OMAP4+ Remoteproc Devices
=========================

The OMAP family of SoCs usually have one or more slave processor sub-systems
that are used to offload some of the processor-intensive tasks, or to manage
other hardware accelerators, for achieving various system level goals.

The processor cores in the sub-system are usually behind an IOMMU, and may
contain additional sub-modules like Internal RAM and/or ROMs, L1 and/or L2
caches, an Interrupt Controller, a Cache Controller etc.

The OMAP SoCs usually have a DSP processor sub-system and/or an IPU processor
sub-system. The DSP processor sub-system can contain any of the TI's C64x,
C66x or C67x family of DSP cores as the main execution unit. The IPU processor
sub-system usually contains either a Dual-Core Cortex-M3 or Dual-Core Cortex-M4
processors.

Remote Processor Node:
======================
Each remote processor sub-system is represented as a single DT node. Each node
has a number of required or optional properties that enable the OS running on
the host processor (MPU) to perform the device management of the remote
processor and to communicate with the remote processor. The various properties
can be classified as constant or variable. The constant properties are dictated
by the SoC and does not change from one board to another having the same SoC.
Examples of constant properties include 'iommus', 'reg'. The variable properties
are dictated by the system integration aspects such as memory on the board, or
configuration used within the corresponding firmware image. Examples of variable
properties include 'mboxes', 'memory-region', 'timers', 'watchdog-timers' etc.

Required properties:
--------------------
The following are the mandatory properties:

- compatible:	Should be one of the following,
		    "ti,omap4-dsp" for DSPs on OMAP4 SoCs
		    "ti,omap5-dsp" for DSPs on OMAP5 SoCs
		    "ti,dra7-dsp" for DSPs on DRA7xx SoCs
		    "ti,omap4-ipu" for IPUs on OMAP4 SoCs
		    "ti,omap5-ipu" for IPUs on OMAP5 SoCs
		    "ti,dra7-ipu" for IPUs on DRA7xx SoCs

- ti,hwmods:	Name of the hwmod associated with the remoteproc device

- iommus:	phandles to OMAP IOMMU nodes, that need to be programmed
		for this remote processor to access any external RAM memory or
		other peripheral device address spaces. This property usually
		has only a single phandle. Multiple phandles are used only in
		cases where the sub-system has different ports for different
		sub-modules within the processor sub-system (eg: DRA7 DSPs),
		and need the same programming in both the MMUs.

- mboxes:	OMAP Mailbox specifier denoting the sub-mailbox, to be used for
		communication with the remote processor. The specifier format is
		as per the bindings,
		Documentation/devicetree/bindings/mailbox/omap-mailbox.txt
		This property should match with the sub-mailbox node used in
		the firmware image.

Optional properties:
--------------------
Some of these properties are mandatory on some SoCs, and some are optional
depending on the configuration of the firmware image to be executed on the
remote processor. The conditions are mentioned for each property.

The following are the optional properties:
- reg:			Address space for any remoteproc memories present on
			the SoC. Should contain an entry for each value in
			'reg-names'. These are mandatory for all DSP and IPU
			processors that have them (OMAP4/OMAP5 DSPs do not have
			any RAMs)

- reg-names:		Required names for each of the address spaces defined in
			the 'reg' property. Should contain a string from among
			the following names, each representing the corresponding
			internal RAM memory region,
			   "l2ram" for L2 RAM,
			   "l1pram" for L1 Program RAM Memory/Cache,
			   "l1dram" for L1 Data RAM Memory/Cache,

			All devices may not have all the above memories.

- syscon-bootreg:	Should be a pair of the phandle to the System Control
			Configuration region that contains the boot address
			register, and the register offset of the boot address
			register within the System Control module. This property
			is required for all the DSP instances on OMAP4, OMAP5
			and DRA7xx SoCs.

- memory-region:	phandle to the reserved memory node to be associated
			with the remoteproc device. The reserved memory node
			should be a CMA memory node, and should be defined as
			per the bindings,
			Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt

- mbox-names:		Optional names for the OMAP mailbox specifiers mentioned
			in the 'mboxes' property, one per specifier value

- timers:		One or more phandles to OMAP DMTimer nodes, that serve
			as System/Tick timers for the OS running on the remote
			processors. This will usually be a single timer if the
			processor sub-system is running in SMP mode, or one per
			core in the processor sub-system.

			This property is mandatory on remote processors requiring
			external tick wakeup, and to support Power Management
			features. The timers to be used should match with the
			timers used in the firmware image.

- watchdog-timers:	One or more phandles to OMAP DMTimer nodes, used to
			serve as Watchdog timers for the processor cores. This
			will usually be one per executing processor core, even
			if the processor sub-system is running a SMP OS.

			The timers to be used should match with the watchdog
			timers used in the firmware image.

- ti,rproc-standby-info: Standby data for the remote processor. This is
			 mandatory to support Power Management for the OMAP
			 remoteprocs, and should contain the address containing
			 the module standby status.

Example:
--------

/* OMAP4 DSP node in SoC DTS file */
ocp {
	dsp: dsp {
		compatible = "ti,omap4-dsp";
		ti,hwmods = "dsp";
		syscon-bootreg = <&scm_conf 0x304>;
		iommus = <&mmu_dsp>;
		mboxes = <&mailbox &mbox_dsp>;
		ti,rproc-standby-info = <0x4a004420>;
		status = "disabled";
	};
};

/* OMAP4 DSP node additional fields in a Board DTS file */
&dsp {
	status = "okay";
	memory-region = <&dsp_cma_pool>;
	timers = <&timer5>;
	watchdog-timers = <&timer6>;
};