[PATCH] ALSA: hda: codecs: hdmi: disable keep-alive before audio format change

[PATCH] ALSA: hda: codecs: hdmi: disable keep-alive before audio format change

[Kai Vehmanen]

When a keep-alive (KAE) silent stream is active on an Intel HDMI/DP
codec, opening a real PCM stream reprograms the converter format and the
audio infoframe in snd_hda_hdmi_generic_pcm_prepare(). Part of that
reprogramming - the converter channel count and the channel mapping in
snd_hda_hdmi_setup_audio_infoframe() - is not safe to do while a
keep-alive stream is active. This is most visible when switching to a
multichannel PCM configuration, where the active channel count actually
changes. In that case the newly opened PCM stream plays no sound.

Add an optional hdmi_ops .prepare hook, called at the start of the
PCM prepare sequence (before the format and infoframe are touched), and
implement it for HSW+ to release keep-alive. Keep-alive is then
re-enabled as before once the new stream has been set up, in the
setup_stream op.

Fixes: 15175a4f2bbb ("ALSA: hda/hdmi: add keep-alive support for ADL-P and DG2")
Reported-by: Alexander Kaplan <alexander.kaplan@sms-medipool.de>
Closes: https://gitlab.freedesktop.org/drm/xe/kernel/-/work_items/8412
Tested-by: Alexander Kaplan <alexander.kaplan@sms-medipool.de>
Cc: <stable@vger.kernel.org>
Signed-off-by: Kai Vehmanen <kai.vehmanen@linux.intel.com>
---
 sound/hda/codecs/hdmi/hdmi.c       |  3 +++
 sound/hda/codecs/hdmi/hdmi_local.h |  9 ++++++++
 sound/hda/codecs/hdmi/intelhdmi.c  | 36 +++++++++++++++++++++++++-----
 3 files changed, 42 insertions(+), 6 deletions(-)

diff --git a/sound/hda/codecs/hdmi/hdmi.c b/sound/hda/codecs/hdmi/hdmi.c
index 0b6816018a42..053c41d98028 100644
--- a/sound/hda/codecs/hdmi/hdmi.c
+++ b/sound/hda/codecs/hdmi/hdmi.c
@@ -1688,6 +1688,9 @@ int snd_hda_hdmi_generic_pcm_prepare(struct hda_pcm_stream *hinfo,
 		per_pin->channels = substream->runtime->channels;
 		per_pin->setup = true;
 
+		if (spec->ops.prepare)
+			spec->ops.prepare(codec, per_pin);
+
 		if (get_wcaps(codec, cvt_nid) & AC_WCAP_STRIPE) {
 			stripe = snd_hdac_get_stream_stripe_ctl(&codec->bus->core,
 								substream);
diff --git a/sound/hda/codecs/hdmi/hdmi_local.h b/sound/hda/codecs/hdmi/hdmi_local.h
index 548241ad3fa9..dce9a335cff2 100644
--- a/sound/hda/codecs/hdmi/hdmi_local.h
+++ b/sound/hda/codecs/hdmi/hdmi_local.h
@@ -74,6 +74,15 @@ struct hdmi_ops {
 			    hda_nid_t pin_nid, int dev_id, u32 stream_tag,
 			    int format);
 
+	/*
+	 * Optional hook invoked at the beginning of the PCM prepare
+	 * sequence, before the audio infoframe and stream format are
+	 * (re)programmed. Used to disable keep-alive / silent stream so
+	 * that the format change is not done while keep-alive is active.
+	 */
+	void (*prepare)(struct hda_codec *codec,
+			struct hdmi_spec_per_pin *per_pin);
+
 	void (*pin_cvt_fixup)(struct hda_codec *codec,
 			      struct hdmi_spec_per_pin *per_pin,
 			      hda_nid_t cvt_nid);
diff --git a/sound/hda/codecs/hdmi/intelhdmi.c b/sound/hda/codecs/hdmi/intelhdmi.c
index 6a7882544ab7..73141046d502 100644
--- a/sound/hda/codecs/hdmi/intelhdmi.c
+++ b/sound/hda/codecs/hdmi/intelhdmi.c
@@ -418,6 +418,28 @@ static void intel_not_share_assigned_cvt_nid(struct hda_codec *codec,
 		intel_not_share_assigned_cvt(codec, pin_nid, dev_id, mux_idx);
 }
 
