ppc600_set_clock_freqs.c

来自「qnx powerpc MPC8245的 BSP源文件」· C语言 代码 · 共 53 行

/*
 * $QNXLicenseC: 
 * Copyright 2007, QNX Software Systems.  
 *  
 * Licensed under the Apache License, Version 2.0 (the "License"). You  
 * may not reproduce, modify or distribute this software except in  
 * compliance with the License. You may obtain a copy of the License  
 * at: http://www.apache.org/licenses/LICENSE-2.0  
 *  
 * Unless required by applicable law or agreed to in writing, software  
 * distributed under the License is distributed on an "AS IS" basis,  
 * WITHOUT WARRANTIES OF ANY KIND, either express or implied. 
 * 
 * This file may contain contributions from others, either as  
 * contributors under the License or as licensors under other terms.   
 * Please review this entire file for other proprietary rights or license  
 * notices, as well as the QNX Development Suite License Guide at  
 * http://licensing.qnx.com/license-guide/ for other information. 
 * $ 
 */

#include "startup.h"
#include "hidpll.h"
#include <ppc/603cpu.h>


/*
 * ppc600_set_clock_freqs.c
 * Set the cpu_freq, cycles_freq, and timer_freq variables, based on
 * the main system clock
 *
 */

void
ppc600_set_clock_freqs(unsigned clock) {
	unsigned	pll;

	if(cycles_freq == 0) cycles_freq = clock / 4;
	if(timer_freq == 0)  timer_freq  = clock / 4;
	
	if(cpu_freq == 0) {
		if(hid_pll_bits == NULL) {
			crash("PLL information unknown\n");
		}
		// Now decode PLL multiplier bits
		pll = (get_spr(PPC603_SPR_HID1) >> HID_SHIFT(hid_pll_bits)) 
				& HID_MASK(hid_pll_bits);
	
		cpu_freq = (clock * HID_GETMULT(hid_pll_bits, pll)) / HID_SCALE(hid_pll_bits);
	}
}