drm/i915: use VDD AUX for panel power around detection and in prepare

Mode setting sequence specifies that we use VDD AUX for configuration
and detection, and early in the mode set sequence.  Only later (after
DP_A has started training) should we actually enable panel power.
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
[ickle: checkpatch.pl complaining about whitespace]
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

drivers/gpu/drm/i915/intel_dp.c

@@ -813,6 +813,28 @@ static void ironlake_edp_panel_off (struct drm_device *dev)
 	POSTING_READ(PCH_PP_CONTROL);
 }
 
+static void ironlake_edp_panel_vdd_on(struct drm_device *dev)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	u32 pp;
+
+	pp = I915_READ(PCH_PP_CONTROL);
+	pp |= EDP_FORCE_VDD;
+	I915_WRITE(PCH_PP_CONTROL, pp);
+	POSTING_READ(PCH_PP_CONTROL);
+}
+
+static void ironlake_edp_panel_vdd_off(struct drm_device *dev)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	u32 pp;
+
+	pp = I915_READ(PCH_PP_CONTROL);
+	pp &= ~EDP_FORCE_VDD;
+	I915_WRITE(PCH_PP_CONTROL, pp);
+	POSTING_READ(PCH_PP_CONTROL);
+}
+
 static void ironlake_edp_backlight_on (struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
@@ -868,7 +890,7 @@ static void intel_dp_prepare(struct drm_encoder *encoder)
 
 	if (IS_eDP(intel_dp) || IS_PCH_eDP(intel_dp)) {
 		ironlake_edp_backlight_off(dev);
-		ironlake_edp_panel_on(dev);
+		ironlake_edp_panel_vdd_on(dev);
 		ironlake_edp_pll_on(encoder);
 	}
 	if (dp_reg & DP_PORT_EN)
@@ -885,8 +907,10 @@ static void intel_dp_commit(struct drm_encoder *encoder)
 	if (!(dp_reg & DP_PORT_EN)) {
 		intel_dp_link_train(intel_dp);
 	}
-	if (IS_eDP(intel_dp) || IS_PCH_eDP(intel_dp))
+	if (IS_eDP(intel_dp) || IS_PCH_eDP(intel_dp)) {
+		ironlake_edp_panel_on(dev);
 		ironlake_edp_backlight_on(dev);
+	}
 }
 
 static void
@@ -1371,11 +1395,10 @@ ironlake_dp_detect(struct drm_connector *connector)
 	struct drm_encoder *encoder = intel_attached_encoder(connector);
 	struct intel_dp *intel_dp = enc_to_intel_dp(encoder);
 	enum drm_connector_status status;
-	bool was_on = false;
 
 	/* Panel needs power for AUX to work */
 	if (IS_eDP(intel_dp) || IS_PCH_eDP(intel_dp))
-		was_on = ironlake_edp_panel_on(connector->dev);
+		ironlake_edp_panel_vdd_on(connector->dev);
 	status = connector_status_disconnected;
 	if (intel_dp_aux_native_read(intel_dp,
 				     0x000, intel_dp->dpcd,
@@ -1386,8 +1409,8 @@ ironlake_dp_detect(struct drm_connector *connector)
 	}
 	DRM_DEBUG_KMS("DPCD: %hx%hx%hx%hx\n", intel_dp->dpcd[0],
 		      intel_dp->dpcd[1], intel_dp->dpcd[2], intel_dp->dpcd[3]);
-	if ((IS_eDP(intel_dp) || IS_PCH_eDP(intel_dp)) && !was_on)
-		ironlake_edp_panel_off(connector->dev);
+	if (IS_eDP(intel_dp) || IS_PCH_eDP(intel_dp))
+		ironlake_edp_panel_vdd_off(connector->dev);
 	return status;
 }