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 14:59:48 +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 02:16:06AM GMT, Andy Shevchenko wrote:
> On Wed, Apr 24, 2024 at 1:41 AM Aren Moynihan <aren@...cevolution.org> wrote:
> >
> > From: Ondrej Jirman <megi@....cz>
> >
> > VDD power input can be used to completely power off the chip during
> > system suspend. Do so if available.
> 
> ...
> 
> >         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.

Original code has a bug that IRQ is enabled before registering the
IIO device, 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. :)

kind regards,
	o.

> Side note, you may make the driver neater with help of
> 
>   struct device *dev = &client->dev;
> 
> defined in this patch.
> 
> ...
> 
> >  static int stk3310_suspend(struct device *dev)
> >  {
> >         struct stk3310_data *data;
> 
> >         data = iio_priv(i2c_get_clientdata(to_i2c_client(dev)));
> 
> Side note: This may be updated (in a separate change) to use
> dev_get_drvdata() directly.
> 
> Jonathan, do we have something like iio_priv_from_drvdata(struct
> device *dev)? Seems many drivers may utilise it.
> 
> >  }
> 
> ...
> 
> >  static int stk3310_resume(struct device *dev)
> 
> Ditto.
> 
> --
> With Best Regards,
> Andy Shevchenko