usb: gadget: u_ether: remove interrupt throttling

According to Dave Miller "the networking stack has a
hard requirement that all SKBs which are transmitted
must have their completion signalled in a fininte
amount of time. This is because, until the SKB is
freed by the driver, it holds onto socket,
netfilter, and other subsystem resources."

In summary, this means that using TX IRQ throttling
for the networking gadgets is, at least, complex and
we should avoid it for the time being.

Cc: <stable@vger.kernel.org>
Reported-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Tested-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Suggested-by: David Miller <davem@davemloft.net>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

diff --git a/drivers/usb/gadget/function/u_ether.c b/drivers/usb/gadget/function/u_ether.c
index fe1811650dbc3d9fb0fc6a983486cbae3b653475..5d1bd13a56c11f61b50c0b0ec4a772311946672b 100644 (file)
--- a/drivers/usb/gadget/function/u_ether.c
+++ b/drivers/usb/gadget/function/u_ether.c
@@ -588,14 +588,6 @@ static netdev_tx_t eth_start_xmit(struct sk_buff *skb,
 
        req->length = length;
 
-       /* throttle high/super speed IRQ rate back slightly */
-       if (gadget_is_dualspeed(dev->gadget))
-               req->no_interrupt = (((dev->gadget->speed == USB_SPEED_HIGH ||
-                                      dev->gadget->speed == USB_SPEED_SUPER)) &&
-                                       !list_empty(&dev->tx_reqs))
-                       ? ((atomic_read(&dev->tx_qlen) % dev->qmult) != 0)
-                       : 0;
-
        retval = usb_ep_queue(in, req, GFP_ATOMIC);
        switch (retval) {
        default: