1// SPDX-License-Identifier: GPL-2.0
2/*
3 * I/O delay strategies for inb_p/outb_p
4 *
5 * Allow for a DMI based override of port 0x80, needed for certain HP laptops
6 * and possibly other systems. Also allow for the gradual elimination of
7 * outb_p/inb_p API uses.
8 */
9#include <linux/kernel.h>
10#include <linux/export.h>
11#include <linux/delay.h>
12#include <linux/init.h>
13#include <linux/dmi.h>
14#include <linux/io.h>
15
16#define IO_DELAY_TYPE_0X80 0
17#define IO_DELAY_TYPE_0XED 1
18#define IO_DELAY_TYPE_UDELAY 2
19#define IO_DELAY_TYPE_NONE 3
20
21#if defined(CONFIG_IO_DELAY_0X80)
22#define DEFAULT_IO_DELAY_TYPE IO_DELAY_TYPE_0X80
23#elif defined(CONFIG_IO_DELAY_0XED)
24#define DEFAULT_IO_DELAY_TYPE IO_DELAY_TYPE_0XED
25#elif defined(CONFIG_IO_DELAY_UDELAY)
26#define DEFAULT_IO_DELAY_TYPE IO_DELAY_TYPE_UDELAY
27#elif defined(CONFIG_IO_DELAY_NONE)
28#define DEFAULT_IO_DELAY_TYPE IO_DELAY_TYPE_NONE
29#endif
30
31int io_delay_type __read_mostly = DEFAULT_IO_DELAY_TYPE;
32
33static int __initdata io_delay_override;
34
35/*
36 * Paravirt wants native_io_delay to be a constant.
37 */
38void native_io_delay(void)
39{
40 switch (io_delay_type) {
41 default:
42 case IO_DELAY_TYPE_0X80:
43 asm volatile ("outb %al, $0x80");
44 break;
45 case IO_DELAY_TYPE_0XED:
46 asm volatile ("outb %al, $0xed");
47 break;
48 case IO_DELAY_TYPE_UDELAY:
49 /*
50 * 2 usecs is an upper-bound for the outb delay but
51 * note that udelay doesn't have the bus-level
52 * side-effects that outb does, nor does udelay() have
53 * precise timings during very early bootup (the delays
54 * are shorter until calibrated):
55 */
56 udelay(usec: 2);
57 break;
58 case IO_DELAY_TYPE_NONE:
59 break;
60 }
61}
62EXPORT_SYMBOL(native_io_delay);
63
64static int __init dmi_io_delay_0xed_port(const struct dmi_system_id *id)
65{
66 if (io_delay_type == IO_DELAY_TYPE_0X80) {
67 pr_notice("%s: using 0xed I/O delay port\n", id->ident);
68 io_delay_type = IO_DELAY_TYPE_0XED;
69 }
70
71 return 0;
72}
73
74/*
75 * Quirk table for systems that misbehave (lock up, etc.) if port
76 * 0x80 is used:
77 */
78static const struct dmi_system_id io_delay_0xed_port_dmi_table[] __initconst = {
79 {
80 .callback = dmi_io_delay_0xed_port,
81 .ident = "Compaq Presario V6000",
82 .matches = {
83 DMI_MATCH(DMI_BOARD_VENDOR, "Quanta"),
84 DMI_MATCH(DMI_BOARD_NAME, "30B7")
85 }
86 },
87 {
88 .callback = dmi_io_delay_0xed_port,
89 .ident = "HP Pavilion dv9000z",
90 .matches = {
91 DMI_MATCH(DMI_BOARD_VENDOR, "Quanta"),
92 DMI_MATCH(DMI_BOARD_NAME, "30B9")
93 }
94 },
95 {
96 .callback = dmi_io_delay_0xed_port,
97 .ident = "HP Pavilion dv6000",
98 .matches = {
99 DMI_MATCH(DMI_BOARD_VENDOR, "Quanta"),
100 DMI_MATCH(DMI_BOARD_NAME, "30B8")
101 }
102 },
103 {
104 .callback = dmi_io_delay_0xed_port,
105 .ident = "HP Pavilion tx1000",
106 .matches = {
107 DMI_MATCH(DMI_BOARD_VENDOR, "Quanta"),
108 DMI_MATCH(DMI_BOARD_NAME, "30BF")
109 }
110 },
111 {
112 .callback = dmi_io_delay_0xed_port,
113 .ident = "Presario F700",
114 .matches = {
115 DMI_MATCH(DMI_BOARD_VENDOR, "Quanta"),
116 DMI_MATCH(DMI_BOARD_NAME, "30D3")
117 }
118 },
119 { }
120};
121
122void __init io_delay_init(void)
123{
124 if (!io_delay_override)
125 dmi_check_system(list: io_delay_0xed_port_dmi_table);
126}
127
128static int __init io_delay_param(char *s)
129{
130 if (!s)
131 return -EINVAL;
132
133 if (!strcmp(s, "0x80"))
134 io_delay_type = IO_DELAY_TYPE_0X80;
135 else if (!strcmp(s, "0xed"))
136 io_delay_type = IO_DELAY_TYPE_0XED;
137 else if (!strcmp(s, "udelay"))
138 io_delay_type = IO_DELAY_TYPE_UDELAY;
139 else if (!strcmp(s, "none"))
140 io_delay_type = IO_DELAY_TYPE_NONE;
141 else
142 return -EINVAL;
143
144 io_delay_override = 1;
145 return 0;
146}
147
148early_param("io_delay", io_delay_param);
149