1 files changed, 31 insertions, 3 deletions

diff --git a/sound/usb/pcm.c b/sound/usb/pcm.c
index b8dcbf4..0220b0f 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);