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From: Nicolai Stange <nicstange@gmail.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
        Nicolai Stange <nicstange@gmail.com>,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
        "H. Peter Anvin" <hpa@zytor.com>, x86@kernel.org,
        Borislav Petkov <bp@suse.de>, Viresh Kumar <viresh.kumar@linaro.org>,
        Hidehiro Kawai <hidehiro.kawai.ez@hitachi.com>,
        Len Brown <len.brown@intel.com>,
        "Christopher S. Hall" <christopher.s.hall@intel.com>,
        Adrian Hunter <adrian.hunter@intel.com>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 1/3] arch, x86, tsc deadline clockevent dev: reduce frequency roundoff error
References: <20160713130344.8319-1-nicstange@gmail.com>
	<20160713130344.8319-2-nicstange@gmail.com>
	<20160713134900.GU30154@twins.programming.kicks-ass.net>
	<fe5b1c72-2371-bdaa-3f56-dd6e49368d35@redhat.com>
Date: Wed, 13 Jul 2016 16:31:51 +0200
In-Reply-To: <fe5b1c72-2371-bdaa-3f56-dd6e49368d35@redhat.com> (Paolo
	Bonzini's message of "Wed, 13 Jul 2016 15:51:57 +0200")
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Paolo Bonzini <pbonzini@redhat.com> writes:

> On 13/07/2016 15:49, Peter Zijlstra wrote:
>> On Wed, Jul 13, 2016 at 03:03:42PM +0200, Nicolai Stange wrote:
>> 
>>>  		clockevents_config_and_register(levt,
>>> +						(u32)(((u64)tsc_khz * 1000) /
>>> +							TSC_DIVISOR),
>>>  						0xF, ~0UL);
>> 
>> div_u64() perhaps ?
>
> Or just squash together the two patches and do
>
> 	tsc_khz * (1000 / TSC_DIVISOR)
>
> because with TSC_DIVISOR equal to 2/4/8 there is no error from
> reassociating the operation.

Oh great, I didn't see this. Will resend.

Thanks,

Nicolai