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 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()

CC: sta...@vger.kernel.org
Signed-off-by: Lyude <cp...@redhat.com>
---
 drivers/gpu/drm/i915/intel_runtime_pm.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_runtime_pm.c 
b/drivers/gpu/drm/i915/intel_runtime_pm.c
index 80e8bd4..0eae08a 100644
--- a/drivers/gpu/drm/i915/intel_runtime_pm.c
+++ b/drivers/gpu/drm/i915/intel_runtime_pm.c
@@ -902,6 +902,7 @@ static bool vlv_power_well_enabled(struct drm_i915_private 
*dev_priv,
 
 static void vlv_display_power_well_init(struct drm_i915_private *dev_priv)
 {
+       struct intel_encoder *encoder;
        enum pipe pipe;
 
        /*
@@ -935,6 +936,12 @@ static void vlv_display_power_well_init(struct 
drm_i915_private *dev_priv)
 
        intel_hpd_init(dev_priv);
 
+       /* Re-enable the ADPA, if we have one */
+       for_each_intel_encoder(dev_priv->dev, encoder) {
+               if (encoder->type == INTEL_OUTPUT_ANALOG)
+                       encoder->base.funcs->reset(&encoder->base);
+       }
+
        i915_redisable_vga_power_on(dev_priv->dev);
 }
 
-- 
2.5.5

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