[Intel-gfx] [PATCH] i915: Fix CRT hotplug regression in 2.6.35-rc1

[Andy Lutomirski]

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 at mit.edu>
---

The regression was introduced by the Extra CRT hotplug paranoia patch,
and it makes 2.6.35-rc2+ as well as 2.6.34 with that patch
cherry-picked essentially unusable on my X200s / GM45 machine.  Even
with this fix, there are still hotplug storm issues, but at least
they're now no worse than they used to be.

Please apply this or something similar to 2.6.35/

 drivers/gpu/drm/i915/i915_irq.c  |   12 +++++++++++-
 drivers/gpu/drm/i915/i915_reg.h  |    1 -
 drivers/gpu/drm/i915/intel_crt.c |    6 ------
 3 files changed, 11 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index 864acaa..2199c58 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -1413,8 +1413,18 @@ 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);
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index d31355b..ad0e255 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -1054,7 +1054,6 @@
 #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)
diff --git a/drivers/gpu/drm/i915/intel_crt.c b/drivers/gpu/drm/i915/intel_crt.c
index e700ca1..cbe1413 100644
--- a/drivers/gpu/drm/i915/intel_crt.c
+++ b/drivers/gpu/drm/i915/intel_crt.c
@@ -217,14 +217,8 @@ 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 */
-- 
1.7.0.1