mirror of
https://github.com/rust-embedded/rust-raspberrypi-OS-tutorials.git
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82 lines
2.5 KiB
C
82 lines
2.5 KiB
C
/*
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* Copyright (C) 2018 bzt (bztsrc@github)
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*
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* Permission is hereby granted, free of charge, to any person
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* obtaining a copy of this software and associated documentation
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* files (the "Software"), to deal in the Software without
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* restriction, including without limitation the rights to use, copy,
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* modify, merge, publish, distribute, sublicense, and/or sell copies
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* of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be
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* included in all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
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* HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
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* WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
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* DEALINGS IN THE SOFTWARE.
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*
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*/
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#include "gpio.h"
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#define SYSTMR_LO ((volatile unsigned int*)(MMIO_BASE+0x00003004))
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#define SYSTMR_HI ((volatile unsigned int*)(MMIO_BASE+0x00003008))
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/**
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* Wait N CPU cycles (ARM CPU only)
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*/
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void wait_cycles(unsigned int n)
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{
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if(n) while(n--) { asm volatile("nop"); }
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}
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/**
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* Wait N microsec (ARM CPU only)
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*/
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void wait_msec(unsigned int n)
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{
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register unsigned long f, t, r;
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// get the current counter frequency
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asm volatile ("mrs %0, cntfrq_el0" : "=r"(f));
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// read the current counter
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asm volatile ("mrs %0, cntpct_el0" : "=r"(t));
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// calculate expire value for counter
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t+=((f/1000)*n)/1000;
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do{asm volatile ("mrs %0, cntpct_el0" : "=r"(r));}while(r<t);
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}
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/**
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* Get System Timer's counter
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*/
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unsigned long get_system_timer()
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{
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unsigned int h=-1, l;
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// we must read MMIO area as two separate 32 bit reads
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h=*SYSTMR_HI;
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l=*SYSTMR_LO;
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// we have to repeat it if high word changed during read
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if(h!=*SYSTMR_HI) {
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h=*SYSTMR_HI;
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l=*SYSTMR_LO;
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}
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// compose long int value
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return ((unsigned long) h << 32) | l;
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}
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/**
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* Wait N microsec (with BCM System Timer)
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*/
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void wait_msec_st(unsigned int n)
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{
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unsigned long t=get_system_timer();
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// we must check if it's non-zero, because qemu does not emulate
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// system timer, and returning constant zero would mean infinite loop
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if(t) while(get_system_timer() < t+n);
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}
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