sound: usb-audio: allow period sizes less than 1 ms

To enable periods shorter than 1 ms, we have to make sure that short
periods are only available for alternate settings that have a small
enough data packet interval.  Furthermore, the code that aligns URBs to
USB frames is now superfluous.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

1 files changed, 86 insertions, 20 deletions

diff --git a/sound/usb/usbaudio.c b/sound/usb/usbaudio.c
index 3f974a64c55e..823296d7d578 100644
--- a/sound/usb/usbaudio.c
+++ b/sound/usb/usbaudio.c
@@ -171,7 +171,6 @@ struct snd_usb_substream {
         unsigned int curframesize;      /* current packet size in frames (for capture) */
         unsigned int fill_max: 1;       /* fill max packet size always */
         unsigned int fmt_type;          /* USB audio format type (1-3) */
-        unsigned int packs_per_ms;      /* packets per millisecond (for playback) */
 
         unsigned int running: 1;        /* running status */
 
@@ -608,9 +607,7 @@ static int prepare_playback_urb(struct snd_usb_substream *subs,
                                 break;
                         }
                 }
-                /* finish at the frame boundary at/after the period boundary */
-                if (period_elapsed &&
-                    (i & (subs->packs_per_ms - 1)) == subs->packs_per_ms - 1)
+                if (period_elapsed) /* finish at the period boundary */
                         break;
         }
         if (subs->hwptr_done + offs > runtime->buffer_size) {
@@ -1068,7 +1065,6 @@ static int init_substream_urbs(struct snd_usb_substream *subs, unsigned int peri
                 packs_per_ms = 8 >> subs->datainterval;
         else
                 packs_per_ms = 1;
-        subs->packs_per_ms = packs_per_ms;
 
         if (is_playback) {
                 urb_packs = max(nrpacks, 1);
@@ -1088,18 +1084,17 @@ static int init_substream_urbs(struct snd_usb_substream *subs, unsigned int peri
                         minsize -= minsize >> 3;
                 minsize = max(minsize, 1u);
                 total_packs = (period_bytes + minsize - 1) / minsize;
-                /* round up to multiple of packs_per_ms */
-                total_packs = (total_packs + packs_per_ms - 1)
-                                & ~(packs_per_ms - 1);
                 /* we need at least two URBs for queueing */
-                if (total_packs < 2 * packs_per_ms) {
-                        total_packs = 2 * packs_per_ms;
+                if (total_packs < 2) {
+                        total_packs = 2;
                 } else {
                         /* and we don't want too long a queue either */
                         maxpacks = max(MAX_QUEUE * packs_per_ms, urb_packs * 2);
                         total_packs = min(total_packs, maxpacks);
                 }
         } else {
+                while (urb_packs > 1 && urb_packs * maxsize >= period_bytes)
+                        urb_packs >>= 1;
                 total_packs = MAX_URBS * urb_packs;
         }
         subs->nurbs = (total_packs + urb_packs - 1) / urb_packs;
@@ -1564,11 +1559,15 @@ static struct snd_pcm_hardware snd_usb_hardware =
 #define hwc_debug(fmt, args...) /**/
 #endif
 
-static int hw_check_valid_format(struct snd_pcm_hw_params *params, struct audioformat *fp)
+static int hw_check_valid_format(struct snd_usb_substream *subs,
+                                 struct snd_pcm_hw_params *params,
+                                 struct audioformat *fp)
 {
         struct snd_interval *it = hw_param_interval(params, SNDRV_PCM_HW_PARAM_RATE);
         struct snd_interval *ct = hw_param_interval(params, SNDRV_PCM_HW_PARAM_CHANNELS);
         struct snd_mask *fmts = hw_param_mask(params, SNDRV_PCM_HW_PARAM_FORMAT);
+        struct snd_interval *pt = hw_param_interval(params, SNDRV_PCM_HW_PARAM_PERIOD_TIME);
+        unsigned int ptime;
 
