path: root/drivers/usb/core/hub.c
diff options
authorSarah Sharp <sarah.a.sharp@linux.intel.com>2012-10-03 11:18:05 -0700
committerSarah Sharp <sarah.a.sharp@linux.intel.com>2012-10-08 11:48:07 -0700
commitae8963adb4ad8c5f2a89ca1d99fb7bb721e7599f (patch)
tree9a689446b605b40fda63b20e2c1164c4102945b5 /drivers/usb/core/hub.c
parentd01f87c0ffa96cb44faa78710711eb6e974b891c (diff)
usb: Don't enable LPM if the exit latency is zero.
Some USB 3.0 devices signal that they don't implement Link PM by having all zeroes in the U1/U2 exit latencies in their SuperSpeed BOS descriptor. Don found that a Western Digital device he has experiences transfer errors when LPM is enabled. The lsusb shows the U1/U2 exit latencies are set to zero: Binary Object Store Descriptor: bLength 5 bDescriptorType 15 wTotalLength 22 bNumDeviceCaps 2 SuperSpeed USB Device Capability: bLength 10 bDescriptorType 16 bDevCapabilityType 3 bmAttributes 0x00 Latency Tolerance Messages (LTM) Supported wSpeedsSupported 0x000e Device can operate at Full Speed (12Mbps) Device can operate at High Speed (480Mbps) Device can operate at SuperSpeed (5Gbps) bFunctionalitySupport 1 Lowest fully-functional device speed is Full Speed (12Mbps) bU1DevExitLat 0 micro seconds bU2DevExitLat 0 micro seconds The fix is to not enable LPM for a particular link state if we find its corresponding exit latency is zero. This patch should be backported to kernels as old as 3.5, that contain the commit 1ea7e0e8e3d0f50901d335ea4178ab2aa8c88201 "USB: Add support to enable/disable USB3 link states." Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com> Reported-by: Don Zickus <dzickus@redhat.com> Tested-by: Don Zickus <dzickus@redhat.com> Cc: stable@vger.kernel.org
Diffstat (limited to 'drivers/usb/core/hub.c')
1 files changed, 10 insertions, 0 deletions
diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index 673ee469626..8f047870932 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -3415,6 +3415,16 @@ static void usb_enable_link_state(struct usb_hcd *hcd, struct usb_device *udev,
enum usb3_link_state state)
int timeout;
+ __u8 u1_mel = udev->bos->ss_cap->bU1devExitLat;
+ __le16 u2_mel = udev->bos->ss_cap->bU2DevExitLat;
+ /* If the device says it doesn't have *any* exit latency to come out of
+ * U1 or U2, it's probably lying. Assume it doesn't implement that link
+ * state.
+ */
+ if ((state == USB3_LPM_U1 && u1_mel == 0) ||
+ (state == USB3_LPM_U2 && u2_mel == 0))
+ return;
/* We allow the host controller to set the U1/U2 timeout internally
* first, so that it can change its schedule to account for the