[Qemu-devel] [PATCH v4 3/5] audio/hda: tweak timer adjust logic

[Gerd Hoffmann <kraxel@redhat.com>]

We have some jitter in the audio timer call frequency and buffer sizes.
So it is rather pointless trying to be very exact, effect is a constant
up+down adjustment.  So adjust only in case we are off too much.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
---
 hw/audio/hda-codec.c  | 20 +++++++++++++-------
 hw/audio/trace-events |  1 +
 2 files changed, 14 insertions(+), 7 deletions(-)

diff --git a/hw/audio/hda-codec.c b/hw/audio/hda-codec.c
index a08516cbf8..870448a687 100644
--- a/hw/audio/hda-codec.c
+++ b/hw/audio/hda-codec.c
@@ -129,7 +129,6 @@ static void hda_codec_parse_fmt(uint32_t format, struct audsettings *as)
 #include  "hda-codec-common.h"
 
 #define HDA_TIMER_TICKS (SCALE_MS)
-#define MAX_CORR (SCALE_US * 100)
 #define B_SIZE sizeof(st->buf)
 #define B_MASK (sizeof(st->buf) - 1)
 
@@ -196,13 +195,20 @@ static inline int64_t hda_bytes_per_second(HDAAudioStream *st)
 
 static inline void hda_timer_sync_adjust(HDAAudioStream *st, int64_t target_pos)
 {
-    int64_t corr =
-        NANOSECONDS_PER_SECOND * target_pos / hda_bytes_per_second(st);
-    if (corr > MAX_CORR) {
-        corr = MAX_CORR;
-    } else if (corr < -MAX_CORR) {
-        corr = -MAX_CORR;
+    int64_t limit = B_SIZE / 8;
+    int64_t corr = 0;
+
+    if (target_pos > limit) {
+        corr = HDA_TIMER_TICKS;
     }
+    if (target_pos < -limit) {
+        corr = -HDA_TIMER_TICKS;
+    }
+    if (corr == 0) {
+        return;
+    }
+
+    trace_hda_audio_adjust(st->node->name, target_pos);
     atomic_fetch_add(&st->buft_start, corr);
 }
 
diff --git a/hw/audio/trace-events b/hw/audio/trace-events
index 03340b9359..30112d97c4 100644
--- a/hw/audio/trace-events
+++ b/hw/audio/trace-events
@@ -21,3 +21,4 @@ milkymist_ac97_out_cb_transferred(int transferred) "transferred %d"
 # hw/audio/hda-codec.c
 hda_audio_running(const char *stream, int nr, bool running) "st %s, nr %d, run %d"
 hda_audio_format(const char *stream, int chan, const char *fmt, int freq) "st %s, %d x %s @ %d Hz"
+hda_audio_adjust(const char *stream, int pos) "st %s, pos %d"
-- 
2.9.3