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/*
* asm-blackfin/time.h:
*
* Copyright 2004-2008 Analog Devices Inc.
*
* Licensed under the GPL-2 or later.
*/
#ifndef _ASM_BLACKFIN_TIME_H
#define _ASM_BLACKFIN_TIME_H
/*
* The way that the Blackfin core timer works is:
* - CCLK is divided by a programmable 8-bit pre-scaler (TSCALE)
* - Every time TSCALE ticks, a 32bit is counted down (TCOUNT)
*
* If you take the fastest clock (1ns, or 1GHz to make the math work easier)
* 10ms is 10,000,000 clock ticks, which fits easy into a 32-bit counter
* (32 bit counter is 4,294,967,296ns or 4.2 seconds) so, we don't need
* to use TSCALE, and program it to zero (which is pass CCLK through).
* If you feel like using it, try to keep HZ * TIMESCALE to some
* value that divides easy (like power of 2).
*/
#ifndef CONFIG_CPU_FREQ
#define TIME_SCALE 1
#else
/*
* Blackfin CPU frequency scaling supports max Core Clock 1, 1/2 and 1/4 .
* Whenever we change the Core Clock frequency changes we immediately
* adjust the Core Timer Presale Register. This way we don't lose time.
*/
#define TIME_SCALE 4
#endif
#endif
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