On Sat, Jan 04, 2014 at 12:09:27PM -0500, Alan Stern wrote:
> On Fri, 3 Jan 2014, Sarah Sharp wrote:
>
> > Occasionally when a USB 3.0 device is disconnected, the roothub port
> > goes into the SS.Inactive state, rather than reporting a disconnect. A
> > warm reset is the only way to get out of this state. khubd notices the
> > link state in hub_port_events(),
>
> Do you mean hub_events()? There is no hub_port_events() routine.
Yes.
> LPM is disabled before the port is reset. At that time, the port is
> still in the SS.Inactive state, and the port-connect bit is the same as
> it was when hub_events() first read the port status. So how will your
> new hub_is_device_disconnected() routine be able to do any better than
> the existing code already does?
>
> It sounds like what you really want to do is balance the LPM count but
> skip sending the actual request if the port is in the SS.Inactive
> state.
Yes, that's what this patch is trying to do. It skips sending the
U1/U2 disable request if the device is disconnected. The connect status
bit is always set to disconnected if the port is in SS.Inactive.
Hmm, and now I see why you're confused. The current code in
hub_events() skips usb_reset_device() if the connect status is
disconnected:
if (hub_port_warm_reset_required(hub, portstatus)) {
int status;
struct usb_device *udev =
hub->ports[i - 1]->child;
dev_dbg(hub_dev, "warm reset port %d\n", i);
if (!udev ||
!(portstatus & USB_PORT_STAT_CONNECTION) ||
udev->state == USB_STATE_NOTATTACHED) {
status = hub_port_reset(hub, i,
NULL, HUB_BH_RESET_TIME,
true);
if (status < 0)
hub_port_disable(hub, i, 1);
} else {
usb_lock_device(udev);
status = usb_reset_device(udev);
usb_unlock_device(udev);
connect_change = 0;
}
I missed that when preparing the patch. I now suspect that the only
reason Girish and Hemanth ran into the U1/U2 timeout issue is because
they're working on an older kernel that doesn't have commit
f3e94aa15dc3d9155f8fc4a3295866d7a207b4e5 "usb: core: don't try to
reset_device() a port that got just disconnected" (added in 3.12).
I'm extremely sorry for the noise, please ignore this patch.
Sarah Sharp
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