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>
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
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);
/* 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.
*/