drm/i915/bxt: Sanitize DC state tracking during system resume

After suspend-to-ram or -disk we don't know what power state the display
HW will be, DC0 or DC9 are both possible states, so reset the software
DC state tracking in these cases. This gets rid of 'DC state mismatch'
error messages during resuming from ram or disk where we expected to be
in DC9 (as set by the suspend handler) but we are in DC0.

v2:
- Remove extra WS in gen9_sanitize_dc_state() (Bob)
Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Bob Paauwe <bob.j.paauwe@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1461173277-16090-4-git-send-email-imre.deak@intel.com

drivers/gpu/drm/i915/i915_drv.c

@@ -867,10 +867,13 @@ static int i915_drm_resume_early(struct drm_device *dev)
 
 	intel_uncore_early_sanitize(dev, true);
 
-	if (IS_BROXTON(dev))
+	if (IS_BROXTON(dev)) {
+		if (!dev_priv->suspended_to_idle)
+			gen9_sanitize_dc_state(dev_priv);
 		bxt_disable_dc9(dev_priv);
-	else if (IS_HASWELL(dev_priv) || IS_BROADWELL(dev_priv))
+	} else if (IS_HASWELL(dev_priv) || IS_BROADWELL(dev_priv)) {
 		hsw_disable_pc8(dev_priv);
+	}
 
 	intel_uncore_sanitize(dev);
 

drivers/gpu/drm/i915/intel_drv.h

@@ -1235,6 +1235,7 @@ bool broxton_cdclk_verify_state(struct drm_i915_private *dev_priv);
 void broxton_ddi_phy_init(struct drm_i915_private *dev_priv);
 void broxton_ddi_phy_uninit(struct drm_i915_private *dev_priv);
 void broxton_ddi_phy_verify_state(struct drm_i915_private *dev_priv);
+void gen9_sanitize_dc_state(struct drm_i915_private *dev_priv);
 void bxt_enable_dc9(struct drm_i915_private *dev_priv);
 void bxt_disable_dc9(struct drm_i915_private *dev_priv);
 void skl_init_cdclk(struct drm_i915_private *dev_priv);

drivers/gpu/drm/i915/intel_runtime_pm.c

@@ -492,10 +492,9 @@ static void gen9_write_dc_state(struct drm_i915_private *dev_priv,
 			      state, rewrites);
 }
 
-static void gen9_set_dc_state(struct drm_i915_private *dev_priv, uint32_t state)
+static u32 gen9_dc_mask(struct drm_i915_private *dev_priv)
 {
-	uint32_t val;
-	uint32_t mask;
+	u32 mask;
 
 	mask = DC_STATE_EN_UPTO_DC5;
 	if (IS_BROXTON(dev_priv))
@@ -503,10 +502,30 @@ static void gen9_set_dc_state(struct drm_i915_private *dev_priv, uint32_t state)
 	else
 		mask |= DC_STATE_EN_UPTO_DC6;
 
+	return mask;
+}
+
+void gen9_sanitize_dc_state(struct drm_i915_private *dev_priv)
+{
+	u32 val;
+
+	val = I915_READ(DC_STATE_EN) & gen9_dc_mask(dev_priv);
+
+	DRM_DEBUG_KMS("Resetting DC state tracking from %02x to %02x\n",
+		      dev_priv->csr.dc_state, val);
+	dev_priv->csr.dc_state = val;
+}
+
+static void gen9_set_dc_state(struct drm_i915_private *dev_priv, uint32_t state)
+{
+	uint32_t val;
+	uint32_t mask;
+
 	if (WARN_ON_ONCE(state & ~dev_priv->csr.allowed_dc_mask))
 		state &= dev_priv->csr.allowed_dc_mask;
 
 	val = I915_READ(DC_STATE_EN);
+	mask = gen9_dc_mask(dev_priv);
 	DRM_DEBUG_KMS("Setting DC state from %02x to %02x\n",
 		      val & mask, state);