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867e359b97
This change is the core kernel support for TILEPro and TILE64 chips. No driver support (except the console driver) is included yet. This includes the relevant Linux headers in asm/; the low-level low-level "Tile architecture" headers in arch/, which are shared with the hypervisor, etc., and are build-system agnostic; and the relevant hypervisor headers in hv/. Signed-off-by: Chris Metcalf <cmetcalf@tilera.com> Acked-by: Arnd Bergmann <arnd@arndb.de> Acked-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp> Reviewed-by: Paul Mundt <lethal@linux-sh.org>
65 lines
1.7 KiB
C
65 lines
1.7 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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* This file is included into spinlock_32.c or _64.c.
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*/
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/*
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* The mfspr in __spinlock_relax() is 5 or 6 cycles plus 2 for loop
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* overhead.
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*/
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#ifdef __tilegx__
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#define CYCLES_PER_RELAX_LOOP 7
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#else
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#define CYCLES_PER_RELAX_LOOP 8
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#endif
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/*
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* Idle the core for CYCLES_PER_RELAX_LOOP * iterations cycles.
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*/
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static inline void
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relax(int iterations)
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{
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for (/*above*/; iterations > 0; iterations--)
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__insn_mfspr(SPR_PASS);
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barrier();
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}
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/* Perform bounded exponential backoff.*/
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void delay_backoff(int iterations)
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{
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u32 exponent, loops;
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/*
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* 2^exponent is how many times we go around the loop,
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* which takes 8 cycles. We want to start with a 16- to 31-cycle
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* loop, so we need to go around minimum 2 = 2^1 times, so we
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* bias the original value up by 1.
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*/
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exponent = iterations + 1;
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/*
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* Don't allow exponent to exceed 7, so we have 128 loops,
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* or 1,024 (to 2,047) cycles, as our maximum.
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*/
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if (exponent > 8)
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exponent = 8;
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loops = 1 << exponent;
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/* Add a randomness factor so two cpus never get in lock step. */
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loops += __insn_crc32_32(stack_pointer, get_cycles_low()) &
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(loops - 1);
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relax(1 << exponent);
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}
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