Re: [linux-usb-devel] 2.6.17: dmesg flooded with "ohci_hcd 0000:00:02.0: wakeup"

From: Andrey Borzenkov
Date: Mon Jun 19 2006 - 14:37:54 EST


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On Sunday 18 June 2006 22:16, David Brownell wrote:
> On Sunday 18 June 2006 10:29 am, Andrey Borzenkov wrote:
> > On Sunday 18 June 2006 20:29, David Brownell wrote:
> > > An alternative (but post-boot) workaround _should_ be
> > >
> > > echo disabled > /sys/bus/pci/devices/0000:00:02.0/power/wakeup
>
> Did that work?
>

No. But

echo -n disabled > /sys/devices/pci0000:00/0000:00:02.0/usb1/power/wakeup

did.

Now I noticed that when I boot 2.6.16 hub has only 'Self Powered' attribite
(0xc0) while in 2.6.17 it adds 'Remote Wakeup':

Bus 001 Device 001: ID 0000:0000
Device Descriptor:
bLength 18
bDescriptorType 1
bcdUSB 1.10
bDeviceClass 9 Hub
...
bmAttributes 0xe0
Self Powered
Remote Wakeup

It apparently makes OHCI believe controller can correctly do suspend/wakeup.
The suspend does not come from upper layer - it is ohci_hub itself attempting
to put controller in lower power mode:

ohci_hub_status_data (struct usb_hcd *hcd, char *buf)
{
...
int can_suspend =
device_may_wakeup(&hcd->self.root_hub->dev);
...
#ifdef CONFIG_PM
/* save power by suspending idle root hubs;
* INTR_RD wakes us when there's work
*/
if (can_suspend
&& !changed
&& !ohci->ed_rm_list
&& ((OHCI_CTRL_HCFS | OHCI_SCHED_ENABLES)
& ohci->hc_control)
== OHCI_USB_OPER
&& time_after (jiffies, ohci->next_statechange)
&& usb_trylock_device (hcd->self.root_hub) == 0
) {
ohci_vdbg (ohci, "autosuspend\n");
(void) ohci_bus_suspend (hcd);
usb_unlock_device (hcd->self.root_hub);
}
#endif

can_suspend is true while it was apparently false in 2.6.16.

- -andrey
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