linux-kernel - Re: [PATCH 2/2] hwmon: ina3221: Add suspend and resume functions

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Date:   Sat, 29 Sep 2018 08:33:46 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Nicolin Chen <nicoleotsuka@...il.com>
Cc:     jdelvare@...e.com, afd@...com, linux-hwmon@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] hwmon: ina3221: Add suspend and resume functions

On Fri, Sep 28, 2018 at 02:49:21PM -0700, Nicolin Chen wrote:
> Depending on the hardware design, an INA3221 chip might lose
> its power during system suspend/resume. So this patch adds
> a pair of suspend and resume functions to cache the register
> values including config register value and limit settings.
> 
> Signed-off-by: Nicolin Chen <nicoleotsuka@...il.com>
> ---
>  drivers/hwmon/ina3221.c | 54 +++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 54 insertions(+)
> 
> diff --git a/drivers/hwmon/ina3221.c b/drivers/hwmon/ina3221.c
> index cfe65ff01051..26f66f728b27 100644
> --- a/drivers/hwmon/ina3221.c
> +++ b/drivers/hwmon/ina3221.c
> @@ -91,11 +91,13 @@ static const unsigned int register_channel[] = {
>   * @regmap: Register map of the device
>   * @fields: Register fields of the device
>   * @shunt_resistors: Array of resistor values per channel
> + * @reg_config: Register value of INA3221_CONFIG
>   */
>  struct ina3221_data {
>  	struct regmap *regmap;
>  	struct regmap_field *fields[F_MAX_FIELDS];
>  	int shunt_resistors[INA3221_NUM_CHANNELS];
> +	u32 reg_config;
>  };
>  
>  static int ina3221_read_value(struct ina3221_data *ina, unsigned int reg,
> @@ -415,8 +417,59 @@ static int ina3221_probe(struct i2c_client *client,
>  		return PTR_ERR(hwmon_dev);
>  	}
>  
> +	dev_set_drvdata(dev, ina);
> +
> +	return 0;
> +}
> +
> +#ifdef CONFIG_PM
> +static int ina3221_suspend(struct device *dev)
> +{
> +	struct ina3221_data *ina = dev_get_drvdata(dev);
> +	int ret;
> +
> +	/* Save config register value and enable cache-only */
> +	ret = regmap_read(ina->regmap, INA3221_CONFIG, &ina->reg_config);
> +	if (ret)
> +		return ret;
> +

Would it make sense to explicitly disable all channels here ?

Thanks,
Guenter

> +	regcache_cache_only(ina->regmap, true);
> +	regcache_mark_dirty(ina->regmap);
> +
> +	return 0;
> +}
> +
> +static int ina3221_resume(struct device *dev)
> +{
> +	struct ina3221_data *ina = dev_get_drvdata(dev);
> +	int ret;
> +
> +	regcache_cache_only(ina->regmap, false);
> +
> +	/* Software reset the chip */
> +	ret = regmap_field_write(ina->fields[F_RST], true);
> +	if (ret) {
> +		dev_err(dev, "Unable to reset device\n");
> +		return ret;
> +	}
> +
> +	/* Restore cached register values to hardware */
> +	ret = regcache_sync(ina->regmap);
> +	if (ret)
> +		return ret;
> +
> +	/* Restore config register value to hardware */
> +	ret = regmap_write(ina->regmap, INA3221_CONFIG, ina->reg_config);
> +	if (ret)
> +		return ret;
> +
>  	return 0;
>  }
> +#endif
> +
> +static const struct dev_pm_ops ina3221_pm = {
> +	SET_SYSTEM_SLEEP_PM_OPS(ina3221_suspend, ina3221_resume)
> +};
>  
>  static const struct of_device_id ina3221_of_match_table[] = {
>  	{ .compatible = "ti,ina3221", },
> @@ -435,6 +488,7 @@ static struct i2c_driver ina3221_i2c_driver = {
>  	.driver = {
>  		.name = INA3221_DRIVER_NAME,
>  		.of_match_table = ina3221_of_match_table,
> +		.pm = &ina3221_pm,
>  	},
>  	.id_table = ina3221_ids,
>  };
> -- 
> 2.17.1
>