diff options
| author | David Daney <ddaney@caviumnetworks.com> | 2010-01-08 23:47:36 +0100 |
|---|---|---|
| committer | Ralf Baechle <ralf@linux-mips.org> | 2010-01-12 18:19:36 +0100 |
| commit | 0e8a1d8262f41d6e8c1d736a408882bbb7a5c0a6 (patch) | |
| tree | b8943db01b333cbd3629555e2de92a8670f39404 /arch | |
| parent | MIPS: Malta, PowerTV: Remove unnecessary "Linux started" (diff) | |
| download | linux-0e8a1d8262f41d6e8c1d736a408882bbb7a5c0a6.tar.xz linux-0e8a1d8262f41d6e8c1d736a408882bbb7a5c0a6.zip | |
MIPS: Octeon: Use non-overflowing arithmetic in sched_clock
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>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/mips/cavium-octeon/csrc-octeon.c | 31 |
1 files changed, 28 insertions, 3 deletions
diff --git a/arch/mips/cavium-octeon/csrc-octeon.c b/arch/mips/cavium-octeon/csrc-octeon.c index 96df821fbd81..0bf4bbe04ae2 100644 --- a/arch/mips/cavium-octeon/csrc-octeon.c +++ b/arch/mips/cavium-octeon/csrc-octeon.c @@ -52,9 +52,34 @@ static struct clocksource clocksource_mips = { unsigned long long notrace sched_clock(void) { - return clocksource_cyc2ns(read_c0_cvmcount(), - clocksource_mips.mult, - clocksource_mips.shift); + /* 64-bit arithmatic can overflow, so use 128-bit. */ +#if (__GNUC__ < 4) || ((__GNUC__ == 4) && (__GNUC_MINOR__ <= 3)) + u64 t1, t2, t3; + unsigned long long rv; + u64 mult = clocksource_mips.mult; + u64 shift = clocksource_mips.shift; + u64 cnt = read_c0_cvmcount(); + + asm ( + "dmultu\t%[cnt],%[mult]\n\t" + "nor\t%[t1],$0,%[shift]\n\t" + "mfhi\t%[t2]\n\t" + "mflo\t%[t3]\n\t" + "dsll\t%[t2],%[t2],1\n\t" + "dsrlv\t%[rv],%[t3],%[shift]\n\t" + "dsllv\t%[t1],%[t2],%[t1]\n\t" + "or\t%[rv],%[t1],%[rv]\n\t" + : [rv] "=&r" (rv), [t1] "=&r" (t1), [t2] "=&r" (t2), [t3] "=&r" (t3) + : [cnt] "r" (cnt), [mult] "r" (mult), [shift] "r" (shift) + : "hi", "lo"); + return rv; +#else + /* GCC > 4.3 do it the easy way. */ + unsigned int __attribute__((mode(TI))) t; + t = read_c0_cvmcount(); + t = t * clocksource_mips.mult; + return (unsigned long long)(t >> clocksource_mips.shift); +#endif } void __init plat_time_init(void) |