drivers/delay_timer/generic_delay_timer.c

/*
 * Copyright (c) 2016, ARM Limited and Contributors. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * Redistributions of source code must retain the above copyright notice, this
 * list of conditions and the following disclaimer.
 *
 * Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation
 * and/or other materials provided with the distribution.
 *
 * Neither the name of ARM nor the names of its contributors may be used
 * to endorse or promote products derived from this software without specific
 * prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#include <arch_helpers.h>
#include <assert.h>
#include <bl_common.h>
#include <debug.h>
#include <delay_timer.h>
#include <platform.h>

/* Ticks elapsed in one second by a signal of 1 MHz */
#define MHZ_TICKS_PER_SEC 1000000

static timer_ops_t ops;

static uint32_t get_timer_value(void)
{
	/*
	 * Generic delay timer implementation expects the timer to be a down
	 * counter. We apply bitwise NOT operator to the tick values returned
	 * by read_cntpct_el0() to simulate the down counter. The value is
	 * clipped from 64 to 32 bits.
	 */
	return (uint32_t)(~read_cntpct_el0());
}

void generic_delay_timer_init_args(uint32_t mult, uint32_t div)
{
	ops.get_timer_value	= get_timer_value;
	ops.clk_mult		= mult;
	ops.clk_div		= div;

	timer_init(&ops);

	VERBOSE("Generic delay timer configured with mult=%u and div=%u\n",
		mult, div);
}

void generic_delay_timer_init(void)
{
	/* Value in ticks */
	unsigned int mult = MHZ_TICKS_PER_SEC;

	/* Value in ticks per second (Hz) */
	unsigned int div  = plat_get_syscnt_freq2();

	/* Reduce multiplier and divider by dividing them repeatedly by 10 */
	while ((mult % 10 == 0) && (div % 10 == 0)) {
		mult /= 10;
		div /= 10;
	}

	generic_delay_timer_init_args(mult, div);
}