[PATCH 5.19 333/717] ALSA: usb-audio: Properly refcounting clock rate

Greg Kroah-Hartman
2022-10-22T11:22:10Z

From: Takashi Iwai <tiwai@suse.de>

[ Upstream commit 9a737e7f8b371e97eb649904276407cee2c9cf30 ]

We fixed the bug introduced by the patch for managing the shared
clocks at the commit 809f44a0cc5a ("ALSA: usb-audio: Clear fixed clock
rate at closing EP"), but it was merely a workaround. By this change,
the clock reference rate is cleared at each EP close, hence the still
remaining EP may need a re-setup of rate unnecessarily.

This patch introduces the proper refcounting for the clock reference
object so that the clock setup is done only when needed.

Fixes: 809f44a0cc5a ("ALSA: usb-audio: Clear fixed clock rate at closing EP")
Fixes: c11117b634f4 ("ALSA: usb-audio: Refcount multiple accesses on the single clock")
Link: https://lore.kernel.org/r/20220920181126.4912-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
sound/usb/endpoint.c | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)

--- a/sound/usb/endpoint.c
+++ b/sound/usb/endpoint.c
@@ -39,6 +39,7 @@ struct snd_usb_iface_ref {
struct snd_usb_clock_ref {
unsigned char clock;
atomic_t locked;
+ int opened;
int rate;
struct list_head list;
};
@@ -802,6 +803,7 @@ snd_usb_endpoint_open(struct snd_usb_aud
ep = NULL;
goto unlock;
}
+ ep->clock_ref->opened++;
}

ep->cur_audiofmt = fp;
@@ -925,8 +927,10 @@ void snd_usb_endpoint_close(struct snd_u
endpoint_set_interface(chip, ep, false);

if (!--ep->opened) {
- if (ep->clock_ref && !atomic_read(&ep->clock_ref->locked))
- ep->clock_ref->rate = 0;
+ if (ep->clock_ref) {
+ if (!--ep->clock_ref->opened)
+ ep->clock_ref->rate = 0;
+ }
ep->iface = 0;
ep->altsetting = 0;
ep->cur_audiofmt = NULL;
@@ -1633,8 +1637,7 @@ void snd_usb_endpoint_stop(struct snd_us
WRITE_ONCE(ep->sync_source->sync_sink, NULL);
stop_urbs(ep, false, keep_pending);
if (ep->clock_ref)
- if (!atomic_dec_return(&ep->clock_ref->locked))
- ep->clock_ref->rate = 0;
+ atomic_dec(&ep->clock_ref->locked);
}
}