The patch below does not apply to the 3.10-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable@xxxxxxxxxxxxxxx>. thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From dcc01c0864823f91c3bf3ffca6613e2351702b87 Mon Sep 17 00:00:00 2001 From: Sarah Sharp <sarah.a.sharp@xxxxxxxxxxxxxxx> Date: Mon, 30 Sep 2013 17:26:29 +0300 Subject: [PATCH] usb: Disable USB 2.0 Link PM before device reset. Before the USB core resets a device, we need to disable the L1 timeout for the roothub, if USB 2.0 Link PM is enabled. Otherwise the port may transition into L1 in between descriptor fetches, before we know if the USB device descriptors changed. LPM will be re-enabled after the full device descriptors are fetched, and we can confirm the device still supports USB 2.0 LPM after the reset. We don't need to wait for the USB device to exit L1 before resetting the device, since the xHCI roothub port diagrams show a transition to the Reset state from any of the Ux states (see Figure 34 in the 2012-08-14 xHCI specification update). This patch should be backported to kernels as old as 3.2, that contain the commit 65580b4321eb36f16ae8b5987bfa1bb948fc5112 "xHCI: set USB2 hardware LPM". That was the first commit to enable USB 2.0 hardware-driven Link Power Management. Signed-off-by: Sarah Sharp <sarah.a.sharp@xxxxxxxxxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c index 3f8933f1..d3a1d79d 100644 --- a/drivers/usb/core/hub.c +++ b/drivers/usb/core/hub.c @@ -5090,6 +5090,12 @@ static int usb_reset_and_verify_device(struct usb_device *udev) } parent_hub = usb_hub_to_struct_hub(parent_hdev); + /* Disable USB2 hardware LPM. + * It will be re-enabled by the enumeration process. + */ + if (udev->usb2_hw_lpm_enabled == 1) + usb_set_usb2_hardware_lpm(udev, 0); + bos = udev->bos; udev->bos = NULL; -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html