linux-kernel - Re: [PATCH v3 3/5] proximity: vl53l0x: Handle the VDD regulator

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Date:   Thu, 12 May 2022 17:55:22 +0100
From:   Jonathan Cameron <Jonathan.Cameron@...wei.com>
To:     Markuss Broks <markuss.broks@...il.com>
CC:     <linux-kernel@...r.kernel.org>,
        <~postmarketos/upstreaming@...ts.sr.ht>,
        <phone-devel@...r.kernel.org>,
        Konrad Dybcio <konrad.dybcio@...ainline.org>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...ainline.org>,
        Song Qiang <songqiang1304521@...il.com>,
        Jonathan Cameron <jic23@...nel.org>,
        "Lars-Peter Clausen" <lars@...afoo.de>,
        Rob Herring <robh+dt@...nel.org>,
        "Krzysztof Kozlowski" <krzysztof.kozlowski+dt@...aro.org>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        "Liam Girdwood" <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>, <linux-iio@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <linux-arm-msm@...r.kernel.org>
Subject: Re: [PATCH v3 3/5] proximity: vl53l0x: Handle the VDD regulator

On Thu, 12 May 2022 14:07:55 +0300
Markuss Broks <markuss.broks@...il.com> wrote:

> Handle the regulator supplying the VDD pin of VL53L0X.
> 
> Signed-off-by: Markuss Broks <markuss.broks@...il.com>
Hi Markuss,

One ordering question inline.

> ---
>  drivers/iio/proximity/vl53l0x-i2c.c | 37 +++++++++++++++++++++++++++++
>  1 file changed, 37 insertions(+)
> 
> diff --git a/drivers/iio/proximity/vl53l0x-i2c.c b/drivers/iio/proximity/vl53l0x-i2c.c
> index 12a3e2eff464..d8523e3981e8 100644
> --- a/drivers/iio/proximity/vl53l0x-i2c.c
> +++ b/drivers/iio/proximity/vl53l0x-i2c.c
> @@ -43,6 +43,7 @@
>  struct vl53l0x_data {
>  	struct i2c_client *client;
>  	struct completion completion;
> +	struct regulator *vdd_supply;
>  };
>  
>  static irqreturn_t vl53l0x_handle_irq(int irq, void *priv)
> @@ -192,10 +193,31 @@ static const struct iio_info vl53l0x_info = {
>  	.read_raw = vl53l0x_read_raw,
>  };
>  
> +static void vl53l0x_power_off(void *_data)
> +{
> +	struct vl53l0x_data *data = _data;
> +
> +	regulator_disable(data->vdd_supply);
> +}
> +
> +static int vl53l0x_power_on(struct vl53l0x_data *data)
> +{
> +	int ret;
> +
> +	ret = regulator_enable(data->vdd_supply);
> +	if (ret)
> +		return ret;
> +
> +	usleep_range(3200, 5000);
> +
> +	return 0;
> +}
> +
>  static int vl53l0x_probe(struct i2c_client *client)
>  {
>  	struct vl53l0x_data *data;
>  	struct iio_dev *indio_dev;
> +	int error;
>  
>  	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
>  	if (!indio_dev)
> @@ -210,6 +232,21 @@ static int vl53l0x_probe(struct i2c_client *client)
>  				     I2C_FUNC_SMBUS_BYTE_DATA))
>  		return -EOPNOTSUPP;
>  
> +	data->vdd_supply = devm_regulator_get_optional(&client->dev, "vdd");
> +	if (IS_ERR(data->vdd_supply))
> +		return dev_err_probe(&client->dev, PTR_ERR(data->vdd_supply),
> +				     "Unable to get VDD regulator\n");
> +
> +	error = devm_add_action_or_reset(&client->dev, vl53l0x_power_off, data);

I don't follow why you have this before the power_on.  We haven't enabled the
regulator yet so shouldn't be turning it off if we get an error whilst trying
to enable it.  The or_reset part is to ensure that even if this call
fails to register a devm action it will still call the callback thus allowing
you safely do this after turning the power on.

> +	if (error)
> +		return dev_err_probe(&client->dev, error,
> +				     "Failed to install poweroff action\n");
> +
> +	error = vl53l0x_power_on(data);
> +	if (error)
> +		return dev_err_probe(&client->dev, error,
> +				     "Failed to power on the chip\n");
> +
>  	indio_dev->name = "vl53l0x";
>  	indio_dev->info = &vl53l0x_info;
>  	indio_dev->channels = vl53l0x_channels;