usb: gadget: u_audio: improve uac compatibility

Some PC USB Hosts (e.g Dell laptop) fail to send
SetInterface(AltSet=0) to stop capture/playback
when PC enter suspend or play YouTube Video.

To be compatible with these PC, add this patch to
stop capture/playback prior to start again if the
stream_state is true.

Change-Id: Iced57de39b6b88a7c987897dcb123cf8d7cf6473
Signed-off-by: William Wu <william.wu@rock-chips.com>
Signed-off-by: Frank Wang <frank.wang@rock-chips.com>

drivers/usb/gadget/function/u_audio.c

@@ -601,6 +601,15 @@ int u_audio_start_capture(struct g_audio *audio_dev)
 	struct uac_params *params = &audio_dev->params;
 	int req_len, i;
 
+	/*
+	 * For better compatibility on some PC Hosts which
+	 * failed to send SetInterface(AltSet=0) to stop
+	 * capture last time. It needs to stop capture
+	 * prior to start capture next time.
+	 */
+	if (audio_dev->stream_state[STATE_OUT])
+		u_audio_stop_capture(audio_dev);
+
 	audio_dev->usb_state[SET_INTERFACE_OUT] = true;
 	audio_dev->stream_state[STATE_OUT] = true;
 	schedule_work(&audio_dev->work);
@@ -705,6 +714,15 @@ int u_audio_start_playback(struct g_audio *audio_dev)
 	int req_len, i;
 	unsigned int p_pktsize;
 
+	/*
+	 * For better compatibility on some PC Hosts which
+	 * failed to send SetInterface(AltSet=0) to stop
+	 * playback last time. It needs to stop playback
+	 * prior to start playback next time.
+	 */
+	if (audio_dev->stream_state[STATE_IN])
+		u_audio_stop_playback(audio_dev);
+
 	audio_dev->usb_state[SET_INTERFACE_IN] = true;
 	audio_dev->stream_state[STATE_IN] = true;
 	schedule_work(&audio_dev->work);