+/*
+ * prepare ops override for HSW+
+ *
+ * Disable keep-alive before the converter format and audio infoframe are
+ * reprogrammed by the PCM prepare sequence. Changing the audio format (e.g.
+ * the channel count when switching to multichannel PCM) while a keep-alive
+ * stream is active is not safe, so release keep-alive here, early in the
+ * sequence. It is re-enabled once the new stream has been set up, in
+ * i915_hsw_setup_stream().
+ */
+static void i915_hsw_prepare(struct hda_codec *codec,
+			     struct hdmi_spec_per_pin *per_pin)
+{
+	struct hdmi_spec *spec = codec->spec;
+
+	if (spec->silent_stream_type == SILENT_STREAM_KAE && per_pin->silent_stream) {
+		silent_stream_set_kae(codec, per_pin, false);
+		/* wait for pending transfers in codec to clear */
+		usleep_range(100, 200);
+	}
+}
+
 /* setup_stream ops override for HSW+ */
 static int i915_hsw_setup_stream(struct hda_codec *codec, hda_nid_t cvt_nid,
 				 hda_nid_t pin_nid, int dev_id, u32 stream_tag,
@@ -435,15 +457,16 @@ static int i915_hsw_setup_stream(struct hda_codec *codec, hda_nid_t cvt_nid,
 
 	haswell_verify_D0(codec, cvt_nid, pin_nid);
 
-	if (spec->silent_stream_type == SILENT_STREAM_KAE && per_pin && per_pin->silent_stream) {
-		silent_stream_set_kae(codec, per_pin, false);
-		/* wait for pending transfers in codec to clear */
-		usleep_range(100, 200);
-	}
-
 	res = snd_hda_hdmi_setup_stream(codec, cvt_nid, pin_nid, dev_id,
 					stream_tag, format);
 
+	/*
+	 * Keep-alive was disabled in i915_hsw_prepare(), re-enable it now.
+	 * The pin lookup above resolves to the same per_pin that prepare
+	 * used (pin_nid comes from that per_pin), so this stays balanced; a
+	 * NULL per_pin only occurs on a lookup failure that also implies no
+	 * active keep-alive stream to restore.
+	 */
 	if (spec->silent_stream_type == SILENT_STREAM_KAE && per_pin && per_pin->silent_stream) {
 		usleep_range(100, 200);
 		silent_stream_set_kae(codec, per_pin, true);
@@ -607,6 +630,7 @@ static int intel_hsw_common_init(struct hda_codec *codec, hda_nid_t vendor_nid,
 	codec->depop_delay = 0;
 	codec->auto_runtime_pm = 1;
 
+	spec->ops.prepare = i915_hsw_prepare;
 	spec->ops.setup_stream = i915_hsw_setup_stream;
 	spec->ops.pin_cvt_fixup = i915_pin_cvt_fixup;
 	spec->ops.silent_stream = i915_set_silent_stream;

base-commit: 41f1f6d8d2cfaba1fba07af993c9319a1ff2c81f
-- 
2.43.0

Re: [PATCH] ALSA: hda: codecs: hdmi: disable keep-alive before audio format change

[Takashi Iwai]

On Wed, 15 Jul 2026 20:06:10 +0200,
Kai Vehmanen wrote:
> 
> When a keep-alive (KAE) silent stream is active on an Intel HDMI/DP
> codec, opening a real PCM stream reprograms the converter format and the
> audio infoframe in snd_hda_hdmi_generic_pcm_prepare(). Part of that
> reprogramming - the converter channel count and the channel mapping in
> snd_hda_hdmi_setup_audio_infoframe() - is not safe to do while a
> keep-alive stream is active. This is most visible when switching to a
> multichannel PCM configuration, where the active channel count actually
> changes. In that case the newly opened PCM stream plays no sound.
> 
> Add an optional hdmi_ops .prepare hook, called at the start of the
> PCM prepare sequence (before the format and infoframe are touched), and
> implement it for HSW+ to release keep-alive. Keep-alive is then
> re-enabled as before once the new stream has been set up, in the
> setup_stream op.
> 
> Fixes: 15175a4f2bbb ("ALSA: hda/hdmi: add keep-alive support for ADL-P and DG2")
> Reported-by: Alexander Kaplan <alexander.kaplan@sms-medipool.de>
> Closes: https://gitlab.freedesktop.org/drm/xe/kernel/-/work_items/8412
> Tested-by: Alexander Kaplan <alexander.kaplan@sms-medipool.de>
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Kai Vehmanen <kai.vehmanen@linux.intel.com>

Applied now.  Thanks.


Takashi