1/* SPDX-License-Identifier: MIT */
 2/*
 3 * Copyright © 2014-2021 Intel Corporation
 4 */
 5
 6#ifndef _ABI_GUC_COMMUNICATION_MMIO_ABI_H
 7#define _ABI_GUC_COMMUNICATION_MMIO_ABI_H
 8
 9/**
10 * DOC: GuC MMIO based communication
11 *
12 * The MMIO based communication between Host and GuC relies on special
13 * hardware registers which format could be defined by the software
14 * (so called scratch registers).
15 *
16 * Each MMIO based message, both Host to GuC (H2G) and GuC to Host (G2H)
17 * messages, which maximum length depends on number of available scratch
18 * registers, is directly written into those scratch registers.
19 *
20 * For Gen9+, there are 16 software scratch registers 0xC180-0xC1B8,
21 * but no H2G command takes more than 4 parameters and the GuC firmware
22 * itself uses an 4-element array to store the H2G message.
23 *
24 * For Gen11+, there are additional 4 registers 0x190240-0x19024C, which
25 * are, regardless on lower count, preferred over legacy ones.
26 *
27 * The MMIO based communication is mainly used during driver initialization
28 * phase to setup the `CTB based communication`_ that will be used afterwards.
29 */
30
31#define GUC_MAX_MMIO_MSG_LEN		4
32
33/**
34 * DOC: MMIO HXG Message
35 *
36 * Format of the MMIO messages follows definitions of `HXG Message`_.
37 *
38 *  +---+-------+--------------------------------------------------------------+
39 *  |   | Bits  | Description                                                  |
40 *  +===+=======+==============================================================+
41 *  | 0 |  31:0 |                                                              |
42 *  +---+-------+                                                              |
43 *  |...|       | [Embedded `HXG Message`_]                                    |
44 *  +---+-------+                                                              |
45 *  | n |  31:0 |                                                              |
46 *  +---+-------+--------------------------------------------------------------+
47 */
48
49#endif