sysadmin/ipxe
1
0
Fork 0
mirror of https://github.com/ipxe/ipxe synced 2025-12-28 18:42:53 +03:00
Code Issues Packages Projects Releases Wiki Activity

[time] Allow timer to be selected at runtime

Browse Source 
Allow the active timer (providing udelay() and currticks()) to be
selected at runtime based on probing during the INIT_EARLY stage of
initialisation.

TICKS_PER_SEC is now a fixed compile-time constant for all builds, and
is independent of the underlying clock tick rate.  We choose the value
1024 to allow multiplications and divisions on seconds to be converted
to bit shifts.

TICKS_PER_MS is defined as 1, allowing multiplications and divisions
on milliseconds to be omitted entirely.  The 2% inaccuracy in this
definition is negligible when using the standard BIOS timer (running
at around 18.2Hz).

TIMER_RDTSC now checks for a constant TSC before claiming to be a
usable timer.  (This timer can be tested in KVM via the command-line
option "-cpu host,+invtsc".)

Signed-off-by: Michael Brown <mcb30@ipxe.org>
This commit is contained in:
Michael Brown
2017-01-25 20:59:15 +00:00
parent d37e025b81
commit 302f1eeb80
24 changed files with 369 additions and 318 deletions
Download Patch File Download Diff File Expand all files Collapse all files

37
src/arch/x86/interface/pcbios/bios_timer.c
View File

@@ -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,
};