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authorSarah Sharp <sarah.a.sharp@linux.intel.com>2013-09-30 18:26:29 +0400
committerSarah Sharp <sarah.a.sharp@linux.intel.com>2013-10-16 23:24:17 +0400
commitdcc01c0864823f91c3bf3ffca6613e2351702b87 (patch)
tree10356c08e7527447a06a9409fed4a03bf5ded746 /drivers/usb/core
parentc00809d330cfe42469fcd1cfd63f0690b47ea9bb (diff)
downloadlinux-dcc01c0864823f91c3bf3ffca6613e2351702b87.tar.xz
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@linux.intel.com> Cc: stable@vger.kernel.org
Diffstat (limited to 'drivers/usb/core')
-rw-r--r--drivers/usb/core/hub.c6
1 files changed, 6 insertions, 0 deletions
diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index 3f8933f10e7d..d3a1d79d663d 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;