[PATCH v3] drm/i915/audio: treat UHBR SST like MST for cpu_transcoder signalling

[Mitul Golani <mitulkumar.ajitkumar.golani@intel.com>]

Both DP MST and UHBR SST require the audio component to use a real
cpu_transcoder (>= 0) value to identify the audio stream on a port.
For DP MST this was already handled; for UHBR SST it was not, causing
pin_eld_notify() to signal cpu_transcoder = -1 (the legacy SST sentinel)
and find_audio_state() to skip the per-transcoder entry for the UHBR
stream.

After suspend/resume or replug, the ELD lookup fails and audio goes
silent. Fix by detecting UHBR SST alongside DP MST when deciding
whether a real cpu_transcoder value must be used for audio state
addressing, in both the pin_eld_notify() signalling and the
find_audio_state() lookup paths.

--v2:
- Commit message and comment update. (Suraj)
- Change function name has_mst_transcoder. (Suraj)
- Avoid Live crtc access in find_audio_state. (Suraj)

--v3:
- Minor comment changes to avoid MST over 128b/132b confusion. (Suraj)

Signed-off-by: Kai Vehmanen <kai.vehmanen@linux.intel.com>
Signed-off-by: Mitul Golani <mitulkumar.ajitkumar.golani@intel.com>
Reviewed-by: Suraj Kandpal <suraj.kandpal@intel.com>
---
 drivers/gpu/drm/i915/display/intel_audio.c    | 55 ++++++++++++++-----
 .../gpu/drm/i915/display/intel_display_core.h |  1 +
 2 files changed, 41 insertions(+), 15 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_audio.c b/drivers/gpu/drm/i915/display/intel_audio.c
index 9729f1837d2c..fb0d7ed6fbd6 100644
--- a/drivers/gpu/drm/i915/display/intel_audio.c
+++ b/drivers/gpu/drm/i915/display/intel_audio.c
@@ -38,6 +38,7 @@
 #include "intel_de.h"
 #include "intel_display_types.h"
 #include "intel_display_wa.h"
+#include "intel_dp.h"
 #include "intel_lpe_audio.h"
 
 /**
@@ -696,6 +697,13 @@ static void ibx_audio_codec_enable(struct intel_encoder *encoder,
 	mutex_unlock(&display->audio.mutex);
 }
 
+static
+bool intel_audio_needs_cpu_transcoder_id(const struct intel_crtc_state *crtc_state)
+{
+	return intel_crtc_has_type(crtc_state, INTEL_OUTPUT_DP_MST) ||
+	       intel_dp_is_uhbr(crtc_state);
+}
+
 bool intel_audio_compute_config(struct intel_encoder *encoder,
 				struct intel_crtc_state *crtc_state,
 				struct drm_connector_state *conn_state)
@@ -762,6 +770,8 @@ void intel_audio_codec_enable(struct intel_encoder *encoder,
 	audio_state = &display->audio.state[cpu_transcoder];
 
 	audio_state->encoder = encoder;
+	audio_state->needs_cpu_transcoder_id =
+			intel_audio_needs_cpu_transcoder_id(crtc_state);
 	BUILD_BUG_ON(sizeof(audio_state->eld) != sizeof(crtc_state->eld));
 	memcpy(audio_state->eld, crtc_state->eld, sizeof(audio_state->eld));
 
@@ -769,8 +779,12 @@ void intel_audio_codec_enable(struct intel_encoder *encoder,
 
 	if (acomp && acomp->base.audio_ops &&
 	    acomp->base.audio_ops->pin_eld_notify) {
-		/* audio drivers expect cpu_transcoder = -1 to indicate Non-MST cases */
-		if (!intel_crtc_has_type(crtc_state, INTEL_OUTPUT_DP_MST))
+		/*
+		 * Audio drivers expect cpu_transcoder = -1 to indicate
+		 * Non-MST/HBR cases. MST and UHBR SST are addressed by
+		 * a real cpu_transcoder.
+		 */
+		if (!intel_audio_needs_cpu_transcoder_id(crtc_state))
 			cpu_transcoder = -1;
 		acomp->base.audio_ops->pin_eld_notify(acomp->base.audio_ops->audio_ptr,
 						      (int)port, (int)cpu_transcoder);
@@ -819,14 +833,19 @@ void intel_audio_codec_disable(struct intel_encoder *encoder,
 	audio_state = &display->audio.state[cpu_transcoder];
 
