src/arch/x86/interface/efi/efix86_nap.c

   1 /*
   2  * Copyright (C) 2008 Michael Brown <mbrown@fensystems.co.uk>.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public License as
   6  * published by the Free Software Foundation; either version 2 of the
   7  * License, or any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful, but
  10  * WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12  * General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, write to the Free Software
  16  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  17  */
  18
  19 FILE_LICENCE ( GPL2_OR_LATER );
  20
  21 #include <gpxe/nap.h>
  22 #include <gpxe/efi/efi.h>
  23
  24 /** @file
  25  *
  26  * gPXE CPU sleeping API for EFI
  27  *
  28  */
  29
  30 /**
  31  * Sleep until next interrupt
  32  *
  33  */
  34 static void efix86_cpu_nap ( void ) {
  35         /*
  36          * I can't find any EFI API that allows us to put the CPU to
  37          * sleep.  The CpuSleep() function is defined in CpuLib.h, but
  38          * isn't part of any exposed protocol so we have no way to
  39          * call it.
  40          *
  41          * The EFI shell doesn't seem to bother sleeping the CPU; it
  42          * just sits there idly burning power.
  43          *
  44          */
  45         __asm__ __volatile__ ( "hlt" );
  46 }
  47
  48 PROVIDE_NAP ( efix86, cpu_nap, efix86_cpu_nap );