policy: Avoid unnecessary set_parameter calls

APM calls a set_parameter on primary output with key fm_volume
whenever a checkAndSetVolume is called. This is done irrespective
of whether the volume values are same of different.

A side effect of doing so is that the FastMixer associated with
the MixerThread will be put into HOT_IDLE unnecessarily which in turn
can cause glitches/breaks in audio.

CRs-Fixed: 948361
Change-Id: I7fd8b7340e6c78ee6d00b41ccf679582338c011a

2 files changed, 11 insertions, 4 deletions

diff --git a/policy_hal/AudioPolicyManager.cpp b/policy_hal/AudioPolicyManager.cpp
index 829982c7..52ead1bd 100644
--- a/policy_hal/AudioPolicyManager.cpp
+++ b/policy_hal/AudioPolicyManager.cpp
@@ -1226,9 +1226,14 @@ status_t AudioPolicyManagerCustom::checkAndSetVolume(audio_stream_type_t stream,
 #ifdef FM_POWER_OPT
     } else if (stream == AUDIO_STREAM_MUSIC && hasPrimaryOutput() &&
                outputDesc == mPrimaryOutput) {
-        AudioParameter param = AudioParameter();
-        param.addFloat(String8("fm_volume"), Volume::DbToAmpl(volumeDb));
-        mpClientInterface->setParameters(mPrimaryOutput->mIoHandle, param.toString(), delayMs);
+        /* Avoid unnecessary set_parameter calls as it puts the primary
+           outputs FastMixer in HOT_IDLE leading to breaks in audio */
+        if (volumeDb != mPrevFMVolumeDb) {
+            mPrevFMVolumeDb = volumeDb;
+            AudioParameter param = AudioParameter();
+            param.addFloat(String8("fm_volume"), Volume::DbToAmpl(volumeDb));
+            mpClientInterface->setParameters(mPrimaryOutput->mIoHandle, param.toString(), delayMs);
+        }
 #endif /* FM_POWER_OPT end */
     }
 
@@ -1949,7 +1954,8 @@ AudioPolicyManagerCustom::AudioPolicyManagerCustom(AudioPolicyClientInterface *c
     : AudioPolicyManager(clientInterface),
       mHdmiAudioDisabled(false),
       mHdmiAudioEvent(false),
-      mPrevPhoneState(0)
+      mPrevPhoneState(0),
+      mPrevFMVolumeDb(0.0f)
 {
     char ssr_enabled[PROPERTY_VALUE_MAX] = {0};
     bool prop_ssr_enabled = false;
diff --git a/policy_hal/AudioPolicyManager.h b/policy_hal/AudioPolicyManager.h
index f70cfb00..4df5e6ba 100644
--- a/policy_hal/AudioPolicyManager.h
+++ b/policy_hal/AudioPolicyManager.h
@@ -145,6 +145,7 @@ private:
         // Used for record + playback concurrency
         bool mIsInputRequestOnProgress;
 #endif
+        float mPrevFMVolumeDb;
 };
 
 };