[Intel-gfx] [PATCH] drm/i915/audio: fix hdmi audio noise issue

[libin.yang at intel.com]

From: Libin Yang <libin.yang at intel.com>

This issue is caused by:
6014ac12: drm/i915/audio: set proper N/M in modeset

Some special monitors will have noise or even no sound after
applying the patch 6014ac12.

In patch 6014ac12, it will reset the cts value to 0 for HDMI.
However, we need disable Enable CTS or M Prog bit. This is
the initial setting after HW reset.

Signed-off-by: Libin Yang <libin.yang at intel.com>
---
 drivers/gpu/drm/i915/intel_audio.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_audio.c b/drivers/gpu/drm/i915/intel_audio.c
index 813fd74..a472d35 100644
--- a/drivers/gpu/drm/i915/intel_audio.c
+++ b/drivers/gpu/drm/i915/intel_audio.c
@@ -332,6 +332,13 @@ hsw_hdmi_audio_config_update(struct intel_crtc *intel_crtc, enum port port,
 	int n;
 	u32 tmp;
 
+	/* reset CTS value to 0 */
+	tmp = I915_READ(HSW_AUD_M_CTS_ENABLE(pipe));
+	tmp &= ~AUD_CONFIG_M_MASK;
+	tmp &= ~AUD_M_CTS_M_VALUE_INDEX;
+	tmp |= AUD_M_CTS_M_PROG_ENABLE;
+	I915_WRITE(HSW_AUD_M_CTS_ENABLE(pipe), tmp);
+
 	tmp = I915_READ(HSW_AUD_CFG(pipe));
 	tmp &= ~AUD_CONFIG_N_VALUE_INDEX;
 	tmp &= ~AUD_CONFIG_PIXEL_CLOCK_HDMI_MASK;
@@ -351,10 +358,12 @@ hsw_hdmi_audio_config_update(struct intel_crtc *intel_crtc, enum port port,
 
 	I915_WRITE(HSW_AUD_CFG(pipe), tmp);
 
+	/*
+	 * Let's disable "Enable CTS or M Prog bit"
+	 * and let HW calculate the value
+	 */
 	tmp = I915_READ(HSW_AUD_M_CTS_ENABLE(pipe));
-	tmp &= ~AUD_CONFIG_M_MASK;
-	tmp &= ~AUD_M_CTS_M_VALUE_INDEX;
-	tmp |= AUD_M_CTS_M_PROG_ENABLE;
+	tmp &= ~AUD_M_CTS_M_PROG_ENABLE;
 	I915_WRITE(HSW_AUD_M_CTS_ENABLE(pipe), tmp);
 }
 
-- 
2.7.4