Merge branch 'acpi-dsc'

Merge new ACPI device configuration object _DSC support for 5.16-rc1.

* acpi-dsc:
  Documentation: ACPI: Fix non-D0 probe _DSC object example
  at24: Support probing while in non-zero ACPI D state
  media: i2c: imx319: Support device probe in non-zero ACPI D state
  ACPI: Add a convenience function to tell a device is in D0 state
  Documentation: ACPI: Document _DSC object usage for enum power state
  i2c: Allow an ACPI driver to manage the device's power state during probe
  ACPI: scan: Obtain device's desired enumeration power state

Documentation/firmware-guide/acpi/index.rst

@@ -26,5 +26,6 @@ ACPI Support
    acpi-lid
    lpit
    video_extension
+   non-d0-probe
    extcon-intel-int3496
    intel-pmc-mux

Documentation/firmware-guide/acpi/non-d0-probe.rst

@@ -0,0 +1,78 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+========================================
+Probing devices in other D states than 0
+========================================
+
+Introduction
+============
+
+In some cases it may be preferred to leave certain devices powered off for the
+entire system bootup if powering on these devices has adverse side effects,
+beyond just powering on the said device.
+
+How it works
+============
+
+The _DSC (Device State for Configuration) object that evaluates to an integer
+may be used to tell Linux the highest allowed D state for a device during
+probe. The support for _DSC requires support from the kernel bus type if the
+bus driver normally sets the device in D0 state for probe.
+
+The downside of using _DSC is that as the device is not powered on, even if
+there's a problem with the device, the driver likely probes just fine but the
+first user will find out the device doesn't work, instead of a failure at probe
+time. This feature should thus be used sparingly.
+
+I²C
+---
+
+If an I²C driver indicates its support for this by setting the
+I2C_DRV_ACPI_WAIVE_D0_PROBE flag in struct i2c_driver.flags field and the
+_DSC object evaluates to integer higher than the D state of the device,
+the device will not be powered on (put in D0 state) for probe.
+
+D states
+--------
+
+The D states and thus also the allowed values for _DSC are listed below. Refer
+to [1] for more information on device power states.
+
+.. code-block:: text
+
+	Number	State	Description
+	0	D0	Device fully powered on
+	1	D1
+	2	D2
+	3	D3hot
+	4	D3cold	Off
+
+References
+==========
+
+[1] https://uefi.org/specifications/ACPI/6.4/02_Definition_of_Terms/Definition_of_Terms.html#device-power-state-definitions
+
+Example
+=======
+
+An ASL example describing an ACPI device using _DSC object to tell Operating
+System the device should remain powered off during probe looks like this. Some
+objects not relevant from the example point of view have been omitted.
+
+.. code-block:: text
+
+	Device (CAM0)
+	{
+		Name (_HID, "SONY319A")
+		Name (_UID, Zero)
+		Name (_CRS, ResourceTemplate ()
+		{
+			I2cSerialBus(0x0020, ControllerInitiated, 0x00061A80,
+				     AddressingMode7Bit, "\\_SB.PCI0.I2C0",
+				     0x00, ResourceConsumer)
+		})
+		Method (_DSC, 0, NotSerialized)
+		{
+			Return (0x4)
+		}
+	}

drivers/acpi/device_pm.c

@@ -1400,4 +1400,30 @@ bool acpi_storage_d3(struct device *dev)
 }
 EXPORT_SYMBOL_GPL(acpi_storage_d3);
 
+/**
+ * acpi_dev_state_d0 - Tell if the device is in D0 power state
+ * @dev: Physical device the ACPI power state of which to check
+ *
+ * On a system without ACPI, return true. On a system with ACPI, return true if
+ * the current ACPI power state of the device is D0, or false otherwise.
+ *
+ * Note that the power state of a device is not well-defined after it has been
+ * passed to acpi_device_set_power() and before that function returns, so it is
+ * not valid to ask for the ACPI power state of the device in that time frame.
+ *
+ * This function is intended to be used in a driver's probe or remove
+ * function. See Documentation/firmware-guide/acpi/low-power-probe.rst for
+ * more information.
+ */
+bool acpi_dev_state_d0(struct device *dev)
+{
+	struct acpi_device *adev = ACPI_COMPANION(dev);
+
+	if (!adev)
+		return true;
+
+	return adev->power.state == ACPI_STATE_D0;
+}
+EXPORT_SYMBOL_GPL(acpi_dev_state_d0);
+
 #endif /* CONFIG_PM */

drivers/acpi/scan.c

@@ -1017,6 +1017,7 @@ static void acpi_bus_init_power_state(struct acpi_device *device, int state)
 
 static void acpi_bus_get_power_flags(struct acpi_device *device)
 {
+	unsigned long long dsc = ACPI_STATE_D0;
 	u32 i;
 
