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[efi] Use a timer event to generate the currticks() timer

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We currently use the EFI_CPU_ARCH_PROTOCOL's GetTimerValue() method to
generate the currticks() timer, calibrated against a 1ms delay from
the boot services Stall() method.

This does not work on ARM platforms, where GetTimerValue() is an empty
stub which just returns EFI_UNSUPPORTED.

Fix by instead creating a periodic timer event, and using this event
to increment a current tick counter.

Signed-off-by: Michael Brown <mcb30@ipxe.org>
This commit is contained in:
Michael Brown
2016-05-04 13:04:33 +01:00
parent 1e066431a4
commit 757ab98381
3 changed files with 88 additions and 354 deletions
Download Patch File Download Diff File Expand all files Collapse all files

122
src/interface/efi/efi_timer.c
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@@ -25,12 +25,10 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
#include <string.h>
#include <errno.h>
#include <limits.h>
#include <assert.h>
#include <unistd.h>
#include <ipxe/timer.h>
#include <ipxe/init.h>
#include <ipxe/efi/efi.h>
#include <ipxe/efi/Protocol/Cpu.h>
/** @file
*
@@ -38,19 +36,14 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
*
*/
/** 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.
*/
#define EFI_TIMER0_SHIFT 12
/** Current tick count */
static unsigned long efi_jiffies;
/** Calibration time */
#define EFI_CALIBRATE_DELAY_MS 1
/** Timer tick event */
static EFI_EVENT efi_tick_event;
/** CPU protocol */
static EFI_CPU_ARCH_PROTOCOL *cpu_arch;
EFI_REQUIRE_PROTOCOL ( EFI_CPU_ARCH_PROTOCOL, &cpu_arch );
/** Colour for debug messages */
#define colour &efi_jiffies
/**
* Delay for a fixed number of microseconds
@@ -64,8 +57,8 @@ static void efi_udelay ( unsigned long usecs ) {
if ( ( efirc = bs->Stall ( usecs ) ) != 0 ) {
rc = -EEFI ( efirc );
DBG ( "EFI could not delay for %ldus: %s\n",
usecs, strerror ( rc ) );
DBGC ( colour, "EFI could not delay for %ldus: %s\n",
usecs, strerror ( rc ) );
/* Probably screwed */
}
}
@@ -76,53 +69,78 @@ static void efi_udelay ( unsigned long usecs ) {
* @ret ticks Current time, in ticks
*/
static unsigned long efi_currticks ( void ) {
UINT64 time;
EFI_STATUS efirc;
int rc;
/* Read CPU timer 0 (TSC) */
if ( ( efirc = cpu_arch->GetTimerValue ( cpu_arch, 0, &time,
NULL ) ) != 0 ) {
rc = -EEFI ( efirc );
DBG ( "EFI could not read CPU timer: %s\n", strerror ( rc ) );
/* Probably screwed */
return -1UL;
}
return ( time >> EFI_TIMER0_SHIFT );
return efi_jiffies;
}
/**
* Get number of ticks per second
* Timer tick
*
* @ret ticks_per_sec Number of ticks per second
* @v event Timer tick event
* @v context Event context
*/
static unsigned long efi_ticks_per_sec ( void ) {
static unsigned long ticks_per_sec = 0;
static EFIAPI void efi_tick ( EFI_EVENT event __unused,
void *context __unused ) {
/* 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;
/* Increment tick count */
efi_jiffies++;
}
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 );
/**
* Start timer tick
*
*/
static void efi_tick_startup ( void ) {
EFI_BOOT_SERVICES *bs = efi_systab->BootServices;
EFI_STATUS efirc;
int rc;
/* Create timer tick event */
if ( ( efirc = bs->CreateEvent ( ( EVT_TIMER | EVT_NOTIFY_SIGNAL ),
TPL_CALLBACK, efi_tick, NULL,
&efi_tick_event ) ) != 0 ) {
rc = -EEFI ( efirc );
DBGC ( colour, "EFI could not create timer tick: %s\n",
strerror ( rc ) );
/* Nothing we can do about it */
return;
}
return ticks_per_sec;
/* Start timer tick */
if ( ( efirc = bs->SetTimer ( efi_tick_event, TimerPeriodic,
( 10000000 / EFI_TICKS_PER_SEC ) ) ) !=0){
rc = -EEFI ( efirc );
DBGC ( colour, "EFI could not start timer tick: %s\n",
strerror ( rc ) );
/* Nothing we can do about it */
return;
}
DBGC ( colour, "EFI timer started at %d ticks per second\n",
EFI_TICKS_PER_SEC );
}
/**
* Stop timer tick
*
* @v booting System is shutting down in order to boot
*/
static void efi_tick_shutdown ( int booting __unused ) {
EFI_BOOT_SERVICES *bs = efi_systab->BootServices;
/* Stop timer tick */
bs->SetTimer ( efi_tick_event, TimerCancel, 0 );
DBGC ( colour, "EFI timer stopped\n" );
/* Destroy timer tick event */
bs->CloseEvent ( efi_tick_event );
}
/** Timer tick startup function */
struct startup_fn efi_tick_startup_fn __startup_fn ( STARTUP_EARLY ) = {
.startup = efi_tick_startup,
.shutdown = efi_tick_shutdown,
};
PROVIDE_TIMER ( efi, udelay, efi_udelay );
PROVIDE_TIMER ( efi, currticks, efi_currticks );
PROVIDE_TIMER ( efi, ticks_per_sec, efi_ticks_per_sec );
PROVIDE_TIMER_INLINE ( efi, ticks_per_sec );