drm/i915/vlv: Reset the ADPA in vlv_display_power_well_init()

commit 9504a892 upstream.

While VGA hotplugging worked(ish) before, it looks like that was mainly
because we'd unintentionally enable it in
valleyview_crt_detect_hotplug() when we did a force trigger. This
doesn't work reliably enough because whenever the display powerwell on
vlv gets disabled, the values set in VLV_ADPA get cleared and
consequently VGA hotplugging gets disabled. This causes bugs such as one
we found on an Intel NUC, where doing the following sequence of
hotplugs:

      - Disconnect all monitors
      - Connect VGA
      - Disconnect VGA
      - Connect HDMI

Would result in VGA hotplugging becoming disabled, due to the powerwells
getting toggled in the process of connecting HDMI.

Changes since v3:
 - Expose intel_crt_reset() through intel_drv.h and call that in
   vlv_display_power_well_init() instead of
   encoder->base.funcs->reset(&encoder->base);

Changes since v2:
 - Use intel_encoder structs instead of drm_encoder structs

Changes since v1:
 - Instead of handling the register writes ourself, we just reuse
   intel_crt_detect()
 - Instead of resetting the ADPA during display IRQ installation, we now
   reset them in vlv_display_power_well_init()
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Lyude <cpaul@redhat.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
[danvet: Rebase over dev_priv/drm_device embedding.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
[bwh: Backported to 3.16:
 - Adjust filename, context
 - Open-code for_each_intel_encoder()]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/gpu/drm/i915/intel_crt.c

@@ -742,7 +742,7 @@ static int intel_crt_set_property(struct drm_connector *connector,
 	return 0;
 }
 
-static void intel_crt_reset(struct drm_encoder *encoder)
+void intel_crt_reset(struct drm_encoder *encoder)
 {
 	struct drm_device *dev = encoder->dev;
 	struct drm_i915_private *dev_priv = dev->dev_private;

drivers/gpu/drm/i915/intel_drv.h

@@ -690,7 +690,7 @@ void i9xx_check_fifo_underruns(struct drm_device *dev);
 
 /* intel_crt.c */
 void intel_crt_init(struct drm_device *dev);
-
+void intel_crt_reset(struct drm_encoder *encoder);
 
 /* intel_ddi.c */
 void intel_prepare_ddi(struct drm_device *dev);

drivers/gpu/drm/i915/intel_pm.c

@@ -5897,6 +5897,8 @@ static bool vlv_power_well_enabled(struct drm_i915_private *dev_priv,
 static void vlv_display_power_well_enable(struct drm_i915_private *dev_priv,
 					  struct i915_power_well *power_well)
 {
+	struct intel_encoder *encoder;
+
 	WARN_ON_ONCE(power_well->data != PUNIT_POWER_WELL_DISP2D);
 
 	vlv_set_power_well(dev_priv, power_well, true);
@@ -5914,6 +5916,13 @@ static void vlv_display_power_well_enable(struct drm_i915_private *dev_priv,
 
 	intel_hpd_init(dev_priv->dev);
 
+	/* Re-enable the ADPA, if we have one */
+	list_for_each_entry(encoder, &dev_priv->dev->mode_config.encoder_list,
+			    base.head) {
+		if (encoder->type == INTEL_OUTPUT_ANALOG)
+			intel_crt_reset(&encoder->base);
+	}
+
 	i915_redisable_vga_power_on(dev_priv->dev);
 }