73 lines
2.4 KiB
C
73 lines
2.4 KiB
C
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/*
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* Copyright (c) 2010, Stefan Lankes, RWTH Aachen University
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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* * Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* * Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this
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* software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE FOR ANY
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* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include <eduos/stddef.h>
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#include <eduos/stdio.h>
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#include <eduos/string.h>
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#include <eduos/time.h>
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#include <eduos/processor.h>
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#include <eduos/tasks.h>
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static uint32_t cpu_freq = 0;
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uint32_t detect_cpu_frequency(void)
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{
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uint64_t start, end, diff;
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uint64_t ticks, old;
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if (BUILTIN_EXPECT(cpu_freq > 0, 0))
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return cpu_freq;
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old = get_clock_tick();
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/* wait for the next time slice */
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while((ticks = get_clock_tick()) - old == 0)
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HALT;
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rmb();
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start = rdtsc();
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/* wait a second to determine the frequency */
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while(get_clock_tick() - ticks < TIMER_FREQ)
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HALT;
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rmb();
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end = rdtsc();
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diff = end > start ? end - start : start - end;
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cpu_freq = (uint32_t) (diff / (uint64_t) 1000000);
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return cpu_freq;
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}
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uint32_t get_cpu_frequency(void)
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{
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if (cpu_freq > 0)
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return cpu_freq;
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return detect_cpu_frequency();
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}
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