         /* check the format */
         if (!snd_mask_test(fmts, fp->format)) {
@@ -1589,6 +1588,14 @@ static int hw_check_valid_format(struct snd_pcm_hw_params *params, struct audiof
                 hwc_debug("   > check: rate_max %d < min %d\n", fp->rate_max, it->min);
                 return 0;
         }
+        /* check whether the period time is >= the data packet interval */
+        if (snd_usb_get_speed(subs->dev) == USB_SPEED_HIGH) {
+                ptime = 125 * (1 << fp->datainterval);
+                if (ptime > pt->max || (ptime == pt->max && pt->openmax)) {
+                        hwc_debug("   > check: ptime %u > max %u\n", ptime, pt->max);
+                        return 0;
+                }
+        }
         return 1;
 }
 
@@ -1607,7 +1614,7 @@ static int hw_rule_rate(struct snd_pcm_hw_params *params,
         list_for_each(p, &subs->fmt_list) {
                 struct audioformat *fp;
                 fp = list_entry(p, struct audioformat, list);
-                if (!hw_check_valid_format(params, fp))
+                if (!hw_check_valid_format(subs, params, fp))
                         continue;
                 if (changed++) {
                         if (rmin > fp->rate_min)
@@ -1661,7 +1668,7 @@ static int hw_rule_channels(struct snd_pcm_hw_params *params,
         list_for_each(p, &subs->fmt_list) {
                 struct audioformat *fp;
                 fp = list_entry(p, struct audioformat, list);
-                if (!hw_check_valid_format(params, fp))
+                if (!hw_check_valid_format(subs, params, fp))
                         continue;
                 if (changed++) {
                         if (rmin > fp->channels)
@@ -1714,7 +1721,7 @@ static int hw_rule_format(struct snd_pcm_hw_params *params,
         list_for_each(p, &subs->fmt_list) {
                 struct audioformat *fp;
                 fp = list_entry(p, struct audioformat, list);
-                if (!hw_check_valid_format(params, fp))
+                if (!hw_check_valid_format(subs, params, fp))
                         continue;
                 fbits |= (1ULL << fp->format);
         }
@@ -1732,6 +1739,44 @@ static int hw_rule_format(struct snd_pcm_hw_params *params,
         return changed;
 }
 
+static int hw_rule_period_time(struct snd_pcm_hw_params *params,
+                               struct snd_pcm_hw_rule *rule)
+{
+        struct snd_usb_substream *subs = rule->private;
+        struct audioformat *fp;
+        struct snd_interval *it;
+        unsigned char min_datainterval;
+        unsigned int pmin;
+        int changed;
+
+        it = hw_param_interval(params, SNDRV_PCM_HW_PARAM_PERIOD_TIME);
+        hwc_debug("hw_rule_period_time: (%u,%u)\n", it->min, it->max);
+        min_datainterval = 0xff;
+        list_for_each_entry(fp, &subs->fmt_list, list) {
+                if (!hw_check_valid_format(subs, params, fp))
+                        continue;
+                min_datainterval = min(min_datainterval, fp->datainterval);
+        }
+        if (min_datainterval == 0xff) {
+                hwc_debug("  --> get emtpy\n");
+                it->empty = 1;
+                return -EINVAL;
+        }
+        pmin = 125 * (1 << min_datainterval);
+        changed = 0;
+        if (it->min < pmin) {
+                it->min = pmin;
+                it->openmin = 0;
+                changed = 1;
+        }
+        if (snd_interval_checkempty(it)) {
+                it->empty = 1;
+                return -EINVAL;
+        }
+        hwc_debug("  --> (%u,%u) (changed = %d)\n", it->min, it->max, changed);
+        return changed;
+}
+
 /*
  *  If the device supports unusual bit rates, does the request meet these?
  */
@@ -1777,6 +1822,8 @@ static int snd_usb_pcm_check_knot(struct snd_pcm_runtime *runtime,
 static int setup_hw_info(struct snd_pcm_runtime *runtime, struct snd_usb_substream *subs)
 {
         struct list_head *p;
+        unsigned int pt, ptmin;
+        int param_period_time_if_needed;
         int err;
 
