original_kernel/arch/c6x/kernel/time.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 *  Port on Texas Instruments TMS320C6x architecture
 *
 *  Copyright (C) 2004, 2009, 2010, 2011 Texas Instruments Incorporated
 *  Author: Aurelien Jacquiot (aurelien.jacquiot@jaluna.com)
 */

#include <linux/kernel.h>
#include <linux/clocksource.h>
#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/param.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/interrupt.h>
#include <linux/timex.h>
#include <linux/profile.h>

#include <asm/special_insns.h>
#include <asm/timer64.h>

static u32 sched_clock_multiplier;
#define SCHED_CLOCK_SHIFT 16

static u64 tsc_read(struct clocksource *cs)
{
	return get_cycles();
}

static struct clocksource clocksource_tsc = {
	.name		= "timestamp",
	.rating		= 300,
	.read		= tsc_read,
	.mask		= CLOCKSOURCE_MASK(64),
	.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
};

/*
 * scheduler clock - returns current time in nanoseconds.
 */
u64 sched_clock(void)
{
	u64 tsc = get_cycles();

	return (tsc * sched_clock_multiplier) >> SCHED_CLOCK_SHIFT;
}

void __init time_init(void)
{
	u64 tmp = (u64)NSEC_PER_SEC << SCHED_CLOCK_SHIFT;

	do_div(tmp, c6x_core_freq);
	sched_clock_multiplier = tmp;

	clocksource_register_hz(&clocksource_tsc, c6x_core_freq);

	/* write anything into TSCL to enable counting */
	set_creg(TSCL, 0);

	/* probe for timer64 event timer */
	timer64_init();
}