USB: cdc-wdm: support back-to-back USB_CDC_NOTIFY_RESPONSE_AVAILABLE notifications

Some MBIM devices send back-to-back USB_CDC_NOTIFY_RESPONSE_AVAILABLE notifications
when sending a message over multiple fragments or when there are unsolicited
messages available.

Count up the number of USB_CDC_NOTIFY_RESPONSE_AVAILABLE notifications received
and decrement the count and submit the urb for the next response each time userspace
completes a read the response.

Signed-off-by: Greg Suarez <gsuarez@smithmicro.com>
Acked-by: Bjørn Mork <bjorn@mork.no>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 34 insertions, 4 deletions

diff --git a/drivers/usb/class/cdc-wdm.c b/drivers/usb/class/cdc-wdm.c
index d3318a0df8ee..589ea58d5d66 100644
--- a/drivers/usb/class/cdc-wdm.c
+++ b/drivers/usb/class/cdc-wdm.c
@@ -101,6 +101,7 @@ struct wdm_device {
         struct work_struct      rxwork;
         int                     werr;
         int                     rerr;
+        int                     resp_count;
 
         struct list_head        device_list;
         int                     (*manage_power)(struct usb_interface *, int);
@@ -262,9 +263,9 @@ static void wdm_int_callback(struct urb *urb)
         }
 
         spin_lock(&desc->iuspin);
-        clear_bit(WDM_READ, &desc->flags);
         responding = test_and_set_bit(WDM_RESPONDING, &desc->flags);
-        if (!responding && !test_bit(WDM_DISCONNECTING, &desc->flags)
+        if (!desc->resp_count++ && !responding
+                && !test_bit(WDM_DISCONNECTING, &desc->flags)
                 && !test_bit(WDM_SUSPENDING, &desc->flags)) {
                 rv = usb_submit_urb(desc->response, GFP_ATOMIC);
                 dev_dbg(&desc->intf->dev, "%s: usb_submit_urb %d",
@@ -521,10 +522,36 @@ retry:
 
         desc->length -= cntr;
         /* in case we had outstanding data */
-        if (!desc->length)
+        if (!desc->length) {
                 clear_bit(WDM_READ, &desc->flags);
 
-        spin_unlock_irq(&desc->iuspin);
+                if (--desc->resp_count) {
+                        set_bit(WDM_RESPONDING, &desc->flags);
+                        spin_unlock_irq(&desc->iuspin);
+
+                        rv = usb_submit_urb(desc->response, GFP_KERNEL);
+                        if (rv) {
+                                dev_err(&desc->intf->dev,
+                                        "%s: usb_submit_urb failed with result %d\n",
+                                        __func__, rv);
+                                spin_lock_irq(&desc->iuspin);
+                                clear_bit(WDM_RESPONDING, &desc->flags);
+                                spin_unlock_irq(&desc->iuspin);
+
+                                if (rv == -ENOMEM) {
+                                        rv = schedule_work(&desc->rxwork);
+                                        if (rv)
+                                                dev_err(&desc->intf->dev, "Cannot schedule work\n");
+                                } else {
+                                        spin_lock_irq(&desc->iuspin);
+                                        desc->resp_count = 0;
+                                        spin_unlock_irq(&desc->iuspin);
+                                }
+                        }
+                } else
+                        spin_unlock_irq(&desc->iuspin);
+        } else
+                spin_unlock_irq(&desc->iuspin);
 
         rv = cntr;
 
@@ -635,6 +662,9 @@ static int wdm_release(struct inode *inode, struct file *file)
                 if (!test_bit(WDM_DISCONNECTING, &desc->flags)) {
                         dev_dbg(&desc->intf->dev, "wdm_release: cleanup");
                         kill_urbs(desc);
+                        spin_lock_irq(&desc->iuspin);
+                        desc->resp_count = 0;
+                        spin_unlock_irq(&desc->iuspin);
                         desc->manage_power(desc->intf, 0);
                 } else {
                         /* must avoid dev_printk here as desc->intf is invalid */