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- /*
- * Copyright (C) 2008 Michael Brown <mbrown@fensystems.co.uk>.
- *
- * This program is free software; you can redistribute it and/or
- * modify it under the terms of the GNU General Public License as
- * published by the Free Software Foundation; either version 2 of the
- * License, or any later version.
- *
- * This program is distributed in the hope that it will be useful, but
- * WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- * General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
- * 02110-1301, USA.
- *
- * You can also choose to distribute this program under the terms of
- * the Unmodified Binary Distribution Licence (as given in the file
- * COPYING.UBDL), provided that you have satisfied its requirements.
- */
-
- FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
-
- #include <string.h>
- #include <errno.h>
- #include <unistd.h>
- #include <ipxe/timer.h>
- #include <ipxe/init.h>
- #include <ipxe/efi/efi.h>
-
- /** @file
- *
- * iPXE timer API for EFI
- *
- */
-
- /**
- * Number of jiffies per second
- *
- * This is a policy decision.
- */
- #define EFI_JIFFIES_PER_SEC 32
-
- /** Current tick count */
- static unsigned long efi_jiffies;
-
- /** Timer tick event */
- static EFI_EVENT efi_tick_event;
-
- /** Colour for debug messages */
- #define colour &efi_jiffies
-
- /**
- * Delay for a fixed number of microseconds
- *
- * @v usecs Number of microseconds for which to delay
- */
- static void efi_udelay ( unsigned long usecs ) {
- EFI_BOOT_SERVICES *bs = efi_systab->BootServices;
- EFI_STATUS efirc;
- int rc;
-
- if ( ( efirc = bs->Stall ( usecs ) ) != 0 ) {
- rc = -EEFI ( efirc );
- DBGC ( colour, "EFI could not delay for %ldus: %s\n",
- usecs, strerror ( rc ) );
- /* Probably screwed */
- }
- }
-
- /**
- * Get current system time in ticks
- *
- * @ret ticks Current time, in ticks
- */
- static unsigned long efi_currticks ( void ) {
- EFI_BOOT_SERVICES *bs = efi_systab->BootServices;
-
- /* UEFI manages to ingeniously combine the worst aspects of
- * both polling and interrupt-driven designs. There is no way
- * to support proper interrupt-driven operation, since there
- * is no way to hook in an interrupt service routine. A
- * mockery of interrupts is provided by UEFI timers, which
- * trigger at a preset rate and can fire at any time.
- *
- * We therefore have all of the downsides of a polling design
- * (inefficiency and inability to sleep until something
- * interesting happens) combined with all of the downsides of
- * an interrupt-driven design (the complexity of code that
- * could be preempted at any time).
- *
- * The UEFI specification expects us to litter the entire
- * codebase with calls to RaiseTPL() as needed for sections of
- * code that are not reentrant. Since this doesn't actually
- * gain us any substantive benefits (since even with such
- * calls we would still be suffering from the limitations of a
- * polling design), we instead choose to run at TPL_CALLBACK
- * almost all of the time, dropping to TPL_APPLICATION to
- * allow timer ticks to occur.
- *
- *
- * For added excitement, UEFI provides no clean way for device
- * drivers to shut down in preparation for handover to a
- * booted operating system. The platform firmware simply
- * doesn't bother to call the drivers' Stop() methods.
- * Instead, all non-trivial drivers must register an
- * EVT_SIGNAL_EXIT_BOOT_SERVICES event to be signalled when
- * ExitBootServices() is called, and clean up without any
- * reference to the EFI driver model.
- *
- * Unfortunately, all timers silently stop working when
- * ExitBootServices() is called. Even more unfortunately, and
- * for no discernible reason, this happens before any
- * EVT_SIGNAL_EXIT_BOOT_SERVICES events are signalled. The
- * net effect of this entertaining design choice is that any
- * timeout loops on the shutdown path (e.g. for gracefully
- * closing outstanding TCP connections) may wait indefinitely.
- *
- * There is no way to report failure from currticks(), since
- * the API lazily assumes that the host system continues to
- * travel through time in the usual direction. Work around
- * EFI's violation of this assumption by falling back to a
- * simple free-running monotonic counter during shutdown.
- */
- if ( efi_shutdown_in_progress ) {
- efi_jiffies++;
- } else {
- bs->RestoreTPL ( TPL_APPLICATION );
- bs->RaiseTPL ( TPL_CALLBACK );
- }
-
- return ( efi_jiffies * ( TICKS_PER_SEC / EFI_JIFFIES_PER_SEC ) );
- }
-
- /**
- * Timer tick
- *
- * @v event Timer tick event
- * @v context Event context
- */
- static EFIAPI void efi_tick ( EFI_EVENT event __unused,
- void *context __unused ) {
-
- /* Increment tick count */
- efi_jiffies++;
- }
-
- /**
- * 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;
- }
-
- /* Start timer tick */
- if ( ( efirc = bs->SetTimer ( efi_tick_event, TimerPeriodic,
- ( 10000000 / EFI_JIFFIES_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_JIFFIES_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;
- EFI_STATUS efirc;
- int rc;
-
- /* Stop timer tick */
- if ( ( efirc = bs->SetTimer ( efi_tick_event, TimerCancel, 0 ) ) != 0 ){
- rc = -EEFI ( efirc );
- DBGC ( colour, "EFI could not stop timer tick: %s\n",
- strerror ( rc ) );
- /* Self-destruct initiated */
- return;
- }
- DBGC ( colour, "EFI timer stopped\n" );
-
- /* Destroy timer tick event */
- if ( ( efirc = bs->CloseEvent ( efi_tick_event ) ) != 0 ) {
- rc = -EEFI ( efirc );
- DBGC ( colour, "EFI could not destroy timer tick: %s\n",
- strerror ( rc ) );
- /* Probably non-fatal */
- return;
- }
- }
-
- /** Timer tick startup function */
- struct startup_fn efi_tick_startup_fn __startup_fn ( STARTUP_EARLY ) = {
- .name = "efi_tick",
- .startup = efi_tick_startup,
- .shutdown = efi_tick_shutdown,
- };
-
- /** EFI timer */
- struct timer efi_timer __timer ( TIMER_NORMAL ) = {
- .name = "efi",
- .currticks = efi_currticks,
- .udelay = efi_udelay,
- };
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