usb: gadget: f_midi: drop substreams when disabling endpoint

This change makes sure that the ALSA buffers are cleaned if an endpoint
becomes disabled.

Before this change, if the internal ALSA buffer did overflow, the MIDI
function would stop sending MIDI to the host.
Signed-off-by: Felipe F. Tonello <eu@felipetonello.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

drivers/usb/gadget/function/f_midi.c

@@ -305,6 +305,19 @@ f_midi_complete(struct usb_ep *ep, struct usb_request *req)
 	}
 }
 
+static void f_midi_drop_out_substreams(struct f_midi *midi)
+{
+	unsigned int i;
+
+	for (i = 0; i < midi->in_ports; i++) {
+		struct gmidi_in_port *port = midi->in_ports_array + i;
+		struct snd_rawmidi_substream *substream = port->substream;
+
+		if (port->active && substream)
+			snd_rawmidi_drop_output(substream);
+	}
+}
+
 static int f_midi_start_ep(struct f_midi *midi,
 			   struct usb_function *f,
 			   struct usb_ep *ep)
@@ -402,6 +415,8 @@ static void f_midi_disable(struct usb_function *f)
 	/* release IN requests */
 	while (kfifo_get(&midi->in_req_fifo, &req))
 		free_ep_req(midi->in_ep, req);
+
+	f_midi_drop_out_substreams(midi);
 }
 
 static int f_midi_snd_free(struct snd_device *device)
@@ -571,18 +586,6 @@ static void f_midi_transmit_byte(struct usb_request *req,
 	port->state = next_state;
 }
 
-static void f_midi_drop_out_substreams(struct f_midi *midi)
-{
-	unsigned int i;
-
-	for (i = 0; i < midi->in_ports; i++) {
-		struct gmidi_in_port *port = midi->in_ports_array + i;
-		struct snd_rawmidi_substream *substream = port->substream;
-		if (port->active && substream)
-			snd_rawmidi_drop_output(substream);
-	}
-}
-
 static int f_midi_do_transmit(struct f_midi *midi, struct usb_ep *ep)
 {
 	struct usb_request *req = NULL;