 	/* Presence of _PS0|_PR0 indicates 'power manageable' */
@@ -1038,6 +1039,9 @@ static void acpi_bus_get_power_flags(struct acpi_device *device)
 	if (acpi_has_method(device->handle, "_DSW"))
 		device->power.flags.dsw_present = 1;
 
+	acpi_evaluate_integer(device->handle, "_DSC", NULL, &dsc);
+	device->power.state_for_enumeration = dsc;
+
 	/*
 	 * Enumerate supported power management states
 	 */

drivers/i2c/i2c-core-acpi.c

@@ -526,6 +526,16 @@ struct i2c_client *i2c_acpi_new_device(struct device *dev, int index,
 }
 EXPORT_SYMBOL_GPL(i2c_acpi_new_device);
 
+bool i2c_acpi_waive_d0_probe(struct device *dev)
+{
+	struct i2c_driver *driver = to_i2c_driver(dev->driver);
+	struct acpi_device *adev = ACPI_COMPANION(dev);
+
+	return driver->flags & I2C_DRV_ACPI_WAIVE_D0_PROBE &&
+		adev && adev->power.state_for_enumeration >= adev->power.state;
+}
+EXPORT_SYMBOL_GPL(i2c_acpi_waive_d0_probe);
+
 #ifdef CONFIG_ACPI_I2C_OPREGION
 static int acpi_gsb_i2c_read_bytes(struct i2c_client *client,
 		u8 cmd, u8 *data, u8 data_len)

drivers/i2c/i2c-core-base.c

@@ -551,7 +551,8 @@ static int i2c_device_probe(struct device *dev)
 	if (status < 0)
 		goto err_clear_wakeup_irq;
 
-	status = dev_pm_domain_attach(&client->dev, true);
+	status = dev_pm_domain_attach(&client->dev,
+				      !i2c_acpi_waive_d0_probe(dev));
 	if (status)
 		goto err_clear_wakeup_irq;
 
@@ -590,7 +591,7 @@ 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, true);
+	dev_pm_domain_detach(&client->dev, !i2c_acpi_waive_d0_probe(dev));
 err_clear_wakeup_irq:
 	dev_pm_clear_wake_irq(&client->dev);
 	device_init_wakeup(&client->dev, false);
@@ -621,7 +622,7 @@ static void i2c_device_remove(struct device *dev)
 
 	devres_release_group(&client->dev, client->devres_group_id);
 
-	dev_pm_domain_detach(&client->dev, true);
+	dev_pm_domain_detach(&client->dev, !i2c_acpi_waive_d0_probe(dev));
 	if (!pm_runtime_status_suspended(&client->dev) && adap->bus_regulator)
 		regulator_disable(adap->bus_regulator);
 

drivers/media/i2c/imx319.c

@@ -140,6 +140,8 @@ struct imx319 {
 
 	/* Streaming on/off */
 	bool streaming;
+	/* True if the device has been identified */
+	bool identified;
 };
 
 static const struct imx319_reg imx319_global_regs[] = {
@@ -2084,6 +2086,31 @@ imx319_set_pad_format(struct v4l2_subdev *sd,
 	return 0;
 }
 
+/* Verify chip ID */
+static int imx319_identify_module(struct imx319 *imx319)
+{
+	struct i2c_client *client = v4l2_get_subdevdata(&imx319->sd);
+	int ret;
+	u32 val;
+
+	if (imx319->identified)
+		return 0;
+
+	ret = imx319_read_reg(imx319, IMX319_REG_CHIP_ID, 2, &val);
+	if (ret)
+		return ret;
+
+	if (val != IMX319_CHIP_ID) {
+		dev_err(&client->dev, "chip id mismatch: %x!=%x",
+			IMX319_CHIP_ID, val);
+		return -EIO;
+	}
+
+	imx319->identified = true;
+
+	return 0;
+}
+
 /* Start streaming */
 static int imx319_start_streaming(struct imx319 *imx319)
 {
@@ -2091,6 +2118,10 @@ static int imx319_start_streaming(struct imx319 *imx319)
 	const struct imx319_reg_list *reg_list;
 	int ret;
 
+	ret = imx319_identify_module(imx319);
+	if (ret)
+		return ret;
+
 	/* Global Setting */
 	reg_list = &imx319_global_setting;
 	ret = imx319_write_regs(imx319, reg_list->regs, reg_list->num_of_regs);
@@ -2206,26 +2237,6 @@ error:
 	return ret;
 }
 
