1337173148
The current implementations of __ndelay and __udelay call a hypervisor service to delay, but the hypervisor service isn't actually implemented very well, and the consensus is that Linux should handle figuring this out natively and not use a hypervisor service. By converting nanoseconds to cycles, and then spinning until the cycle counter reaches the desired cycle, we get several benefits: first, we are sensitive to the actual clock speed; second, we use less power by issuing a slow SPR read once every six cycles while we delay; and third, we properly handle the case of an interrupt by exiting at the target time rather than after some number of cycles. Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>
50 lines
1.6 KiB
C
50 lines
1.6 KiB
C
/*
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* Copyright 2010 Tilera Corporation. All Rights Reserved.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation, version 2.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
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* NON INFRINGEMENT. See the GNU General Public License for
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* more details.
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*/
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#ifndef _ASM_TILE_TIMEX_H
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#define _ASM_TILE_TIMEX_H
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/*
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* This rate should be a multiple of the possible HZ values (100, 250, 1000)
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* and a fraction of the possible hardware timer frequencies. Our timer
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* frequency is highly tunable but also quite precise, so for the primary use
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* of this value (setting ACT_HZ from HZ) we just pick a value that causes
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* ACT_HZ to be set to HZ. We make the value somewhat large just to be
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* more robust in case someone tries out a new value of HZ.
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*/
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#define CLOCK_TICK_RATE 1000000
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typedef unsigned long long cycles_t;
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#if CHIP_HAS_SPLIT_CYCLE()
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cycles_t get_cycles(void);
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#else
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static inline cycles_t get_cycles(void)
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{
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return __insn_mfspr(SPR_CYCLE);
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}
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#endif
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cycles_t get_clock_rate(void);
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/* Convert nanoseconds to core clock cycles. */
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cycles_t ns2cycles(unsigned long nsecs);
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/* Called at cpu initialization to set some low-level constants. */
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void setup_clock(void);
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/* Called at cpu initialization to start the tile-timer clock device. */
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void setup_tile_timer(void);
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#endif /* _ASM_TILE_TIMEX_H */
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