[PATCH 1/1] [Oneiric] [Precise] drm/i915: reinstate GM45 TV detection fix

[Brad Figg]

From: Daniel Vetter <daniel.vetter at ffwll.ch>

BugLink: http://bugs.launchpad.net/bugs/638939

This reverts commmit d4b74bf07873da2e94219a7b67a334fc1c3ce649 which
reverted the origin fix fb8b5a39b6310379d7b54c0c7113703a8eaf4a57.

We have at least 3 different bug reports that this fixes things and no
indication what is exactly wrong with this. So try again.

To make matters slightly more fun, the commit itself was cc: stable
whereas the revert has not been.

According to Peter Clifton he discussed this with Zhao Yakui and this
seems to be in contradiction of the GM45 PRM, but rumours have it that
this is how the BIOS does it ... let's see.

Reviewed-by: Rodrigo Vivi <rodrigo.vivi at gmail.com>
Tested-by: Peter Clifton <Peter.Clifton at clifton-electronics.com>
Cc: Zhao Yakui <yakui.zhao at intel.com>
Cc: Dave Airlie <airlied at redhat.com>
Cc: Eric Anholt <eric at anholt.net>
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=16236
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=25913
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=14792
Signed-Off-by: Daniel Vetter <daniel.vetter at ffwll.ch>
Signed-off-by: Brad Figg <brad.figg at canonical.com>
---
 drivers/gpu/drm/i915/intel_tv.c |    9 +++++++++
 1 files changed, 9 insertions(+), 0 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_tv.c b/drivers/gpu/drm/i915/intel_tv.c
index 2b1fcad..0436b45 100644
--- a/drivers/gpu/drm/i915/intel_tv.c
+++ b/drivers/gpu/drm/i915/intel_tv.c
@@ -1275,6 +1275,15 @@ intel_tv_detect_type(struct intel_tv *intel_tv,
 		   DAC_B_0_7_V |
 		   DAC_C_0_7_V);
 
+
+	/*
+	 * The TV sense state should be cleared to zero on cantiga platform. Otherwise
+	 * the TV is misdetected. This is hardware requirement.
+	 */
+	if (IS_GM45(dev))
+		tv_dac &= ~(TVDAC_STATE_CHG_EN | TVDAC_A_SENSE_CTL |
+			    TVDAC_B_SENSE_CTL | TVDAC_C_SENSE_CTL);
+
 	I915_WRITE(TV_CTL, tv_ctl);
 	I915_WRITE(TV_DAC, tv_dac);
 	POSTING_READ(TV_DAC);
-- 
1.7.9.1