linux-kernel - Re: [PATCH] usb: echi-hcd: Add ehci_setup check before echi

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Message-ID: <CAPBZ5Qf6VtfGrfx1LaR5d9gL3zcBCZ_MeUpxX+E6dpi1HP+QpQ@mail.gmail.com>
Date:	Fri, 20 May 2016 10:33:56 -0500
From:	Andy Gross <andy.gross@...aro.org>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-usb@...r.kernel.org,
	Linux Kernel list <linux-kernel@...r.kernel.org>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] usb: echi-hcd: Add ehci_setup check before echi_shutdown

On 20 May 2016 at 09:31, Alan Stern <stern@...land.harvard.edu> wrote:
> On Thu, 19 May 2016, Andy Gross wrote:
>
>> On 19 May 2016 at 05:12, Srinivas Kandagatla
>> <srinivas.kandagatla@...aro.org> wrote:
>>
>> <snip>
>>
>> > +++ b/drivers/usb/host/ehci-hcd.c
>> > @@ -368,6 +368,15 @@ static void ehci_shutdown(struct usb_hcd *hcd)
>> >  {
>> >         struct ehci_hcd *ehci = hcd_to_ehci(hcd);
>> >
>> > +       /**
>> > +        * Protect the system from crashing at system shutdown in cases where
>> > +        * usb host is not added yet from OTG controller driver.
>> > +        * As ehci_setup() not done yet, so stop accessing registers or
>> > +        * variables initialized in ehci_setup()
>> > +        */
>> > +       if (!ehci->sbrn)
>> > +               return;
>> > +
>> >         spin_lock_irq(&ehci->lock);
>> >         ehci->shutdown = true;
>> >         ehci->rh_state = EHCI_RH_STOPPING;
>>
>>
>> Should we also not check this in ehci_suspend and ehci_resume?  If I
>> do suspend/resume, it crashes in a similar manner.  I know this goes
>> beyond the problem scope of the patch.  Perhaps I should send in an
>> additional patch with the code?
>>
>> Are there any other places in the ehci-hcd where this needs to be checked?
>
> Really, this is an indication that the problem lies not in ehci-hcd but
> rather in the platform glue code.  The platform code allows itself to
> be registered as the driver of the controller device but does not
> initialize the ehci-hcd parts.
>
> Neither ehci_suspend nor ehci_resume is called directly by the driver
> core; the calls all have to pass through the glue code.  So maybe the
> glue layer needs to be careful about invoking these routines in
> ehci-hcd before ehci-hcd has been initialized.

That's a good point.  Perhaps all of this should be in the glue,
including the shutdown case.

Regards,

Andy