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.
Alexandra Yates (1):
xhci-hub: Roothub USB2.0 descriptor for BESL DBESL
drivers/usb/host/xhci-hub.c | 53 +++++++++++++++++++++++++++++++++++++++----
drivers/usb/host/xhci.h | 3 +++
2 files changed, 51 insertions(+), 5 deletions(-)
--
1.7.9.5
--
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
