drm/i915: Don't lock panel registers when downclocking

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@chromium.org>
Acked-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index db7ccbb..ba287ca 100644 (file)
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -7006,9 +7006,7 @@ 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);
@@ -7017,9 +7015,6 @@ 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 */
@@ -7049,9 +7044,7 @@ 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);
@@ -7059,9 +7052,6 @@ 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);
        }
 
 }