
Browse files

drm/i915: Use I915_READ_FW in i915_get_vblank_counter() 



Optimize the multi-register read in i915_get_vblank_counter() a little
bit by grabbing the uncore lock manually and using I915_READ_FW().

Signed-off-by: default avatarVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170309154434.29303-2-ville.syrjala@linux.intel.com


Reviewed-by: default avatarMaarten Lankhorst <maarten.lankhorst@linux.intel.com>
parent c750bdd3

drivers/gpu/drm/i915/i915_irq.c

+8 −3
Original line number Diff line number Diff line
@@ -723,6 +723,7 @@ static u32 i915_get_vblank_counter(struct drm_device *dev, unsigned int pipe) 
	struct intel_crtc *intel_crtc = intel_get_crtc_for_pipe(dev_priv,

								pipe);

	const struct drm_display_mode *mode = &intel_crtc->base.hwmode;

	unsigned long irqflags;



	htotal = mode->crtc_htotal;

	hsync_start = mode->crtc_hsync_start;
@@ -739,17 +740,21 @@ static u32 i915_get_vblank_counter(struct drm_device *dev, unsigned int pipe) 
	high_frame = PIPEFRAME(pipe);

	low_frame = PIPEFRAMEPIXEL(pipe);



	spin_lock_irqsave(&dev_priv->uncore.lock, irqflags);



	/*

	 * High & low register fields aren't synchronized, so make sure

	 * we get a low value that's stable across two reads of the high

	 * register.

	 */

	do {

		high1 = I915_READ(high_frame) & PIPE_FRAME_HIGH_MASK;

		low   = I915_READ(low_frame);

		high2 = I915_READ(high_frame) & PIPE_FRAME_HIGH_MASK;

		high1 = I915_READ_FW(high_frame) & PIPE_FRAME_HIGH_MASK;

		low   = I915_READ_FW(low_frame);

		high2 = I915_READ_FW(high_frame) & PIPE_FRAME_HIGH_MASK;

	} while (high1 != high2);



	spin_unlock_irqrestore(&dev_priv->uncore.lock, irqflags);



	high1 >>= PIPE_FRAME_HIGH_SHIFT;

	pixel = low & PIPE_PIXEL_MASK;

	low >>= PIPE_FRAME_LOW_SHIFT;