linux-kernel - Re: [PATCH V7] iio: light: isl29018: add vcc regulator operation support

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Date:   Sat, 22 Dec 2018 17:14:34 +0000
From:   Jonathan Cameron <jic23@...nel.org>
To:     Anson Huang <anson.huang@....com>
Cc:     "knaack.h@....de" <knaack.h@....de>,
        "lars@...afoo.de" <lars@...afoo.de>,
        "pmeerw@...erw.net" <pmeerw@...erw.net>,
        "linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "festevam@...il.com" <festevam@...il.com>,
        "preid@...ctromag.com.au" <preid@...ctromag.com.au>,
        dl-linux-imx <linux-imx@....com>
Subject: Re: [PATCH V7] iio: light: isl29018: add vcc regulator operation
 support

On Mon, 17 Dec 2018 03:25:17 +0000
Anson Huang <anson.huang@....com> wrote:

> The light sensor's power supply could be controllable by regulator
> on some platforms, such as i.MX6Q-SABRESD board, the light sensor
> isl29023's power supply is controlled by a GPIO fixed regulator,
> need to make sure the regulator is enabled before any operation of
> sensor, this patch adds vcc regulator operation support.
> 
> Signed-off-by: Anson Huang <Anson.Huang@....com>
Hi Anson

See below.

> ---
> ChangeLog since V6
>     - using devm_regulator_get() instead of devm_regulator_get_optional() since the regulator is
>       there anyway, if dtb does NOT specify one, regulator framework will assign dummy regulator for it;
>     - Setup devm action for cleaning up regulator resource for error handling.
> ---
>  drivers/iio/light/isl29018.c | 58 ++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 58 insertions(+)
> 
> diff --git a/drivers/iio/light/isl29018.c b/drivers/iio/light/isl29018.c
> index b45400f..63f7b9d 100644
> --- a/drivers/iio/light/isl29018.c
> +++ b/drivers/iio/light/isl29018.c
> @@ -23,6 +23,7 @@
>  #include <linux/mutex.h>
>  #include <linux/delay.h>
>  #include <linux/regmap.h>
> +#include <linux/regulator/consumer.h>
>  #include <linux/slab.h>
>  #include <linux/iio/iio.h>
>  #include <linux/iio/sysfs.h>
> @@ -95,6 +96,7 @@ struct isl29018_chip {
>  	struct isl29018_scale	scale;
>  	int			prox_scheme;
>  	bool			suspended;
> +	struct regulator	*vcc_reg;
>  };
>  
>  static int isl29018_set_integration_time(struct isl29018_chip *chip,
> @@ -708,6 +710,17 @@ static const char *isl29018_match_acpi_device(struct device *dev, int *data)
>  	return dev_name(dev);
>  }
>  
> +static void isl29018_disable_regulator_action(void *_data)
> +{
> +	struct isl29018_chip *chip = _data;
> +	int err;
> +
> +	err = regulator_disable(chip->vcc_reg);
> +	if (err)
> +		dev_err(regmap_get_device(chip->regmap),
> +			"failed to disable VCC regulator!\n");
> +}
> +
>  static int isl29018_probe(struct i2c_client *client,
>  			  const struct i2c_device_id *id)
>  {
> @@ -742,6 +755,37 @@ static int isl29018_probe(struct i2c_client *client,
>  	chip->scale = isl29018_scales[chip->int_time][0];
>  	chip->suspended = false;
>  
> +	chip->vcc_reg = devm_regulator_get(&client->dev, "vcc");
> +	if (IS_ERR(chip->vcc_reg)) {
> +		err = PTR_ERR(chip->vcc_reg);
> +		if (err != -EPROBE_DEFER)
> +			dev_err(&client->dev, "failed to get VCC regulator!\n");
> +		return err;
> +	}
> +
> +	err = regulator_enable(chip->vcc_reg);
> +	if (err) {
> +		dev_err(&client->dev, "failed to enable VCC regulator!\n");
> +		return err;
> +	}
> +
> +	chip->regmap = devm_regmap_init_i2c(client,
> +				isl29018_chip_info_tbl[dev_id].regmap_cfg);
> +	if (IS_ERR(chip->regmap)) {
> +		err = PTR_ERR(chip->regmap);
> +		dev_err(&client->dev, "regmap initialization fails: %d\n", err);
> +		regulator_disable(chip->vcc_reg);
> +		return err;
> +	}
> +
> +	err = devm_add_action(&client->dev, isl29018_disable_regulator_action,
> +				 chip);
> +	if (err) {

I'm a little confused, why not do this before devm_regmap_init_i2c.
That way you won't have to disable the regulator in that one error path.
Also, devm_add_action_or_reset will call isl29018_disable_regulator_action for
you on error.

> +		isl29018_disable_regulator_action(chip);
> +		dev_err(&client->dev, "failed to setup regulator cleanup action!\n");
> +		return err;
> +	}
> +
>  	chip->regmap = devm_regmap_init_i2c(client,
>  				isl29018_chip_info_tbl[dev_id].regmap_cfg);
>  	if (IS_ERR(chip->regmap)) {
> @@ -768,6 +812,7 @@ static int isl29018_probe(struct i2c_client *client,
>  static int isl29018_suspend(struct device *dev)
>  {
>  	struct isl29018_chip *chip = iio_priv(dev_get_drvdata(dev));
> +	int ret;
>  
>  	mutex_lock(&chip->lock);
>  
> @@ -777,6 +822,12 @@ static int isl29018_suspend(struct device *dev)
>  	 * So we do not have much to do here.
>  	 */
>  	chip->suspended = true;
> +	ret = regulator_disable(chip->vcc_reg);
> +	if (ret) {
> +		dev_err(dev, "failed to disable VCC regulator\n");
> +		mutex_unlock(&chip->lock);
> +		return ret;

Given you are about to unlock anyway a common pattern is to not
check ret until after the unlock, thus simplifying the code.

> +	}
>  
>  	mutex_unlock(&chip->lock);
>  
> @@ -790,6 +841,13 @@ static int isl29018_resume(struct device *dev)
>  
>  	mutex_lock(&chip->lock);
>  
> +	err = regulator_enable(chip->vcc_reg);
> +	if (err) {
> +		dev_err(dev, "failed to enable VCC regulator\n");
> +		mutex_unlock(&chip->lock);
> +		return err;
> +	}
> +
>  	err = isl29018_chip_init(chip);
>  	if (!err)
>  		chip->suspended = false;