drm/i915: Fix CRT hotplug regression in 2.6.35-rc1

Commit 7a772c492fcfffae812ffca78a628e76fa57fe58 has two bugs which
made the hotplug problems on my laptop worse instead of better.

First, it did not, in fact, disable the CRT plug interrupt -- it
disabled all the other hotplug interrupts.  It seems rather doubtful
that that bit of the patch fixed anything, so let's just remove it.
(If you want to add it back, you probably meant ~CRT_HOTPLUG_INT_EN.)

Second, on at least my GM45, setting CRT_HOTPLUG_ACTIVATION_PERIOD_64
and CRT_HOTPLUG_VOLTAGE_COMPARE_50 (when they were previously unset)
causes a hotplug interrupt about three seconds later.  The old code
never restored PORT_HOTPLUG_EN so this could only happen once, but
they new code restores those registers.  So just set those bits when
we set up the interrupt in the first place.

Signed-off-by: Andy Lutomirski <luto@mit.edu>
Signed-off-by: Eric Anholt <eric@anholt.net>

drivers/gpu/drm/i915/i915_irq.c

@@ -1434,8 +1434,18 @@ int i915_driver_irq_postinstall(struct drm_device *dev)
 			hotplug_en |= SDVOC_HOTPLUG_INT_EN;
 		if (dev_priv->hotplug_supported_mask & SDVOB_HOTPLUG_INT_STATUS)
 			hotplug_en |= SDVOB_HOTPLUG_INT_EN;
-		if (dev_priv->hotplug_supported_mask & CRT_HOTPLUG_INT_STATUS)
+		if (dev_priv->hotplug_supported_mask & CRT_HOTPLUG_INT_STATUS) {
 			hotplug_en |= CRT_HOTPLUG_INT_EN;
+
+			/* Programming the CRT detection parameters tends
+			   to generate a spurious hotplug event about three
+			   seconds later.  So just do it once.
+			*/
+			if (IS_G4X(dev))
+				hotplug_en |= CRT_HOTPLUG_ACTIVATION_PERIOD_64;
+			hotplug_en |= CRT_HOTPLUG_VOLTAGE_COMPARE_50;
+		}
+
 		/* Ignore TV since it's buggy */
 
 		I915_WRITE(PORT_HOTPLUG_EN, hotplug_en);

drivers/gpu/drm/i915/i915_reg.h

@@ -1134,7 +1134,6 @@
 #define CRT_HOTPLUG_DETECT_DELAY_2G		(1 << 4)
 #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 PORT_HOTPLUG_STAT	0x61114
 #define   HDMIB_HOTPLUG_INT_STATUS		(1 << 29)

drivers/gpu/drm/i915/intel_crt.c

@@ -234,14 +234,8 @@ static bool intel_crt_detect_hotplug(struct drm_connector *connector)
 	else
 		tries = 1;
 	hotplug_en = orig = I915_READ(PORT_HOTPLUG_EN);
-	hotplug_en &= CRT_HOTPLUG_MASK;
 	hotplug_en |= CRT_HOTPLUG_FORCE_DETECT;
 
-	if (IS_G4X(dev))
-		hotplug_en |= CRT_HOTPLUG_ACTIVATION_PERIOD_64;
-
-	hotplug_en |= CRT_HOTPLUG_VOLTAGE_COMPARE_50;
-
 	for (i = 0; i < tries ; i++) {
 		unsigned long timeout;
 		/* turn on the FORCE_DETECT */