On Tue, Jun 30, 2020 at 01:49:50PM +0300, Alexander Tsoy wrote:
В Пн, 29/06/2020 в 11:37 -0400, Sasha Levin пишет:
From: Alexander Tsoy <alexander@xxxxxxx>
[ Upstream commit f0bd62b64016508938df9babe47f65c2c727d25c ]
For computation of the the next frame size current value of fs/fps
and
accumulated fractional parts of fs/fps are used, where values are
stored
in Q16.16 format. This is quite natural for computing frame size for
asynchronous endpoints driven by explicit feedback, since in this
case
fs/fps is a value provided by the feedback endpoint and it's already
in
the Q format. If an error is accumulated over time, the device can
adjust fs/fps value to prevent buffer overruns/underruns.
But for synchronous endpoints the accuracy provided by these
computations
is not enough. Due to accumulated error the driver periodically
produces
frames with incorrect size (+/- 1 audio sample).
This patch fixes this issue by implementing a different algorithm for
frame size computation. It is based on accumulating of the remainders
from division fs/fps and it doesn't accumulate errors over time. This
new method is enabled for synchronous and adaptive playback
endpoints.
Signed-off-by: Alexander Tsoy <alexander@xxxxxxx>
Link:
https://lore.kernel.org/r/20200424022449.14972-1-alexander@xxxxxxx
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
sound/usb/card.h | 4 ++++
sound/usb/endpoint.c | 43 ++++++++++++++++++++++++++++++++++++++--
---
sound/usb/endpoint.h | 1 +
sound/usb/pcm.c | 2 ++
4 files changed, 45 insertions(+), 5 deletions(-)
Please drop this patch from the queue for now (and for 4.4 as well). It
introduced a regression for some devices. The fix is available, but not
accepted yet.
I've dropped it from the older branches, but note that it's already in
newer released stable kernels. Should it be reverted or should we wait
for the fix?
--
Thanks,
Sasha
