[SLOF] xhci in slof issues

Nikunj A Dadhania nikunj at linux.vnet.ibm.com
Tue Apr 26 20:19:35 AEST 2016

Nikunj A Dadhania <nikunj at linux.vnet.ibm.com> writes:

> Thomas Huth <thuth at redhat.com> writes:
>> On 21.04.2016 12:36, Dinar Valeev wrote:
>>> Hi,
>>> While trying to fix my usb over vnc automated issues, I switched to
>>> xhci, which helped a lot OS wise, but I see a regression in SLOF.
>>> As you can see [1] we want to type an install repo url.  But at some
>>> point capitalization of some characters are lost. Nope
>>> openSUsE-tumbleweed instead of openSUSE-Tumbleweed.
>> I recently also hit a problem with XHCI keyboard ... and maybe they are
>> related. My problem is that "key?" is incredibly slow when using XHCI.
>> For example, run the following Forth code at the SLOF prompt:
>>  get-msecs 10 0 do key? . cr loop get-msecs swap - .d cr
>> With XHCI, this takes more than 7.5 seconds to finish here, while with
>> OHCI, this loop finishs within 400ms!
>> Nikunj, do you have a clue what might be wrong here?
> Nothing that comes out immediately, i was reviewing the code, here is
> the call chain:
> usb_key_available()
>  ->usb_poll_key()
>     ->usb_poll_intr()
>       ->xhci_poll_intr()
>         ->xhci_poll_event() (there is a 5sec timeout, which obviously
>                              its not hitting).
>                              Either this is taking around 700msec per
>                              call, which looks very wierd.

There is a transfer report packet that is getting generated every 500ms,
thats where the poll_event is exiting, and because of which we are
seeing this delay. I am trying to rework the interrupt handling here to
exit earlier.

> Will spend some more time and debug.
> Regards
> Nikunj

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