linux-kernel - Re: [PATCH v2 1/1] mfd: intel-lpss: Fix too early PM enablement in the ACPI ->probe()

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Date:   Tue, 16 Nov 2021 15:53:21 +0000
From:   Lee Jones <lee.jones@...aro.org>
To:     Aditya Garg <gargaditya08@...e.com>
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Orlando Chamberlain <redecorating@...tonmail.com>
Subject: Re: [PATCH v2 1/1] mfd: intel-lpss: Fix too early PM enablement in
 the ACPI ->probe()

On Mon, 15 Nov 2021, Aditya Garg wrote:

> 
> ________________________________
> From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> Sent: Monday, November 15, 2021 4:06 PM
> To: Aditya Garg
> Cc: Lee Jones; linux-kernel@...r.kernel.org; Orlando Chamberlain
> Subject: Re: [PATCH v2 1/1] mfd: intel-lpss: Fix too early PM enablement in the ACPI ->probe()
> 
> On Tue, Nov 02, 2021 at 05:42:35AM +0000, Aditya Garg wrote:
> > > On 02-Nov-2021, at 12:30 AM, Andy Shevchenko <andriy.shevchenko@...ux.intel.com> wrote:
> 
> > > The runtime PM callback may be called as soon as the runtime PM facility
> > > is enabled and activated. It means that ->suspend() may be called before
> > > we finish probing the device in the ACPI case. Hence, NULL pointer
> > > dereference:
> > >
> > >  intel-lpss INT34BA:00: IRQ index 0 not found
> > >  BUG: kernel NULL pointer dereference, address: 0000000000000030
> > >  ...
> > >  Workqueue: pm pm_runtime_work
> > >  RIP: 0010:intel_lpss_suspend+0xb/0x40 [intel_lpss]
> > >
> > > To fix this, first try to register the device and only after that enable
> > > runtime PM facility.
> > >
> > > Fixes: 4b45efe85263 ("mfd: Add support for Intel Sunrisepoint LPSS devices")
> > > Reported-by: Orlando Chamberlain <redecorating@...tonmail.com>
> > > Reported-by: Aditya Garg <gargaditya08@...e.com>
> > > Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> > > Tested-by: Aditya Garg <gargaditya08@...e.com>
> > > ---
> > > v2: added tag (Aditya), returned 0 explicitly at the end of ->probe()
> 
> > It works
> 
> Thanks for testing again!
> 
> Lee, can we have this as a fix material for v5.16-rcX?

Generally not, no.

We usually only push patches for the -rcs if they fix something that
was broken during the merge window.  Not 6+ years ago. :)

However, if other valid fixes appear, I'll shove it into the PR too.

> I would like to have it backported to stable 5.15 too.

Yes, once it's merged into mainline, it will be back-ported as far
back as it applies cleanly.

If you have a specific kernel in mind, you should indicate it on the
end of the Fixes line.

-- 
Lee Jones [李琼斯]
Senior Technical Lead - Developer Services
Linaro.org │ Open source software for Arm SoCs
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