drm/i915: Make sure PORT_HOTPLUG_EN is written

Add posting read to make sure PORT_HOTPLUG_EN is written in i915_hpd_irq_setup().

---
 drivers/gpu/drm/i915/i915_irq.c | 1 +
 1 file changed, 1 insertion(+)

index 1f3a971..a38372b 100644
@@ -2805,6 +2805,7 @@ static void i915_hpd_irq_setup(struct drm_device *dev)
 
 		/* Ignore TV since it's buggy */
 		I915_WRITE(PORT_HOTPLUG_EN, hotplug_en);
+		POSTING_READ(PORT_HOTPLUG_EN);
 	}
 }
 

1.8.1.4

It's not vital that the write be flushed here. On the deferred reenable path a further delay in rearming is not significant, and inside the irq handler (for disabling) the write will be flushed.

In terms of the patch itself, you would also need to fixup ibx_hpd_irq_setup as well.
-Chris

Chris Wilson, Intel Open Source Technology Centre

We can probably drop this patch. It was one try figuring why HPD interrupts are still seeen on pins which have been disabled. It turned out that the root cause was a mixup in the mapping of pins to enable bits due to incorrect documentation.

Cheers,
Egbert.