On Thu, Jan 16, 2020 at 10:56:37AM +0800, Bibby Hsieh wrote:
> Although in the most platforms, the bus power of i2c
> are alway on, some platforms disable the i2c bus power
> in order to meet low power request.
> 
> We get and enable bulk regulator in i2c adapter device.
> 
> Signed-off-by: Bibby Hsieh <bibby.hsieh@mediatek.com>

...

> +#ifdef CONFIG_PM_SLEEP
> +static int i2c_resume(struct device *dev)
> +{
> +	struct i2c_client *client = i2c_verify_client(dev);
> +	struct i2c_adapter *adap = client->adapter;
> +	int err;
> +
> +	if (pm_runtime_status_suspended(&adap->dev)) {
> +		err = regulator_enable(adap->bus_reg);
> +		if (err)
> +			return err;
> +	}
> +
> +	return pm_generic_resume(dev);
> +}
> +
> +static int i2c_suspend(struct device *dev)
> +{
> +	struct i2c_client *client = i2c_verify_client(dev);
> +	struct i2c_adapter *adap = client->adapter;
> +	int err;
> +
> +	if (!pm_runtime_status_suspended(&adap->dev)) {
> +		err = regulator_disable(adap->bus_reg);
> +		if (err)
> +			return err;
> +	}
> +
> +	return pm_generic_suspend(dev);
> +}
> +#endif
> +
> +#ifdef CONFIG_PM
> +static int i2c_runtime_resume(struct device *dev)
> +{
> +	struct i2c_client *client = i2c_verify_client(dev);
> +	struct i2c_adapter *adap = client->adapter;
> +	int err;
> +
> +	err = regulator_enable(adap->bus_reg);
> +	if (err)
> +		return err;
> +
> +	return pm_generic_runtime_resume(dev);
> +}
> +
> +static int i2c_runtime_suspend(struct device *dev)
> +{
> +	struct i2c_client *client = i2c_verify_client(dev);
> +	struct i2c_adapter *adap = client->adapter;
> +	int err;
> +
> +	err = pm_generic_runtime_suspend(dev);
> +	if (err)
> +		return err;
> +
> +	return regulator_disable(adap->bus_reg);
> +}
> +#endif
> +
> +static const struct dev_pm_ops i2c_device_pm = {
> +	SET_SYSTEM_SLEEP_PM_OPS(i2c_suspend, i2c_resume)
> +	SET_RUNTIME_PM_OPS(i2c_runtime_suspend, i2c_runtime_resume, NULL)
> +};
> +

It looks good to me, yet I am not a PM expert. An ack from someone more
into that topic would be great, if possible.

>  static void i2c_device_shutdown(struct device *dev)
>  {
>  	struct i2c_client *client = i2c_verify_client(dev);
> @@ -488,6 +563,7 @@ struct bus_type i2c_bus_type = {
>  	.probe		= i2c_device_probe,
>  	.remove		= i2c_device_remove,
>  	.shutdown	= i2c_device_shutdown,
> +	.pm		= &i2c_device_pm,
>  };
>  EXPORT_SYMBOL_GPL(i2c_bus_type);
>  
> @@ -1351,6 +1427,11 @@ static int i2c_register_adapter(struct i2c_adapter *adap)
>  		goto out_reg;
>  
>  	dev_dbg(&adap->dev, "adapter [%s] registered\n", adap->name);
> +	adap->bus_reg = devm_regulator_get(&adap->dev, "bus");
> +	if (IS_ERR(adap->bus_reg)) {
> +		res = PTR_ERR(adap->bus_reg);
> +		goto out_reg;
> +	}
>  
>  	pm_runtime_no_callbacks(&adap->dev);
>  	pm_suspend_ignore_children(&adap->dev, true);
> diff --git a/include/linux/i2c.h b/include/linux/i2c.h
> index d2f786706657..833b81a680da 100644
> --- a/include/linux/i2c.h
> +++ b/include/linux/i2c.h
> @@ -15,6 +15,7 @@
>  #include <linux/device.h>	/* for struct device */
>  #include <linux/sched.h>	/* for completion */
>  #include <linux/mutex.h>
> +#include <linux/regulator/consumer.h>
>  #include <linux/rtmutex.h>
>  #include <linux/irqdomain.h>		/* for Host Notify IRQ */
>  #include <linux/of.h>		/* for struct device_node */
> @@ -330,6 +331,7 @@ struct i2c_client {
>  	int init_irq;			/* irq set at initialization	*/
>  	int irq;			/* irq issued by device		*/
>  	struct list_head detected;
> +
>  #if IS_ENABLED(CONFIG_I2C_SLAVE)
>  	i2c_slave_cb_t slave_cb;	/* callback for slave mode	*/
>  #endif
> @@ -723,6 +725,7 @@ struct i2c_adapter {
>  	const struct i2c_adapter_quirks *quirks;
>  
>  	struct irq_domain *host_notify_domain;
> +	struct regulator *bus_reg;

"bus_regulator" please. "reg" is ambigious with "register".

And what Tomasz said, of course.