drm/i915: add panel reset workaround

Ironlake requires that we clear the reset panel bit during power
sequences and restore it afterwards.  Uncondtionally add code to do that
since it should be harmless on SNB+.

Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index c6629bd9430f03276b2566d3ba0a4cc5258f66f7..d1b4ece4df0075de1736e2076cde4f47a2b583fb 100644 (file)
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -765,6 +765,12 @@ static void ironlake_edp_panel_on (struct drm_device *dev)
                return;
 
        pp = I915_READ(PCH_PP_CONTROL);
+
+       /* ILK workaround: disable reset around power sequence */
+       pp &= ~PANEL_POWER_RESET;
+       I915_WRITE(PCH_PP_CONTROL, pp);
+       POSTING_READ(PCH_PP_CONTROL);
+
        pp |= PANEL_UNLOCK_REGS | POWER_TARGET_ON;
        I915_WRITE(PCH_PP_CONTROL, pp);
 
@@ -773,7 +779,9 @@ static void ironlake_edp_panel_on (struct drm_device *dev)
                          I915_READ(PCH_PP_STATUS));
 
        pp &= ~(PANEL_UNLOCK_REGS | EDP_FORCE_VDD);
+       pp |= PANEL_POWER_RESET; /* restore panel reset bit */
        I915_WRITE(PCH_PP_CONTROL, pp);
+       POSTING_READ(PCH_PP_CONTROL);
 }
 
 static void ironlake_edp_panel_off (struct drm_device *dev)
@@ -782,6 +790,12 @@ static void ironlake_edp_panel_off (struct drm_device *dev)
        u32 pp;
 
        pp = I915_READ(PCH_PP_CONTROL);
+
+       /* ILK workaround: disable reset around power sequence */
+       pp &= ~PANEL_POWER_RESET;
+       I915_WRITE(PCH_PP_CONTROL, pp);
+       POSTING_READ(PCH_PP_CONTROL);
+
        pp &= ~POWER_TARGET_ON;
        I915_WRITE(PCH_PP_CONTROL, pp);
 
@@ -790,8 +804,9 @@ static void ironlake_edp_panel_off (struct drm_device *dev)
                          I915_READ(PCH_PP_STATUS));
 
        /* Make sure VDD is enabled so DP AUX will work */
-       pp |= EDP_FORCE_VDD;
+       pp |= EDP_FORCE_VDD | PANEL_POWER_RESET; /* restore panel reset bit */
        I915_WRITE(PCH_PP_CONTROL, pp);
+       POSTING_READ(PCH_PP_CONTROL);
 }
 
 static void ironlake_edp_backlight_on (struct drm_device *dev)