-/* Verify chip ID */
-static int imx319_identify_module(struct imx319 *imx319)
-{
-	struct i2c_client *client = v4l2_get_subdevdata(&imx319->sd);
-	int ret;
-	u32 val;
-
-	ret = imx319_read_reg(imx319, IMX319_REG_CHIP_ID, 2, &val);
-	if (ret)
-		return ret;
-
-	if (val != IMX319_CHIP_ID) {
-		dev_err(&client->dev, "chip id mismatch: %x!=%x",
-			IMX319_CHIP_ID, val);
-		return -EIO;
-	}
-
-	return 0;
-}
-
 static const struct v4l2_subdev_core_ops imx319_subdev_core_ops = {
 	.subscribe_event = v4l2_ctrl_subdev_subscribe_event,
 	.unsubscribe_event = v4l2_event_subdev_unsubscribe,
@@ -2420,6 +2431,7 @@ out_err:
 static int imx319_probe(struct i2c_client *client)
 {
 	struct imx319 *imx319;
+	bool full_power;
 	int ret;
 	u32 i;
 
@@ -2432,11 +2444,14 @@ static int imx319_probe(struct i2c_client *client)
 	/* Initialize subdev */
 	v4l2_i2c_subdev_init(&imx319->sd, client, &imx319_subdev_ops);
 
-	/* Check module identity */
-	ret = imx319_identify_module(imx319);
-	if (ret) {
-		dev_err(&client->dev, "failed to find sensor: %d", ret);
-		goto error_probe;
+	full_power = acpi_dev_state_d0(&client->dev);
+	if (full_power) {
+		/* Check module identity */
+		ret = imx319_identify_module(imx319);
+		if (ret) {
+			dev_err(&client->dev, "failed to find sensor: %d", ret);
+			goto error_probe;
+		}
 	}
 
 	imx319->hwcfg = imx319_get_hwcfg(&client->dev);
@@ -2488,11 +2503,9 @@ static int imx319_probe(struct i2c_client *client)
 	if (ret < 0)
 		goto error_media_entity;
 
-	/*
-	 * Device is already turned on by i2c-core with ACPI domain PM.
-	 * Enable runtime PM and turn off the device.
-	 */
-	pm_runtime_set_active(&client->dev);
+	/* Set the device's state to active if it's in D0 state. */
+	if (full_power)
+		pm_runtime_set_active(&client->dev);
 	pm_runtime_enable(&client->dev);
 	pm_runtime_idle(&client->dev);
 
@@ -2545,6 +2558,7 @@ static struct i2c_driver imx319_i2c_driver = {
 	},
 	.probe_new = imx319_probe,
 	.remove = imx319_remove,
+	.flags = I2C_DRV_ACPI_WAIVE_D0_PROBE,
 };
 module_i2c_driver(imx319_i2c_driver);
 

drivers/misc/eeprom/at24.c

@@ -595,6 +595,7 @@ static int at24_probe(struct i2c_client *client)
 	bool i2c_fn_i2c, i2c_fn_block;
 	unsigned int i, num_addresses;
 	struct at24_data *at24;
+	bool full_power;
 	struct regmap *regmap;
 	bool writable;
 	u8 test_byte;
@@ -747,14 +748,16 @@ static int at24_probe(struct i2c_client *client)
 
 	i2c_set_clientdata(client, at24);
 
-	err = regulator_enable(at24->vcc_reg);
-	if (err) {
-		dev_err(dev, "Failed to enable vcc regulator\n");
-		return err;
-	}
+	full_power = acpi_dev_state_d0(&client->dev);
+	if (full_power) {
+		err = regulator_enable(at24->vcc_reg);
+		if (err) {
+			dev_err(dev, "Failed to enable vcc regulator\n");
+			return err;
+		}
 
-	/* enable runtime pm */
-	pm_runtime_set_active(dev);
+		pm_runtime_set_active(dev);
+	}
 	pm_runtime_enable(dev);
 
 	at24->nvmem = devm_nvmem_register(dev, &nvmem_config);
@@ -766,15 +769,18 @@ static int at24_probe(struct i2c_client *client)
 	}
 
 	/*
-	 * Perform a one-byte test read to verify that the
-	 * chip is functional.
+	 * Perform a one-byte test read to verify that the chip is functional,
+	 * unless powering on the device is to be avoided during probe (i.e.
+	 * it's powered off right now).
 	 */
-	err = at24_read(at24, 0, &test_byte, 1);
-	if (err) {
-		pm_runtime_disable(dev);
-		if (!pm_runtime_status_suspended(dev))
-			regulator_disable(at24->vcc_reg);
-		return -ENODEV;
+	if (full_power) {
+		err = at24_read(at24, 0, &test_byte, 1);
+		if (err) {
+			pm_runtime_disable(dev);
+			if (!pm_runtime_status_suspended(dev))
+				regulator_disable(at24->vcc_reg);
+			return -ENODEV;
+		}
 	}
 
 	pm_runtime_idle(dev);
@@ -794,9 +800,11 @@ static int at24_remove(struct i2c_client *client)
 	struct at24_data *at24 = i2c_get_clientdata(client);
 
