linux-kernel - Re: [PATCH] usb: ohci-at91: Fix the unhandle interrupt when resume

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Message-ID: <9c702495-a839-43ea-85b7-1c0a0c54ec73@rowland.harvard.edu>
Date:   Fri, 23 Jun 2023 11:52:53 -0400
From:   Alan Stern <stern@...land.harvard.edu>
To:     Guiting Shen <aarongt.shen@...il.com>
Cc:     gregkh@...uxfoundation.org, nicolas.ferre@...rochip.com,
        alexandre.belloni@...tlin.com, claudiu.beznea@...rochip.com,
        linux-usb@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] usb: ohci-at91: Fix the unhandle interrupt when resume

On Fri, Jun 23, 2023 at 11:44:04AM +0800, Guiting Shen wrote:
> 
> 
> On Thu,Jun 22,2023 at 22:29:43PM GMT+8, Alan Stern wrote:
> > On Thu, Jun 22, 2023 at 10:57:39AM +0800, Guiting Shen wrote:
> > > The ohci_hcd_at91_drv_suspend() sets ohci->rh_state to OHCI_RH_HALTED when
> > > suspend which will let the ohci_irq() skip the interrupt after resume. And
> > > nobody to handle this interrupt.
> > > 
> > > Set the ohci->rh_state to OHCI_RH_SUSPEND instead of OHCI_RH_HALTED when
> > > suspend to fix it.
> > > 
> > > Signed-off-by: Guiting Shen <aarongt.shen@...il.com>
> > > ---
> > >   drivers/usb/host/ohci-at91.c | 2 +-
> > >   1 file changed, 1 insertion(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/usb/host/ohci-at91.c b/drivers/usb/host/ohci-at91.c
> > > index b9ce8d80f20b..7a970e573668 100644
> > > --- a/drivers/usb/host/ohci-at91.c
> > > +++ b/drivers/usb/host/ohci-at91.c
> > > @@ -645,7 +645,7 @@ ohci_hcd_at91_drv_suspend(struct device *dev)
> > >   	 * REVISIT: some boards will be able to turn VBUS off...
> > >   	 */
> > >   	if (!ohci_at91->wakeup) {
> > > -		ohci->rh_state = OHCI_RH_HALTED;
> > > +		ohci->rh_state = OHCI_RH_SUSPENDED;
> > 
> > It looks like this change ignores the comment immediately above it
> > (just before the start of this hunk).
> > 
> > If you want to find a way to handle IRQs better after the controller
> > resumes, maybe you should change the resume routine instead of the
> > suspend routine.
> > 
> > Alan Stern
> 
> The comment which was added with commit-id 0365ee0a8f745 may be outdated
> because ohci_suspend() and ohci_at91_port_suspend() is used to suspend
> instead of setting ohci->rh_state to OHCI_RH_HALTED.

The comment says nothing about ohci->rh_state; it talks about the 
integrated transceivers and the 48 MHz clock.  I don't see why you would 
think the comment is outdated.

> What's more, I found that only ohci-at91 driver to set the ohci->rh_state
> which may be unnessory because the ohci_suspend() disable irq emission and
> mark HW unaccessible and ohci_at91_port_suspend() suspend the controller.
> 
> Is it really need to set ohci->rh_state in ohci_hcd_at91_drv_suspend()?
> 
> It maybe confused to set ohci->rh_state to OHCI_RH_SUSPEND in resume
> routine.

I'm not really sure what that assignment was intended to accomplish, but 
maybe it was meant to force a reset when the controller resumes.

You could get the same result by leaving ohci->rh_state set to 
OHCI_RH_SUSPENDED but changing ohci_hcd_at91_drv_resume().  Instead of 
calling ohci_resume(hcd, false), have it call:

	ohci_resume(hcd, !ohci_at91->wakeup);

That way, if the wakeup flag is clear and the clock was stopped, 
ohci_resume() will call ohci_usb_reset().  You should also add a comment 
explaining the reason.

I can't test this because I don't have the AT91 hardware.

Alan Stern