Hi Alan:

Thanks for your reply.

-----Original Message-----
From: Alan Stern [mailto:stern@rowland.harvard.edu]
Sent: Friday, August 17, 2018 10:19 PM
To: Zengtao (B) <redacted>
Cc: gregkh@linuxfoundation.org; mathias.nyman@linux.intel.com;
drinkcat@chromium.org; felipe.balbi@linux.intel.com;
drake@endlessm.com; mike.looijmans@topic.nl; joe@perches.com;
Jonathan Corbet [off-list ref]; Thomas Gleixner [off-list ref];
Ingo Molnar [off-list ref]; Rafael J. Wysocki
[off-list ref]; Marc Zyngier [off-list ref];
Kai-Heng Feng [off-list ref]; Thymo van Beers
[off-list ref]; Frederic Weisbecker [off-list ref];
Konrad Rzeszutek Wilk [off-list ref]; David Rientjes
[off-list ref]; linux-doc@vger.kernel.org;
linux-kernel@vger.kernel.org; linux-usb@vger.kernel.org
Subject: Re: [PATCH v2] usb: hub: try old enumeration scheme first for high
speed devices

On Fri, 17 Aug 2018, Zeng Tao wrote:

quoted

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 <redacted>
---
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,

quoted

 	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.

quoted

+
 	if (udev->speed >= USB_SPEED_SUPER)
 		return false;

-	return USE_NEW_SCHEME(retry, old_scheme_first_port ||

old_scheme_first);

quoted

+	return USE_NEW_SCHEME(retry, old_scheme_first_port ||

old_scheme_first

quoted

+			      || quick_enumeration);
 }

 /* Is a USB 3.0 port in the Inactive or Compliance Mode state?

Aside from that:

Acked-by: Alan Stern <stern@rowland.harvard.edu>

Okay , tag will be applied in v3.