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Commit aa071a92 authored May 28, 2018 by Nicolas Boichat Committed by Greg Kroah-Hartman May 31, 2018

usb: hub: Per-port setting to reduce TRSTRCY to 10 ms



Currently, the USB hub core waits for 50 ms after enumerating the
device. This was added to help "some high speed devices" to
enumerate (b789696a "[PATCH] USB: relax usbcore reset timings").

On some devices, the time-to-active is important, so we provide
a per-port option to reduce the time to what the USB specification
requires: 10 ms.

Signed-off-by: Nicolas Boichat <drinkcat@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 25244227

Documentation/ABI/testing/sysfs-bus-usb

+4 −0

Original line number	Original line	Diff line number	Diff line
	@@ -206,6 +206,10 @@ Description:
	using /sys/module/usbcore/parameters/old_scheme_first, but		using /sys/module/usbcore/parameters/old_scheme_first, but
	it is often not desirable as the new scheme was introduced to		it is often not desirable as the new scheme was introduced to
	increase compatibility with more devices.		increase compatibility with more devices.
			- Bit 1 reduces TRSTRCY to the 10 ms that are required by the
			USB 2.0 specification, instead of the 50 ms that are normally
			used to help make enumeration work better on some high speed
			devices.

	What: /sys/bus/usb/devices/.../(hub interface)/portX/over_current_count		What: /sys/bus/usb/devices/.../(hub interface)/portX/over_current_count
	Date: February 2018		Date: February 2018

drivers/usb/core/hub.c

+5 −1

Original line number	Original line	Diff line number	Diff line
	@@ -2879,7 +2879,11 @@ static int hub_port_reset(struct usb_hub *hub, int port1,
	done:		done:
	if (status == 0) {		if (status == 0) {
	/* TRSTRCY = 10 ms; plus some extra */		/* TRSTRCY = 10 ms; plus some extra */
			if (port_dev->quirks & USB_PORT_QUIRK_FAST_ENUM)
			usleep_range(10000, 12000);
			else
	msleep(10 + 40);		msleep(10 + 40);

	if (udev) {		if (udev) {
	struct usb_hcd *hcd = bus_to_hcd(udev->bus);		struct usb_hcd *hcd = bus_to_hcd(udev->bus);

include/linux/usb.h

+3 −0

Original line number	Original line	Diff line number	Diff line
	@@ -496,6 +496,9 @@ enum usb_port_connect_type {
	/* For the given port, prefer the old (faster) enumeration scheme. */		/* For the given port, prefer the old (faster) enumeration scheme. */
	#define USB_PORT_QUIRK_OLD_SCHEME BIT(0)		#define USB_PORT_QUIRK_OLD_SCHEME BIT(0)

			/* Decrease TRSTRCY to 10ms during device enumeration. */
			#define USB_PORT_QUIRK_FAST_ENUM BIT(1)

	/*		/*
	* USB 2.0 Link Power Management (LPM) parameters.		* USB 2.0 Link Power Management (LPM) parameters.
	*/		*/