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 <drink...@chromium.org>
---
Reduces enumeration time by ~40ms in conjunction with previous
patch/quirk (or ~80ms on its own).
Documentation/ABI/testing/sysfs-bus-usb | 4 ++++
drivers/usb/core/hub.c | 6 +++++-
include/linux/usb.h | 3 +++
3 files changed, 12 insertions(+), 1 deletion(-)
diff --git a/Documentation/ABI/testing/sysfs-bus-usb
b/Documentation/ABI/testing/sysfs-bus-usb
index a31a66d62cbba..08d456e07b538 100644
--- a/Documentation/ABI/testing/sysfs-bus-usb
+++ b/Documentation/ABI/testing/sysfs-bus-usb
@@ -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
diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index f900f66a62856..26c2438d28893 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -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);
diff --git a/include/linux/usb.h b/include/linux/usb.h
index 2ade17992ed66..4cdd515a4385f 100644
--- a/include/linux/usb.h
+++ b/include/linux/usb.h
@@ -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.
*/
--
2.17.0.921.gf22659ad46-goog
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