         runtime->hw.formats = subs->formats;
@@ -1786,6 +1833,7 @@ static int setup_hw_info(struct snd_pcm_runtime *runtime, struct snd_usb_substre
         runtime->hw.channels_min = 256;
         runtime->hw.channels_max = 0;
         runtime->hw.rates = 0;
+        ptmin = UINT_MAX;
         /* check min/max rates and channels */
         list_for_each(p, &subs->fmt_list) {
                 struct audioformat *fp;
@@ -1804,34 +1852,52 @@ static int setup_hw_info(struct snd_pcm_runtime *runtime, struct snd_usb_substre
                         runtime->hw.period_bytes_min = runtime->hw.period_bytes_max =
                                 fp->frame_size;
                 }
+                pt = 125 * (1 << fp->datainterval);
+                ptmin = min(ptmin, pt);
         }
 
-        /* set the period time minimum 1ms */
-        /* FIXME: high-speed mode allows 125us minimum period, but many parts
-         * in the current code assume the 1ms period.
-         */
+        param_period_time_if_needed = SNDRV_PCM_HW_PARAM_PERIOD_TIME;
+        if (snd_usb_get_speed(subs->dev) != USB_SPEED_HIGH)
+                /* full speed devices have fixed data packet interval */
+                ptmin = 1000;
+        if (ptmin == 1000)
+                /* if period time doesn't go below 1 ms, no rules needed */
+                param_period_time_if_needed = -1;
         snd_pcm_hw_constraint_minmax(runtime, SNDRV_PCM_HW_PARAM_PERIOD_TIME,
-                                     1000,
-                                     /*(nrpacks * MAX_URBS) * 1000*/ UINT_MAX);
+                                     ptmin, UINT_MAX);
 
         if ((err = snd_pcm_hw_rule_add(runtime, 0, SNDRV_PCM_HW_PARAM_RATE,
                                        hw_rule_rate, subs,
                                        SNDRV_PCM_HW_PARAM_FORMAT,
                                        SNDRV_PCM_HW_PARAM_CHANNELS,
+                                       param_period_time_if_needed,
                                        -1)) < 0)
                 return err;
         if ((err = snd_pcm_hw_rule_add(runtime, 0, SNDRV_PCM_HW_PARAM_CHANNELS,
                                        hw_rule_channels, subs,
                                        SNDRV_PCM_HW_PARAM_FORMAT,
                                        SNDRV_PCM_HW_PARAM_RATE,
+                                       param_period_time_if_needed,
                                        -1)) < 0)
                 return err;
         if ((err = snd_pcm_hw_rule_add(runtime, 0, SNDRV_PCM_HW_PARAM_FORMAT,
                                        hw_rule_format, subs,
                                        SNDRV_PCM_HW_PARAM_RATE,
                                        SNDRV_PCM_HW_PARAM_CHANNELS,
+                                       param_period_time_if_needed,
                                        -1)) < 0)
                 return err;
+        if (param_period_time_if_needed >= 0) {
+                err = snd_pcm_hw_rule_add(runtime, 0,
+                                          SNDRV_PCM_HW_PARAM_PERIOD_TIME,
+                                          hw_rule_period_time, subs,
+                                          SNDRV_PCM_HW_PARAM_FORMAT,
+                                          SNDRV_PCM_HW_PARAM_CHANNELS,
+                                          SNDRV_PCM_HW_PARAM_RATE,
+                                          -1);
+                if (err < 0)
+                        return err;
+        }
         if ((err = snd_usb_pcm_check_knot(runtime, subs)) < 0)
                 return err;
         return 0;