 	audio_state->encoder = NULL;
+	audio_state->needs_cpu_transcoder_id = false;
 	memset(audio_state->eld, 0, sizeof(audio_state->eld));
 
 	mutex_unlock(&display->audio.mutex);
 
 	if (acomp && acomp->base.audio_ops &&
 	    acomp->base.audio_ops->pin_eld_notify) {
-		/* audio drivers expect cpu_transcoder = -1 to indicate Non-MST cases */
-		if (!intel_crtc_has_type(old_crtc_state, INTEL_OUTPUT_DP_MST))
+		/*
+		 * Audio drivers expect cpu_transcoder = -1 to indicate
+		 * Non-MST/HBR cases. MST and UHBR SST are addressed by
+		 * a real cpu_transcoder.
+		 */
+		if (!intel_audio_needs_cpu_transcoder_id(old_crtc_state))
 			cpu_transcoder = -1;
 		acomp->base.audio_ops->pin_eld_notify(acomp->base.audio_ops->audio_ptr,
 						      (int)port, (int)cpu_transcoder);
@@ -1118,18 +1137,24 @@ static int intel_audio_component_get_cdclk_freq(struct device *kdev)
 }
 
 /*
- * get the intel audio state according to the parameter port and cpu_transcoder
- * MST & (cpu_transcoder >= 0): return the audio.state[cpu_transcoder].encoder],
- *   when port is matched
- * MST & (cpu_transcoder < 0): this is invalid
- * Non-MST & (cpu_transcoder >= 0): only cpu_transcoder = 0 (the first device entry)
- *   will get the right intel_encoder with port matched
- * Non-MST & (cpu_transcoder < 0): get the right intel_encoder with port matched
+ * Get the intel audio state for a given (port, cpu_transcoder).
+ *
+ * Streams are addressed either by a real cpu_transcoder (DP MST and UHBR SST,
+ * i.e. entries whose stored needs_cpu_transcoder_id is true) or by port alone
+ * (legacy SST). Both the signalling side (pin_eld_notify()) and the lookup
+ * side use the same predicate, so the two are symmetric.
+ *
+ * cpu_transcoder >= 0 & needs_cpu_transcoder_id: return audio.state[cpu_transcoder]
+ *   when the port matches.
+ * cpu_transcoder <  0 & !needs_cpu_transcoder_id: return the first port-matching
+ *   entry.
+ * cpu_transcoder =  0 & !needs_cpu_transcoder_id: falls through to the port-only
+ *   loop so the first device entry of a legacy SST port is still found.
  */
 static struct intel_audio_state *find_audio_state(struct intel_display *display,
 						  int port, int cpu_transcoder)
 {
-	/* MST */
+	/* MST, or UHBR SST. */
 	if (cpu_transcoder >= 0) {
 		struct intel_audio_state *audio_state;
 		struct intel_encoder *encoder;
@@ -1142,11 +1167,11 @@ static struct intel_audio_state *find_audio_state(struct intel_display *display,
 		encoder = audio_state->encoder;
 
 		if (encoder && encoder->port == port &&
-		    encoder->type == INTEL_OUTPUT_DP_MST)
+		    audio_state->needs_cpu_transcoder_id)
 			return audio_state;
 	}
 
-	/* Non-MST */
+	/* Legacy SST. */
 	if (cpu_transcoder > 0)
 		return NULL;
 
@@ -1158,7 +1183,7 @@ static struct intel_audio_state *find_audio_state(struct intel_display *display,
 		encoder = audio_state->encoder;
 
 		if (encoder && encoder->port == port &&
-		    encoder->type != INTEL_OUTPUT_DP_MST)
+		    !audio_state->needs_cpu_transcoder_id)
 			return audio_state;
 	}
 
diff --git a/drivers/gpu/drm/i915/display/intel_display_core.h b/drivers/gpu/drm/i915/display/intel_display_core.h
index 17f7d3abdb9c..a6129d0b523f 100644
--- a/drivers/gpu/drm/i915/display/intel_display_core.h
+++ b/drivers/gpu/drm/i915/display/intel_display_core.h
@@ -97,6 +97,7 @@ struct intel_wm_funcs {
 struct intel_audio_state {
 	struct intel_encoder *encoder;
 	u8 eld[MAX_ELD_BYTES];
+	bool needs_cpu_transcoder_id;  /* MST, or SST on UHBR link */
 };
 
 struct intel_audio {
-- 
2.48.1