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Date:   Sat, 22 Dec 2018 17:10:02 +0000
From:   Jonathan Cameron <jic23@kernel.org>
To:     Anson Huang <anson.huang@nxp.com>
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        "peda@axentia.se" <peda@axentia.se>,
        "rtresidd@electromag.com.au" <rtresidd@electromag.com.au>,
        "linux-iio@vger.kernel.org" <linux-iio@vger.kernel.org>,
        "devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
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        dl-linux-imx <linux-imx@nxp.com>
Subject: Re: [PATCH V5 2/2] iio: magnetometer: mag3110: add vdd/vddio
 regulator operation support
Message-ID: <20181222171002.2261bc97@archlinux>
In-Reply-To: <1545021679-4025-2-git-send-email-Anson.Huang@nxp.com>
References: <1545021679-4025-1-git-send-email-Anson.Huang@nxp.com>
        <1545021679-4025-2-git-send-email-Anson.Huang@nxp.com>
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On Mon, 17 Dec 2018 04:47:49 +0000
Anson Huang <anson.huang@nxp.com> wrote:

> The magnetometer's power supplies could be controllable on some platforms,
> such as i.MX6Q-SABRESD board, the mag3110's power supplies are controlled
> by a GPIO fixed regulator, need to make sure the regulators are enabled
> before any communication with mag3110, this patch adds vdd/vddio regulator
> operation support.
> 
> Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
> ---
> ChangeLog since V4:
>     -  using devm_regulator_get() instead of devm_regulator_get_optional() since the regulator is
>        there always, if dtb does NOT specify one, regulator framework will assign dummy regulator for it
> ---
>  drivers/iio/magnetometer/mag3110.c | 92 ++++++++++++++++++++++++++++++++++----
>  1 file changed, 84 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/iio/magnetometer/mag3110.c b/drivers/iio/magnetometer/mag3110.c
> index f063355..32660ce 100644
> --- a/drivers/iio/magnetometer/mag3110.c
> +++ b/drivers/iio/magnetometer/mag3110.c
> @@ -20,6 +20,7 @@
>  #include <linux/iio/buffer.h>
>  #include <linux/iio/triggered_buffer.h>
>  #include <linux/delay.h>
> +#include <linux/regulator/consumer.h>
>  
>  #define MAG3110_STATUS 0x00
>  #define MAG3110_OUT_X 0x01 /* MSB first */
> @@ -56,6 +57,8 @@ struct mag3110_data {
>  	struct mutex lock;
>  	u8 ctrl_reg1;
>  	int sleep_val;
> +	struct regulator *vdd_reg;
> +	struct regulator *vddio_reg;
>  };
>  
>  static int mag3110_request(struct mag3110_data *data)
> @@ -469,17 +472,48 @@ static int mag3110_probe(struct i2c_client *client,
>  	struct iio_dev *indio_dev;
>  	int ret;
>  
> -	ret = i2c_smbus_read_byte_data(client, MAG3110_WHO_AM_I);
> -	if (ret < 0)
> -		return ret;
> -	if (ret != MAG3110_DEVICE_ID)
> -		return -ENODEV;
> -
>  	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
>  	if (!indio_dev)
>  		return -ENOMEM;
>  
>  	data = iio_priv(indio_dev);
> +
> +	data->vdd_reg = devm_regulator_get(&client->dev, "vdd");
> +	if (IS_ERR(data->vdd_reg)) {
> +		ret = PTR_ERR(data->vdd_reg);
> +		if (ret != -EPROBE_DEFER)
> +			dev_err(&client->dev, "failed to get VDD regulator!\n");
> +		return ret;
> +	}
> +
> +	ret = regulator_enable(data->vdd_reg);
> +	if (ret) {
> +		dev_err(&client->dev, "failed to enable VDD regulator!\n");
> +		return ret;
> +	}

Please don't mix managed unwinding (devm) with the manual version.
It makes it harder to reason about any races.  Here there aren't any
but in general please don't do it.

The easy solution here is to reorder so both regulators are acquired
before either is turned on.

