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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 | } |