xref: /openbmc/linux/arch/x86/kernel/cpu/mtrr/centaur.c (revision 08611a3a)
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 
10 static struct {
11 	unsigned long high;
12 	unsigned long low;
13 } centaur_mcr[8];
14 
15 static u8 centaur_mcr_reserved;
16 static 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  */
26 static int
centaur_get_free_region(unsigned long base,unsigned long size,int replace_reg)27 centaur_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 
48 static void
centaur_get_mcr(unsigned int reg,unsigned long * base,unsigned long * size,mtrr_type * type)49 centaur_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 
64 static void
centaur_set_mcr(unsigned int reg,unsigned long base,unsigned long size,mtrr_type type)65 centaur_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 
90 static int
centaur_validate_add_page(unsigned long base,unsigned long size,unsigned int type)91 centaur_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 
105 const 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