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/*
* include/asm-v850/v850e_utils.h -- Utility functions associated with
* V850E CPUs
*
* Copyright (C) 2001,02,03 NEC Electronics Corporation
* Copyright (C) 2001,02,03 Miles Bader <miles@gnu.org>
*
* 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.
*
* Written by Miles Bader <miles@gnu.org>
*/
#include <asm/v850e_utils.h>
/* Calculate counter clock-divider and count values to attain the
desired frequency RATE from the base frequency BASE_FREQ. The
counter is expected to have a clock-divider, which can divide the
system cpu clock by a power of two value from MIN_DIVLOG2 to
MAX_DIV_LOG2, and a word-size of COUNTER_SIZE bits (the counter
counts up and resets whenever it's equal to the compare register,
generating an interrupt or whatever when it does so). The returned
values are: *DIVLOG2 -- log2 of the desired clock divider and *COUNT
-- the counter compare value to use. Returns true if it was possible
to find a reasonable value, otherwise false (and the other return
values will be set to be as good as possible). */
int calc_counter_params (unsigned long base_freq,
unsigned long rate,
unsigned min_divlog2, unsigned max_divlog2,
unsigned counter_size,
unsigned *divlog2, unsigned *count)
{
unsigned _divlog2;
int ok = 0;
/* Find the lowest clock divider setting that can represent RATE. */
for (_divlog2 = min_divlog2; _divlog2 <= max_divlog2; _divlog2++) {
/* Minimum interrupt rate possible using this divider. */
unsigned min_int_rate
= (base_freq >> _divlog2) >> counter_size;
if (min_int_rate <= rate) {
/* This setting is the highest resolution
setting that's slow enough enough to attain
RATE interrupts per second, so use it. */
ok = 1;
break;
}
}
if (_divlog2 > max_divlog2)
/* Can't find correct setting. */
_divlog2 = max_divlog2;
if (divlog2)
*divlog2 = _divlog2;
if (count)
*count = ((base_freq >> _divlog2) + rate/2) / rate;
return ok;
}
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