This is a note to let you know that I've just added the patch titled usb: gadget: u_ether: enable qmult on SuperSpeed Plus as well to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: usb-gadget-u_ether-enable-qmult-on-superspeed-plus-a.patch and it can be found in the queue-4.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit d28428d19afcddc12c428b0c5f61890c11a56826 Author: Lorenzo Colitti <lorenzo@xxxxxxxxxx> Date: Wed Aug 19 01:19:49 2020 +0900 usb: gadget: u_ether: enable qmult on SuperSpeed Plus as well [ Upstream commit 4eea21dc67b0c6ba15ae41b1defa113a680a858e ] The u_ether driver has a qmult setting that multiplies the transmit queue length (which by default is 2). The intent is that it should be enabled at high/super speed, but because the code does not explicitly check for USB_SUPER_PLUS, it is disabled at that speed. Fix this by ensuring that the queue multiplier is enabled for any wired link at high speed or above. Using >= for USB_SPEED_* constants seems correct because it is what the gadget_is_xxxspeed functions do. The queue multiplier substantially helps performance at higher speeds. On a direct SuperSpeed Plus link to a Linux laptop, iperf3 single TCP stream: Before (qmult=1): 1.3 Gbps After (qmult=5): 3.2 Gbps Fixes: 04617db7aa68 ("usb: gadget: add SS descriptors to Ethernet gadget") Reviewed-by: Maciej Żenczykowski <maze@xxxxxxxxxx> Signed-off-by: Lorenzo Colitti <lorenzo@xxxxxxxxxx> Signed-off-by: Felipe Balbi <balbi@xxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/drivers/usb/gadget/function/u_ether.c b/drivers/usb/gadget/function/u_ether.c index e69f20b2a3f44..46c50135ef9f7 100644 --- a/drivers/usb/gadget/function/u_ether.c +++ b/drivers/usb/gadget/function/u_ether.c @@ -96,7 +96,7 @@ struct eth_dev { static inline int qlen(struct usb_gadget *gadget, unsigned qmult) { if (gadget_is_dualspeed(gadget) && (gadget->speed == USB_SPEED_HIGH || - gadget->speed == USB_SPEED_SUPER)) + gadget->speed >= USB_SPEED_SUPER)) return qmult * DEFAULT_QLEN; else return DEFAULT_QLEN;