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

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Date:   Sun, 25 Jun 2023 09:57:43 -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 Sun, Jun 25, 2023 at 12:01:12PM +0800, Guiting Shen wrote:
> On Fri, Jun 23, 2023 at 23:52:53PM GMT+8, Alan Stern wrote:
> >> The comment which was added with commit-id 0365ee0a8f745 may be outdated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 think the comment is outdated.
> > 
> 
> The comment says the reason to discard connection state by reset, but I
> don't see any reset operation at ohci-at91 suspend/resume routine in
> source code.And ohci_suspend() disable irq emission and mark HW
> unaccessible  maybe do the same effect as set ohci->rh_state to
> OHCI_RH_HALTED to discard connection state which I think the comment is
> outdated.

No, it doesn't do the same.  An actual reset is needed.

> >> 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.
> > 
> 
> It works by your methods to force a reset in my sama5d3 soc hardware.
> And I found that the ohci->rh_state was already OHCI_RH_SUSPEND before
> set it OHCI_RH_HALTED in suspend.So the question is whether to set it
> OHCI_RH_HALETED in ohci-at91 suspend routine.
> 
> It also works by comment the ohci->rh_state = OHCI_RH_HALTED in suspend
> routine.But I think it is safer to use your methods.
> 
> Do you have any suggestion on it before I send v2 patch latter.

No suggestions now.  Submit your v2 patch and then maybe I'll have 
something more to say.

Alan Stern