1 files changed, 31 insertions, 3 deletions

diff --git a/sound/usb/pcm.c b/sound/usb/pcm.c
index b8dcbf407bbb..0220b0f335b9 100644
--- a/sound/usb/pcm.c
+++ b/sound/usb/pcm.c
@@ -28,12 +28,36 @@
 #include "card.h"
 #include "quirks.h"
 #include "debug.h"
-#include "urb.h"
+#include "endpoint.h"
 #include "helper.h"
 #include "pcm.h"
 #include "clock.h"
 #include "power.h"
 
+/* return the estimated delay based on USB frame counters */
+snd_pcm_uframes_t snd_usb_pcm_delay(struct snd_usb_substream *subs,
+                                    unsigned int rate)
+{
+        int current_frame_number;
+        int frame_diff;
+        int est_delay;
+
+        current_frame_number = usb_get_current_frame_number(subs->dev);
+        /*
+         * HCD implementations use different widths, use lower 8 bits.
+         * The delay will be managed up to 256ms, which is more than
+         * enough
+         */
+        frame_diff = (current_frame_number - subs->last_frame_number) & 0xff;
+
+        /* Approximation based on number of samples per USB frame (ms),
+           some truncation for 44.1 but the estimate is good enough */
+        est_delay =  subs->last_delay - (frame_diff * rate / 1000);
+        if (est_delay < 0)
+                est_delay = 0;
+        return est_delay;
+}
+
 /*
  * return the current pcm pointer.  just based on the hwptr_done value.
  */
@@ -45,6 +69,8 @@ static snd_pcm_uframes_t snd_usb_pcm_pointer(struct snd_pcm_substream *substream
         subs = (struct snd_usb_substream *)substream->runtime->private_data;
         spin_lock(&subs->lock);
         hwptr_done = subs->hwptr_done;
+        substream->runtime->delay = snd_usb_pcm_delay(subs,
+                                                substream->runtime->rate);
         spin_unlock(&subs->lock);
         return hwptr_done / (substream->runtime->frame_bits >> 3);
 }
@@ -126,7 +152,7 @@ static int init_pitch_v1(struct snd_usb_audio *chip, int iface,
         if ((err = snd_usb_ctl_msg(dev, usb_sndctrlpipe(dev, 0), UAC_SET_CUR,
                                    USB_TYPE_CLASS|USB_RECIP_ENDPOINT|USB_DIR_OUT,
                                    UAC_EP_CS_ATTR_PITCH_CONTROL << 8, ep,
-                                   data, sizeof(data), 1000)) < 0) {
+                                   data, sizeof(data))) < 0) {
                 snd_printk(KERN_ERR "%d:%d:%d: cannot set enable PITCH\n",
                            dev->devnum, iface, ep);
                 return err;
@@ -150,7 +176,7 @@ static int init_pitch_v2(struct snd_usb_audio *chip, int iface,
         if ((err = snd_usb_ctl_msg(dev, usb_sndctrlpipe(dev, 0), UAC2_CS_CUR,
                                    USB_TYPE_CLASS | USB_RECIP_ENDPOINT | USB_DIR_OUT,
                                    UAC2_EP_CS_PITCH << 8, 0,
-                                   data, sizeof(data), 1000)) < 0) {
+                                   data, sizeof(data))) < 0) {
                 snd_printk(KERN_ERR "%d:%d:%d: cannot set enable PITCH (v2)\n",
                            dev->devnum, iface, fmt->altsetting);
                 return err;
@@ -417,6 +443,8 @@ static int snd_usb_pcm_prepare(struct snd_pcm_substream *substream)
         subs->hwptr_done = 0;
         subs->transfer_done = 0;
         subs->phase = 0;
+        subs->last_delay = 0;
+        subs->last_frame_number = 0;
         runtime->delay = 0;
 
         return snd_usb_substream_prepare(subs, runtime);