1/*	$NetBSD: apei_reg.c,v 1.3 2024/03/22 20:48:14 riastradh Exp $	*/
2
3/*-
4 * Copyright (c) 2024 The NetBSD Foundation, Inc.
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 *    notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 *    notice, this list of conditions and the following disclaimer in the
14 *    documentation and/or other materials provided with the distribution.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
17 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
18 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
19 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
20 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
21 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
22 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
23 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
24 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
25 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
26 * POSSIBILITY OF SUCH DAMAGE.
27 */
28
29/*
30 * APEI register access for ERST/EINJ action instructions
31 */
32
33#include <sys/cdefs.h>
34__KERNEL_RCSID(0, "$NetBSD: apei_reg.c,v 1.3 2024/03/22 20:48:14 riastradh Exp $");
35
36#include <sys/types.h>
37
38#include <dev/acpi/acpivar.h>
39#include <dev/acpi/apei_mapreg.h>
40#include <dev/acpi/apei_reg.h>
41
42/*
43 * apei_read_register(Register, map, Mask, &X)
44 *
45 *	Read from Register mapped at map, shifted out of position and
46 *	then masked with Mask, and return the result.
47 *
48 *	https://uefi.org/specs/ACPI/6.5/18_Platform_Error_Interfaces.html#read-register
49 *
50 *	(I'm guessing this applies to both ERST and EINJ, even though
51 *	that section is under the ERST part.)
52 */
53uint64_t
54apei_read_register(ACPI_GENERIC_ADDRESS *Register, struct apei_mapreg *map,
55    uint64_t Mask)
56{
57	const uint8_t BitOffset = Register->BitOffset;
58	uint64_t X;
59
60	X = apei_mapreg_read(Register, map);
61	X >>= BitOffset;
62	X &= Mask;
63
64	return X;
65}
66
67/*
68 * apei_write_register(Register, map, Mask, preserve_register, X)
69 *
70 *	Write X, masked with Mask and shifted into position, to
71 *	Register, mapped at map, preserving other bits if
72 *	preserve_register is true.
73 *
74 *	https://uefi.org/specs/ACPI/6.5/18_Platform_Error_Interfaces.html#write-register
75 *
76 *	Note: The Preserve Register semantics is based on the clearer
77 *	indentation at
78 *	https://uefi.org/sites/default/files/resources/ACPI_5_1release.pdf#page=714
79 *	which has been lost in more recent versions of the spec.
80 */
81void
82apei_write_register(ACPI_GENERIC_ADDRESS *Register, struct apei_mapreg *map,
83    uint64_t Mask, bool preserve_register, uint64_t X)
84{
85	const uint8_t BitOffset = Register->BitOffset;
86
87	X &= Mask;
88	X <<= BitOffset;
89	if (preserve_register) {
90		uint64_t Y;
91
92		Y = apei_mapreg_read(Register, map);
93		Y &= ~(Mask << BitOffset);
94		X |= Y;
95	}
96	apei_mapreg_write(Register, map, X);
97}
98