robijn
5d0b33c5ef
Enhanced(?) timing.h with DELAY_AUTOSELECT. Cheered up some comments, moved #ifndef FOO_H #define FOO_H to just after the copyright and explanation comment.
137 lines
3.3 KiB
C
137 lines
3.3 KiB
C
/*
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* Utility header file for timing functions
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*
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* Made by Guillaume Filion, moved from the HD44780 driver.
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*
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* From hd44780.c:
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* Modified July 2000 by Charles Steinkuehler to use one of 3 methods for delay
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* timing. I/O reads, gettimeofday, and nanosleep. Of the three, nanosleep
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* seems to work best, so that's what is set by default.
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*
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* This file is released under the GNU General Public License. Refer to the
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* COPYING file distributed with this package.
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*
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* Copyright (c) 2001 Guillaume Filion <gfk@logidac.com>
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* 2001 Joris Robijn <joris@robijn.net>
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* 2000 Charles Steinkuehler <cstein@newtek.com>
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*/
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#ifndef _TIMING_H
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#define _TIMING_H
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// Uncomment one of the lines below this paragraph to select your desired
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// delay generation mechanism.
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// Mechanism DELAY_NANOSLEEP seems to provide the best performance.
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// Mechanism DELAY_IOCALLS can be quite inaccurate.
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// Mechanism DELAY_AUTOSELECT lets the system determine a mechanism, and is
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// the default.
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#define DELAY_AUTOSELECT
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//#define DELAY_GETTIMEOFDAY
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//#define DELAY_NANOSLEEP
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//#define DELAY_IOCALLS
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#include <string.h>
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#include <errno.h>
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#include <unistd.h>
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#ifdef HAVE_CONFIG_H
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# include "config.h"
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#endif
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// Autoselect... Does this always work well ?
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#ifdef DELAY_AUTOSELECT
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# ifdef HAVE_SCHED_H
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# define DELAY_NANOSLEEP
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# else
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# define DELAY_GETTIMEOFDAY
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# endif
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#endif
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// Include the correct time.h stuff (regardless of selected mechanism)
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#if TIME_WITH_SYS_TIME
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# include <sys/time.h>
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# include <time.h>
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#else
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# if HAVE_SYS_TIME_H
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# include <sys/time.h>
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# else
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# include <time.h>
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# endif
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#endif
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// Only one alternate delay method at a time, please ;-)
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// And include extra header files here...
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#if defined DELAY_GETTIMEOFDAY
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# undef DELAY_NANOSLEEP
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# undef DELAY_IOCALLS
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#elif defined DELAY_NANOSLEEP
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# undef DELAY_GETTIMEOFDAY
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# undef DELAY_IOCALLS
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# include <sched.h>
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#else // assume DELAY_IOCALLS
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# undef DELAY_GETTIMEOFDAY
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# undef DELAY_NANOSLEEP
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# include "port.h"
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#endif
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/////////////////////////////////////////////////////////////////
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// Initialisation
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//
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static inline int timing_init() {
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#if defined DELAY_NANOSLEEP
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// Change to Round-Robin scheduling for nanosleep
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{
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// Set priority to 1
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struct sched_param param;
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param.sched_priority=1;
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if (( sched_setscheduler(0, SCHED_RR, ¶m)) == -1) {
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fprintf (stderr, "timing_init: failed (%s)\n", strerror (errno));
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return -1;
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}
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}
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#endif
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return 0;
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}
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/////////////////////////////////////////////////////////////////
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// IO delay to avoid a task switch
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//
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static inline void timing_uPause (int usecs) {
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#if defined DELAY_GETTIMEOFDAY
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struct timeval current_time,delay_time,wait_time;
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// Get current time first thing
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gettimeofday(¤t_time,NULL);
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// Calculate when delay is over
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delay_time.tv_sec = 0;
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delay_time.tv_usec = usecs;
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timeradd(¤t_time,&delay_time,&wait_time);
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do {
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gettimeofday(¤t_time,NULL);
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} while (timercmp(¤t_time,&wait_time,<));
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#elif defined DELAY_NANOSLEEP
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struct timespec delay_time,remaining;
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delay_time.tv_sec = 0;
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delay_time.tv_nsec = usecs * 1000;
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while ( nanosleep(&delay_time,&remaining) == -1 )
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{
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delay_time.tv_sec = remaining.tv_sec;
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delay_time.tv_nsec = remaining.tv_nsec;
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}
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#else // using I/O timing
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// Assuming every port I/O takes 1us
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for (int i=0; i < usecs; ++i)
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port_in(port);
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#endif
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}
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#endif // _TIMING_H
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