diff options
Diffstat (limited to 'src/arch/x86/interface/pcbios/bios_timer.c')
| -rw-r--r-- | src/arch/x86/interface/pcbios/bios_timer.c | 37 |
1 files changed, 28 insertions, 9 deletions
diff --git a/src/arch/x86/interface/pcbios/bios_timer.c b/src/arch/x86/interface/pcbios/bios_timer.c index 3299c9aa..49e1d226 100644 --- a/src/arch/x86/interface/pcbios/bios_timer.c +++ b/src/arch/x86/interface/pcbios/bios_timer.c @@ -32,6 +32,18 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL ); #include <ipxe/timer.h> #include <realmode.h> #include <bios.h> +#include <ipxe/pit8254.h> + +/** Number of ticks per day + * + * This seems to be the normative value, as used by e.g. SeaBIOS to + * decide when to set the midnight rollover flag. + */ +#define BIOS_TICKS_PER_DAY 0x1800b0 + +/** Number of ticks per BIOS tick */ +#define TICKS_PER_BIOS_TICK \ + ( ( TICKS_PER_SEC * 60 * 60 * 24 ) / BIOS_TICKS_PER_DAY ) /** * Get current system time in ticks @@ -43,7 +55,7 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL ); * of calling timeofday BIOS interrupt. */ static unsigned long bios_currticks ( void ) { - static int days = 0; + static uint32_t offset; uint32_t ticks; uint8_t midnight; @@ -53,18 +65,25 @@ static unsigned long bios_currticks ( void ) { "nop\n\t" "cli\n\t" ); - get_real ( ticks, BDA_SEG, 0x006c ); - get_real ( midnight, BDA_SEG, 0x0070 ); + /* Read current BIOS time of day */ + get_real ( ticks, BDA_SEG, BDA_TICKS ); + get_real ( midnight, BDA_SEG, BDA_MIDNIGHT ); + /* Handle midnight rollover */ if ( midnight ) { midnight = 0; - put_real ( midnight, BDA_SEG, 0x0070 ); - days += 0x1800b0; + put_real ( midnight, BDA_SEG, BDA_MIDNIGHT ); + offset += BIOS_TICKS_PER_DAY; } + ticks += offset; - return ( days + ticks ); + /* Convert to timer ticks */ + return ( ticks * TICKS_PER_BIOS_TICK ); } -PROVIDE_TIMER_INLINE ( pcbios, udelay ); -PROVIDE_TIMER ( pcbios, currticks, bios_currticks ); -PROVIDE_TIMER_INLINE ( pcbios, ticks_per_sec ); +/** BIOS timer */ +struct timer bios_timer __timer ( TIMER_NORMAL ) = { + .name = "bios", + .currticks = bios_currticks, + .udelay = pit8254_udelay, +}; |