ia64/linux-2.6.18-xen.hg

view arch/v850/kernel/v850e_utils.c @ 854:950b9eb27661

usbback: fix urb interval value for interrupt urbs.

Signed-off-by: Noboru Iwamatsu <n_iwamatsu@jp.fujitsu.com>
author Keir Fraser <keir.fraser@citrix.com>
date Mon Apr 06 13:51:20 2009 +0100 (2009-04-06)
parents 831230e53067
children
line source
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 */
15 #include <asm/v850e_utils.h>
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;
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;
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 }
52 if (_divlog2 > max_divlog2)
53 /* Can't find correct setting. */
54 _divlog2 = max_divlog2;
56 if (divlog2)
57 *divlog2 = _divlog2;
58 if (count)
59 *count = ((base_freq >> _divlog2) + rate/2) / rate;
61 return ok;
62 }