[mirror_ubuntu-bionic-kernel.git] / Documentation / devicetree / bindings / mfd / mfd.txt

Multi-Function Devices (MFD)

These devices comprise a nexus for heterogeneous hardware blocks containing
more than one non-unique yet varying hardware functionality.

A typical MFD can be:

- A mixed signal ASIC on an external bus, sometimes a PMIC (Power Management
  Integrated Circuit) that is manufactured in a lower technology node (rough
  silicon) that handles analog drivers for things like audio amplifiers, LED
  drivers, level shifters, PHY (physical interfaces to things like USB or
  ethernet), regulators etc.

- A range of memory registers containing "miscellaneous system registers" also
  known as a system controller "syscon" or any other memory range containing a
  mix of unrelated hardware devices.

Optional properties:

- compatible : "simple-mfd" - this signifies that the operating system should
  consider all subnodes of the MFD device as separate devices akin to how
  "simple-bus" indicates when to see subnodes as children for a simple
  memory-mapped bus. For more complex devices, when the nexus driver has to
  probe registers to figure out what child devices exist etc, this should not
  be used. In the latter case the child devices will be determined by the
  operating system.

- ranges: Describes the address mapping relationship to the parent. Should set
  the child's base address to 0, the physical address within parent's address
  space, and the length of the address map.

- #address-cells: Specifies the number of cells used to represent physical base
  addresses. Must be present if ranges is used.

- #size-cells: Specifies the number of cells used to represent the size of an
  address. Must be present if ranges is used.

Example:

foo@1000 {
	compatible = "syscon", "simple-mfd";
	reg = <0x01000 0x1000>;

	led@8.0 {
		compatible = "register-bit-led";
		offset = <0x08>;
		mask = <0x01>;
		label = "myled";
		default-state = "on";
	};
};
Commit	Line	Data
22869a9e LW	1	Multi-Function Devices (MFD)
	2
	3	These devices comprise a nexus for heterogeneous hardware blocks containing
	4	more than one non-unique yet varying hardware functionality.
	5
	6	A typical MFD can be:
	7
	8	- A mixed signal ASIC on an external bus, sometimes a PMIC (Power Management
	9	Integrated Circuit) that is manufactured in a lower technology node (rough
	10	silicon) that handles analog drivers for things like audio amplifiers, LED
	11	drivers, level shifters, PHY (physical interfaces to things like USB or
	12	ethernet), regulators etc.
	13
	14	- A range of memory registers containing "miscellaneous system registers" also
	15	known as a system controller "syscon" or any other memory range containing a
	16	mix of unrelated hardware devices.
	17
	18	Optional properties:
	19
	20	- compatible : "simple-mfd" - this signifies that the operating system should
	21	consider all subnodes of the MFD device as separate devices akin to how
bbc741c6	22	"simple-bus" indicates when to see subnodes as children for a simple
22869a9e LW	23	memory-mapped bus. For more complex devices, when the nexus driver has to
	24	probe registers to figure out what child devices exist etc, this should not
	25	be used. In the latter case the child devices will be determined by the
	26	operating system.
	27
0894e987 AJ	28	- ranges: Describes the address mapping relationship to the parent. Should set
	29	the child's base address to 0, the physical address within parent's address
	30	space, and the length of the address map.
	31
	32	- #address-cells: Specifies the number of cells used to represent physical base
	33	addresses. Must be present if ranges is used.
	34
	35	- #size-cells: Specifies the number of cells used to represent the size of an
	36	address. Must be present if ranges is used.
	37
22869a9e LW	38	Example:
	39
	40	foo@1000 {
	41	compatible = "syscon", "simple-mfd";
	42	reg = <0x01000 0x1000>;
	43
48c926cd	44	led@8.0 {
22869a9e LW	45	compatible = "register-bit-led";
	46	offset = <0x08>;
	47	mask = <0x01>;
	48	label = "myled";
	49	default-state = "on";
	50	};
	51	};