 	pm_runtime_disable(&client->dev);
-	if (!pm_runtime_status_suspended(&client->dev))
-		regulator_disable(at24->vcc_reg);
-	pm_runtime_set_suspended(&client->dev);
+	if (acpi_dev_state_d0(&client->dev)) {
+		if (!pm_runtime_status_suspended(&client->dev))
+			regulator_disable(at24->vcc_reg);
+		pm_runtime_set_suspended(&client->dev);
+	}
 
 	return 0;
 }
@@ -833,6 +841,7 @@ static struct i2c_driver at24_driver = {
 	.probe_new = at24_probe,
 	.remove = at24_remove,
 	.id_table = at24_ids,
+	.flags = I2C_DRV_ACPI_WAIVE_D0_PROBE,
 };
 
 static int __init at24_init(void)

include/acpi/acpi_bus.h

@@ -278,6 +278,7 @@ struct acpi_device_power {
 	int state;		/* Current state */
 	struct acpi_device_power_flags flags;
 	struct acpi_device_power_state states[ACPI_D_STATE_COUNT];	/* Power states (D0-D3Cold) */
+	u8 state_for_enumeration; /* Deepest power state for enumeration */
 };
 
 struct acpi_dep_data {

include/linux/acpi.h

@@ -1016,6 +1016,7 @@ int acpi_subsys_runtime_suspend(struct device *dev);
 int acpi_subsys_runtime_resume(struct device *dev);
 int acpi_dev_pm_attach(struct device *dev, bool power_on);
 bool acpi_storage_d3(struct device *dev);
+bool acpi_dev_state_d0(struct device *dev);
 #else
 static inline int acpi_subsys_runtime_suspend(struct device *dev) { return 0; }
 static inline int acpi_subsys_runtime_resume(struct device *dev) { return 0; }
@@ -1027,6 +1028,10 @@ static inline bool acpi_storage_d3(struct device *dev)
 {
 	return false;
 }
+static inline bool acpi_dev_state_d0(struct device *dev)
+{
+	return true;
+}
 #endif
 
 #if defined(CONFIG_ACPI) && defined(CONFIG_PM_SLEEP)

include/linux/i2c.h

@@ -11,6 +11,7 @@
 #define _LINUX_I2C_H
 
 #include <linux/acpi.h>		/* for acpi_handle */
+#include <linux/bits.h>
 #include <linux/mod_devicetable.h>
 #include <linux/device.h>	/* for struct device */
 #include <linux/sched.h>	/* for completion */
@@ -222,6 +223,15 @@ enum i2c_alert_protocol {
 	I2C_PROTOCOL_SMBUS_HOST_NOTIFY,
 };
 
+/**
+ * enum i2c_driver_flags - Flags for an I2C device driver
+ *
+ * @I2C_DRV_ACPI_WAIVE_D0_PROBE: Don't put the device in D0 state for probe
+ */
+enum i2c_driver_flags {
+	I2C_DRV_ACPI_WAIVE_D0_PROBE = BIT(0),
+};
+
 /**
  * struct i2c_driver - represent an I2C device driver
  * @class: What kind of i2c device we instantiate (for detect)
@@ -236,6 +246,7 @@ enum i2c_alert_protocol {
  * @detect: Callback for device detection
  * @address_list: The I2C addresses to probe (for detect)
  * @clients: List of detected clients we created (for i2c-core use only)
+ * @flags: A bitmask of flags defined in &enum i2c_driver_flags
  *
  * The driver.owner field should be set to the module owner of this driver.
  * The driver.name field should be set to the name of this driver.
@@ -294,6 +305,8 @@ struct i2c_driver {
 	int (*detect)(struct i2c_client *client, struct i2c_board_info *info);
 	const unsigned short *address_list;
 	struct list_head clients;
+
+	u32 flags;
 };
 #define to_i2c_driver(d) container_of(d, struct i2c_driver, driver)
 
@@ -1015,6 +1028,7 @@ u32 i2c_acpi_find_bus_speed(struct device *dev);
 struct i2c_client *i2c_acpi_new_device(struct device *dev, int index,
 				       struct i2c_board_info *info);
 struct i2c_adapter *i2c_acpi_find_adapter_by_handle(acpi_handle handle);
+bool i2c_acpi_waive_d0_probe(struct device *dev);
 #else
 static inline bool i2c_acpi_get_i2c_resource(struct acpi_resource *ares,
 					     struct acpi_resource_i2c_serialbus **i2c)
@@ -1038,6 +1052,10 @@ static inline struct i2c_adapter *i2c_acpi_find_adapter_by_handle(acpi_handle ha
 {
 	return NULL;
 }
+static inline bool i2c_acpi_waive_d0_probe(struct device *dev)
+{
+	return false;
+}
 #endif /* CONFIG_ACPI */
 
 #endif /* _LINUX_I2C_H */