1NVIDIA Tegra Hardware Synchronization Primitives (HSP)
2
3The HSP modules are used for the processors to share resources and communicate
4together. It provides a set of hardware synchronization primitives for
5interprocessor communication. So the interprocessor communication (IPC)
6protocols can use hardware synchronization primitives, when operating between
7two processors not in an SMP relationship.
8
9The features that HSP supported are shared mailboxes, shared semaphores,
10arbitrated semaphores and doorbells.
11
12Required properties:
13- name : Should be hsp
14- compatible
15    Array of strings.
16    one of:
17    - "nvidia,tegra186-hsp"
18    - "nvidia,tegra194-hsp", "nvidia,tegra186-hsp"
19- reg : Offset and length of the register set for the device.
20- interrupt-names
21    Array of strings.
22    Contains a list of names for the interrupts described by the interrupt
23    property. May contain the following entries, in any order:
24    - "doorbell"
25    - "sharedN", where 'N' is a number from zero up to the number of
26      external interrupts supported by the HSP instance minus one.
27    Users of this binding MUST look up entries in the interrupt property
28    by name, using this interrupt-names property to do so.
29- interrupts
30    Array of interrupt specifiers.
31    Must contain one entry per entry in the interrupt-names property,
32    in a matching order.
33- #mbox-cells : Should be 2.
34
35The mbox specifier of the "mboxes" property in the client node should contain
36two cells. The first cell determines the HSP type and the second cell is used
37to identify the mailbox that the client is going to use.
38
39For doorbells, the second cell specifies the index of the doorbell to use.
40
41For shared mailboxes, the second cell is composed of two fields:
42- bits 31..24:
43    A bit mask of flags that further specify how the shared mailbox will be
44    used. Valid flags are:
45    - bit 31:
46        Defines the direction of the mailbox. If set, the mailbox will be used
47        as a producer (i.e. used to send data). If cleared, the mailbox is the
48        consumer of data sent by a producer.
49
50- bits 23.. 0:
51    The index of the shared mailbox to use. The number of available mailboxes
52    may vary by instance of the HSP block and SoC generation.
53
54The following file contains definitions that can be used to construct mailbox
55specifiers:
56
57    <dt-bindings/mailbox/tegra186-hsp.h>
58
59Example:
60
61hsp_top0: hsp@3c00000 {
62	compatible = "nvidia,tegra186-hsp";
63	reg = <0x0 0x03c00000 0x0 0xa0000>;
64	interrupts = <GIC_SPI 176 IRQ_TYPE_LEVEL_HIGH>;
65	interrupt-names = "doorbell";
66	#mbox-cells = <2>;
67};
68
69client {
70	...
71	mboxes = <&hsp_top0 TEGRA_HSP_MBOX_TYPE_DB TEGRA_HSP_DB_MASTER_XXX>;
72};
73