112 строки
2.8 KiB
C
112 строки
2.8 KiB
C
/*
|
|
* 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/timex.h>
|
|
|
|
/*
|
|
* Default to the loop-based delay implementation.
|
|
*/
|
|
struct arm_delay_ops arm_delay_ops = {
|
|
.delay = __loop_delay,
|
|
.const_udelay = __loop_const_udelay,
|
|
.udelay = __loop_udelay,
|
|
};
|
|
|
|
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 (!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;
|
|
}
|