Re: Does the xHCI driver has a spec violation?

On 09/22/14 06:58, Kohji Okuno wrote:
> Hi,
>
> I encountered a issue for USB mic.
>
> In fist time, my host controller (xHCI) sends single IN-tokens every
> 8-SOFs. This is expected action. But, after I open, close and open, my
> host controller sends plural IN-tokens between SOF and SOF.
>
> In Intel Lynx Point, I could not reproduce this issue.
> I'm sorry. Unfortunately, I can't explain details about my proprietary
> host controler.
>
> I found the following explanation in the xHCI 1.1 specification
> http://www.intel.com/content/dam/www/public/us/en/documents/technical-specifications/extensible-host-controler-interface-usb-xhci.pdf
>
> In 4.8.3 Endpoint Context State,
>    6. The Configure Endpoint Command (Add (A) = `1' and Drop (D) =`1')
>       shall transition an endpoint, except the Default Control
>       Endpoint, from the Stopped to the Running state.'
>
>
> So, I modify as the following, then I can run expectedly.
> What do you think about this change?

Hi,

I think we should issue the context drop separately. Are we certain that 
if both drop and add bits are set at the same time, that the drop bit 
will be processed before the add?

This might be a bug in your hardware, which apparently doesn't check if 
the context has already been added or not. I'll be glad to make a 
workaround for it once we have settled on a solution.

Can you test the attached patch using both your hardware and the Lynx Point.

Thank you!

--HPS

>
> Best regards,
>   Kohji Okuno