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 -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html