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ARC700 includes 2 in-core 32bit timers TIMER0 and TIMER1. Both have exactly same capabilies. * programmable to count from TIMER<n>_CNT to TIMER<n>_LIMIT * for count 0 and LIMIT ~1, provides a free-running counter by auto-wrapping when limit is reached. * optionally interrupt when LIMIT is reached (oneshot event semantics) * rearming the interrupt provides periodic semantics * run at CPU clk ARC Linux uses TIMER0 for clockevent (periodic/oneshot) and TIMER1 for clocksource (free-running clock). Newer cores provide RTSC insn which gives a 64bit cpu clk snapshot hence is more apt for clocksource when available. SMP poses a bit of challenge for global timekeeping clocksource / sched_clock() backend: -TIMER1 based local clocks are out-of-sync hence can't be used (thus we default to jiffies based cs as well as sched_clock() one/both of which platform can override with it's specific hardware assist) -RTSC is only allowed in SMP if it's cross-core-sync (Kconfig glue ensures that) and thus usable for both requirements. Signed-off-by: Vineet Gupta <vgupta@synopsys.com> Cc: Thomas Gleixner <tglx@linutronix.de>
19 lines
508 B
C
19 lines
508 B
C
/*
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* Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#ifndef _ASM_ARC_TIMEX_H
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#define _ASM_ARC_TIMEX_H
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#define CLOCK_TICK_RATE 80000000 /* slated to be removed */
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#include <asm-generic/timex.h>
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/* XXX: get_cycles() to be implemented with RTSC insn */
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#endif /* _ASM_ARC_TIMEX_H */
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