linux-kernel - Re: [PATCH v2 1/1] i2c: Restore initial power state when we are done.

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Date:   Thu, 10 Nov 2022 18:25:34 +0900
From:   Hidenori Kobayashi <hidenorik@...omium.org>
To:     Ricardo Ribalda <ribalda@...omium.org>
Cc:     Tomasz Figa <tfiga@...omium.org>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Wolfram Sang <wsa@...nel.org>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        linux-kernel@...r.kernel.org, linux-i2c@...r.kernel.org
Subject: Re: [PATCH v2 1/1] i2c: Restore initial power state when we are done.

Hi Ricardo,

On Wed, Nov 09, 2022 at 04:17:06PM +0100, Ricardo Ribalda wrote:
> A driver that supports I2C_DRV_ACPI_WAIVE_D0_PROBE is not expected to
> power off a device that it has not powered on previously.
> 
> For devices operating in "full_power" mode, the first call to
> `i2c_acpi_waive_d0_probe` will return 0, which means that the device
> will be turned on with `dev_pm_domain_attach`.
> 
> If probe fails or the device is removed the second call to
> `i2c_acpi_waive_d0_probe` will return 1, which means that the device
> will not be turned off. This is, it will be left in a different power
> state. Lets fix it.
> 
> Fixes: b18c1ad685d9 ("i2c: Allow an ACPI driver to manage the device's power state during probe")
> Signed-off-by: Ricardo Ribalda <ribalda@...omium.org>
> 
> diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
> index b4edf10e8fd0..96623e0647bd 100644
> --- a/drivers/i2c/i2c-core-base.c
> +++ b/drivers/i2c/i2c-core-base.c
> @@ -545,8 +545,9 @@ static int i2c_device_probe(struct device *dev)
>  	if (status < 0)
>  		goto err_clear_wakeup_irq;
>  
> +	client->turn_off_on_remove = !i2c_acpi_waive_d0_probe(dev);
>  	status = dev_pm_domain_attach(&client->dev,
> -				      !i2c_acpi_waive_d0_probe(dev));
> +				      client->turn_off_on_remove);
>  	if (status)
>  		goto err_clear_wakeup_irq;
>  
> @@ -585,7 +586,7 @@ static int i2c_device_probe(struct device *dev)
>  err_release_driver_resources:
>  	devres_release_group(&client->dev, client->devres_group_id);
>  err_detach_pm_domain:
> -	dev_pm_domain_detach(&client->dev, !i2c_acpi_waive_d0_probe(dev));
> +	dev_pm_domain_detach(&client->dev, client->turn_off_on_remove);
>  err_clear_wakeup_irq:
>  	dev_pm_clear_wake_irq(&client->dev);
>  	device_init_wakeup(&client->dev, false);
> @@ -610,7 +611,7 @@ static void i2c_device_remove(struct device *dev)
>  
>  	devres_release_group(&client->dev, client->devres_group_id);
>  
> -	dev_pm_domain_detach(&client->dev, !i2c_acpi_waive_d0_probe(dev));
> +	dev_pm_domain_detach(&client->dev, client->turn_off_on_remove);
>  
>  	dev_pm_clear_wake_irq(&client->dev);
>  	device_init_wakeup(&client->dev, false);
> diff --git a/include/linux/i2c.h b/include/linux/i2c.h
> index f7c49bbdb8a1..6b2dacb0bae1 100644
> --- a/include/linux/i2c.h
> +++ b/include/linux/i2c.h
> @@ -326,6 +326,8 @@ struct i2c_driver {
>   *	calls it to pass on slave events to the slave driver.
>   * @devres_group_id: id of the devres group that will be created for resources
>   *	acquired when probing this device.
> + * @turn_off_on_remove: Record if we have turned on the device before probing
> + *	so we can restore the initial state after remove/probe error.
>   *
>   * An i2c_client identifies a single device (i.e. chip) connected to an
>   * i2c bus. The behaviour exposed to Linux is defined by the driver
> @@ -355,6 +357,7 @@ struct i2c_client {
>  	i2c_slave_cb_t slave_cb;	/* callback for slave mode	*/
>  #endif
>  	void *devres_group_id;		/* ID of probe devres group	*/
> +	bool turn_off_on_remove;	/* power state when done	*/

Can we have a different name that also makes sense for attach()?
To me, it's kind of hard to see immediately what the second argument to
attach() meant.

Since this is used for both power_on and power_off, I think something
more neutral would be easier to read? For example: power_flag?

Or I guess we could name it like full_power and provide a wrapper for
the detach() cases?

>  };
>  #define to_i2c_client(d) container_of(d, struct i2c_client, dev)
>  
> 
> -- 
> b4 0.11.0-dev-d93f8
>