1  /* SPDX-License-Identifier: GPL-2.0-only */
 2  
 3  #include <arch/lib_helpers.h>
 4  #include <commonlib/bsd/gcd.h>
 5  #include <timer.h>
 6  
 7  void timer_monotonic_get(struct mono_time *mt)
 8  {
 9  	uint64_t tvalue = raw_read_cntpct_el0();
10  	static uint32_t tfreq, mult;
11  	uint32_t div;
12  
13  	/*
14  	 * The value from raw_read_cntfrq_el0() could be large enough to
15  	 * cause overflow when multiplied by USECS_PER_SEC. To prevent this,
16  	 * both USECS_PER_SEC. and tfreq can be reduced by dividing them by
17  	 * their GCD.
18  	 */
19  	if (tfreq == 0) {
20  		tfreq = raw_read_cntfrq_el0();
21  		mult = USECS_PER_SEC;
22  		div = gcd(tfreq, mult);
23  		tfreq /= div;
24  		mult /= div;
25  	}
26  
27  	long usecs = (tvalue * mult) / tfreq;
28  	mono_time_set_usecs(mt, usecs);
29  }