ALSA: usb-audio: Restrict rates for the shared clocks

When a single clock source is shared among several endpoints, we have
to keep the same rate on all active endpoints as long as the clock is
being used.  For dealing with such a case, this patch adds one more
check in the hw params constraint for the rate to take the shared
clocks into account.  The current rate is evaluated from the endpoint
list that applies the same clock source.

BugLink: https://bugzilla.suse.com/show_bug.cgi?id=1190418
Link: https://lore.kernel.org/r/20210929080844.11583-2-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>

diff --git a/sound/usb/card.h b/sound/usb/card.h
index 5b19901f305a3b1d50b00959cd2443c8d34a26a3..3329ce710cb9a7c1c28c0dbbc29e3a40c4ca00e7 100644 (file)
--- a/sound/usb/card.h
+++ b/sound/usb/card.h
@@ -136,6 +136,7 @@ struct snd_usb_endpoint {
        unsigned int cur_period_frames;
        unsigned int cur_period_bytes;
        unsigned int cur_buffer_periods;
+       unsigned char cur_clock;
 
        spinlock_t lock;
        struct list_head list;

diff --git a/sound/usb/endpoint.c b/sound/usb/endpoint.c
index 533919a28856f909878a742829c06506fa4a359c..29c4865966f597912b53ed8ce95470951a653f94 100644 (file)
--- a/sound/usb/endpoint.c
+++ b/sound/usb/endpoint.c
@@ -722,6 +722,7 @@ snd_usb_endpoint_open(struct snd_usb_audio *chip,
                ep->cur_period_frames = params_period_size(params);
                ep->cur_period_bytes = ep->cur_period_frames * ep->cur_frame_bytes;
                ep->cur_buffer_periods = params_periods(params);
+               ep->cur_clock = fp->clock;
 
                if (ep->type == SND_USB_ENDPOINT_TYPE_SYNC)
                        endpoint_set_syncinterval(chip, ep);
@@ -833,6 +834,7 @@ void snd_usb_endpoint_close(struct snd_usb_audio *chip,
                ep->altsetting = 0;
                ep->cur_audiofmt = NULL;
                ep->cur_rate = 0;
+               ep->cur_clock = 0;
                ep->iface_ref = NULL;
                usb_audio_dbg(chip, "EP 0x%x closed\n", ep->ep_num);
        }
@@ -1340,6 +1342,25 @@ unlock:
        return err;
 }
 
+/* get the current rate set to the given clock by any endpoint */
+int snd_usb_endpoint_get_clock_rate(struct snd_usb_audio *chip, int clock)
+{
+       struct snd_usb_endpoint *ep;
+       int rate = 0;
+
+       if (!clock)
+               return 0;
+       mutex_lock(&chip->mutex);
+       list_for_each_entry(ep, &chip->ep_list, list) {
+               if (ep->cur_clock == clock && ep->cur_rate) {
+                       rate = ep->cur_rate;
+                       break;
+               }
+       }
+       mutex_unlock(&chip->mutex);
+       return rate;
+}
+
 /**
  * snd_usb_endpoint_start: start an snd_usb_endpoint
  *

diff --git a/sound/usb/endpoint.h b/sound/usb/endpoint.h
index a668f675b52b0faa58b1b3455738415d0639c59a..a1099ec37e1c96e56284c6009e8271aec59914e1 100644 (file)
--- a/sound/usb/endpoint.h
+++ b/sound/usb/endpoint.h
@@ -19,6 +19,7 @@ void snd_usb_endpoint_close(struct snd_usb_audio *chip,
                            struct snd_usb_endpoint *ep);
 int snd_usb_endpoint_configure(struct snd_usb_audio *chip,
                               struct snd_usb_endpoint *ep);
+int snd_usb_endpoint_get_clock_rate(struct snd_usb_audio *chip, int clock);
 
 bool snd_usb_endpoint_compatible(struct snd_usb_audio *chip,
                                 struct snd_usb_endpoint *ep,

diff --git a/sound/usb/pcm.c b/sound/usb/pcm.c
index 5dc9266180e379217520100092e7379e722d5bdc..19392117de9e828e7176d2f958e7fa71619231d3 100644 (file)
--- a/sound/usb/pcm.c
+++ b/sound/usb/pcm.c
@@ -734,6 +734,7 @@ static int hw_rule_rate(struct snd_pcm_hw_params *params,
                        struct snd_pcm_hw_rule *rule)
 {
        struct snd_usb_substream *subs = rule->private;
+       struct snd_usb_audio *chip = subs->stream->chip;
        const struct audioformat *fp;
        struct snd_interval *it = hw_param_interval(params, SNDRV_PCM_HW_PARAM_RATE);
        unsigned int rmin, rmax, r;
@@ -745,6 +746,14 @@ static int hw_rule_rate(struct snd_pcm_hw_params *params,
        list_for_each_entry(fp, &subs->fmt_list, list) {
                if (!hw_check_valid_format(subs, params, fp))
                        continue;
+               r = snd_usb_endpoint_get_clock_rate(chip, fp->clock);
+               if (r > 0) {
+                       if (!snd_interval_test(it, r))
+                               continue;
+                       rmin = min(rmin, r);
+                       rmax = max(rmax, r);
+                       continue;
+               }
                if (fp->rate_table && fp->nr_rates) {
                        for (i = 0; i < fp->nr_rates; i++) {
                                r = fp->rate_table[i];