drm/i915/skl: Making DC6 entry is the last call in suspend flow.

Mmio register access after dc6/dc5 entry is not allowed when
DC6 power states are enabled according to bspec (bspec-id 0527),
so enabling dc6 as the last call in suspend flow.

Addtional note from Imre:

Currently we keep DC6 enabled during modesets and DPAUX transfers, which
is not allowed according to the specification. This can lead at least to
PLL locking failures, DPAUX timeouts and prevent deeper package power
states (PC9/10). Fix this for now by enabling DC6 only when we know the
above events (modeset, DPAUX) can't happen.

This a temporary solution as some issues are still unsolved as described
in [1] and [2], we'll address those as a follow-up.

[1]
http://lists.freedesktop.org/archives/intel-gfx/2015-October/077669.html
[2]
http://lists.freedesktop.org/archives/intel-gfx/2015-October/077787.html

v1: Initial version.

v2: Based on review comment from Daniel,
- created a seperate patch for csr uninitialization set call.

v3: Rebased on top of latest code.

Cc: Daniel Vetter <daniel.vetter@intel.com>
Cc: Damien Lespiau <damien.lespiau@intel.com>
Cc: Imre Deak <imre.deak@intel.com>
Cc: Sunil Kamath <sunil.kamath@intel.com>
Signed-off-by: Animesh Manna <animesh.manna@intel.com>
Signed-off-by: Vathsala Nagaraju <vathsala.nagaraju@intel.com>
Signed-off-by: Rajneesh Bhardwaj <rajneesh.bhardwaj@intel.com>
Acked-by: Imre Deak <imre.deak@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_drv.c

@@ -1053,10 +1053,20 @@ static int i915_pm_resume(struct device *dev)
 
 static int skl_suspend_complete(struct drm_i915_private *dev_priv)
 {
+	enum csr_state state;
 	/* Enabling DC6 is not a hard requirement to enter runtime D3 */
 
 	skl_uninit_cdclk(dev_priv);
 
+	/* TODO: wait for a completion event or
+	 * similar here instead of busy
+	 * waiting using wait_for function.
+	 */
+	wait_for((state = intel_csr_load_status_get(dev_priv)) !=
+			FW_UNINITIALIZED, 1000);
+	if (state == FW_LOADED)
+		skl_enable_dc6(dev_priv);
+
 	return 0;
 }
 
@@ -1103,6 +1113,9 @@ static int skl_resume_prepare(struct drm_i915_private *dev_priv)
 {
 	struct drm_device *dev = dev_priv->dev;
 
+	if (intel_csr_load_status_get(dev_priv) == FW_LOADED)
+		skl_disable_dc6(dev_priv);
+
 	skl_init_cdclk(dev_priv);
 	intel_csr_load_program(dev);
 

drivers/gpu/drm/i915/intel_drv.h

@@ -1153,6 +1153,8 @@ 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);
 void skl_uninit_cdclk(struct drm_i915_private *dev_priv);
+void skl_enable_dc6(struct drm_i915_private *dev_priv);
+void skl_disable_dc6(struct drm_i915_private *dev_priv);
 void intel_dp_get_m_n(struct intel_crtc *crtc,
 		      struct intel_crtc_state *pipe_config);
 void intel_dp_set_m_n(struct intel_crtc *crtc, enum link_m_n_set m_n);

drivers/gpu/drm/i915/intel_runtime_pm.c

@@ -550,7 +550,7 @@ static void assert_can_disable_dc6(struct drm_i915_private *dev_priv)
 		  "DC6 already programmed to be disabled.\n");
 }
 
-static void skl_enable_dc6(struct drm_i915_private *dev_priv)
+void skl_enable_dc6(struct drm_i915_private *dev_priv)
 {
 	uint32_t val;
 
@@ -567,7 +567,7 @@ static void skl_enable_dc6(struct drm_i915_private *dev_priv)
 	POSTING_READ(DC_STATE_EN);
 }
 
-static void skl_disable_dc6(struct drm_i915_private *dev_priv)
+void skl_disable_dc6(struct drm_i915_private *dev_priv)
 {
 	uint32_t val;
 
@@ -628,10 +628,10 @@ static void skl_set_power_well(struct drm_i915_private *dev_priv,
 				!I915_READ(HSW_PWR_WELL_BIOS),
 				"Invalid for power well status to be enabled, unless done by the BIOS, \
 				when request is to disable!\n");
-			if ((GEN9_ENABLE_DC5(dev) || SKL_ENABLE_DC6(dev)) &&
-				power_well->data == SKL_DISP_PW_2) {
+			if (power_well->data == SKL_DISP_PW_2) {
+				if (GEN9_ENABLE_DC5(dev))
+					gen9_disable_dc5(dev_priv);
 				if (SKL_ENABLE_DC6(dev)) {
-					skl_disable_dc6(dev_priv);
 					/*
 					 * DDI buffer programming unnecessary during driver-load/resume
 					 * as it's already done during modeset initialization then.
@@ -639,8 +639,6 @@ static void skl_set_power_well(struct drm_i915_private *dev_priv,
 					 */
 					if (!dev_priv->power_domains.initializing)
 						intel_prepare_ddi(dev);
-				} else {
-					gen9_disable_dc5(dev_priv);
 				}
 			}
 			I915_WRITE(HSW_PWR_WELL_DRIVER, tmp | req_mask);
@@ -666,7 +664,7 @@ static void skl_set_power_well(struct drm_i915_private *dev_priv,
 				DRM_DEBUG_KMS("Disabling %s\n", power_well->name);
 			}
 
-			if ((GEN9_ENABLE_DC5(dev) || SKL_ENABLE_DC6(dev)) &&
+			if (GEN9_ENABLE_DC5(dev) &&
 				power_well->data == SKL_DISP_PW_2) {
 				enum csr_state state;
 				/* TODO: wait for a completion event or
@@ -679,10 +677,7 @@ static void skl_set_power_well(struct drm_i915_private *dev_priv,
 					DRM_DEBUG("CSR firmware not ready (%d)\n",
 							state);
 				else
-					if (SKL_ENABLE_DC6(dev))
-						skl_enable_dc6(dev_priv);
-					else
-						gen9_enable_dc5(dev_priv);
+					gen9_enable_dc5(dev_priv);
 			}
 		}
 	}