efi_timer.c File Reference

gPXE timer API for EFI More...

#include <limits.h>
#include <assert.h>
#include <unistd.h>
#include <gpxe/timer.h>
#include <gpxe/efi/efi.h>
#include <gpxe/efi/Protocol/Cpu.h>

Go to the source code of this file.

Defines
#define	EFI_TIMER0_SHIFT   12
	Scale factor to apply to CPU timer 0.
#define	EFI_CALIBRATE_DELAY_MS   1
	Calibration time.
Functions
	FILE_LICENCE (GPL2_OR_LATER)
	EFI_REQUIRE_PROTOCOL (EFI_CPU_ARCH_PROTOCOL,&cpu_arch)
static void	efi_udelay (unsigned long usecs)
	Delay for a fixed number of microseconds.
static unsigned long	efi_currticks (void)
	Get current system time in ticks.
static unsigned long	efi_ticks_per_sec (void)
	Get number of ticks per second.
	PROVIDE_TIMER (efi, udelay, efi_udelay)
	PROVIDE_TIMER (efi, currticks, efi_currticks)
	PROVIDE_TIMER (efi, ticks_per_sec, efi_ticks_per_sec)
Variables
static EFI_CPU_ARCH_PROTOCOL *	cpu_arch
	CPU protocol.

---

Detailed Description

gPXE timer API for EFI

Definition in file efi_timer.c.

---

Define Documentation

#define EFI_TIMER0_SHIFT   12

Scale factor to apply to CPU timer 0.

The timer is scaled down in order to ensure that reasonable values for "number of ticks" don't exceed the size of an unsigned long.

Definition at line 39 of file efi_timer.c.

Referenced by efi_currticks().

#define EFI_CALIBRATE_DELAY_MS   1

Calibration time.

Definition at line 42 of file efi_timer.c.

Referenced by efi_ticks_per_sec().

---

Function Documentation

FILE_LICENCE

(

GPL2_OR_LATER

)

EFI_REQUIRE_PROTOCOL	(	EFI_CPU_ARCH_PROTOCOL	,
		&	cpu_arch
	)

static void efi_udelay

(

unsigned long

usecs

)

[static]

Delay for a fixed number of microseconds.

Parameters:

usecs

Number of microseconds for which to delay

Definition at line 53 of file efi_timer.c.

References _EFI_SYSTEM_TABLE::BootServices, DBG, efi_strerror(), efi_systab, and EFI_BOOT_SERVICES::Stall.

                                               {
        EFI_BOOT_SERVICES *bs = efi_systab->BootServices;
        EFI_STATUS efirc;

        if ( ( efirc = bs->Stall ( usecs ) ) != 0 ) {
                DBG ( "EFI could not delay for %ldus: %s\n",
                      usecs, efi_strerror ( efirc ) );
                /* Probably screwed */
        }
}

static unsigned long efi_currticks

(

void

)

[static]

Get current system time in ticks.

Return values:

ticks

Current time, in ticks

Definition at line 69 of file efi_timer.c.

References DBG, efi_strerror(), EFI_TIMER0_SHIFT, _EFI_CPU_ARCH_PROTOCOL::GetTimerValue, NULL, and time().

                                            {
        UINT64 time;
        EFI_STATUS efirc;

        /* Read CPU timer 0 (TSC) */
        if ( ( efirc = cpu_arch->GetTimerValue ( cpu_arch, 0, &time,
                                                 NULL ) ) != 0 ) {
                DBG ( "EFI could not read CPU timer: %s\n",
                      efi_strerror ( efirc ) );
                /* Probably screwed */
                return -1UL;
        }

        return ( time >> EFI_TIMER0_SHIFT );
}

static unsigned long efi_ticks_per_sec

(

void

)

[static]

Get number of ticks per second.

Return values:

ticks_per_sec

Number of ticks per second

Definition at line 90 of file efi_timer.c.

References currticks(), DBG, EFI_CALIBRATE_DELAY_MS, mdelay(), and ticks_per_sec().

                                                {
        static unsigned long ticks_per_sec = 0;

        /* Calibrate timer, if necessary.  EFI does nominally provide
         * the timer speed via the (optional) TimerPeriod parameter to
         * the GetTimerValue() call, but it gets the speed slightly
         * wrong.  By up to three orders of magnitude.  Not helpful.
         */
        if ( ! ticks_per_sec ) {
                unsigned long start;
                unsigned long elapsed;

                DBG ( "Calibrating EFI timer with a %d ms delay\n",
                      EFI_CALIBRATE_DELAY_MS );
                start = currticks();
                mdelay ( EFI_CALIBRATE_DELAY_MS );
                elapsed = ( currticks() - start );
                ticks_per_sec = ( elapsed * ( 1000 / EFI_CALIBRATE_DELAY_MS ));
                DBG ( "EFI CPU timer calibrated at %ld ticks in %d ms (%ld "
                      "ticks/sec)\n", elapsed, EFI_CALIBRATE_DELAY_MS,
                      ticks_per_sec );
        }

        return ticks_per_sec;
}

PROVIDE_TIMER	(	efi	,
		udelay	,
		efi_udelay
	)

PROVIDE_TIMER	(	efi	,
		currticks	,
		efi_currticks
	)

PROVIDE_TIMER	(	efi	,
		ticks_per_sec	,
		efi_ticks_per_sec
	)

---

Variable Documentation

EFI_CPU_ARCH_PROTOCOL* cpu_arch [static]

CPU protocol.

Definition at line 45 of file efi_timer.c.