[PATCH] drm/i915: Implement Audio WA_14020863754

[Uma Shankar <uma.shankar@intel.com>]

WA_14020863754: Corner case with Min Hblank Fix can cause
audio hang

Issue: Previously a fix was made to avoid issues with extremely
small hblanks, called the "Min Hblank Fix". However, this can
potentially cause an audio hang.

Workaround :
During "Audio Programming Sequence" Audio Enabling -
When DP mode is enabled Set mmio offset 0x65F1C bit 18 = 1b,
before step #1 "Enable audio Presence Detect"

During "Audio Programming Sequence" Audio Disabling -
When DP mode is enabled Clear mmio offset 0x65F1C bit 18 = 0b,
after step #6 "Disable Audio PD (Presence Detect)"
If not clearing PD bit, must also not clear 0x65F1C bit 18 (leave = 1b)

Signed-off-by: Uma Shankar <uma.shankar@intel.com>
---
 drivers/gpu/drm/i915/display/intel_audio.c      | 12 ++++++++++++
 drivers/gpu/drm/i915/display/intel_audio_regs.h |  3 +++
 2 files changed, 15 insertions(+)

diff --git a/drivers/gpu/drm/i915/display/intel_audio.c b/drivers/gpu/drm/i915/display/intel_audio.c
index 07e0c73204f3..a8e3e515aaa0 100644
--- a/drivers/gpu/drm/i915/display/intel_audio.c
+++ b/drivers/gpu/drm/i915/display/intel_audio.c
@@ -512,6 +512,12 @@ static void hsw_audio_codec_disable(struct intel_encoder *encoder,
 	intel_de_rmw(i915, HSW_AUD_PIN_ELD_CP_VLD,
 		     AUDIO_OUTPUT_ENABLE(cpu_transcoder), 0);
 
+	/*
+	 * WA_14020863754: Implement Audio Workaround
+	 * Corner case with Min Hblank Fix can cause audio hang
+	 */
+	intel_de_rmw(i915, AUD_CHICKENBIT_REG3, CHICKEN3_SPARE18, 0);
+
 	mutex_unlock(&i915->display.audio.mutex);
 }
 
@@ -637,6 +643,12 @@ static void hsw_audio_codec_enable(struct intel_encoder *encoder,
 	if (intel_crtc_has_type(crtc_state, INTEL_OUTPUT_DP))
 		enable_audio_dsc_wa(encoder, crtc_state);
 
+	/*
+	 * WA_14020863754: Implement Audio Workaround
+	 * Corner case with Min Hblank Fix can cause audio hang
+	 */
+	intel_de_rmw(i915, AUD_CHICKENBIT_REG3, 0, CHICKEN3_SPARE18);
+
 	/* Enable audio presence detect */
 	intel_de_rmw(i915, HSW_AUD_PIN_ELD_CP_VLD,
 		     0, AUDIO_OUTPUT_ENABLE(cpu_transcoder));
diff --git a/drivers/gpu/drm/i915/display/intel_audio_regs.h b/drivers/gpu/drm/i915/display/intel_audio_regs.h
index 616e7b1275c4..6f8d33299ecd 100644
--- a/drivers/gpu/drm/i915/display/intel_audio_regs.h
+++ b/drivers/gpu/drm/i915/display/intel_audio_regs.h
@@ -148,4 +148,7 @@
 #define HBLANK_START_COUNT_96	4
 #define HBLANK_START_COUNT_128	5
 
+#define AUD_CHICKENBIT_REG3		_MMIO(0x65F1C)
+#define  CHICKEN3_SPARE18		REG_BIT(18)
+
 #endif /* __INTEL_AUDIO_REGS_H__ */
-- 
2.42.0