cdc-acm: handle read pipe errors

Read urbs are submitted back only on success, causing read pipe
running out of urbs after few errors. No more characters can
be read from tty device then until it is reopened and no errors
are reported.
Fix that by always submitting urbs back and clearing stall on
-EPIPE.

Signed-off-by: Ladislav Michl <[e-mail]>
Acked-by: Oliver Neukum <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/usb/class/cdc-acm.c

···
 	dev_vdbg(&acm->data->dev, "got urb %d, len %d, status %d\n",
 		rb->index, urb->actual_length, status);
 
+	set_bit(rb->index, &acm->read_urbs_free);
+
 	if (!acm->dev) {
-		set_bit(rb->index, &acm->read_urbs_free);
 		dev_dbg(&acm->data->dev, "%s - disconnected\n", __func__);
 		return;
 	}
 
-	if (status) {
-		set_bit(rb->index, &acm->read_urbs_free);
-		if ((status != -ENOENT) || (urb->actual_length == 0))
-			return;
+	switch (status) {
+	case 0:
+		usb_mark_last_busy(acm->dev);
+		acm_process_read_urb(acm, urb);
+		break;
+	case -EPIPE:
+		set_bit(EVENT_RX_STALL, &acm->flags);
+		schedule_work(&acm->work);
+		return;
+	case -ENOENT:
+	case -ECONNRESET:
+	case -ESHUTDOWN:
+		dev_dbg(&acm->data->dev,
+			"%s - urb shutting down with status: %d\n",
+			__func__, status);
+		return;
+	default:
+		dev_dbg(&acm->data->dev,
+			"%s - nonzero urb status received: %d\n",
+			__func__, status);
+		break;
 	}
 
-	usb_mark_last_busy(acm->dev);
-
-	acm_process_read_urb(acm, urb);
 	/*
 	 * Unthrottle may run on another CPU which needs to see events
 	 * in the same order. Submission has an implict barrier
 	 */
 	smp_mb__before_atomic();
-	set_bit(rb->index, &acm->read_urbs_free);
 
 	/* throttle device if requested by tty */
 	spin_lock_irqsave(&acm->read_lock, flags);
···
 	spin_lock_irqsave(&acm->write_lock, flags);
 	acm_write_done(acm, wb);
 	spin_unlock_irqrestore(&acm->write_lock, flags);
+	set_bit(EVENT_TTY_WAKEUP, &acm->flags);
 	schedule_work(&acm->work);
 }
 
 static void acm_softint(struct work_struct *work)
 {
+	int i;
 	struct acm *acm = container_of(work, struct acm, work);
 
-	tty_port_tty_wakeup(&acm->port);
+	if (test_bit(EVENT_RX_STALL, &acm->flags)) {
+		if (!(usb_autopm_get_interface(acm->data))) {
+			for (i = 0; i < acm->rx_buflimit; i++)
+				usb_kill_urb(acm->read_urbs[i]);
+			usb_clear_halt(acm->dev, acm->in);
+			acm_submit_read_urbs(acm, GFP_KERNEL);
+			usb_autopm_put_interface(acm->data);
+		}
+		clear_bit(EVENT_RX_STALL, &acm->flags);
+	}
+
+	if (test_bit(EVENT_TTY_WAKEUP, &acm->flags)) {
+		tty_port_tty_wakeup(&acm->port);
+		clear_bit(EVENT_TTY_WAKEUP, &acm->flags);
+	}
 }
 
 /*
···
 
 #endif /* CONFIG_PM */
 
+static int acm_pre_reset(struct usb_interface *intf)
+{
+	struct acm *acm = usb_get_intfdata(intf);
+
+	clear_bit(EVENT_RX_STALL, &acm->flags);
+
+	return 0;
+}
+
 #define NOKIA_PCSUITE_ACM_INFO(x) \
 		USB_DEVICE_AND_INTERFACE_INFO(0x0421, x, \
 		USB_CLASS_COMM, USB_CDC_SUBCLASS_ACM, \
···
 	.resume =	acm_resume,
 	.reset_resume =	acm_reset_resume,
 #endif
+	.pre_reset =	acm_pre_reset,
 	.id_table =	acm_ids,
 #ifdef CONFIG_PM
 	.supports_autosuspend = 1,

drivers/usb/class/cdc-acm.h

···
 	spinlock_t write_lock;
 	struct mutex mutex;
 	bool disconnected;
+	unsigned long flags;
+#		define EVENT_TTY_WAKEUP	0
+#		define EVENT_RX_STALL	1
 	struct usb_cdc_line_coding line;		/* bits, stop, parity */
 	struct work_struct work;			/* work queue entry for line discipline waking up */
 	unsigned int ctrlin;				/* input control lines (DCD, DSR, RI, break, overruns) */