On Wed, Oct 03, 2012 at 11:29:00AM -0700, Sarah Sharp wrote:
> Hi Don,
>
> Please test this patch on top of the other patch.
So yeah, that seemed to work. :-)
Thanks!
Cheers,
Don
>
> Sarah Sharp
>
> >8-------------------------------------------------------------------8<
> 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.
>
> Signed-off-by: Sarah Sharp <sarah.a.sharp@xxxxxxxxxxxxxxx>
> Reported-by: Don Zickus <dzickus@xxxxxxxxxx>
> ---
> drivers/usb/core/hub.c | 14 ++++++++++----
> 1 files changed, 10 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
> index 55bef91..2568441 100644
> --- a/drivers/usb/core/hub.c
> +++ b/drivers/usb/core/hub.c
> @@ -3484,8 +3484,16 @@ static void usb_enable_link_state(struct usb_hcd *hcd, struct usb_device *udev,
> enum usb3_link_state state)
> {
> int timeout;
> - __u8 u1_mel;
> - __le16 u2_mel;
> + __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
> @@ -3512,8 +3520,6 @@ static void usb_enable_link_state(struct usb_hcd *hcd, struct usb_device *udev,
> * link commands. This can cause transfer errors, so only enable
> * device-initiated LPM.
> */
> - u1_mel = udev->bos->ss_cap->bU1devExitLat;
> - u2_mel = udev->bos->ss_cap->bU2DevExitLat;
> if ((state == USB3_LPM_U1 && u1_mel == USB_U1_MAX_VALID_MEL) ||
> (state == USB3_LPM_U2 &&
> le16_to_cpu(u2_mel) == USB_U2_MAX_VALID_MEL)) {
> --
> 1.7.9
>
--
To unsubscribe from this list: send the line "unsubscribe linux-usb" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
