FUSB200 xhci issue

[Oleksij Rempel]

Am 06.09.2013 23:09, schrieb Alan Stern:
> On Fri, 6 Sep 2013, Oleksij Rempel wrote:
>
>> Hi Alan,
>>
>> i need more help.
>>
>> We have more test results now. Initial patch was probably fixing
>> fallowing issue - bad performance on EP4/EP3 if Intr transfer is used.
>> It is reproducible only on EHCI, but not reproducible on xHCI controller.
>
> Is this a high-speed device?

yes

> What version of the kernel are you using?

currently it is 3.11.0-rc7-wl-00004-g52e0063, but i can reproduce this 
issue with older kernels too.

>> For example, channel scan function intensively use this endpoints. On
>> xHCI, channel scan is done in 6 seconds. On EHCI it needs 25s. By
>> forcing Bulk transfer on host side, it is possible get same performance
>> on EHCI too. But it isn't working on all controllers because of limited
>> packed size (64B).
>>
>> Dumps are attached. One of them may include some other device, but only
>> ath9k_htc device has EP3 and EP4.
>
> The capture logs show that with EHCI, each endpoint transfers a packet
> every 2.5 ms or so, whereas xHCI transfers 2-3 packets per ms.
>
>> Is it protocol limitation or HC issue?
>
> It's not a protocol limitation.  If it were, the xHCI communication
> would be just as slow as EHCI.
>
> One thing that might help: For each endpoint, keep multiple URBs queued
> (try 10) at all times instead of just a single URB.
>
> It's entirely possible that these results are caused by limitations of
> your EHCI hardware.  Still, using multiple URBs could yield a
> significant improvement.

Same issue on two different intel controllers. I'll try some thing 
different for comparison.
-- 
Regards,
Oleksij