usb: gadget: u_audio: update hw_ptr in iso_complete after data copied

In u_audio_iso_complete, the runtime hw_ptr is updated before the
data is actually copied over to/from the buffer/dma area. When
ALSA uses this hw_ptr, the data may not actually be available to
be used. This causes trash/stale audio to play/record. This
patch updates the hw_ptr after the data has been copied to avoid
this.

Fixes: 132fcb460839 ("usb: gadget: Add Audio Class 2.0 Driver")
Signed-off-by: Joshua Frkuska <joshua_frkuska@mentor.com>
Signed-off-by: Eugeniu Rosca <erosca@de.adit-jv.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

diff --git a/drivers/usb/gadget/function/u_audio.c b/drivers/usb/gadget/function/u_audio.c
index c0a65e1..4c6df71 100644 (file)
--- a/drivers/usb/gadget/function/u_audio.c
+++ b/drivers/usb/gadget/function/u_audio.c
@@ -143,7 +143,6 @@ static void u_audio_iso_complete(struct usb_ep *ep, struct usb_request *req)
                update_alsa = true;
 
        hw_ptr = prm->hw_ptr;
-       prm->hw_ptr = (prm->hw_ptr + req->actual) % prm->dma_bytes;
 
        spin_unlock_irqrestore(&prm->lock, flags);
 
@@ -168,6 +167,11 @@ static void u_audio_iso_complete(struct usb_ep *ep, struct usb_request *req)
                }
        }
 
+       spin_lock_irqsave(&prm->lock, flags);
+       /* update hw_ptr after data is copied to memory */
+       prm->hw_ptr = (hw_ptr + req->actual) % prm->dma_bytes;
+       spin_unlock_irqrestore(&prm->lock, flags);
+
 exit:
        if (usb_ep_queue(ep, req, GFP_ATOMIC))
                dev_err(uac->card->dev, "%d Error!\n", __LINE__);