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/*
* Delay loops based on the OpenRISC implementation.
*
* Copyright (C) 2012 ARM Limited
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
* Author: Will Deacon <will.deacon@arm.com>
*/
#include <linux/clocksource.h>
#include <linux/delay.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/export.h>
#include <linux/timex.h>
/*
* Default to the loop-based delay implementation.
*/
struct arm_delay_ops arm_delay_ops __ro_after_init = {
.delay = __loop_delay,
.const_udelay = __loop_const_udelay,
.udelay = __loop_udelay,
};
EXPORT_SYMBOL(arm_delay_ops);
static const struct delay_timer *delay_timer;
static bool delay_calibrated;
static u64 delay_res;
int read_current_timer(unsigned long *timer_val)
{
if (!delay_timer)
return -ENXIO;
*timer_val = delay_timer->read_current_timer();
return 0;
}
EXPORT_SYMBOL_GPL(read_current_timer);
static inline u64 cyc_to_ns(u64 cyc, u32 mult, u32 shift)
{
return (cyc * mult) >> shift;
}
static void __timer_delay(unsigned long cycles)
{
cycles_t start = get_cycles();
while ((get_cycles() - start) < cycles)
cpu_relax();
}
static void __timer_const_udelay(unsigned long xloops)
{
unsigned long long loops = xloops;
loops *= arm_delay_ops.ticks_per_jiffy;
__timer_delay(loops >> UDELAY_SHIFT);
}
static void __timer_udelay(unsigned long usecs)
{
__timer_const_udelay(usecs * UDELAY_MULT);
}
void __init register_current_timer_delay(const struct delay_timer *timer)
{
u32 new_mult, new_shift;
u64 res;
clocks_calc_mult_shift(&new_mult, &new_shift, timer->freq,
NSEC_PER_SEC, 3600);
res = cyc_to_ns(1ULL, new_mult, new_shift);
if (res > 1000) {
pr_err("Ignoring delay timer %ps, which has insufficient resolution of %lluns\n",
timer, res);
return;
}
if (!delay_calibrated && (!delay_res || (res < delay_res))) {
pr_info("Switching to timer-based delay loop, resolution %lluns\n", res);
delay_timer = timer;
lpj_fine = timer->freq / HZ;
delay_res = res;
/* cpufreq may scale loops_per_jiffy, so keep a private copy */
arm_delay_ops.ticks_per_jiffy = lpj_fine;
arm_delay_ops.delay = __timer_delay;
arm_delay_ops.const_udelay = __timer_const_udelay;
arm_delay_ops.udelay = __timer_udelay;
} else {
pr_info("Ignoring duplicate/late registration of read_current_timer delay\n");
}
}
unsigned long calibrate_delay_is_known(void)
{
delay_calibrated = true;
return lpj_fine;
}
void calibration_delay_done(void)
{
delay_calibrated = true;
}
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