On Thu, Aug 08, 2013 at 05:24:46PM -0700, Alexandra Yates wrote:
> Modified the xHCI roothub descriptor to return USB2.0 extension
> descriptor Best Effort Service Latency (BESL) and Deep Best Effort
> Service Latency (DBESL) values when set on the xHCI host.
>
> On link power management the BESL and DBESL values are used to
> estimate L1 exit latency for USB2.0 host and devices. Tools such as
> PowerTop and lsusb will use BESL and DBESL values to
> monitor LPM L1 exit latency. Additionally, by presenting the host
> controller BESL and DBESL values one could check if the BIOS or
> firmware is setting these values correctly.
>
> Currently the root hub device descriptor bcdUSB value is set to zero by
> the BIOS. Therefore to test this functionality with lsusb, I hard
> coded the usb2_rh_dev_descriptor (not include on patch) to:
> bcdUSB 0x01.
>
> Here is the test output.
> $ sudo lsusb -s 01:01 -v
> ...
> Binary Object Store Descriptor:
> bLength 5
> bDescriptorType 15
> wTotalLength 12
> bNumDeviceCaps 1
> USB 2.0 Extension Device Capability:
> bLength 7
> bDescriptorType 16
> bDevCapabilityType 2
> bmAttributes 0x0000ff1e
> BESL Link Power Management (LPM) Supported
> BESL value 3840 us
> Deep BESL value 61440 us
> Device Status: 0x0001
> Self Powered
>
> Signed-off-by: Alexandra Yates <alexandra.yates@xxxxxxxxxxxxxxx>
> ---
> drivers/usb/host/xhci-hub.c | 53 +++++++++++++++++++++++++++++++++++++++----
> drivers/usb/host/xhci.h | 3 +++
> 2 files changed, 51 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/usb/host/xhci-hub.c b/drivers/usb/host/xhci-hub.c
> index 1d35459..60601df 100644
> --- a/drivers/usb/host/xhci-hub.c
> +++ b/drivers/usb/host/xhci-hub.c
> @@ -30,7 +30,7 @@
> PORT_RC | PORT_PLC | PORT_PE)
>
> /* USB 3.0 BOS descriptor and a capability descriptor, combined */
> -static u8 usb_bos_descriptor [] = {
> +static u8 usb3_bos_descriptor[] = {
> USB_DT_BOS_SIZE, /* __u8 bLength, 5 bytes */
> USB_DT_BOS, /* __u8 bDescriptorType */
> 0x0F, 0x00, /* __le16 wTotalLength, 15 bytes */
> @@ -47,6 +47,28 @@ static u8 usb_bos_descriptor [] = {
> 0x00, 0x00 /* __le16 bU2DevExitLat, set later. */
> };
>
> +/* USB 3.0 BOS descriptor and a capability descriptor, combined */
> +static u8 usb2_bos_descriptor[] = {
I don't think that comment is correct, right?
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