iPXE
efix86_nap.c
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00001 /*
00002  * Copyright (C) 2008 Michael Brown <mbrown@fensystems.co.uk>.
00003  *
00004  * This program is free software; you can redistribute it and/or
00005  * modify it under the terms of the GNU General Public License as
00006  * published by the Free Software Foundation; either version 2 of the
00007  * License, or any later version.
00008  *
00009  * This program is distributed in the hope that it will be useful, but
00010  * WITHOUT ANY WARRANTY; without even the implied warranty of
00011  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00012  * General Public License for more details.
00013  *
00014  * You should have received a copy of the GNU General Public License
00015  * along with this program; if not, write to the Free Software
00016  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
00017  * 02110-1301, USA.
00018  *
00019  * You can also choose to distribute this program under the terms of
00020  * the Unmodified Binary Distribution Licence (as given in the file
00021  * COPYING.UBDL), provided that you have satisfied its requirements.
00022  */
00023 
00024 FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
00025 
00026 #include <ipxe/nap.h>
00027 #include <ipxe/efi/efi.h>
00028 
00029 /** @file
00030  *
00031  * iPXE CPU sleeping API for EFI
00032  *
00033  */
00034 
00035 /**
00036  * Sleep until next interrupt
00037  *
00038  */
00039 static void efix86_cpu_nap ( void ) {
00040         /*
00041          * I can't find any EFI API that allows us to put the CPU to
00042          * sleep.  The CpuSleep() function is defined in CpuLib.h, but
00043          * isn't part of any exposed protocol so we have no way to
00044          * call it.
00045          *
00046          * The EFI shell doesn't seem to bother sleeping the CPU; it
00047          * just sits there idly burning power.
00048          *
00049          */
00050         __asm__ __volatile__ ( "hlt" );
00051 }
00052 
00053 PROVIDE_NAP ( efix86, cpu_nap, efix86_cpu_nap );