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ALSA: hda/hdmi: Add Intel silent stream support 

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@intel.com>
Signed-off-by: Emmanuel Jillela <emmanuel.jillela@intel.com>
Reviewed-by: Kai Vehmanen <kai.vehmanen@linux.intel.com>
Reported-by: kernel test robot <lkp@intel.com>
Link: https://lore.kernel.org/r/1594068797-14011-1-git-send-email-harshapriya.n@intel.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Harsha Priya 2020-07-06 13:53:17 -07:00 committed by Takashi Iwai
parent ad1e0b7de0
commit 951894cf30
2 changed files with 78 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
sound/pci/hda/Kconfig
View File

@ -240,6 +240,20 @@ 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

64
sound/pci/hda/patch_hdmi.c
View File

@ -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);
}