drm/i915: Clarify flow for disabling IRQs on storms

This is rather confusing to look at as-is:
dev_priv->display.hpd_irq_setup(dev_priv); in intel_hpd_irq_handler()
handles disabling the actual HPD IRQ, while
intel_hpd_irq_storm_disable() handles moving the HPD pin state over from
MARK_DISABLED to DISABLED along with enabling polling for it.

Changes since v3:
- Rename i915_hpd_irq_storm_disable() to
  i915_hpd_irq_storm_switch_to_polling() - Rodrigo Vivi
Signed-off-by: Lyude Paul <lyude@redhat.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181106213017.14563-5-lyude@redhat.com

drivers/gpu/drm/i915/intel_hotplug.c

@@ -161,7 +161,8 @@ static bool intel_hpd_irq_storm_detect(struct drm_i915_private *dev_priv,
 	return storm;
 }
 
-static void intel_hpd_irq_storm_disable(struct drm_i915_private *dev_priv)
+static void
+intel_hpd_irq_storm_switch_to_polling(struct drm_i915_private *dev_priv)
 {
 	struct drm_device *dev = &dev_priv->drm;
 	struct intel_connector *intel_connector;
@@ -351,8 +352,8 @@ static void i915_hotplug_work_func(struct work_struct *work)
 	hpd_event_bits = dev_priv->hotplug.event_bits;
 	dev_priv->hotplug.event_bits = 0;
 
-	/* Disable hotplug on connectors that hit an irq storm. */
-	intel_hpd_irq_storm_disable(dev_priv);
+	/* Enable polling for connectors which had HPD IRQ storms */
+	intel_hpd_irq_storm_switch_to_polling(dev_priv);
 
 	spin_unlock_irq(&dev_priv->irq_lock);
 
@@ -458,6 +459,10 @@ void intel_hpd_irq_handler(struct drm_i915_private *dev_priv,
 		}
 	}
 
+	/*
+	 * Disable any IRQs that storms were detected on. Polling enablement
+	 * happens later in our hotplug work.
+	 */
 	if (storm_detected && dev_priv->display_irqs_enabled)
 		dev_priv->display.hpd_irq_setup(dev_priv);
 	spin_unlock(&dev_priv->irq_lock);