[Intel-gfx] [PATCH] drm/i915: Don't lock panel registers when downclocking

[Sean Paul]

This patch replaces the locking from the downclock routines with an assert
to ensure the registers are indeed unlocked. Without this patch, pre-SNB
devices would lock the registers when downclocking which would cause a
WARNING on suspend/resume with downclocking enabled.

Note: To hit this bug, you need to have lvds downclocking enabled.

Signed-off-by: Sean Paul <seanpaul at chromium.org>
---
 drivers/gpu/drm/i915/intel_display.c |   14 ++------------
 1 files changed, 2 insertions(+), 12 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index ebe71ed..33ef4f3 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -6968,9 +6968,7 @@ static void intel_increase_pllclock(struct drm_crtc *crtc)
 	if (!HAS_PIPE_CXSR(dev) && (dpll & DISPLAY_RATE_SELECT_FPA1)) {
 		DRM_DEBUG_DRIVER("upclocking LVDS\n");
 
-		/* Unlock panel regs */
-		I915_WRITE(PP_CONTROL,
-			   I915_READ(PP_CONTROL) | PANEL_UNLOCK_REGS);
+		assert_panel_unlocked(dev_priv, pipe);
 
 		dpll &= ~DISPLAY_RATE_SELECT_FPA1;
 		I915_WRITE(dpll_reg, dpll);
@@ -6979,9 +6977,6 @@ static void intel_increase_pllclock(struct drm_crtc *crtc)
 		dpll = I915_READ(dpll_reg);
 		if (dpll & DISPLAY_RATE_SELECT_FPA1)
 			DRM_DEBUG_DRIVER("failed to upclock LVDS!\n");
-
-		/* ...and lock them again */
-		I915_WRITE(PP_CONTROL, I915_READ(PP_CONTROL) & 0x3);
 	}
 
 	/* Schedule downclock */
@@ -7011,9 +7006,7 @@ static void intel_decrease_pllclock(struct drm_crtc *crtc)
 	if (!HAS_PIPE_CXSR(dev) && intel_crtc->lowfreq_avail) {
 		DRM_DEBUG_DRIVER("downclocking LVDS\n");
 
-		/* Unlock panel regs */
-		I915_WRITE(PP_CONTROL, I915_READ(PP_CONTROL) |
-			   PANEL_UNLOCK_REGS);
+		assert_panel_unlocked(dev_priv, pipe);
 
 		dpll |= DISPLAY_RATE_SELECT_FPA1;
 		I915_WRITE(dpll_reg, dpll);
@@ -7021,9 +7014,6 @@ static void intel_decrease_pllclock(struct drm_crtc *crtc)
 		dpll = I915_READ(dpll_reg);
 		if (!(dpll & DISPLAY_RATE_SELECT_FPA1))
 			DRM_DEBUG_DRIVER("failed to downclock LVDS!\n");
-
-		/* ...and lock them again */
-		I915_WRITE(PP_CONTROL, I915_READ(PP_CONTROL) & 0x3);
 	}
 
 }
-- 
1.7.7.3