Re: [PATCH] iio: flow: slf3s: restart measurement if VDD disable fails

[Nuno Sá]

On Wed, Aug 05, 2026 at 07:02:55PM +0800, Linmao Li wrote:
> slf3s_suspend() stops continuous measurement before disabling VDD. If
> regulator_disable() fails while the supply remains enabled, the system
> sleep transition is aborted. Since the PM core does not call the
> corresponding resume callback for a device whose suspend callback failed,
> the sensor remains idle after the system returns to the running state and
> subsequent reads fail.
> 
> Attempt to restart continuous measurement on this error path. Preserve the
> regulator error and warn if restarting the measurement also fails.
> 
> Fixes: d240b0b8a1ce ("iio: flow: add Sensirion SLF3S liquid flow sensor driver")
> Signed-off-by: Linmao Li <lilinmao@xxxxxxxxxx>
> ---
>  drivers/iio/flow/slf3s.c | 12 +++++++++++-
>  1 file changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/iio/flow/slf3s.c b/drivers/iio/flow/slf3s.c
> index dfa7c14090454..75ee82fbd3295 100644
> --- a/drivers/iio/flow/slf3s.c
> +++ b/drivers/iio/flow/slf3s.c
> @@ -462,6 +462,7 @@ static int slf3s_suspend(struct device *dev)
>  {
>  	struct iio_dev *indio_dev = dev_get_drvdata(dev);
>  	struct slf3s_data *sf = iio_priv(indio_dev);
> +	int restart_ret;
>  	int ret;
>  
>  	guard(mutex)(&sf->lock);

Side note and not related to this patch but, AFAIK, there's no point in the
locking the mutex on the PM callbacks.

> @@ -470,7 +471,16 @@ static int slf3s_suspend(struct device *dev)
>  	if (ret)
>  		return ret;
>  
> -	return regulator_disable(sf->vdd);
> +	ret = regulator_disable(sf->vdd);
> +	if (!ret)
> +		return 0;
> +
> +	restart_ret = slf3s_start_meas(sf, sf->medium);
> +	if (restart_ret)
> +		dev_warn(dev, "failed to restart measurement after suspend failure: %d\n",
> +			 restart_ret);
> +
> +	return ret;

I'm also not sure about the above. If the regulator fails to disable I
would say things are already in a bad state anyways. Is there any strong
reason to do `slf3s_send_cmd(sf->client, slf3s_cmd_stop_meas)` before
disabling vdd? I would assume that without vdd things will terminate
anyways. Asking because if we just disable it then the above stops
being a question. Though I do understand it's better to gracefully
terminate things. Just not sure if there's any added value for that in
this path.

Just my 2 cents. No strong feelings so if the driver author is fine with
this, also looks like a sensible change.

- Nuno Sá

>  }
>  
>  static int slf3s_resume(struct device *dev)
> 
> base-commit: 0efaefce4e95a3331550329c0078b2fb38b3ff1f
> -- 
> 2.25.1
>