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android-review.linaro.org / platform / external / syslinux / refs/heads/oreo-m2-s5-release / . / gpxe / src / arch / i386 / firmware / pcbios / gateA20.c
blob: 1a71472dc2ebe115dee4fb6676494e343283b554 [file] [log] [blame]
Greg Hartman76d05dc2016-11-23 15:51:27 -0800[diff] [blame]1FILE_LICENCE ( GPL2_OR_LATER );
2
3#include <stdio.h>
4#include <realmode.h>
5#include <bios.h>
6#include <gpxe/io.h>
7#include <gpxe/timer.h>
8
9#define K_RDWR 0x60 /* keyboard data & cmds (read/write) */
10#define K_STATUS 0x64 /* keyboard status */
11#define K_CMD 0x64 /* keybd ctlr command (write-only) */
12
13#define K_OBUF_FUL 0x01 /* output buffer full */
14#define K_IBUF_FUL 0x02 /* input buffer full */
15
16#define KC_CMD_WIN 0xd0 /* read output port */
17#define KC_CMD_WOUT 0xd1 /* write output port */
18#define KC_CMD_NULL 0xff /* null command ("pulse nothing") */
19#define KB_SET_A20 0xdf /* enable A20,
20 enable output buffer full interrupt
21 enable data line
22 disable clock line */
23#define KB_UNSET_A20 0xdd /* enable A20,
24 enable output buffer full interrupt
25 enable data line
26 disable clock line */
27
28#define SCP_A 0x92 /* System Control Port A */
29
30enum { Disable_A20 = 0x2400, Enable_A20 = 0x2401, Query_A20_Status = 0x2402,
31 Query_A20_Support = 0x2403 };
32
33enum a20_methods {
34 A20_UNKNOWN = 0,
35 A20_INT15,
36 A20_KBC,
37 A20_SCPA,
38};
39
40#define A20_MAX_RETRIES 32
41#define A20_INT15_RETRIES 32
42#define A20_KBC_RETRIES (2^21)
43#define A20_SCPA_RETRIES (2^21)
44
45/**
46 * Drain keyboard controller
47 */
48static void empty_8042 ( void ) {
49 unsigned long time;
50
51 time = currticks() + TICKS_PER_SEC; /* max wait of 1 second */
52 while ( ( inb ( K_CMD ) & ( K_IBUF_FUL | K_OBUF_FUL ) ) &&
53 currticks() < time ) {
54 iodelay();
55 ( void ) inb_p ( K_RDWR );
56 iodelay();
57 }
58}
59
60/**
61 * Fast test to see if gate A20 is already set
62 *
63 * @v retries Number of times to retry before giving up
64 * @ret set Gate A20 is set
65 */
66static int gateA20_is_set ( int retries ) {
67 static uint32_t test_pattern = 0xdeadbeef;
68 physaddr_t test_pattern_phys = virt_to_phys ( &test_pattern );
69 physaddr_t verify_pattern_phys = ( test_pattern_phys ^ 0x100000 );
70 userptr_t verify_pattern_user = phys_to_user ( verify_pattern_phys );
71 uint32_t verify_pattern;
72
73 do {
74 /* Check for difference */
75 copy_from_user ( &verify_pattern, verify_pattern_user, 0,
76 sizeof ( verify_pattern ) );
77 if ( verify_pattern != test_pattern )
78 return 1;
79
80 /* Avoid false negatives */
81 test_pattern++;
82
83 iodelay();
84
85 /* Always retry at least once, to avoid false negatives */
86 } while ( retries-- >= 0 );
87
88 /* Pattern matched every time; gate A20 is not set */
89 return 0;
90}
91
92/*
93 * Gate A20 for high memory
94 *
95 * Note that this function gets called as part of the return path from
96 * librm's real_call, which is used to make the int15 call if librm is
97 * being used. To avoid an infinite recursion, we make gateA20_set
98 * return immediately if it is already part of the call stack.
99 */
100void gateA20_set ( void ) {
101 static char reentry_guard = 0;
102 static int a20_method = A20_UNKNOWN;
103 unsigned int discard_a;
104 unsigned int scp_a;
105 int retries = 0;
106
107 /* Avoid potential infinite recursion */
108 if ( reentry_guard )
109 return;
110 reentry_guard = 1;
111
112 /* Fast check to see if gate A20 is already enabled */
113 if ( gateA20_is_set ( 0 ) )
114 goto out;
115
116 for ( ; retries < A20_MAX_RETRIES ; retries++ ) {
117 switch ( a20_method ) {
118 case A20_UNKNOWN:
119 case A20_INT15:
120 /* Try INT 15 method */
121 __asm__ __volatile__ ( REAL_CODE ( "int $0x15" )
122 : "=a" ( discard_a )
123 : "a" ( Enable_A20 ) );
124 if ( gateA20_is_set ( A20_INT15_RETRIES ) ) {
125 DBG ( "Enabled gate A20 using BIOS\n" );
126 a20_method = A20_INT15;
127 goto out;
128 }
129 /* fall through */
130 case A20_KBC:
131 /* Try keyboard controller method */
132 empty_8042();
133 outb ( KC_CMD_WOUT, K_CMD );
134 empty_8042();
135 outb ( KB_SET_A20, K_RDWR );
136 empty_8042();
137 outb ( KC_CMD_NULL, K_CMD );
138 empty_8042();
139 if ( gateA20_is_set ( A20_KBC_RETRIES ) ) {
140 DBG ( "Enabled gate A20 using "
141 "keyboard controller\n" );
142 a20_method = A20_KBC;
143 goto out;
144 }
145 /* fall through */
146 case A20_SCPA:
147 /* Try "Fast gate A20" method */
148 scp_a = inb ( SCP_A );
149 scp_a &= ~0x01; /* Avoid triggering a reset */
150 scp_a |= 0x02; /* Enable A20 */
151 iodelay();
152 outb ( scp_a, SCP_A );
153 iodelay();
154 if ( gateA20_is_set ( A20_SCPA_RETRIES ) ) {
155 DBG ( "Enabled gate A20 using "
156 "Fast Gate A20\n" );
157 a20_method = A20_SCPA;
158 goto out;
159 }
160 }
161 }
162
163 /* Better to die now than corrupt memory later */
164 printf ( "FATAL: Gate A20 stuck\n" );
165 while ( 1 ) {}
166
167 out:
168 if ( retries )
169 DBG ( "%d attempts were required to enable A20\n",
170 ( retries + 1 ) );
171 reentry_guard = 0;
172}
173
174void gateA20_unset ( void ) {
175 /* Not currently implemented */
176}