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

[Jonathan Cameron]

On Wed,  5 Aug 2026 19:02:55 +0800
Linmao Li <lilinmao@xxxxxxxxxx> 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);
> @@ -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);
Similar to previous thread I replied to, I'm not convinced spending much
effort to recover from this sort of condition is useful.
If we have a regulator that doesn't respond reliably to instruction chances
are we very unlikely to recover, and adding the recovery logic complicates
the driver somewhat.

I we do decide this is worth doing then not this style.  Keep the error handling
as the out of line path
	if (ret) {
		int restart_ret;

		restart_ret = ....

Makes it easier to spot that it is an error path.

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