Jonathan

> +
> +	data->vddio_reg = devm_regulator_get(&client->dev, "vddio");
> +	if (IS_ERR(data->vddio_reg)) {
> +		ret = PTR_ERR(data->vddio_reg);
> +		if (ret != -EPROBE_DEFER)
> +			dev_err(&client->dev, "failed to get VDDIO regulator!\n");
> +		goto disable_regulator_vdd;
> +	}
> +
> +	ret = regulator_enable(data->vddio_reg);
> +	if (ret) {
> +		dev_err(&client->dev, "failed to enable VDDIO regulator!\n");
> +		goto disable_regulator_vdd;
> +	}
> +
> +	ret = i2c_smbus_read_byte_data(client, MAG3110_WHO_AM_I);
> +	if (ret < 0)
> +		goto disable_regulators;
> +	if (ret != MAG3110_DEVICE_ID) {
> +		ret = -ENODEV;
> +		goto disable_regulators;
> +	}
> +
>  	data->client = client;
>  	mutex_init(&data->lock);
>  
> @@ -499,7 +533,7 @@ static int mag3110_probe(struct i2c_client *client,
>  
>  	ret = mag3110_change_config(data, MAG3110_CTRL_REG1, data->ctrl_reg1);
>  	if (ret < 0)
> -		return ret;
> +		goto disable_regulators;
>  
>  	ret = i2c_smbus_write_byte_data(client, MAG3110_CTRL_REG2,
>  		MAG3110_CTRL_AUTO_MRST_EN);
> @@ -520,16 +554,24 @@ static int mag3110_probe(struct i2c_client *client,
>  	iio_triggered_buffer_cleanup(indio_dev);
>  standby_on_error:
>  	mag3110_standby(iio_priv(indio_dev));
> +disable_regulators:
> +	regulator_disable(data->vddio_reg);
> +disable_regulator_vdd:
> +	regulator_disable(data->vdd_reg);
> +
>  	return ret;
>  }
>  
>  static int mag3110_remove(struct i2c_client *client)
>  {
>  	struct iio_dev *indio_dev = i2c_get_clientdata(client);
> +	struct mag3110_data *data = iio_priv(indio_dev);
>  
>  	iio_device_unregister(indio_dev);
>  	iio_triggered_buffer_cleanup(indio_dev);
>  	mag3110_standby(iio_priv(indio_dev));
> +	regulator_disable(data->vddio_reg);
> +	regulator_disable(data->vdd_reg);
>  
>  	return 0;
>  }
> @@ -537,14 +579,48 @@ static int mag3110_remove(struct i2c_client *client)
>  #ifdef CONFIG_PM_SLEEP
>  static int mag3110_suspend(struct device *dev)
>  {
> -	return mag3110_standby(iio_priv(i2c_get_clientdata(
> +	struct mag3110_data *data = iio_priv(i2c_get_clientdata(
> +		to_i2c_client(dev)));
> +	int ret;
> +
> +	ret = mag3110_standby(iio_priv(i2c_get_clientdata(
>  		to_i2c_client(dev))));
> +	if (ret)
> +		return ret;
> +
> +	ret = regulator_disable(data->vddio_reg);
> +	if (ret) {
> +		dev_err(dev, "failed to disable VDDIO regulator\n");
> +		return ret;
> +	}
> +
> +	ret = regulator_disable(data->vdd_reg);
> +	if (ret) {
> +		dev_err(dev, "failed to disable VDD regulator\n");
> +		return ret;
> +	}
> +
> +	return 0;
>  }
>  
>  static int mag3110_resume(struct device *dev)
>  {
>  	struct mag3110_data *data = iio_priv(i2c_get_clientdata(
>  		to_i2c_client(dev)));
> +	int ret;
> +
> +	ret = regulator_enable(data->vdd_reg);
> +	if (ret) {
> +		dev_err(dev, "failed to enable VDD regulator\n");
> +		return ret;
> +	}
> +
> +	ret = regulator_enable(data->vddio_reg);
> +	if (ret) {
> +		dev_err(dev, "failed to enable VDDIO regulator\n");
> +		regulator_disable(data->vdd_reg);
> +		return ret;
> +	}
>  
>  	return i2c_smbus_write_byte_data(data->client, MAG3110_CTRL_REG1,
>  		data->ctrl_reg1);