linux-kernel - Re: [RFC PATCH v2 03/14] x86/hpet: Calculate ticks-per-second in a separate function

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Message-ID: <20190409020405.GA7070@ranerica-svr.sc.intel.com>
Date:   Mon, 8 Apr 2019 19:04:05 -0700
From:   Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Ingo Molnar <mingo@...nel.org>, Borislav Petkov <bp@...e.de>,
        Ashok Raj <ashok.raj@...el.com>,
        Andi Kleen <andi.kleen@...el.com>,
        Peter Zijlstra <peterz@...radead.org>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org,
        Ricardo Neri <ricardo.neri@...el.com>,
        "H. Peter Anvin" <hpa@...or.com>, Tony Luck <tony.luck@...el.com>,
        Clemens Ladisch <clemens@...isch.de>,
        Arnd Bergmann <arnd@...db.de>,
        Philippe Ombredanne <pombredanne@...b.com>,
        Kate Stewart <kstewart@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>
Subject: Re: [RFC PATCH v2 03/14] x86/hpet: Calculate ticks-per-second in a
 separate function

On Tue, Mar 26, 2019 at 10:03:02PM +0100, Thomas Gleixner wrote:
> On Wed, 27 Feb 2019, Ricardo Neri wrote:
> >  int hpet_alloc(struct hpet_data *hdp)
> >  {
> >  	u64 cap, mcfg;
> > @@ -845,7 +868,6 @@ int hpet_alloc(struct hpet_data *hdp)
> >  	size_t siz;
> >  	struct hpet __iomem *hpet;
> >  	static struct hpets *last;
> > -	unsigned long period;
> >  	unsigned long long temp;
> >  	u32 remainder;
> >  
> > @@ -881,6 +903,8 @@ int hpet_alloc(struct hpet_data *hdp)
> >  
> >  	cap = readq(&hpet->hpet_cap);
> >  
> > +	temp = hpet_get_ticks_per_sec(cap);
> 
> Just putting stuff to random places does not make the code any better.

This seems to not be needed. I'll remove it and directly save the result
in hpetp->hp_tick_freq;

> 
> >  	ntimer = ((cap & HPET_NUM_TIM_CAP_MASK) >> HPET_NUM_TIM_CAP_SHIFT) + 1;
> >  
> >  	if (hpetp->hp_ntimer != ntimer) {
> > @@ -897,11 +921,6 @@ int hpet_alloc(struct hpet_data *hdp)
> >  
> >  	last = hpetp;
> >  
> > -	period = (cap & HPET_COUNTER_CLK_PERIOD_MASK) >>
> > -		HPET_COUNTER_CLK_PERIOD_SHIFT; /* fs, 10^-15 */
> > -	temp = 1000000000000000uLL; /* 10^15 femtoseconds per second */
> > -	temp += period >> 1; /* round */
> > -	do_div(temp, period);
> >  	hpetp->hp_tick_freq = temp; /* ticks per second */
> 
> What's wrong with the obvious:
> 
>        hpetp->hp_tick_freq = hpet_get_ticks_per_sec(cap);
> 
> Hmm?

Nothing wrong. I'll implement this change.

Thanks and BR,
Ricardo