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OMAP2+ Mailbox Driver
=====================
The OMAP mailbox hardware facilitates communication between different processors
using a queued mailbox interrupt mechanism. The IP block is external to the
various processor subsystems and is connected on an interconnect bus. The
communication is achieved through a set of registers for message storage and
interrupt configuration registers.
Each mailbox IP block has a certain number of h/w fifo queues and output
interrupt lines. An output interrupt line is routed to an interrupt controller
within a processor subsystem, and there can be more than one line going to a
specific processor's interrupt controller. The interrupt line connections are
fixed for an instance and are dictated by the IP integration into the SoC
(excluding the SoCs that have a Interrupt Crossbar IP). Each interrupt line is
programmable through a set of interrupt configuration registers, and have a rx
and tx interrupt source per h/w fifo. Communication between different processors
is achieved through the appropriate programming of the rx and tx interrupt
sources on the appropriate interrupt lines.
The number of h/w fifo queues and interrupt lines dictate the usable registers.
All the current OMAP SoCs except for the newest DRA7xx SoC has a single IP
instance. DRA7xx has multiple instances with different number of h/w fifo queues
and interrupt lines between different instances. The interrupt lines can also be
routed to different processor sub-systems on DRA7xx as they are routed through
the Crossbar, a kind of interrupt router/multiplexer.
Mailbox Device Node:
====================
A Mailbox device node is used to represent a Mailbox IP instance within a SoC.
The sub-mailboxes are represented as child nodes of this parent node.
Required properties:
--------------------
- compatible: Should be one of the following,
"ti,omap2-mailbox" for OMAP2420, OMAP2430 SoCs
"ti,omap3-mailbox" for OMAP3430, OMAP3630 SoCs
"ti,omap4-mailbox" for OMAP44xx, OMAP54xx, AM33xx,
AM43xx and DRA7xx SoCs
- reg: Contains the mailbox register address range (base
address and length)
- interrupts: Contains the interrupt information for the mailbox
device. The format is dependent on which interrupt
controller the OMAP device uses
- ti,hwmods: Name of the hwmod associated with the mailbox
- #mbox-cells: Common mailbox binding property to identify the number
of cells required for the mailbox specifier. Should be
1
- ti,mbox-num-users: Number of targets (processor devices) that the mailbox
device can interrupt
- ti,mbox-num-fifos: Number of h/w fifo queues within the mailbox IP block
Child Nodes:
============
A child node is used for representing the actual sub-mailbox device that is
used for the communication between the host processor and a remote processor.
Each child node should have a unique node name across all the different
mailbox device nodes.
Required properties:
--------------------
- ti,mbox-tx: sub-mailbox descriptor property defining a Tx fifo
- ti,mbox-rx: sub-mailbox descriptor property defining a Rx fifo
Sub-mailbox Descriptor Data
---------------------------
Each of the above ti,mbox-tx and ti,mbox-rx properties should have 3 cells of
data that represent the following:
Cell #1 (fifo_id) - mailbox fifo id used either for transmitting
(ti,mbox-tx) or for receiving (ti,mbox-rx)
Cell #2 (irq_id) - irq identifier index number to use from the parent's
interrupts data. Should be 0 for most of the cases, a
positive index value is seen only on mailboxes that have
multiple interrupt lines connected to the MPU processor.
Cell #3 (usr_id) - mailbox user id for identifying the interrupt line
associated with generating a tx/rx fifo interrupt.
Mailbox Users:
==============
A device needing to communicate with a target processor device should specify
them using the common mailbox binding properties, "mboxes" and the optional
"mbox-names" (please see Documentation/devicetree/bindings/mailbox/mailbox.txt
for details). Each value of the mboxes property should contain a phandle to the
mailbox controller device node and an args specifier that will be the phandle to
the intended sub-mailbox child node to be used for communication. The equivalent
"mbox-names" property value can be used to give a name to the communication channel
to be used by the client user.
Example:
--------
/* OMAP4 */
mailbox: mailbox@4a0f4000 {
compatible = "ti,omap4-mailbox";
reg = <0x4a0f4000 0x200>;
interrupts = <GIC_SPI 26 IRQ_TYPE_LEVEL_HIGH>;
ti,hwmods = "mailbox";
#mbox-cells = <1>;
ti,mbox-num-users = <3>;
ti,mbox-num-fifos = <8>;
mbox_ipu: mbox_ipu {
ti,mbox-tx = <0 0 0>;
ti,mbox-rx = <1 0 0>;
};
mbox_dsp: mbox_dsp {
ti,mbox-tx = <3 0 0>;
ti,mbox-rx = <2 0 0>;
};
};
dsp {
...
mboxes = <&mailbox &mbox_dsp>;
...
};
/* AM33xx */
mailbox: mailbox@480C8000 {
compatible = "ti,omap4-mailbox";
reg = <0x480C8000 0x200>;
interrupts = <77>;
ti,hwmods = "mailbox";
#mbox-cells = <1>;
ti,mbox-num-users = <4>;
ti,mbox-num-fifos = <8>;
mbox_wkupm3: wkup_m3 {
ti,mbox-tx = <0 0 0>;
ti,mbox-rx = <0 0 3>;
};
};
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