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 (b789696af8 "[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>
This commit is contained in:
Nicolas Boichat 2018-05-28 14:32:19 +08:00 committed by Greg Kroah-Hartman
parent 2524422715
commit aa071a92bb
3 changed files with 12 additions and 1 deletions

View file

@ -206,6 +206,10 @@ Description:
using /sys/module/usbcore/parameters/old_scheme_first, but
it is often not desirable as the new scheme was introduced to
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
Date: February 2018

View file

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

View file

@ -496,6 +496,9 @@ enum usb_port_connect_type {
/* For the given port, prefer the old (faster) enumeration scheme. */
#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.
*/