Commit 6ab34301 authored by Mika Westerberg's avatar Mika Westerberg Committed by Lee Jones
Browse files

mfd: Add ACPI support 



If an MFD device is backed by ACPI namespace, we should allow subdevice
drivers to access their corresponding ACPI companion devices through normal
means (e.g using ACPI_COMPANION()).

This patch adds such support to the MFD core. If the MFD parent device
does not specify any ACPI _HID/_CID for the child device, the child
device will share the parent ACPI companion device. Otherwise the child
device will be assigned with the corresponding ACPI companion, if found
in the namespace below the parent.

Signed-off-by: default avatarMika Westerberg <mika.westerberg@linux.intel.com>
Reviewed-by: default avatarDarren Hart <dvhart@linux.intel.com>
Signed-off-by: default avatarLee Jones <lee.jones@linaro.org>
parent 7be180cc

Documentation/acpi/enumeration.txt

+27 −0
Original line number Diff line number Diff line
@@ -312,3 +312,30 @@ a code like this: 


There are also devm_* versions of these functions which release the

descriptors once the device is released.



MFD devices

~~~~~~~~~~~

The MFD devices register their children as platform devices. For the child

devices there needs to be an ACPI handle that they can use to reference

parts of the ACPI namespace that relate to them. In the Linux MFD subsystem

we provide two ways:



	o The children share the parent ACPI handle.

	o The MFD cell can specify the ACPI id of the device.



For the first case, the MFD drivers do not need to do anything. The

resulting child platform device will have its ACPI_COMPANION() set to point

to the parent device.



If the ACPI namespace has a device that we can match using an ACPI id,

the id should be set like:



	static struct mfd_cell my_subdevice_cell = {

		.name = "my_subdevice",

		/* set the resources relative to the parent */

		.acpi_pnpid = "XYZ0001",

	};



The ACPI id "XYZ0001" is then used to lookup an ACPI device directly under

the MFD device and if found, that ACPI companion device is bound to the

resulting child platform device.

drivers/mfd/mfd-core.c

+40 −0
Original line number Diff line number Diff line
@@ -78,6 +78,44 @@ static int mfd_platform_add_cell(struct platform_device *pdev, 
	return 0;

}



#if IS_ENABLED(CONFIG_ACPI)

static void mfd_acpi_add_device(const struct mfd_cell *cell,

				struct platform_device *pdev)

{

	struct acpi_device *parent_adev;

	struct acpi_device *adev;



	parent_adev = ACPI_COMPANION(pdev->dev.parent);

	if (!parent_adev)

		return;



	/*

	 * MFD child device gets its ACPI handle either from the ACPI

	 * device directly under the parent that matches the acpi_pnpid or

	 * it will use the parent handle if is no acpi_pnpid is given.

	 */

	adev = parent_adev;

	if (cell->acpi_pnpid) {

		struct acpi_device_id ids[2] = {};

		struct acpi_device *child_adev;



		strlcpy(ids[0].id, cell->acpi_pnpid, sizeof(ids[0].id));

		list_for_each_entry(child_adev, &parent_adev->children, node)

			if (acpi_match_device_ids(child_adev, ids)) {

				adev = child_adev;

				break;

			}

	}



	ACPI_COMPANION_SET(&pdev->dev, adev);

}

#else

static inline void mfd_acpi_add_device(const struct mfd_cell *cell,

				       struct platform_device *pdev)

{

}

#endif



static int mfd_add_device(struct device *parent, int id,

			  const struct mfd_cell *cell, atomic_t *usage_count,

			  struct resource *mem_base,
@@ -119,6 +157,8 @@ static int mfd_add_device(struct device *parent, int id, 
		}

	}



	mfd_acpi_add_device(cell, pdev);



	if (cell->pdata_size) {

		ret = platform_device_add_data(pdev,

					cell->platform_data, cell->pdata_size);

include/linux/mfd/core.h

+3 −0
Original line number Diff line number Diff line
@@ -44,6 +44,9 @@ struct mfd_cell { 
	 */

	const char		*of_compatible;



	/* Matches ACPI PNP id, either _HID or _CID */

	const char		*acpi_pnpid;



	/*

	 * These resources can be specified relative to the parent device.

	 * For accessing hardware you should use resources from the platform dev

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