Messages in this thread Patch in this message | | | From | Wen Yang <> | Subject | [PATCH] x86/tsc: improve arithmetic division | Date | Thu, 30 Jan 2020 21:08:38 +0800 |
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do_div() does a 64-by-32 division. Use div64_ul64() or div64_ul() instead of it if the divisor is 'ul64' or 'unsigned long', to avoid truncation to lower 32-bit. And as a nice side effect also cleans up the function a bit.
Signed-off-by: Wen Yang <wenyang@linux.alibaba.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: x86@kernel.org Cc: linux-kernel@vger.kernel.org --- arch/x86/kernel/tsc.c | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-)
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c index 7e322e2daaf5..4c0320e68699 100644 --- a/arch/x86/kernel/tsc.c +++ b/arch/x86/kernel/tsc.c @@ -357,9 +357,7 @@ static unsigned long calc_pmtimer_ref(u64 deltatsc, u64 pm1, u64 pm2) pm2 -= pm1; tmp = pm2 * 1000000000LL; do_div(tmp, PMTMR_TICKS_PER_SEC); - do_div(deltatsc, tmp); - - return (unsigned long) deltatsc; + return (unsigned long) div64_u64(deltatsc, tmp); } #define CAL_MS 10 @@ -778,8 +776,7 @@ static unsigned long pit_hpet_ptimer_calibrate_cpu(void) tsc_ref_min = min(tsc_ref_min, (unsigned long) tsc2); /* Check the reference deviation */ - delta = ((u64) tsc_pit_min) * 100; - do_div(delta, tsc_ref_min); + delta = div64_ul(((u64) tsc_pit_min) * 100, tsc_ref_min); /* * If both calibration results are inside a 10% window -- 2.23.0
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