Re: [RFC v3] xhci-hub: Roothub USB2.0 descriptor for BESL DBESL

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Hi Alex,

For just one patch, you don't need to send a cover letter, especially
when it contains the contents of your patch description.  Also, please
use PATCH instead of RFC in the future.

I'll test this patch out, and try to come up with a way to get the USB
core to use bcdUSB 2.10 for xHCI USB 2.0 roothubs.

Sarah Sharp

On Fri, Aug 09, 2013 at 12:20:49PM -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.
> 
> 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
> 
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