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 /* _ABI_GUC_COMMUNICATION_MMIO_ABI_H */
50