/*-
* Copyright (c) 2005-2007, Kohsuke Ohtani
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. 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.
* 3. Neither the name of the author nor the names of any co-contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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.
*/
/*
* delay.c - driver delay routine
*/
#include <driver.h>
#include <delay.h>
#ifdef DEBUG
#define DPRINTF(a) printf a
#else
#define DPRINTF(a)
#endif
static u_long delay_count; /* Loop count for 1ms */
static
void delay_loop(u_long count)
{
volatile u_int i;
for (i = 0; i < count; i++);
}
/*
* Delay micro seconds (non-blocking)
* timer_udelay() can be called from ISR at interrupt level.
*/
void
delay_usec(u_long usec)
{
delay_loop(delay_count * usec / 1000);
}
/*
* Compute the loop count for 1ms.
* Assumes clock interrupt is enabled.
*/
void
calibrate_delay(void)
{
u_long ticks, test_bit;
DPRINTF(("Calibrating delay loop... "));
delay_count = 1;
for (;;) {
delay_count <<= 1;
ticks = timer_count();
while (ticks == timer_count());
ticks = timer_count();
delay_loop(delay_count);
if (ticks != timer_count())
break;
}
delay_count >>= 1;
test_bit = delay_count;
for (;;) {
test_bit >>= 1;
if (test_bit == 0)
break;
delay_count |= test_bit;
ticks = timer_count();
while (ticks == timer_count());
ticks = timer_count();
delay_loop(delay_count);
if (ticks != timer_count())
delay_count &= ~test_bit;
}
delay_count *= 1000; /* count per 1sec */
delay_count /= 1000; /* count per 1ms */
DPRINTF(("ok count=%d\n", delay_count));
}