Linux Kernel  3.7.1
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time.h
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1 /*
2  * asm-blackfin/time.h:
3  *
4  * Copyright 2004-2008 Analog Devices Inc.
5  *
6  * Licensed under the GPL-2 or later.
7  */
8 
9 #ifndef _ASM_BLACKFIN_TIME_H
10 #define _ASM_BLACKFIN_TIME_H
11 
12 /*
13  * The way that the Blackfin core timer works is:
14  * - CCLK is divided by a programmable 8-bit pre-scaler (TSCALE)
15  * - Every time TSCALE ticks, a 32bit is counted down (TCOUNT)
16  *
17  * If you take the fastest clock (1ns, or 1GHz to make the math work easier)
18  * 10ms is 10,000,000 clock ticks, which fits easy into a 32-bit counter
19  * (32 bit counter is 4,294,967,296ns or 4.2 seconds) so, we don't need
20  * to use TSCALE, and program it to zero (which is pass CCLK through).
21  * If you feel like using it, try to keep HZ * TIMESCALE to some
22  * value that divides easy (like power of 2).
23  */
24 
25 #ifndef CONFIG_CPU_FREQ
26 # define TIME_SCALE 1
27 #else
28 /*
29  * Blackfin CPU frequency scaling supports max Core Clock 1, 1/2 and 1/4 .
30  * Whenever we change the Core Clock frequency changes we immediately
31  * adjust the Core Timer Presale Register. This way we don't lose time.
32  */
33 #define TIME_SCALE 4
34 
35 # ifdef CONFIG_CYCLES_CLOCKSOURCE
36 extern unsigned long long __bfin_cycles_off;
37 extern unsigned int __bfin_cycles_mod;
38 # endif
39 #endif
40 
41 #if defined(CONFIG_TICKSOURCE_CORETMR)
42 extern void bfin_coretmr_init(void);
43 extern void bfin_coretmr_clockevent_init(void);
44 #endif
45 
46 #endif