linux-kernel - [PATCH v4 1/1] i2c: Restore initial power state when we are done.

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Message-Id: <20221109-i2c-waive-v4-1-e4496462833b@chromium.org>
Date:   Thu, 10 Nov 2022 15:11:43 +0100
From:   Ricardo Ribalda <ribalda@...omium.org>
To:     Tomasz Figa <tfiga@...omium.org>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Wolfram Sang <wsa@...nel.org>
Cc:     Hidenori Kobayashi <hidenorik@...gle.com>,
        Ricardo Ribalda <ribalda@...omium.org>,
        linux-kernel@...r.kernel.org, linux-i2c@...r.kernel.org
Subject: [PATCH v4 1/1] i2c: Restore initial power state when we are done.

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..09a6bb89a352 100644
--- a/drivers/i2c/i2c-core-base.c
+++ b/drivers/i2c/i2c-core-base.c
@@ -467,6 +467,7 @@ static int i2c_device_probe(struct device *dev)
 {
 	struct i2c_client	*client = i2c_verify_client(dev);
 	struct i2c_driver	*driver;
+	bool do_power_on;
 	int status;
 
 	if (!client)
@@ -545,8 +546,8 @@ static int i2c_device_probe(struct device *dev)
 	if (status < 0)
 		goto err_clear_wakeup_irq;
 
-	status = dev_pm_domain_attach(&client->dev,
-				      !i2c_acpi_waive_d0_probe(dev));
+	do_power_on = !i2c_acpi_waive_d0_probe(dev);
+	status = dev_pm_domain_attach(&client->dev, do_power_on);
 	if (status)
 		goto err_clear_wakeup_irq;
 
@@ -580,12 +581,14 @@ static int i2c_device_probe(struct device *dev)
 	if (status)
 		goto err_release_driver_resources;
 
+	client->turn_off_on_remove = do_power_on;
+
 	return 0;
 
 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, do_power_on);
 err_clear_wakeup_irq:
 	dev_pm_clear_wake_irq(&client->dev);
 	device_init_wakeup(&client->dev, false);
@@ -610,7 +613,7 @@ 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..412ac2b7cb2e 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 turn off the device at removal.
  *
  * 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 +357,8 @@ 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;	/* if device needs to be turned	*/
+					/* off by framework at removal	*/
 };
 #define to_i2c_client(d) container_of(d, struct i2c_client, dev)
 

-- 
b4 0.11.0-dev-d93f8