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USB: gadget: f_audio_source: Adjust packet timing to reduce glitches

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Increase max packet size and clean up timing logic so we can better
recover from not getting an interrupt in time for a SOF.

Signed-off-by: Mike Lockwood <lockwood@google.com>
This commit is contained in:
Mike Lockwood 2012-05-27 15:41:53 -07:00
parent 5df2eb9d22
commit 0daae7684b
1 changed files with 9 additions and 8 deletions
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17
drivers/usb/gadget/f_audio_source.c
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@ -25,11 +25,11 @@
/* Each frame is two 16 bit integers (one per channel) */
#define BYTES_PER_FRAME 4
#define FRAMES_PER_MSEC (SAMPLE_RATE / 1000)
/* Add one to FRAMES_PER_MSEC to adjust for round-off above */
#define IN_EP_MAX_PACKET_SIZE ((FRAMES_PER_MSEC + 1) * BYTES_PER_FRAME)
#define IN_EP_MAX_PACKET_SIZE 256
/* Number of requests to allocate */
#define IN_EP_REQ_COUNT 16
#define IN_EP_REQ_COUNT 4
#define AUDIO_AC_INTERFACE 0
#define AUDIO_AS_INTERFACE 1
@ -339,13 +339,10 @@ static void audio_send(struct audio_dev *audio)
runtime = audio->substream->runtime;
/* compute number of frames to send */
now = ktime_get();
msecs = ktime_to_ns(now) - ktime_to_ns(audio->start_time);
do_div(msecs, 1000000);
/* Add a bit to msecs so we queue some extra requests in case
* we miss a few SOFs due to interrupts being disabled or CPU load.
*/
msecs += IN_EP_REQ_COUNT/2;
frames = msecs * SAMPLE_RATE;
do_div(frames, 1000);
@ -353,11 +350,15 @@ static void audio_send(struct audio_dev *audio)
* If we get too far behind it is better to drop some frames than
* to keep sending data too fast in an attempt to catch up.
*/
if (frames - audio->frames_sent > 2 * FRAMES_PER_MSEC * IN_EP_REQ_COUNT)
if (frames - audio->frames_sent > 10 * FRAMES_PER_MSEC)
audio->frames_sent = frames - FRAMES_PER_MSEC;
frames -= audio->frames_sent;
/* We need to send something to keep the pipeline going */
if (frames <= 0)
frames = FRAMES_PER_MSEC;
while (frames > 0) {
req = audio_req_get(audio);
if (!req)