| Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 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). */ |
| 28 | int 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 | } |