linux/arch/mips/cavium-octeon/csrc-octeon.c

/*
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 * Copyright (C) 2007 by Ralf Baechle
 */
#include <linux/clocksource.h>
#include <linux/init.h>

#include <asm/time.h>

#include <asm/octeon/octeon.h>
#include <asm/octeon/cvmx-ipd-defs.h>

/*
 * Set the current core's cvmcount counter to the value of the
 * IPD_CLK_COUNT.  We do this on all cores as they are brought
 * on-line.  This allows for a read from a local cpu register to
 * access a synchronized counter.
 *
 */
void octeon_init_cvmcount(void)
{
	unsigned long flags;
	unsigned loops = 2;

	/* Clobber loops so GCC will not unroll the following while loop. */
	asm("" : "+r" (loops));

	local_irq_save(flags);
	/*
	 * Loop several times so we are executing from the cache,
	 * which should give more deterministic timing.
	 */
	while (loops--)
		write_c0_cvmcount(cvmx_read_csr(CVMX_IPD_CLK_COUNT));
	local_irq_restore(flags);
}

static cycle_t octeon_cvmcount_read(struct clocksource *cs)
{
	return read_c0_cvmcount();
}

static struct clocksource clocksource_mips = {
	.name		= "OCTEON_CVMCOUNT",
	.read		= octeon_cvmcount_read,
	.mask		= CLOCKSOURCE_MASK(64),
	.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
};

unsigned long long notrace sched_clock(void)
{
	/* 64-bit arithmatic can overflow, so use 128-bit.  */
#if (__GNUC__ < 4) || ((__GNUC__ == 4) && (__GNUC_MINOR__ <= 3))
	u64 t1, t2, t3;
	unsigned long long rv;
	u64 mult = clocksource_mips.mult;
	u64 shift = clocksource_mips.shift;
	u64 cnt = read_c0_cvmcount();

	asm (
		"dmultu\t%[cnt],%[mult]\n\t"
		"nor\t%[t1],$0,%[shift]\n\t"
		"mfhi\t%[t2]\n\t"
		"mflo\t%[t3]\n\t"
		"dsll\t%[t2],%[t2],1\n\t"
		"dsrlv\t%[rv],%[t3],%[shift]\n\t"
		"dsllv\t%[t1],%[t2],%[t1]\n\t"
		"or\t%[rv],%[t1],%[rv]\n\t"
		: [rv] "=&r" (rv), [t1] "=&r" (t1), [t2] "=&r" (t2), [t3] "=&r" (t3)
		: [cnt] "r" (cnt), [mult] "r" (mult), [shift] "r" (shift)
		: "hi", "lo");
	return rv;
#else
	/* GCC > 4.3 do it the easy way.  */
	unsigned int __attribute__((mode(TI))) t;
	t = read_c0_cvmcount();
	t = t * clocksource_mips.mult;
	return (unsigned long long)(t >> clocksource_mips.shift);
#endif
}

void __init plat_time_init(void)
{
	clocksource_mips.rating = 300;
	clocksource_set_clock(&clocksource_mips, mips_hpt_frequency);
	clocksource_register(&clocksource_mips);
}