usb: hub: try old enumeration scheme first for high speed devices (bd0e6c96) · Commits · 戴 / test

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@hisilicon.com> Acked-by:

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

Roger Quadros <rogerq@ti.com> Signed-off-by:

Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/admin-guide/kernel-parameters.txt

+2 −1

Original line number	Diff line number	Diff line
		@@ -4610,7 +4610,8 @@

		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

drivers/usb/core/hub.c

+3 −1

Original line number	Diff line number	Diff line
		@@ -2661,11 +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);

		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?

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