We only execute intel_decrease_pllclock for pre-PCH hardware, typically gen4 mobiles. However, in the variable declaration we did read from the non-PCH DPLL register, quite naughty and detected by SandyBridge. Reported-by: Andrey Rahmatullin <wrar at wrar.name> References: https://bugs.freedesktop.org/show_bug.cgi?id=49025 Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk> --- drivers/gpu/drm/i915/intel_display.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c index e1716be..10fefdd 100644 --- a/drivers/gpu/drm/i915/intel_display.c +++ b/drivers/gpu/drm/i915/intel_display.c @@ -5486,9 +5486,6 @@ static void intel_decrease_pllclock(struct drm_crtc *crtc) struct drm_device *dev = crtc->dev; drm_i915_private_t *dev_priv = dev->dev_private; struct intel_crtc *intel_crtc = to_intel_crtc(crtc); - int pipe = intel_crtc->pipe; - int dpll_reg = DPLL(pipe); - int dpll = I915_READ(dpll_reg); if (HAS_PCH_SPLIT(dev)) return; @@ -5501,10 +5498,15 @@ static void intel_decrease_pllclock(struct drm_crtc *crtc) * the manual case. */ if (!HAS_PIPE_CXSR(dev) && intel_crtc->lowfreq_avail) { + int pipe = intel_crtc->pipe; + int dpll_reg = DPLL(pipe); + u32 dpll; + DRM_DEBUG_DRIVER("downclocking LVDS\n"); assert_panel_unlocked(dev_priv, pipe); + dpll = I915_READ(dpll_reg); dpll |= DISPLAY_RATE_SELECT_FPA1; I915_WRITE(dpll_reg, dpll); intel_wait_for_vblank(dev, pipe); @@ -5512,7 +5514,6 @@ static void intel_decrease_pllclock(struct drm_crtc *crtc) if (!(dpll & DISPLAY_RATE_SELECT_FPA1)) DRM_DEBUG_DRIVER("failed to downclock LVDS!\n"); } - } /** -- 1.7.10
