RE: xhci crash at xhci_disable_hub_port_wake when system suspend.

[Jun Li <jun.li@nxp.com>]

> -----Original Message-----
> From: Peter Chen <peter.chen@kernel.org>
> Sent: Wednesday, January 12, 2022 8:48 PM
> To: Mathias Nyman <mathias.nyman@linux.intel.com>
> Cc: Frank Li <frank.li@nxp.com>; linux-usb@vger.kernel.org; Jun Li
> <jun.li@nxp.com>; Zhi Li <lznuaa@gmail.com>
> Subject: Re: xhci crash at xhci_disable_hub_port_wake when system suspend.
> 
> On 22-01-10 23:07:48, Mathias Nyman wrote:
> > On 10.1.2022 14.33, Peter Chen wrote:
> > > On 22-01-07 15:58:26, Frank Li wrote:
> > >> Mathias Nyman
> > >>
> > >> 	Recently we found a crash at xhci_disable_hub_port_wake when system
> suspend if enable remote wake up.
> > >>
> > >> 	Basial flow is.
> > >>
> > >> 	1. run time suspend call xhci_suspend, xhci parent devices gate the
> clock.
> > >> 	2. echo mem >/sys/power/state, system _device_suspend call
> xhci_suspend
> > >> 	3. xhci_suspend call xhci_disable_hub_port_wake, which access
> register, but clock already gated by run time pm.
> > >>
> > >> 	Why find this issue now, that is because previous power domain driver
> will call run time resume before it. But the below commit remove it.
> > >>
> > >> c1df456d0f06eb9275c1cd4c66548fc5738ea428
> > >> Author: Ulf Hansson ulf.hansson@linaro.org
> > >> Date:   Thu Mar 4 20:28:43 2021 +0100
> > >>
> > >>     PM: domains: Don't runtime resume devices at genpd_prepare()
> > >>
> > >>
> > >>
> > >> According to HCD_FLAG_HW_ACCESSIBLE logic, xhci should not access
> hardware when second time call xhci_suspend without call xhci_resume.
> > >>
> > >>         xhci_disable_hub_port_wake(xhci, &xhci->usb3_rhub,
> do_wakeup);
> > >>         xhci_disable_hub_port_wake(xhci, &xhci->usb2_rhub,
> > >> do_wakeup);
> > >>
> > >>         if (!HCD_HW_ACCESSIBLE(hcd))
> > >>                 return 0;
> > >>
> > >>         .....
> > >>         clear_bit(HCD_FLAG_HW_ACCESSIBLE, &hcd->flags);
> > >>         clear_bit(HCD_FLAG_HW_ACCESSIBLE,
> > >> &xhci->shared_hcd->flags);
> > >>
> > >> I am not sure if it is safe to move xhci_disable_hub_port_wake after
> HCD_HW_ACCESSIBLE check, Or need add additional run_time_resume before it.
> >
> > We probably need to runtime resume first in case we need to adjust the
> > wakeup settings
> >
> > >
> > > Frank, I prefer adding runtime resume at xhci-plat.c like below,
> > > let's see what Mathias says.
> > >
> > >
> > > diff --git a/drivers/usb/host/xhci-plat.c
> > > b/drivers/usb/host/xhci-plat.c index c1edcc9b13ce..47a5a10381a7
> > > 100644
> > > --- a/drivers/usb/host/xhci-plat.c
> > > +++ b/drivers/usb/host/xhci-plat.c
> > > @@ -440,6 +440,9 @@ static int __maybe_unused xhci_plat_suspend(struct
> device *dev)
> > >  	ret = xhci_priv_suspend_quirk(hcd);
> > >  	if (ret)
> > >  		return ret;
> > > +
> > > +	if (pm_runtime_suspended(dev))
> > > +		pm_runtime_resume(dev);
> > >  	/*
> > >  	 * xhci_suspend() needs `do_wakeup` to know whether host is allowed
> > >  	 * to do wakeup during suspend.
> > >
> >
> > Yes, looks like a solution to me.
> > Just checked that driver-api/pm/devices.rst also suggest calling
> > pm_runtime_resume() in ->suspend callback if device needs to adjust
> > wakeup capabilities.
> >
> > Frank Li, does this work for you?
> >
> > Peter, if we now make sure xhci host is not runtime suspended at
> > system suspend, does it mean that the !HCD_HW_ACCESSIBLE(hcd) check
> > you added to xhci_suspend() is no longer needed?
> 
> Yes, it is no longer needed if xhci host is not runtime suspended.

Looks like existing non xhci-plat user(xhci-tegra) is also calling xhci_resume()
before calling xhci_suspend(), so it's safe to remove it.

Li Jun
 
> 
> --
> 
> Thanks,
> Peter Chen