Re: Re: USB storage problems on OHCI..

[David Brownell <david-b@pacbell.net>]

Linus Torvalds wrote:
> On Mon, 22 Sep 2003, Alan Stern wrote:
> 
>>This problem has been cropping up with many, many USB storage devices.  
> 
> 
> Interesting data-point: the device is a happy EHCI camper, and is totally 
> able to read codepage 8 on EHCI.
> 
> However, if I put it behind a USB-1 hub on the EHCI port, I see the same 
> problems I saw with OHCI.

Can you be more clear?  Is that

    (EHCI/OHCI) root port --> USB 2.0 hub --> USB 1.1 hub --> storage device

Or instead

    (EHCI/OHCI) root port --> USB 1.1 hub --> storage device

The former is certainly using EHCI, and the transaction translator in
that USB 2.0 hub ... but I'd expect it to give a different failure mode.
Maybe the same net result, but a different fault code (not -EOVERFLOW),
and likely different recovery procedure in usb-storage/scsi.

The latter is identical with the OHCI-only case, the only involvement
of EHCI being to hand that port over to the (OHCI) companion.


> So it is somehow related to USB-1 vs USB-2. I don't understand why the 
> device would make a difference for something like mode page 8, but it 
> looks like it transfers data fine for _small_ mode page requests under 
> USB-1, and under USB-2 it works even for big ones.

It could be some kind of logic in the device forgetting that to use
the right maxpacket setting in that specific case.

I'm a bit more used to seeing failures the other way around, where
the storage adapter doesn't quite respond correctly at high speed.

- Dave


> 
> 		Linus
> 
> 




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