On Fri, 17 Aug 2018, Zeng Tao wrote: > The new scheme is required just to support legacy low and full-speed > devices. For high speed devices, it will slower the enumeration speed. > So in this patch we try the "old" enumeration scheme first for high speed > devices, and this is what Windows does since Windows 8. > > Signed-off-by: Zeng Tao <prime.zeng@xxxxxxxxxxxxx> > --- > Changes in v2: > 1. As suggested by Alan, mention in the commit log that this change is > follow what the Window does. > 2. As suggested by Roger, update the kernel-parameter description. > --- > Documentation/admin-guide/kernel-parameters.txt | 3 ++- > drivers/usb/core/hub.c | 5 ++++- > 2 files changed, 6 insertions(+), 2 deletions(-) > > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt > index 533ff5c..95db23c 100644 > --- a/Documentation/admin-guide/kernel-parameters.txt > +++ b/Documentation/admin-guide/kernel-parameters.txt > @@ -4453,7 +4453,8 @@ > > usbcore.old_scheme_first= > [USB] Start with the old device initialization > - scheme (default 0 = off). > + scheme, applies only to low and full-speed devices > + (default 0 = off). > > usbcore.usbfs_memory_mb= > [USB] Memory limit (in MB) for buffers allocated by > diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c > index 1fb2668..d265b19 100644 > --- a/drivers/usb/core/hub.c > +++ b/drivers/usb/core/hub.c > @@ -2661,10 +2661,13 @@ static bool use_new_scheme(struct usb_device *udev, int retry, > int old_scheme_first_port = > port_dev->quirks & USB_PORT_QUIRK_OLD_SCHEME; > > + int quick_enumeration = (udev->speed == USB_SPEED_HIGH); Minor style point: the preceding blank line should be eliminated. > + > if (udev->speed >= USB_SPEED_SUPER) > return false; > > - return USE_NEW_SCHEME(retry, old_scheme_first_port || old_scheme_first); > + return USE_NEW_SCHEME(retry, old_scheme_first_port || old_scheme_first > + || quick_enumeration); > } > > /* Is a USB 3.0 port in the Inactive or Compliance Mode state? Aside from that: Acked-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
