linux-kernel - Re: [PATCH v2] i2c: core: Disable client irq on reboot/shutdown

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Date:   Sun, 20 Jun 2021 22:26:19 -0700
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     Wolfram Sang <wsa@...nel.org>, Stephen Boyd <swboyd@...omium.org>,
        linux-kernel@...r.kernel.org, linux-i2c@...r.kernel.org,
        kernel test robot <lkp@...el.com>
Subject: Re: [PATCH v2] i2c: core: Disable client irq on reboot/shutdown

On Sun, Jun 20, 2021 at 11:04:23PM +0200, Wolfram Sang wrote:
> On Fri, Jun 04, 2021 at 04:27:44PM -0700, Stephen Boyd wrote:
> > From: Dmitry Torokhov <dmitry.torokhov@...il.com>
> > 
> > If an i2c client receives an interrupt during reboot or shutdown it may
> > be too late to service it by making an i2c transaction on the bus
> > because the i2c controller has already been shutdown. This can lead to
> > system hangs if the i2c controller tries to make a transfer that is
> > doomed to fail because the access to the i2c pins is already shut down,
> > or an iommu translation has been torn down so i2c controller register
> > access doesn't work.
> > 
> > Let's simply disable the irq if there isn't a shutdown callback for an
> > i2c client when there is an irq associated with the device. This will
> > make sure that irqs don't come in later than the time that we can handle
> > it. We don't do this if the i2c client device already has a shutdown
> > callback because presumably they're doing the right thing and quieting
> > the device so irqs don't come in after the shutdown callback returns.
> > 
> > Cc: Dmitry Torokhov <dmitry.torokhov@...il.com>
> > Reported-by: kernel test robot <lkp@...el.com>
> > [swboyd@...omium.org: Dropped newline, added commit text, added
> > interrupt.h for robot build error]
> > Signed-off-by: Stephen Boyd <swboyd@...omium.org>
> 
> I think this is for-current material because it fixes hangs. Or better
> for-next to check for side-effects?
> 

We lived with this issue for many years, so letting it cook in next will
not hurt us IMO.

Thanks.

-- 
Dmitry