usb: gadget: uac: stop sending audio when disconnect

The sending process may still work if disconnect from
PC, for the sending function is called in the complete
call back function. So set alt to 0 when disconnect or
reset, and stop follow-up sending in complete function
if alt is 0.

Change-Id: I073f122fe2ce2faf8cf6fb036fb983f9f3325f34
Signed-off-by: Meng Dongyang <daniel.meng@rock-chips.com>

Author: Meng Dongyang

drivers/usb/gadget/function/f_audio_source.c

@@ -674,7 +674,8 @@ static void audio_data_complete(struct usb_ep *ep, struct usb_request *req)
 		snd_pcm_period_elapsed(audio->substream);
 		audio->period_offset = 0;
 	}
-	audio_send(audio);
+	if (audio->alt)
+		audio_send(audio);
 }
 
 static int audio_set_endpoint_req(struct usb_function *f,
@@ -913,6 +914,9 @@ static void audio_disable(struct usb_function *f)
 {
 	struct audio_dev	*audio = func_to_audio(f);
 
+	audio->alt = 0;
+	schedule_work(&audio->work);
+
 	pr_debug("audio_disable\n");
 	usb_ep_disable(audio->in_ep);
 }
@@ -1064,9 +1068,11 @@ audio_unbind(struct usb_configuration *c, struct usb_function *f)
 
 static void audio_pcm_playback_start(struct audio_dev *audio)
 {
-	audio->start_time = ktime_get();
-	audio->frames_sent = 0;
-	audio_send(audio);
+	if (audio->alt) {
+		audio->start_time = ktime_get();
+		audio->frames_sent = 0;
+		audio_send(audio);
+	}
 }
 
 static void audio_pcm_playback_stop(struct audio_dev *audio)