drm/i915/gen4: Extra CRT hotplug paranoia

Disable the CRT plug interrupt while doing the force cycle, explicitly
clear any CRT interrupt we may have generated, and restore when done.
Should mitigate interrupt storms from hotplug detection.

Signed-off-by: Adam Jackson <ajax@redhat.com>
Signed-off-by: Eric Anholt <eric@anholt.net>

2 files changed, 14 insertions, 8 deletions

diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 784cf3c914e9..7a726840efa7 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -1067,7 +1067,6 @@
 #define CRT_HOTPLUG_DETECT_VOLTAGE_325MV        (0 << 2)
 #define CRT_HOTPLUG_DETECT_VOLTAGE_475MV        (1 << 2)
 #define CRT_HOTPLUG_MASK                        (0x3fc) /* Bits 9-2 */
-#define CRT_FORCE_HOTPLUG_MASK                  0xfffffe1f
 
 #define PORT_HOTPLUG_STAT       0x61114
 #define   HDMIB_HOTPLUG_INT_STATUS              (1 << 29)
diff --git a/drivers/gpu/drm/i915/intel_crt.c b/drivers/gpu/drm/i915/intel_crt.c
index d5c130202396..22ff38455731 100644
--- a/drivers/gpu/drm/i915/intel_crt.c
+++ b/drivers/gpu/drm/i915/intel_crt.c
@@ -217,7 +217,8 @@ static bool intel_crt_detect_hotplug(struct drm_connector *connector)
 {
         struct drm_device *dev = connector->dev;
         struct drm_i915_private *dev_priv = dev->dev_private;
-        u32 hotplug_en;
+        u32 hotplug_en, orig, stat;
+        bool ret = false;
         int i, tries = 0;
 
         if (HAS_PCH_SPLIT(dev))
@@ -232,8 +233,8 @@ static bool intel_crt_detect_hotplug(struct drm_connector *connector)
                 tries = 2;
         else
                 tries = 1;
-        hotplug_en = I915_READ(PORT_HOTPLUG_EN);
-        hotplug_en &= CRT_FORCE_HOTPLUG_MASK;
+        hotplug_en = orig = I915_READ(PORT_HOTPLUG_EN);
+        hotplug_en &= CRT_HOTPLUG_MASK;
         hotplug_en |= CRT_HOTPLUG_FORCE_DETECT;
 
         if (IS_G4X(dev))
@@ -255,11 +256,17 @@ static bool intel_crt_detect_hotplug(struct drm_connector *connector)
                 } while (time_after(timeout, jiffies));
         }
 
-        if ((I915_READ(PORT_HOTPLUG_STAT) & CRT_HOTPLUG_MONITOR_MASK) !=
-            CRT_HOTPLUG_MONITOR_NONE)
-                return true;
+        stat = I915_READ(PORT_HOTPLUG_STAT);
+        if ((stat & CRT_HOTPLUG_MONITOR_MASK) != CRT_HOTPLUG_MONITOR_NONE)
+                ret = true;
+
+        /* clear the interrupt we just generated, if any */
+        I915_WRITE(PORT_HOTPLUG_STAT, CRT_HOTPLUG_INT_STATUS);
 
-        return false;
+        /* and put the bits back */
+        I915_WRITE(PORT_HOTPLUG_EN, orig);
+
+        return ret;
 }
 
 static bool intel_crt_detect_ddc(struct drm_encoder *encoder)