Commit 2c49daba authored by Rafael J. Wysocki's avatar Rafael J. Wysocki
Browse files

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
parents 452a3e72 dff5acfd

Documentation/firmware-guide/acpi/index.rst

+1 −0
Original line number Diff line number Diff line
@@ -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 → 100644
+78 −0
Original line number Diff line number Diff line 
.. 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

+26 −0
Original line number Diff line number Diff line
@@ -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

+4 −0
Original line number Diff line number Diff line
@@ -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

+10 −0
Original line number Diff line number Diff line
@@ -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)