drm/i915: Implement Audio WA_14020863754

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)

v2: Update the platform checks (Jani Nikula)

v3: Limited the WA to LNL and BMG, added a helper (Matt Roper)

v4: Updated the bit naming, fixed redundant if statement
Signed-off-by: Uma Shankar <uma.shankar@intel.com>
Reviewed-by: Chaitanya Kumar Borah <chaitanya.kumar.borah@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240509053508.2807834-1-uma.shankar@intel.com

drivers/gpu/drm/i915/display/intel_audio.c

@@ -183,6 +183,15 @@ static const struct hdmi_aud_ncts hdmi_aud_ncts_36bpp[] = {
 	{ 192000, TMDS_445_5M, 20480, 371250 },
 };
 
+/*
+ * WA_14020863754: Implement Audio Workaround
+ * Corner case with Min Hblank Fix can cause audio hang
+ */
+static bool needs_wa_14020863754(struct drm_i915_private *i915)
+{
+	return (DISPLAY_VER(i915) == 20 || IS_BATTLEMAGE(i915));
+}
+
 /* get AUD_CONFIG_PIXEL_CLOCK_HDMI_* value for mode */
 static u32 audio_config_hdmi_pixel_clock(const struct intel_crtc_state *crtc_state)
 {
@@ -415,6 +424,9 @@ 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);
 
+	if (needs_wa_14020863754(i915))
+		intel_de_rmw(i915, AUD_CHICKENBIT_REG3, DACBE_DISABLE_MIN_HBLANK_FIX, 0);
+
 	mutex_unlock(&i915->display.audio.mutex);
 }
 
@@ -540,6 +552,9 @@ 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);
 
+	if (needs_wa_14020863754(i915))
+		intel_de_rmw(i915, AUD_CHICKENBIT_REG3, 0, DACBE_DISABLE_MIN_HBLANK_FIX);
+
 	/* Enable audio presence detect */
 	intel_de_rmw(i915, HSW_AUD_PIN_ELD_CP_VLD,
 		     0, AUDIO_OUTPUT_ENABLE(cpu_transcoder));

drivers/gpu/drm/i915/display/intel_audio_regs.h

@@ -164,4 +164,7 @@
 							 _VLV_AUD_PORT_EN_D_DBG)
 #define VLV_AMP_MUTE		        (1 << 1)
 
+#define AUD_CHICKENBIT_REG3		_MMIO(0x65F1C)
+#define  DACBE_DISABLE_MIN_HBLANK_FIX	REG_BIT(18)
+
 #endif /* __INTEL_AUDIO_REGS_H__ */