From 694e409daa90f2e21a97e43121c943a84e843bf9 Mon Sep 17 00:00:00 2001 From: =?utf8?q?Ville=20Syrj=C3=A4l=C3=A4?= Date: Thu, 9 Mar 2017 17:44:30 +0200 Subject: [PATCH] drm/i915: Use I915_READ_FW in i915_get_vblank_counter() MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit 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: Ville Syrjälä Link: http://patchwork.freedesktop.org/patch/msgid/20170309154434.29303-2-ville.syrjala@linux.intel.com Reviewed-by: Maarten Lankhorst --- drivers/gpu/drm/i915/i915_irq.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c index b8a0afd..da5137f 100644 --- a/drivers/gpu/drm/i915/i915_irq.c +++ b/drivers/gpu/drm/i915/i915_irq.c @@ -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; -- 2.7.4