[PATCH v2] usb: gadget: u_ether: enable qmult on SuperSpeed Plus as well

[PATCH v2] usb: gadget: u_ether: enable qmult on SuperSpeed Plus as well

[Lorenzo Colitti]

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")
Signed-off-by: Lorenzo Colitti <lorenzo@google.com>
---
 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 c3cc6bd14e..31ea76adcc 100644
--- a/drivers/usb/gadget/function/u_ether.c
+++ b/drivers/usb/gadget/function/u_ether.c
@@ -93,7 +93,7 @@ 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;
-- 
2.28.0.220.ged08abb693-goog

Re: [PATCH v2] usb: gadget: u_ether: enable qmult on SuperSpeed Plus as well

[Maciej Żenczykowski]

On Tue, Aug 18, 2020 at 9:19 AM Lorenzo Colitti <lorenzo@google.com> wrote:
>
> 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")
> Signed-off-by: Lorenzo Colitti <lorenzo@google.com>
> ---
>  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 c3cc6bd14e..31ea76adcc 100644
> --- a/drivers/usb/gadget/function/u_ether.c
> +++ b/drivers/usb/gadget/function/u_ether.c
> @@ -93,7 +93,7 @@ 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;
> --
> 2.28.0.220.ged08abb693-goog
>

Reviewed-by: Maciej Żenczykowski <maze@google.com>

Re: [PATCH v2] usb: gadget: u_ether: enable qmult on SuperSpeed Plus as well

[Lorenzo Colitti]

On Wed, Aug 19, 2020 at 6:07 AM Maciej Żenczykowski
<zenczykowski@gmail.com> wrote:
>
> > The u_ether driver has a qmult setting that multiplies the
> > transmit queue length (which by default is 2).
>
> Reviewed-by: Maciej Żenczykowski <maze@google.com>

Felipe, Greg: Is there anything that I should be doing about this
patch, or should I just expect it to be merged at some point?

If you were thinking of looking at it again when the comments on the
NCM SuperSpeed patches are addressed, I just posted a new version of
those (v3), with a cover letter to explain what changed.

Thanks,
Lorenzo