On Sat, 22 Sep 2012, Ming Lei wrote:
> The hub status endpoint has a long 'bInterval', which is 255ms
> for FS/LS device and 256ms for HS device according to USB 2.0 spec,
> so the device connection change may be reported later more than 255ms
> via status pipe.
>
> The connection change in hub may have been happened already on the
> downstream ports, but no status URB completes when it is killed
> in hub_suspend(auto), so the connection change may be missed by some
> buggy hub devices, which won't generate remote wakeup signal after
> their remote wakeup is enabled and they are put into suspend state.
>
> The problem can be observed at least on the below Genesys Logic, Inc.
> hub devices:
>
> 0x05e3,0x0606
> 0x05e3,0x0608
>
> In theory, there is no way to fix the problem completely, but we
> can make it less likely to occur by this patch.
>
> This patch introduces one quirk of HUB_QUIRK_CHECK_PORTS_AUTOSUSPEND
> to check ports' change at the end of hub_suspend(auto) for the buggy
> devices. If ports' change is found, terminate the auto suspend and
> return to working state.
>
> So for the buggy hubs, if the connection change happend before
> the ports' check, it can be handled correctly. If it happens between
> the ports' check and enabling remote wakeup/entering suspend, it
> will be missed. Considered the interval is quite short, it is very
> less likely to happen during the window.
This is basically okay. I have a couple of suggestions.
> @@ -3192,6 +3214,15 @@ static int hub_suspend(struct usb_interface *intf,
> pm_message_t msg)
>
> /* stop khubd and related activity */
> hub_quiesce(hub, HUB_SUSPEND);
> +
> + if (PMSG_IS_AUTO(msg) && hub->quirk_check_port_auto_suspend) {
The correct condition is hdev->do_remote_wakeup != 0, not PMSG_IS_AUTO.
> + /* check if there are changes pending on hub ports */
> + if (check_ports_changed(hub)) {
> + hub_activate(hub, HUB_RESUME);
> + return -EBUSY;
> + }
> + }
If the new code is moved up before the hub_quiesce() call then you
won't need to call hub_activate().
Alan Stern
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