External HDMI receivers have analog circuitry that needs to be powered-on
when exiting standby, and a mechanism to detect PCM v. IEC61937 data.
These two steps take time and up to 2-3 seconds of audio may be muted
when starting playback.
Intel hardware (Haswell and beyond) can keep the link active
with a 'silent stream', so that the receiver does not go through those
two steps when valid audio is transmitted. This mechanism relies
on an setting the channel_id as 0xf, sending info packet and preventing
the codec from going to D3, which will increase the platform
static power consumption. The info packet assumes a basic 2ch stereo,
and the silent stream is enabled when connecting a monitor.
In case of format changes the detection of PCM v. IEC61937 needs to
be re-run. In this case there is no way to avoid the 2-3s mute.
The silent stream is enabled with a Kconfig option, as well as a kernel
parameter should there be a need to override the build time default.
This approach is used based on the power_save capability as an example,
but in the future, it may be used with a kcontrol,
depending on UCM support for HDaudio legacy.
Signed-off-by: Harsha Priya <harshapriya.n@xxxxxxxxx>
Signed-off-by: Emmanuel Jillela <emmanuel.jillela@xxxxxxxxx>
Reviewed-by: Kai Vehmanen <kai.vehmanen@xxxxxxxxxxxxxxx>
Reported-by: kernel test robot <lkp@xxxxxxxxx>
---
Change History:
v3:
- Removed eld_valid check along side of silent stream enable check
as its redundant with the monitor_present variable
- Limited the change to take affect only for Haswell and beyond Intel platforms
- As per the spec, setting the channel_id as 0xf before sending info packet
- Fixed issue reported by Kernel Test Robot (tag added)
- Tested on Intel Cometlake based Chromebook connected to few different monitors
and docks.
v2:
- Kconfig symbol depends on SND_HDA_INTEL.
- Added valid eld check to along side of silent stream enable check,
under which silent stream is enabled.
- Error prints added for codec power up, power down functions.
- The silent stream is enabled with a Kconfig/module parameter
following the power_save capability as an example. But in the future,
it may be used with a kcontrol, depending on UCM support for HDaudio legacy.
v1:
- Initial version.
sound/pci/hda/Kconfig | 14 ++++++++++
sound/pci/hda/patch_hdmi.c | 64 ++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 78 insertions(+)
diff --git a/sound/pci/hda/Kconfig b/sound/pci/hda/Kconfig
index 3f9abda..bf213e5 100644
--- a/sound/pci/hda/Kconfig
+++ b/sound/pci/hda/Kconfig
@@ -239,6 +239,20 @@ config SND_HDA_POWER_SAVE_DEFAULT
The default time-out value in seconds for HD-audio automatic
power-save mode. 0 means to disable the power-save mode.
+config SND_HDA_INTEL_HDMI_SILENT_STREAM
+ bool "Enable Silent Stream always for HDMI"
+ depends on SND_HDA_INTEL
+ help
+ Intel hardware has a feature called 'silent stream', that
+ keeps external HDMI receiver's analog circuitry powered on
+ avoiding 2-3 sec silence during playback start. This mechanism
+ relies on setting channel_id as 0xf, sending info packet and
+ preventing codec D3 entry (increasing platform static power
+ consumption when HDMI receiver is plugged-in). 2-3 sec silence
+ at the playback start is expected whenever there is format change.
+ (default is 2 channel format).
+ Say Y to enable Silent Stream feature.
