drm/i915: make sure eDP panel is turned on

When enabling the eDP port, we need to make sure the panel is turned on
after training the link.  If we don't, it likely won't come back after
suspend or may not come up at all.

For unknown reasons, unlocking the panel regs before initiating a power
on sequence is necessary.  There are known bugs in the PCH panel
sequencing logic, apparently this is one possible workaround.

Fixes https://bugs.freedesktop.org/show_bug.cgi?id=28739.
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Tested-by: "Paulo J. S. Silva" <pjssilva@gmail.com>
Signed-off-by: Eric Anholt <eric@anholt.net>

drivers/gpu/drm/i915/intel_dp.c

@@ -717,6 +717,51 @@ intel_dp_mode_set(struct drm_encoder *encoder, struct drm_display_mode *mode,
 	}
 }
 
+static void ironlake_edp_panel_on (struct drm_device *dev)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	unsigned long timeout = jiffies + msecs_to_jiffies(5000);
+	u32 pp, pp_status;
+
+	pp_status = I915_READ(PCH_PP_STATUS);
+	if (pp_status & PP_ON)
+		return;
+
+	pp = I915_READ(PCH_PP_CONTROL);
+	pp |= PANEL_UNLOCK_REGS | POWER_TARGET_ON;
+	I915_WRITE(PCH_PP_CONTROL, pp);
+	do {
+		pp_status = I915_READ(PCH_PP_STATUS);
+	} while (((pp_status & PP_ON) == 0) && !time_after(jiffies, timeout));
+
+	if (time_after(jiffies, timeout))
+		DRM_DEBUG_KMS("panel on wait timed out: 0x%08x\n", pp_status);
+
+	pp &= ~(PANEL_UNLOCK_REGS | EDP_FORCE_VDD);
+	I915_WRITE(PCH_PP_CONTROL, pp);
+}
+
+static void ironlake_edp_panel_off (struct drm_device *dev)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	unsigned long timeout = jiffies + msecs_to_jiffies(5000);
+	u32 pp, pp_status;
+
+	pp = I915_READ(PCH_PP_CONTROL);
+	pp &= ~POWER_TARGET_ON;
+	I915_WRITE(PCH_PP_CONTROL, pp);
+	do {
+		pp_status = I915_READ(PCH_PP_STATUS);
+	} while ((pp_status & PP_ON) && !time_after(jiffies, timeout));
+
+	if (time_after(jiffies, timeout))
+		DRM_DEBUG_KMS("panel off wait timed out\n");
+
+	/* Make sure VDD is enabled so DP AUX will work */
+	pp |= EDP_FORCE_VDD;
+	I915_WRITE(PCH_PP_CONTROL, pp);
+}
+
 static void ironlake_edp_backlight_on (struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
@@ -751,14 +796,18 @@ intel_dp_dpms(struct drm_encoder *encoder, int mode)
 	if (mode != DRM_MODE_DPMS_ON) {
 		if (dp_reg & DP_PORT_EN) {
 			intel_dp_link_down(intel_encoder, dp_priv->DP);
-			if (IS_eDP(intel_encoder))
+			if (IS_eDP(intel_encoder)) {
 				ironlake_edp_backlight_off(dev);
+				ironlake_edp_backlight_off(dev);
+			}
 		}
 	} else {
 		if (!(dp_reg & DP_PORT_EN)) {
 			intel_dp_link_train(intel_encoder, dp_priv->DP, dp_priv->link_configuration);
-			if (IS_eDP(intel_encoder))
+			if (IS_eDP(intel_encoder)) {
+				ironlake_edp_panel_on(dev);
 				ironlake_edp_backlight_on(dev);
+			}
 		}
 	}
 	dp_priv->dpms_mode = mode;