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/* $Id$ */
/*
* ppc_idle.c
*
* Authorship
* ----------
* This software was created by
* Till Straumann <strauman@slac.stanford.edu>, 2010,
* Stanford Linear Accelerator Center, Stanford University.
*
* Acknowledgement of sponsorship
* ------------------------------
* This software was produced by
* the Stanford Linear Accelerator Center, Stanford University,
* under Contract DE-AC03-76SFO0515 with the Department of Energy.
*
* Government disclaimer of liability
* ----------------------------------
* Neither the United States nor the United States Department of Energy,
* nor any of their employees, makes any warranty, express or implied, or
* assumes any legal liability or responsibility for the accuracy,
* completeness, or usefulness of any data, apparatus, product, or process
* disclosed, or represents that its use would not infringe privately owned
* rights.
*
* Stanford disclaimer of liability
* --------------------------------
* Stanford University makes no representations or warranties, express or
* implied, nor assumes any liability for the use of this software.
*
* Stanford disclaimer of copyright
* --------------------------------
* Stanford University, owner of the copyright, hereby disclaims its
* copyright and all other rights in this software. Hence, anyone may
* freely use it for any purpose without restriction.
*
* Maintenance of notices
* ----------------------
* In the interest of clarity regarding the origin and status of this
* SLAC software, this and all the preceding Stanford University notices
* are to remain affixed to any copy or derivative of this software made
* or distributed by the recipient and are to be affixed to any copy of
* software made or distributed by the recipient that contains a copy or
* derivative of this software.
*
* ------------------ SLAC Software Notices, Set 4 OTT.002a, 2004 FEB 03
*/
#include <bsp.h>
#include <stdint.h>
#ifdef BSP_IDLE_TASK_BODY
/* Provide an idle-task body which switches the
* CPU into power-save mode when idle. Any exception
* (including an interrupt/external-exception)
* wakes it up.
*
* IIRC - this cannot be used on real hardware due
* to errata on many chips which is a real
* pity. However, when used under qemu it
* saves host-CPU cycles.
* While qemu-0.12.4 needed to be patched
* (would otherwise hang because an exception
* didn't clear MSR_POW) qemu-0.14.1 seems
* to work fine.
*/
#include <rtems/powerpc/registers.h>
#include <libcpu/cpuIdent.h>
#include <libcpu/spr.h>
SPR_RW(HID0)
void *
bsp_ppc_idle_task_body(uintptr_t ignored)
{
uint32_t msr;
switch ( current_ppc_cpu ) {
case PPC_7400:
case PPC_7455:
case PPC_7457:
/* Must enable NAP mode in HID0 for MSR_POW to work */
_write_HID0( _read_HID0() | HID0_NAP );
break;
default:
break;
}
for ( ;; ) {
_CPU_MSR_GET(msr);
msr |= MSR_POW;
asm volatile(
"1: sync \n"
" mtmsr %0 \n"
" isync \n"
" b 1b \n"
::"r"(msr)
);
}
return 0;
}
#endif
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