Re: USB Mass Storage devices continually reenumerate

On 11/6/07, Alan Stern <[email protected]> wrote:
> On Mon, 5 Nov 2007, Mike Nuss wrote:
> > Nov  5 14:50:02 usb-storage: Status code -62; transferred 192/65536
> > Nov  5 14:50:02 usb-storage: -- unknown error
> > Nov  5 14:50:02 End usb_stor_bulk_transfer_sglist: Wait 10s
> > Nov  5 14:50:02 hub 1-0:1.0: state 7 ports 2 chg 0000 evt 0004
> > Nov  5 14:50:02 ohci_hcd 0000:00:13.0: GetStatus roothub.portstatus
> > [1] = 0x00030101 PESC CSC PPS CCS
>
> Aha!  So the controller thinks the device really did signal a
> disconnect condition (CSC is set).

Good point. Does that mean the kernel should have previously seen a
status report with CSC and no CCS? Or if the disconnect condition was
short enough, would I only see the reconnect status, as above? (It's
not clear to me whether the OHCI root hub status is always polled or
if changes are interrupt-based.)

> > I don't see the reset in the scope or on the analyzer until 14:50:11
> > (presumably coinciding with my DO ROOT PORT RESET message). It looks
> > like the HC has disabled the port before the driver has had a chance
> > to react - notice the PESC and lack of PES in the first status change
> > message. And the spec says that HCD-initiated actions do not set PESC.
>
> Right.  Would your scope show a brief disconnect signal?  According to
> the spec, disconnect can occur after as little as 2 us of SE0.

It certainly has enough resolution. I'll check my trigger setup to
make sure I set the delay properly.

Mike

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