[PATCH v3] iio: adc: rockchip_saradc: add voltage notifier so get referenced voltage once at probe

[Jonathan Cameron]

On Mon,  9 Aug 2021 09:15:17 +0800
Simon Xue <xxm at rock-chips.com> wrote:

> From: David Wu <david.wu at rock-chips.com>
> 
> Add voltage notifier, no need to query regulator voltage for
> every saradc read, just get regulator voltage once at probe.
> 
> Signed-off-by: David Wu <david.wu at rock-chips.com>
> Signed-off-by: Simon Xue <xxm at rock-chips.com>
> Reviewed-by: Heiko Stuebner <heiko at sntech.de>

Was just about to apply this, but noticed one last thing :( 
See inline.

> ---
>  drivers/iio/adc/rockchip_saradc.c | 46 ++++++++++++++++++++++++++-----
>  1 file changed, 39 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/iio/adc/rockchip_saradc.c b/drivers/iio/adc/rockchip_saradc.c
> index f3eb8d2e50dc..33c7dd635eb9 100644
> --- a/drivers/iio/adc/rockchip_saradc.c
> +++ b/drivers/iio/adc/rockchip_saradc.c
> @@ -49,10 +49,12 @@ struct rockchip_saradc {
>  	struct clk		*clk;
>  	struct completion	completion;
>  	struct regulator	*vref;
> +	int			uv_vref;
>  	struct reset_control	*reset;
>  	const struct rockchip_saradc_data *data;
>  	u16			last_val;
>  	const struct iio_chan_spec *last_chan;
> +	struct notifier_block nb;
>  };
>  
>  static void rockchip_saradc_power_down(struct rockchip_saradc *info)
> @@ -105,13 +107,7 @@ static int rockchip_saradc_read_raw(struct iio_dev *indio_dev,
>  		mutex_unlock(&indio_dev->mlock);
>  		return IIO_VAL_INT;
>  	case IIO_CHAN_INFO_SCALE:
> -		ret = regulator_get_voltage(info->vref);
> -		if (ret < 0) {
> -			dev_err(&indio_dev->dev, "failed to get voltage\n");
> -			return ret;
> -		}
> -
> -		*val = ret / 1000;
> +		*val = info->uv_vref / 1000;
>  		*val2 = chan->scan_type.realbits;
>  		return IIO_VAL_FRACTIONAL_LOG2;
>  	default:
> @@ -298,6 +294,26 @@ static irqreturn_t rockchip_saradc_trigger_handler(int irq, void *p)
>  	return IRQ_HANDLED;
>  }
>  
> +static int rockchip_saradc_volt_notify(struct notifier_block *nb,
> +						   unsigned long event,
> +						   void *data)
> +{
> +	struct rockchip_saradc *info =
> +			container_of(nb, struct rockchip_saradc, nb);
> +
> +	if (event & REGULATOR_EVENT_VOLTAGE_CHANGE)
> +		info->uv_vref = (unsigned long)data;
> +
> +	return NOTIFY_OK;
> +}
> +
> +static void rockchip_saradc_regulator_action(void *data)

This is not a well named function.  What is 'action'?
Perhaps
rockchip_saradc_reg_unreg_notifier() or something along those lines?

> +{
> +	struct rockchip_saradc *info = data;
> +
> +	regulator_unregister_notifier(info->vref, &info->nb);
> +}
> +
>  static int rockchip_saradc_probe(struct platform_device *pdev)
>  {
>  	struct rockchip_saradc *info = NULL;
> @@ -410,6 +426,12 @@ static int rockchip_saradc_probe(struct platform_device *pdev)
>  		return ret;
>  	}
>  
> +	ret = regulator_get_voltage(info->vref);
> +	if (ret < 0)
> +		return ret;
> +
> +	info->uv_vref = ret;
> +
>  	ret = clk_prepare_enable(info->pclk);
>  	if (ret < 0) {
>  		dev_err(&pdev->dev, "failed to enable pclk\n");
> @@ -450,6 +472,16 @@ static int rockchip_saradc_probe(struct platform_device *pdev)
>  	if (ret)
>  		return ret;
>  
> +	info->nb.notifier_call = rockchip_saradc_volt_notify;
> +	ret = regulator_register_notifier(info->vref, &info->nb);
> +	if (ret)
> +		return ret;
> +
> +	ret = devm_add_action_or_reset(&pdev->dev,
> +				       rockchip_saradc_regulator_action, info);
> +	if (ret)
> +		return ret;
> +
>  	return devm_iio_device_register(&pdev->dev, indio_dev);
>  }
>