linux-kernel - Re: [PATCH v2 2/6] iio: light: stk3310: Implement vdd supply and power it off during suspend

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Date: Wed, 24 Apr 2024 18:14:10 +0200
From: Ondřej Jirman <megi@....cz>
To: Andy Shevchenko <andy.shevchenko@...il.com>
Cc: Aren Moynihan <aren@...cevolution.org>, 
	Jonathan Cameron <jic23@...nel.org>, Lars-Peter Clausen <lars@...afoo.de>, 
	Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>, 
	Conor Dooley <conor+dt@...nel.org>, Chen-Yu Tsai <wens@...e.org>, 
	Jernej Skrabec <jernej.skrabec@...il.com>, Samuel Holland <samuel@...lland.org>, 
	Liam Girdwood <lgirdwood@...il.com>, Mark Brown <broonie@...nel.org>, 
	Uwe Kleine-König <u.kleine-koenig@...gutronix.de>, linux-iio@...r.kernel.org, phone-devel@...r.kernel.org, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org, linux-sunxi@...ts.linux.dev, 
	Willow Barraco <contact@...lowbarraco.fr>
Subject: Re: [PATCH v2 2/6] iio: light: stk3310: Implement vdd supply and
 power it off during suspend

On Wed, Apr 24, 2024 at 06:20:41PM GMT, Andy Shevchenko wrote:
> On Wed, Apr 24, 2024 at 3:59 PM Ondřej Jirman <megi@....cz> wrote:
> > On Wed, Apr 24, 2024 at 02:16:06AM GMT, Andy Shevchenko wrote:
> > > On Wed, Apr 24, 2024 at 1:41 AM Aren Moynihan <aren@...cevolution.org> wrote:
> 
> ...
> 
> > > >         ret = stk3310_init(indio_dev);
> > > >         if (ret < 0)
> > > > -               return ret;
> > > > +               goto err_vdd_disable;
> > >
> > > This is wrong. You will have the regulator being disabled _before_
> > > IRQ. Note, that the original code likely has a bug which sets states
> > > before disabling IRQ and removing a handler.
> >
> > How so? stk3310_init is called before enabling the interrupt.
> 
> Exactly, IRQ is registered with devm and hence the error path and
> remove stages will got it in a wrong order.

Makes no sense. IRQ is not enabled here, yet. So in error path, the code will
just disable the regulator and devm will unref it later on. IRQ doesn't enter
the picture here at all in the error path.

> > Original code has a bug that IRQ is enabled before registering the
> > IIO device,
> 
> Indeed, but this is another bug.
> 
> > so if IRQ is triggered before registration, iio_push_event
> > from IRQ handler may be called on a not yet registered IIO device.
> >
> > Never saw it happen, though. :)
> 
> Because nobody cares enough to enable DEBUG_SHIRQ.

Nice debug tool. I bet it makes quite a mess when enabled. :)

Kind regards,
	o.

> -- 
> With Best Regards,
> Andy Shevchenko