1/* 2 * include/asm-v850/v850e_utils.h -- Utility functions associated with 3 * V850E CPUs 4 * 5 * Copyright (C) 2001,02,03 NEC Electronics Corporation 6 * Copyright (C) 2001,02,03 Miles Bader <miles@gnu.org> 7 * 8 * This file is subject to the terms and conditions of the GNU General 9 * Public License. See the file COPYING in the main directory of this 10 * archive for more details. 11 * 12 * Written by Miles Bader <miles@gnu.org> 13 */ 14 15#include <asm/v850e_utils.h> 16 17/* Calculate counter clock-divider and count values to attain the 18 desired frequency RATE from the base frequency BASE_FREQ. The 19 counter is expected to have a clock-divider, which can divide the 20 system cpu clock by a power of two value from MIN_DIVLOG2 to 21 MAX_DIV_LOG2, and a word-size of COUNTER_SIZE bits (the counter 22 counts up and resets whenever it's equal to the compare register, 23 generating an interrupt or whatever when it does so). The returned 24 values are: *DIVLOG2 -- log2 of the desired clock divider and *COUNT 25 -- the counter compare value to use. Returns true if it was possible 26 to find a reasonable value, otherwise false (and the other return 27 values will be set to be as good as possible). */ 28int calc_counter_params (unsigned long base_freq, 29 unsigned long rate, 30 unsigned min_divlog2, unsigned max_divlog2, 31 unsigned counter_size, 32 unsigned *divlog2, unsigned *count) 33{ 34 unsigned _divlog2; 35 int ok = 0; 36 37 /* Find the lowest clock divider setting that can represent RATE. */ 38 for (_divlog2 = min_divlog2; _divlog2 <= max_divlog2; _divlog2++) { 39 /* Minimum interrupt rate possible using this divider. */ 40 unsigned min_int_rate 41 = (base_freq >> _divlog2) >> counter_size; 42 43 if (min_int_rate <= rate) { 44 /* This setting is the highest resolution 45 setting that's slow enough enough to attain 46 RATE interrupts per second, so use it. */ 47 ok = 1; 48 break; 49 } 50 } 51 52 if (_divlog2 > max_divlog2) 53 /* Can't find correct setting. */ 54 _divlog2 = max_divlog2; 55 56 if (divlog2) 57 *divlog2 = _divlog2; 58 if (count) 59 *count = ((base_freq >> _divlog2) + rate/2) / rate; 60 61 return ok; 62} 63