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      1 /*	$NetBSD: mips3_clock.c,v 1.15 2020/05/29 12:30:40 rin Exp $	*/
      2 
      3 /*
      4  * Copyright (c) 1988 University of Utah.
      5  * Copyright (c) 1992, 1993
      6  *	The Regents of the University of California.  All rights reserved.
      7  *
      8  * This code is derived from software contributed to Berkeley by
      9  * the Systems Programming Group of the University of Utah Computer
     10  * Science Department and Ralph Campbell.
     11  *
     12  * Redistribution and use in source and binary forms, with or without
     13  * modification, are permitted provided that the following conditions
     14  * are met:
     15  * 1. Redistributions of source code must retain the above copyright
     16  *    notice, this list of conditions and the following disclaimer.
     17  * 2. Redistributions in binary form must reproduce the above copyright
     18  *    notice, this list of conditions and the following disclaimer in the
     19  *    documentation and/or other materials provided with the distribution.
     20  * 3. Neither the name of the University nor the names of its contributors
     21  *    may be used to endorse or promote products derived from this software
     22  *    without specific prior written permission.
     23  *
     24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     34  * SUCH DAMAGE.
     35  *
     36  * from: Utah Hdr: clock.c 1.18 91/01/21
     37  *
     38  *	@(#)clock.c	8.1 (Berkeley) 6/10/93
     39  */
     40 
     41 #include <sys/cdefs.h>			/* RCS ID & Copyright macro defns */
     42 
     43 #include "opt_multiprocessor.h"
     44 
     45 __KERNEL_RCSID(0, "$NetBSD: mips3_clock.c,v 1.15 2020/05/29 12:30:40 rin Exp $");
     46 
     47 #include <sys/param.h>
     48 #include <sys/cpu.h>
     49 #include <sys/intr.h>
     50 #include <sys/kernel.h>
     51 #include <sys/timetc.h>
     52 
     53 #include <mips/mips3_clock.h>
     54 
     55 #include <mips/locore.h>
     56 
     57 /*
     58  * Wait for at least "n" microseconds.
     59  */
     60 void
     61 mips3_delay(int n)
     62 {
     63 	u_long divisor_delay;
     64 	uint32_t cur, last, delta, usecs;
     65 
     66 	last = mips3_cp0_count_read();
     67 	delta = usecs = 0;
     68 
     69 	divisor_delay = curcpu()->ci_divisor_delay;
     70 	if (divisor_delay == 0) {
     71 		/*
     72 		 * Frequency values in curcpu() are not initialized.
     73 		 * Assume faster frequency since longer delays are harmless.
     74 		 * Note CPU_MIPS_DOUBLE_COUNT is ignored here.
     75 		 */
     76 #define FAST_FREQ	(300 * 1000 * 1000)	/* fast enough? */
     77 		divisor_delay = FAST_FREQ / (1000 * 1000);
     78 	}
     79 
     80 	while (n > usecs) {
     81 		cur = mips3_cp0_count_read();
     82 
     83 		/*
     84 		 * The MIPS3 CP0 counter always counts upto UINT32_MAX,
     85 		 * so no need to check wrapped around case.
     86 		 */
     87 		delta += (cur - last);
     88 
     89 		last = cur;
     90 
     91 		while (delta >= divisor_delay) {
     92 			/*
     93 			 * delta is not so larger than divisor_delay here,
     94 			 * and using DIV/DIVU ops could be much slower.
     95 			 * (though longer delay may be harmless)
     96 			 */
     97 			usecs++;
     98 			delta -= divisor_delay;
     99 		}
    100 	}
    101 }
    102 
    103 /*
    104  * Support for using the MIPS 3 clock as a timecounter.
    105  */
    106 
    107 void
    108 mips3_init_tc(void)
    109 {
    110 #if !defined(MULTIPROCESSOR)
    111 	static struct timecounter tc =  {
    112 		.tc_get_timecount = (timecounter_get_t *)mips3_cp0_count_read,
    113 		.tc_counter_mask = ~0u,
    114 		.tc_name = "mips3_cp0_counter",
    115 		.tc_quality = 100,
    116 	};
    117 
    118 	tc.tc_frequency = curcpu()->ci_cpu_freq;
    119 	if (mips_options.mips_cpu_flags & CPU_MIPS_DOUBLE_COUNT) {
    120 		tc.tc_frequency /= 2;
    121 	}
    122 	curcpu()->ci_cctr_freq = tc.tc_frequency;
    123 
    124 	tc_init(&tc);
    125 #endif
    126 }
    127 
    128 __weak_alias(delay, mips3_delay);
    129