1 FILE_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 30 enum { Disable_A20 = 0x2400, Enable_A20 = 0x2401, Query_A20_Status = 0x2402, 31 Query_A20_Support = 0x2403 }; 32 33 enum 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 */ 48 static 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 */ 66 static 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 */ 100 void 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 } 173 174 void gateA20_unset ( void ) { 175 /* Not currently implemented */ 176 } 177
