Hi Alan: Thanks for your reply. >-----Original Message----- >From: Alan Stern [mailto:stern@xxxxxxxxxxxxxxxxxxx] >Sent: Friday, August 17, 2018 10:19 PM >To: Zengtao (B) <prime.zeng@xxxxxxxxxxxxx> >Cc: gregkh@xxxxxxxxxxxxxxxxxxx; mathias.nyman@xxxxxxxxxxxxxxx; >drinkcat@xxxxxxxxxxxx; felipe.balbi@xxxxxxxxxxxxxxx; >drake@xxxxxxxxxxxx; mike.looijmans@xxxxxxxx; joe@xxxxxxxxxxx; >Jonathan Corbet <corbet@xxxxxxx>; Thomas Gleixner <tglx@xxxxxxxxxxxxx>; >Ingo Molnar <mingo@xxxxxxxxxx>; Rafael J. Wysocki ><rafael.j.wysocki@xxxxxxxxx>; Marc Zyngier <marc.zyngier@xxxxxxx>; >Kai-Heng Feng <kai.heng.feng@xxxxxxxxxxxxx>; Thymo van Beers ><thymovanbeers@xxxxxxxxx>; Frederic Weisbecker <frederic@xxxxxxxxxx>; >Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>; David Rientjes ><rientjes@xxxxxxxxxx>; linux-doc@xxxxxxxxxxxxxxx; >linux-kernel@xxxxxxxxxxxxxxx; linux-usb@xxxxxxxxxxxxxxx >Subject: Re: [PATCH v2] usb: hub: try old enumeration scheme first for high >speed devices > >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); > Okey, will fix in v3 >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> Okay , tag will be applied in v3.
