1 files changed, 38 insertions, 1 deletions

diff --git a/sound/usb/usbaudio.c b/sound/usb/usbaudio.c
index a6b88482637b..c7b902358b7b 100644
--- a/sound/usb/usbaudio.c
+++ b/sound/usb/usbaudio.c
@@ -627,6 +627,7 @@ static int prepare_playback_urb(struct snd_usb_substream *subs,
         subs->hwptr_done += offs;
         if (subs->hwptr_done >= runtime->buffer_size)
                 subs->hwptr_done -= runtime->buffer_size;
+        runtime->delay += offs;
         spin_unlock_irqrestore(&subs->lock, flags);
         urb->transfer_buffer_length = offs * stride;
         if (period_elapsed)
@@ -636,12 +637,22 @@ static int prepare_playback_urb(struct snd_usb_substream *subs,
 
 /*
  * process after playback data complete
- * - nothing to do
+ * - decrease the delay count again
  */
 static int retire_playback_urb(struct snd_usb_substream *subs,
                                struct snd_pcm_runtime *runtime,
                                struct urb *urb)
 {
+        unsigned long flags;
+        int stride = runtime->frame_bits >> 3;
+        int processed = urb->transfer_buffer_length / stride;
+
+        spin_lock_irqsave(&subs->lock, flags);
+        if (processed > runtime->delay)
+                runtime->delay = 0;
+        else
+                runtime->delay -= processed;
+        spin_unlock_irqrestore(&subs->lock, flags);
         return 0;
 }
 
@@ -1520,6 +1531,7 @@ static int snd_usb_pcm_prepare(struct snd_pcm_substream *substream)
         subs->hwptr_done = 0;
         subs->transfer_done = 0;
         subs->phase = 0;
+        runtime->delay = 0;
 
         /* clear urbs (to be sure) */
         deactivate_urbs(subs, 0, 1);
@@ -3279,6 +3291,25 @@ static int snd_usb_cm106_boot_quirk(struct usb_device *dev)
         return snd_usb_cm106_write_int_reg(dev, 2, 0x8004);
 }
 
+/*
+ * C-Media CM6206 is based on CM106 with two additional
+ * registers that are not documented in the data sheet.
+ * Values here are chosen based on sniffing USB traffic
+ * under Windows.
+ */
+static int snd_usb_cm6206_boot_quirk(struct usb_device *dev)
+{
+        int err, reg;
+        int val[] = {0x200c, 0x3000, 0xf800, 0x143f, 0x0000, 0x3000};
+
+        for (reg = 0; reg < ARRAY_SIZE(val); reg++) {
+                err = snd_usb_cm106_write_int_reg(dev, reg, val[reg]);
+                if (err < 0)
+                        return err;
+        }
+
+        return err;
+}
 
 /*
  * Setup quirks
@@ -3565,6 +3596,12 @@ static void *snd_usb_audio_probe(struct usb_device *dev,
                         goto __err_val;
         }
 
+        /* C-Media CM6206 / CM106-Like Sound Device */
+        if (id == USB_ID(0x0d8c, 0x0102)) {
+                if (snd_usb_cm6206_boot_quirk(dev) < 0)
+                        goto __err_val;
+        }
+
         /*
          * found a config.  now register to ALSA
          */