+
endif
endmenu
diff --git a/sound/pci/hda/patch_hdmi.c b/sound/pci/hda/patch_hdmi.c
index e2b21ef..18eabcf 100644
--- a/sound/pci/hda/patch_hdmi.c
+++ b/sound/pci/hda/patch_hdmi.c
@@ -42,6 +42,11 @@ static bool enable_acomp = true;
module_param(enable_acomp, bool, 0444);
MODULE_PARM_DESC(enable_acomp, "Enable audio component binding (default=yes)");
+static bool enable_silent_stream =
+IS_ENABLED(CONFIG_SND_HDA_INTEL_HDMI_SILENT_STREAM);
+module_param(enable_silent_stream, bool, 0644);
+MODULE_PARM_DESC(enable_silent_stream, "Enable Silent Stream for HDMI devices");
+
struct hdmi_spec_per_cvt {
hda_nid_t cvt_nid;
int assigned;
@@ -167,6 +172,7 @@ struct hdmi_spec {
hda_nid_t vendor_nid;
const int *port_map;
int port_num;
+ bool send_silent_stream; /* Flag to enable silent stream feature */
};
#ifdef CONFIG_SND_HDA_COMPONENT
@@ -1634,21 +1640,72 @@ static void hdmi_present_sense_via_verbs(struct hdmi_spec_per_pin *per_pin,
snd_hda_power_down_pm(codec);
}
+static void silent_stream_enable(struct hda_codec *codec,
+ struct hdmi_spec_per_pin *per_pin)
+{
+ unsigned int newval, oldval;
+
+ codec_dbg(codec, "hdmi: enabling silent stream for NID %d\n",
+ per_pin->pin_nid);
+
+ mutex_lock(&per_pin->lock);
+
+ if (!per_pin->channels)
+ per_pin->channels = 2;
+
+ oldval = snd_hda_codec_read(codec, per_pin->pin_nid, 0,
+ AC_VERB_GET_CONV, 0);
+ newval = (oldval & 0xF0) | 0xF;
+ snd_hda_codec_write(codec, per_pin->pin_nid, 0,
+ AC_VERB_SET_CHANNEL_STREAMID, newval);
+
+ hdmi_setup_audio_infoframe(codec, per_pin, per_pin->non_pcm);
+
+ mutex_unlock(&per_pin->lock);
+}
+
/* update ELD and jack state via audio component */
static void sync_eld_via_acomp(struct hda_codec *codec,
struct hdmi_spec_per_pin *per_pin)
{
struct hdmi_spec *spec = codec->spec;
struct hdmi_eld *eld = &spec->temp_eld;
+ bool monitor_prev, monitor_next;
mutex_lock(&per_pin->lock);
eld->monitor_present = false;
+ monitor_prev = per_pin->sink_eld.monitor_present;
eld->eld_size = snd_hdac_acomp_get_eld(&codec->core, per_pin->pin_nid,
per_pin->dev_id, &eld->monitor_present,
eld->eld_buffer, ELD_MAX_SIZE);
eld->eld_valid = (eld->eld_size > 0);
update_eld(codec, per_pin, eld, 0);
+ monitor_next = per_pin->sink_eld.monitor_present;
mutex_unlock(&per_pin->lock);
+
+ /*
+ * Power-up will call hdmi_present_sense, so the PM calls
+ * have to be done without mutex held.
+ */
+
+ if (spec->send_silent_stream) {
+ int pm_ret;
+
+ if (!monitor_prev && monitor_next) {
+ pm_ret = snd_hda_power_up_pm(codec);
+ if (pm_ret < 0)
+ codec_err(codec,
+ "Monitor plugged-in, Failed to power up codec ret=[%d]\n",
+ pm_ret);
+ silent_stream_enable(codec, per_pin);
+ } else if (monitor_prev && !monitor_next) {
+ pm_ret = snd_hda_power_down_pm(codec);
+ if (pm_ret < 0)
+ codec_err(codec,
+ "Monitor plugged-out, Failed to power down codec ret=[%d]\n",
+ pm_ret);
+ }
+ }
}
static void hdmi_present_sense(struct hdmi_spec_per_pin *per_pin, int repoll)
@@ -2791,6 +2848,13 @@ static int intel_hsw_common_init(struct hda_codec *codec, hda_nid_t vendor_nid,
spec->ops.setup_stream = i915_hsw_setup_stream;
spec->ops.pin_cvt_fixup = i915_pin_cvt_fixup;
+ /*
+ * Enable silent stream feature, if it is enabled via
+ * module param or Kconfig option
+ */
+ if (enable_silent_stream)
+ spec->send_silent_stream = true;
+
return parse_intel_hdmi(codec);
}
--
2.7.4
