[PATCH] sound: oss: dmasound: kick queued output before extending tail fragment

[PATCH] sound: oss: dmasound: kick queued output before extending tail fragment

[Cássio Gabriel]

sq_write() currently clears POST and then immediately appends
to the current rear fragment.

If the queue already contains complete fragments ahead of that
incomplete tail, playback is not kicked until the queue-full wait
path or the final sq_play() at the end of the write. That wastes
the slack those queued samples would otherwise provide while the driver
spends more time copying and translating more data into the tail fragment.

All in-tree dmasound playback backends still refuse to queue
an incomplete last fragment while !syncing, but they can start
earlier complete fragments.

Call sq_play() immediately after clearing POST and before extending
the rear fragment so already-queued complete output can start earlier.

Signed-off-by: Cássio Gabriel <cassiogabrielcontato@gmail.com>
---
 sound/oss/dmasound/dmasound_core.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/sound/oss/dmasound/dmasound_core.c b/sound/oss/dmasound/dmasound_core.c
index a718b75bb6a0..e80f730d0803 100644
--- a/sound/oss/dmasound/dmasound_core.c
+++ b/sound/oss/dmasound/dmasound_core.c
@@ -574,11 +574,6 @@ static ssize_t sq_write(struct file *file, const char __user *src, size_t uLeft,
 		uWritten = 0 ;
 	}
 
-/* FIXME: I think that this may be the wrong behaviour when we get strapped
-	for time and the cpu is close to being (or actually) behind in sending data.
-	- because we've lost the time that the N samples, already in the buffer,
-	would have given us to get here with the next lot from the user.
-*/
 	/* The interrupt doesn't start to play the last, incomplete frame.
 	 * Thus we can append to it without disabling the interrupts! (Note
 	 * also that write_sq.rear isn't affected by the interrupt.)
@@ -598,6 +593,11 @@ static ssize_t sq_write(struct file *file, const char __user *src, size_t uLeft,
 	write_sq.syncing &= ~2 ; /* take out POST status */
 	spin_unlock_irqrestore(&dmasound.lock, flags);
 
+	/* Start any already-complete fragments before we spend
+	 * more time extending the incomplete tail fragment.
+	 */
+	sq_play();
+
 	if (write_sq.count > 0 &&
 	    (bLeft = write_sq.block_size-write_sq.rear_size) > 0) {
 		dest = write_sq.buffers[write_sq.rear];

---
base-commit: 702806986e6bd2b2b37186be47aa63774bd62198
change-id: 20260427-dmasound-sq-play-445c22fd9432

Best regards,
--  
Cássio Gabriel <cassiogabrielcontato@gmail.com>

Re: [PATCH] sound: oss: dmasound: kick queued output before extending tail fragment

[Takashi Iwai]

On Tue, 28 Apr 2026 00:13:28 +0200,
Cássio Gabriel wrote:
> 
> sq_write() currently clears POST and then immediately appends
> to the current rear fragment.
> 
> If the queue already contains complete fragments ahead of that
> incomplete tail, playback is not kicked until the queue-full wait
> path or the final sq_play() at the end of the write. That wastes
> the slack those queued samples would otherwise provide while the driver
> spends more time copying and translating more data into the tail fragment.
> 
> All in-tree dmasound playback backends still refuse to queue
> an incomplete last fragment while !syncing, but they can start
> earlier complete fragments.
> 
> Call sq_play() immediately after clearing POST and before extending
> the rear fragment so already-queued complete output can start earlier.
> 
> Signed-off-by: Cássio Gabriel <cassiogabrielcontato@gmail.com>

Applied to for-next branch now.  Thanks.


Takashi