0e8a1d8262
With typical mult and shift values, the calculation for Octeon's sched_clock overflows when using 64-bit arithmetic. Use 128-bit calculations instead. Signed-off-by: David Daney <ddaney@caviumnetworks.com> To: linux-mips@linux-mips.org Patchwork: http://patchwork.linux-mips.org/patch/849/ Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
91 lines
2.3 KiB
C
91 lines
2.3 KiB
C
/*
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* This file is subject to the terms and conditions of the GNU General Public
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* License. See the file "COPYING" in the main directory of this archive
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* for more details.
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*
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* Copyright (C) 2007 by Ralf Baechle
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*/
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#include <linux/clocksource.h>
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#include <linux/init.h>
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#include <asm/time.h>
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#include <asm/octeon/octeon.h>
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#include <asm/octeon/cvmx-ipd-defs.h>
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/*
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* Set the current core's cvmcount counter to the value of the
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* IPD_CLK_COUNT. We do this on all cores as they are brought
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* on-line. This allows for a read from a local cpu register to
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* access a synchronized counter.
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*
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*/
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void octeon_init_cvmcount(void)
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{
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unsigned long flags;
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unsigned loops = 2;
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/* Clobber loops so GCC will not unroll the following while loop. */
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asm("" : "+r" (loops));
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local_irq_save(flags);
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/*
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* Loop several times so we are executing from the cache,
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* which should give more deterministic timing.
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*/
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while (loops--)
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write_c0_cvmcount(cvmx_read_csr(CVMX_IPD_CLK_COUNT));
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local_irq_restore(flags);
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}
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static cycle_t octeon_cvmcount_read(struct clocksource *cs)
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{
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return read_c0_cvmcount();
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}
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static struct clocksource clocksource_mips = {
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.name = "OCTEON_CVMCOUNT",
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.read = octeon_cvmcount_read,
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.mask = CLOCKSOURCE_MASK(64),
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.flags = CLOCK_SOURCE_IS_CONTINUOUS,
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};
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unsigned long long notrace sched_clock(void)
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{
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/* 64-bit arithmatic can overflow, so use 128-bit. */
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#if (__GNUC__ < 4) || ((__GNUC__ == 4) && (__GNUC_MINOR__ <= 3))
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u64 t1, t2, t3;
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unsigned long long rv;
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u64 mult = clocksource_mips.mult;
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u64 shift = clocksource_mips.shift;
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u64 cnt = read_c0_cvmcount();
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asm (
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"dmultu\t%[cnt],%[mult]\n\t"
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"nor\t%[t1],$0,%[shift]\n\t"
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"mfhi\t%[t2]\n\t"
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"mflo\t%[t3]\n\t"
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"dsll\t%[t2],%[t2],1\n\t"
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"dsrlv\t%[rv],%[t3],%[shift]\n\t"
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"dsllv\t%[t1],%[t2],%[t1]\n\t"
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"or\t%[rv],%[t1],%[rv]\n\t"
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: [rv] "=&r" (rv), [t1] "=&r" (t1), [t2] "=&r" (t2), [t3] "=&r" (t3)
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: [cnt] "r" (cnt), [mult] "r" (mult), [shift] "r" (shift)
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: "hi", "lo");
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return rv;
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#else
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/* GCC > 4.3 do it the easy way. */
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unsigned int __attribute__((mode(TI))) t;
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t = read_c0_cvmcount();
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t = t * clocksource_mips.mult;
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return (unsigned long long)(t >> clocksource_mips.shift);
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#endif
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}
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void __init plat_time_init(void)
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{
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clocksource_mips.rating = 300;
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clocksource_set_clock(&clocksource_mips, mips_hpt_frequency);
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clocksource_register(&clocksource_mips);
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}
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