This is a note to let you know that I've just added the patch titled
usb: Don't enable LPM if the exit latency is zero.
to the 3.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
usb-don-t-enable-lpm-if-the-exit-latency-is-zero.patch
and it can be found in the queue-3.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From ae8963adb4ad8c5f2a89ca1d99fb7bb721e7599f Mon Sep 17 00:00:00 2001
From: Sarah Sharp <[email protected]>
Date: Wed, 3 Oct 2012 11:18:05 -0700
Subject: usb: Don't enable LPM if the exit latency is zero.
From: Sarah Sharp <[email protected]>
commit ae8963adb4ad8c5f2a89ca1d99fb7bb721e7599f upstream.
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 <[email protected]>
Reported-by: Don Zickus <[email protected]>
Tested-by: Don Zickus <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
drivers/usb/core/hub.c | 10 ++++++++++
1 file changed, 10 insertions(+)
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -3353,6 +3353,16 @@ static void usb_enable_link_state(struct
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
Patches currently in stable-queue which might be from
[email protected] are
queue-3.6/usb-send-set-sel-before-enabling-parent-u1-u2-timeout.patch
queue-3.6/usb-enable-lpm-after-a-failed-probe.patch
queue-3.6/usb-don-t-enable-lpm-if-the-exit-latency-is-zero.patch
queue-3.6/usb-host-xhci-new-system-added-for-compliance-mode-patch-on-sn65lvpe502cp.patch
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