linux-kernel - Re: [PATCH] iio: ad7292: Prevent regulator double disable

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Message-ID: <YwFIfKvuuDYiJywk@marsc.168.1.7>
Date:   Sat, 20 Aug 2022 17:47:56 -0300
From:   Marcelo Schmitt <marcelo.schmitt1@...il.com>
To:     Matti Vaittinen <mazziesaccount@...il.com>
Cc:     Matti Vaittinen <matti.vaittinen@...rohmeurope.com>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Michael Hennerich <Michael.Hennerich@...log.com>,
        Jonathan Cameron <jic23@...nel.org>, linux-iio@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] iio: ad7292: Prevent regulator double disable

Hi Matti, thank you for this patch.

On 08/19, Matti Vaittinen wrote:
> The ad7292 tries to add an devm_action for disabling a regulator at
> device detach using devm_add_action_or_reset(). The
> devm_add_action_or_reset() does call the release function should adding
> action fail. The driver inspects the value returned by
> devm_add_action_or_reset() and manually calls regulator_disable() if
> adding the action has failed. This leads to double disable and messes
> the enable count for regulator.
> 
That's correct. The regulator device even issued a message saying so
fixed-supply: Underflow of regulator enable count

Verified driver behavior on a raspberry pi with eval board.

Thanks again for this fix.

> Do not manually call disable if devm_add_action_or_reset() fails.
> 
> Fixes: 506d2e317a0a ("iio: adc: Add driver support for AD7292")
> Signed-off-by: Matti Vaittinen <mazziesaccount@...il.com>

Jonathan, can we still add more tags to this patch? If so, please add mine

Tested-by: Marcelo Schmitt <marcelo.schmitt1@...il.com>

> 
> ---
> 
> The bug was found during browsing the code. I don't have the hardware to
> test this so reviewing and testing is highly appreciated.
> ---
>  drivers/iio/adc/ad7292.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/drivers/iio/adc/ad7292.c b/drivers/iio/adc/ad7292.c
> index 92c68d467c50..a2f9fda25ff3 100644
> --- a/drivers/iio/adc/ad7292.c
> +++ b/drivers/iio/adc/ad7292.c
> @@ -287,10 +287,8 @@ static int ad7292_probe(struct spi_device *spi)
>  
>  		ret = devm_add_action_or_reset(&spi->dev,
>  					       ad7292_regulator_disable, st);
> -		if (ret) {
> -			regulator_disable(st->reg);
> +		if (ret)
>  			return ret;
> -		}
>  
>  		ret = regulator_get_voltage(st->reg);
>  		if (ret < 0)
> -- 
> 2.37.1
> 
> 
> -- 
> Matti Vaittinen, Linux device drivers
> ROHM Semiconductors, Finland SWDC
> Kiviharjunlenkki 1E
> 90220 OULU
> FINLAND
> 
> ~~~ "I don't think so," said Rene Descartes. Just then he vanished ~~~
> Simon says - in Latin please.
> ~~~ "non cogito me" dixit Rene Descarte, deinde evanescavit ~~~
> Thanks to Simon Glass for the translation =]