linux-kernel - Re: [PATCH] serial: 8250: Clear port->pm on port specific driver unbind

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Message-ID: <20230414094035.GF36234@atomide.com>
Date:   Fri, 14 Apr 2023 12:40:35 +0300
From:   Tony Lindgren <tony@...mide.com>
To:     Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        Johan Hovold <johan@...nel.org>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Vignesh Raghavendra <vigneshr@...com>,
        linux-omap@...r.kernel.org,
        linux-serial <linux-serial@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] serial: 8250: Clear port->pm on port specific driver
 unbind

* Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com> [230414 07:36]:
> On Fri, 14 Apr 2023, Tony Lindgren wrote:
> 
> > * Andy Shevchenko <andriy.shevchenko@...ux.intel.com> [230413 16:06]:
> > > On Thu, Apr 13, 2023 at 10:03:41AM +0300, Tony Lindgren wrote:
> > > > Let's fix the issue by clearing port->pm in serial8250_unregister_port().
> > > 
> > > Sounds to me like a fix that needs a Fixes tag.
> > 
> > Maybe commit c161afe9759d ("8250: allow platforms to override PM hook.").
> > 
> > That's a bit unclear though as the hardware specific functions were
> > available at that point as they were passed in platform data. This can
> > be seen with git blame c161afe9759d drivers/serial/8250.c. To me it seems
> > the port->pm became potentially invalid if a serial port device driver
> > started implementing PM runtime?
> > 
> > Maybe just tagging it with Cc: stable is better if no obvious Fixes tag
> > can be figured out.
> 
> I'd just put that c161afe9759d there. It seems quite harmless even if it 
> would be unnecessary before some driver commit which is much harder to 
> pinpoint (and it would likely turn out old enough to not matter anyway 
> for the kernels stable cares about).

OK works for me.

I'm now wondering still if we should clear all the conditional hardware
specific functions too in addition to port->pm that get set in
serial8250_register_8250_port(). Maybe best done in a separate patch
as needed.. Any suggestions?

> I forgot to give this earlier:
> 
> Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>

Thanks,

Tony