Re: PATCH: ohci-s3c2410 suspend/resume support

On 2/12/07, David Brownell <[email protected]> wrote:
> On Monday 12 February 2007 12:53 pm, Matt Reimer wrote:
> > Attached is a patch against 2.6.20 to implement suspend/resume support
> > for ohci-s3c2410, based on the suspend/resume support in ohci-pxa27x.c
> > and ohci-omap.c.
>
> I can't translate that description into behavior.
>
> Is this basically turning the controller off, so that resume
> sees a controller reset and everything re-initializes?
>
> Or is it a real USB suspend state, from which the OHCI
> controller can issue system wakeup events, and which
> preserves device power sessions?

This patch explicitly preps the controller and turns it off. As I read
the S3C2410 documentation, both USB host and device are powered off
when the cpu is suspended, regardless of whether the clocks are left
on before the suspend, so I don't think it's possible for USB to
trigger a wake-up.

Upon resume, the USB system says:

    usb usb1: root hub lost power or was reset

and reconnects all the devices on that hub, assigning them new addresses.

> One test is:  plug a device in while the system is
> suspended.  Does that wake the system up?

No.

> Another test is:  suspend while a device is connected.
> Unplug it; does that wake the system?  Re-plug it;
> that should *always* show up as a new device when the
> system resumes (different USB address etc).

No it doesn't wake; yes each device that's present when the system
resumes gets a different USB address.

So given that situation, is the call to usb_hcd_resume_root_hub() necessary?

Matt

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