Re: USB Mass Storage devices continually reenumerate

On 11/2/07, Alan Stern <[email protected]> wrote:
> I can explain part of it.  After failure to receive the CSW,
> usb-storage always calls for a device reset.  That explains why you see
> the reset signal on the bus.  Whether or not a "logical disconnect"
> then occurs will depend on how the device behaves following the reset.

Aha! I wanted to convince myself that it was the hardware that was
initiating the reset, so I had commented out the usb_stor_port_reset
in transport.c, but I missed the one in scsiglue.c.

> It certainly sounds like a hardware bug in the host controller.  It's
> as though the controller becomes unable to transmit or receive any data
> over the USB bus for a sort time.

Yes. It still seems to generate SOF though. The analyzer software
collapses all the SOFs but it looks like approximately the correct
number were generated during the delay between the DATA and the reset.

> There's one thing you can try which might work around the problem.
> Edit drivers/usb/storage/transport.c, and change all three occurrences
> of US_BULK_CS_WRAP_LEN to 64.  You'll also have to comment out the "if"
> statement following the third occurence.  Perhaps the controller will
> work better if asked to transfer a full-sized packet instead of just 13
> bytes.

OK, that's worth a try.

Thanks,
Mike

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