[Intel-gfx] [PATCH 1/4] drm/i915: Configure the TV sense state correctly on GM45 to make TV detection reliable

[Zhenyu Wang]

From: ykzhao <yakui.zhao at intel.com>

The TV detection logic is not reliable on the Cantiga platform.
Sometimes the TV will be misdetected as the following two cases:
- TV is misdetected on some laptops. e.g. There is no TV connector
port or no TV is attached. But the TV is shown as connected.
- TV connector type is misdetected. e.g. the component TV is
attached, but the TV is shown as S-video type.

According to the hardware requirement, the TV sense state bits of TV DAC
register should be cleared to zero on Cantiga platfrom.

https://bugzilla.kernel.org/show_bug.cgi?id=14792

Cc: Stable Team <stable at kernel.org>
Signed-off-by: Zhao Yakui <yakui.zhao at intel.com>
Tested-by: Santi <santi at agolina.net>
Signed-off-by: Zhenyu Wang <zhenyuw at linux.intel.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 d7d39b2..eea5930 100644
--- a/drivers/gpu/drm/i915/intel_tv.c
+++ b/drivers/gpu/drm/i915/intel_tv.c
@@ -1399,6 +1399,15 @@ intel_tv_detect_type (struct drm_crtc *crtc, struct intel_encoder *intel_encoder
 		   DAC_A_0_7_V |
 		   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);
 	intel_wait_for_vblank(dev);
-- 
1.6.3.3