qcom/audio/hal: add offset to MMAP input time

Try to fix glitches on AAudio MMAP input on some devices.
The DSP is returning a position/time pair that is too soon.

Set default offset to zero if no property used.
Remove unneeded FIXME.
Improve comments.
Cleanup adding of offset.

This CL combines two CLs from Q master. See Merged-in lines below.

Bug: 122680738
Test: Should see glitch.count = 0 when you run this test.
Test: adb shell aaudio_loopback -tm -s20

Change-Id: Ib4c5b773702923ef76da124a5c6f4773e004ed7e
Merged-In: Ib4c5b773702923ef76da124a5c6f4773e004ed7e
Merged-In: Idd85f8978443e036ba4c5fb6440320a8578a74fd
(cherry picked from commit 07b4288d79e6509b38d0e8252db3898fe4d1fb9f)
diff --git a/hal/audio_hw.c b/hal/audio_hw.c
index f315b5e..85261e8 100644
--- a/hal/audio_hw.c
+++ b/hal/audio_hw.c
@@ -3994,6 +3994,17 @@
     return ret;
 }
 
+// Read offset for the positional timestamp from a persistent vendor property.
+// This is to workaround apparent inaccuracies in the timing information that
+// is used by the AAudio timing model. The inaccuracies can cause glitches.
+static int64_t in_get_mmap_time_offset() {
+    const int32_t kDefaultOffsetMicros = 0;
+    int32_t mmap_time_offset_micros = property_get_int32(
+            "persist.audio.in_mmap_delay_micros", kDefaultOffsetMicros);
+    ALOGI("mmap_time_offset_micros = %d for input", mmap_time_offset_micros);
+    return mmap_time_offset_micros * (int64_t)1000;
+}
+
 static int in_create_mmap_buffer(const struct audio_stream_in *stream,
                                   int32_t min_size_frames,
                                   struct audio_mmap_buffer_info *info)
@@ -4074,6 +4085,8 @@
         goto exit;
     }
 
+    in->mmap_time_offset_nanos = in_get_mmap_time_offset();
+
     in->standby = false;
     ret = 0;
 
@@ -4116,7 +4129,9 @@
         ALOGE("%s: %s", __func__, pcm_get_error(in->pcm));
         goto exit;
     }
-    position->time_nanoseconds = audio_utils_ns_from_timespec(&ts);
+    position->time_nanoseconds = audio_utils_ns_from_timespec(&ts)
+            + in->mmap_time_offset_nanos;
+
 exit:
     pthread_mutex_unlock(&in->lock);
     return ret;
diff --git a/hal/audio_hw.h b/hal/audio_hw.h
index 0b3b028..4306981 100644
--- a/hal/audio_hw.h
+++ b/hal/audio_hw.h
@@ -274,6 +274,7 @@
     bool enable_ns;
     int64_t frames_read; /* total frames read, not cleared when entering standby */
     int64_t frames_muted; /* total frames muted, not cleared when entering standby */
+    int64_t mmap_time_offset_nanos; /* fudge factor to correct inaccuracies in DSP */
 
     audio_io_handle_t capture_handle;
     audio_input_flags_t flags;