[PATCH 4.14 077/191] usb: gadget: u_ether: enable qmult on SuperSpeed Plus as well

Greg Kroah-Hartman
2020-10-27T18:17:55Z

From: Lorenzo Colitti <lorenzo@google.com>

[ 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@google.com>
Signed-off-by: Lorenzo Colitti <lorenzo@google.com>
Signed-off-by: Felipe Balbi <balbi@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/usb/gadget/function/u_ether.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/usb/gadget/function/u_ether.c b/drivers/usb/gadget/function/u_ether.c
index 81d84e0c3c6cd..716edd593a994 100644
--- a/drivers/usb/gadget/function/u_ether.c
+++ b/drivers/usb/gadget/function/u_ether.c
@@ -97,7 +97,7 @@ 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;
--
2.25.1