Hi Alan,
> From: Alan Stern
> Sent: Tuesday, February 14, 2017 1:35 AM
>
> On Mon, 13 Feb 2017, Yoshihiro Shimoda wrote:
>
> > > Hmmm. You're using platform drivers for OHCI and EHCI, not PCI,
> >
> > Yes, I'm using platform drivers for OHCI and EHCI.
> >
> > > right? The resume_common() routine in drivers/usb/core/hcd-pci.c is
> > > careful to resume things in the correct order. It contains this code:
> > >
> > > /*
> > > * Only EHCI controllers have to wait for their companions.
> > > * No locking is needed because PCI controller drivers do not
> > > * get unbound during system resume.
> > > */
> > > if (pci_dev->class == CL_EHCI && event != PM_EVENT_AUTO_RESUME)
> > > for_each_companion(pci_dev, hcd,
> > > ehci_wait_for_companions);
> > >
> > > Probably the equivalent routine in the platform driver needs to do the
> > > same sort of thing. This means it needs to know about companion
> > > controllers.
> >
> > Thank you very much for this information!
> > If I added the following code, the issue disappeared:
> > - The ehci-platform.c calls device_enable_async_suspend(hcd->self.controller)
> > in ehci_platform_probe()
>
> We probably should do that in all the platform drivers anyway.
I got it.
> > - [This is a dirty code, but] hcd_bus_resume() calls device_pm_wait_for_dev(
> > rhdev->bus->controller, ohci_dev)
> >
> > I will consider how to implement such a code for [eo]hci-platform drivers.
> > Especially, like ehci_{pre,post}_add() for platform drivers are needed, I think.
>
> The key point is that the EHCI controller must be resumed _after_ its
> companion controllers. In order to do this properly, the platform
> driver needs to know which other devices the companions are.
>
> There's no way it can figure this out by itself; it has to be told by
> the platform-specific code.
I understood it.
In non-DT case, if we use .id in struct platform_device, there is easy to bind
EHCI and companion controllers. However, in DT environment, there is difficult to
bind them.
So, I have 2 ideas for DT case.
A) We add a new property "companion" as usb-generic.txt and EHCI node(s) have such a property
to bind a companion controller.
B) We assume EHCI controller binds a companion controller if some resources (irq or clock)
are the same and it has a compatible strings as "generic-[uo]hci" for instance.
What do you think?
Best regards,
Yoshihiro Shimoda
> Alan Stern
