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

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Message-ID: <CAHp75VejwJ7h5jaNL+VL7FE4UMbTEP3QA1E=_y-1PSrz99zBKQ@mail.gmail.com>
Date: Wed, 24 Apr 2024 20:31:27 +0300
From: Andy Shevchenko <andy.shevchenko@...il.com>
To: Ondřej Jirman <megi@....cz>, 
	Andy Shevchenko <andy.shevchenko@...il.com>, 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 7:14 PM Ondřej Jirman <megi@....cz> wrote:
> 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.

Huh?!

> 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.

Error path _after_ IRQ handler has been _successfully_ installed.
And complete ->remove() stage.

> > > 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. :)

FWIW, I have had it enabled for ages, but I have only a few devices,
so I fixed a few cases in the past WRT shared IRQ issues.

-- 
With Best Regards,
Andy Shevchenko