1// SPDX-License-Identifier: GPL-2.0
2#include <linux/init.h>
3#include <linux/mm.h>
4
5#include <asm/mtrr.h>
6#include <asm/msr.h>
7
8#include "mtrr.h"
9
10static struct {
11 unsigned long high;
12 unsigned long low;
13} centaur_mcr[8];
14
15static u8 centaur_mcr_reserved;
16static u8 centaur_mcr_type; /* 0 for winchip, 1 for winchip2 */
17
18/**
19 * centaur_get_free_region - Get a free MTRR.
20 *
21 * @base: The starting (base) address of the region.
22 * @size: The size (in bytes) of the region.
23 *
24 * Returns: the index of the region on success, else -1 on error.
25 */
26static int
27centaur_get_free_region(unsigned long base, unsigned long size, int replace_reg)
28{
29 unsigned long lbase, lsize;
30 mtrr_type ltype;
31 int i, max;
32
33 max = num_var_ranges;
34 if (replace_reg >= 0 && replace_reg < max)
35 return replace_reg;
36
37 for (i = 0; i < max; ++i) {
38 if (centaur_mcr_reserved & (1 << i))
39 continue;
40 mtrr_if->get(i, &lbase, &lsize, &ltype);
41 if (lsize == 0)
42 return i;
43 }
44
45 return -ENOSPC;
46}
47
48static void
49centaur_get_mcr(unsigned int reg, unsigned long *base,
50 unsigned long *size, mtrr_type * type)
51{
52 *base = centaur_mcr[reg].high >> PAGE_SHIFT;
53 *size = -(centaur_mcr[reg].low & 0xfffff000) >> PAGE_SHIFT;
54 *type = MTRR_TYPE_WRCOMB; /* write-combining */
55
56 if (centaur_mcr_type == 1 && ((centaur_mcr[reg].low & 31) & 2))
57 *type = MTRR_TYPE_UNCACHABLE;
58 if (centaur_mcr_type == 1 && (centaur_mcr[reg].low & 31) == 25)
59 *type = MTRR_TYPE_WRBACK;
60 if (centaur_mcr_type == 0 && (centaur_mcr[reg].low & 31) == 31)
61 *type = MTRR_TYPE_WRBACK;
62}
63
64static void
65centaur_set_mcr(unsigned int reg, unsigned long base,
66 unsigned long size, mtrr_type type)
67{
68 unsigned long low, high;
69
70 if (size == 0) {
71 /* Disable */
72 high = low = 0;
73 } else {
74 high = base << PAGE_SHIFT;
75 if (centaur_mcr_type == 0) {
76 /* Only support write-combining... */
77 low = -size << PAGE_SHIFT | 0x1f;
78 } else {
79 if (type == MTRR_TYPE_UNCACHABLE)
80 low = -size << PAGE_SHIFT | 0x02; /* NC */
81 else
82 low = -size << PAGE_SHIFT | 0x09; /* WWO, WC */
83 }
84 }
85 centaur_mcr[reg].high = high;
86 centaur_mcr[reg].low = low;
87 wrmsr(MSR_IDT_MCR0 + reg, low, high);
88}
89
90static int
91centaur_validate_add_page(unsigned long base, unsigned long size, unsigned int type)
92{
93 /*
94 * FIXME: Winchip2 supports uncached
95 */
96 if (type != MTRR_TYPE_WRCOMB &&
97 (centaur_mcr_type == 0 || type != MTRR_TYPE_UNCACHABLE)) {
98 pr_warn("mtrr: only write-combining%s supported\n",
99 centaur_mcr_type ? " and uncacheable are" : " is");
100 return -EINVAL;
101 }
102 return 0;
103}
104
105const struct mtrr_ops centaur_mtrr_ops = {
106 .var_regs = 8,
107 .set = centaur_set_mcr,
108 .get = centaur_get_mcr,
109 .get_free_region = centaur_get_free_region,
110 .validate_add_page = centaur_validate_add_page,
111 .have_wrcomb = positive_have_wrcomb,
112};
113

source code of linux/arch/x86/kernel/cpu/mtrr/centaur.c