drm/i915: Configure the TV sense state correctly on GM45 to make TV detection reliable

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@kernel.org>
Signed-off-by: Zhao Yakui <yakui.zhao@intel.com>
Tested-by: Santi <santi@agolina.net>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>
Signed-off-by: Eric Anholt <eric@anholt.net>

diff --git a/drivers/gpu/drm/i915/intel_tv.c b/drivers/gpu/drm/i915/intel_tv.c
index d7d39b2327df37bcb6cb89d5ea9d0740814c1050..eea593071e496d2ce0632f78e5c48f07c78f7479 100644 (file)
--- 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);