linux-kernel - Re: [PATCH v6 15/29] x86/hpet: Add helper function hpet_set_comparator

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Message-ID: <20220517225443.GA8069@ranerica-svr.sc.intel.com>
Date:   Tue, 17 May 2022 15:54:43 -0700
From:   Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     x86@...nel.org, Tony Luck <tony.luck@...el.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Stephane Eranian <eranian@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Joerg Roedel <joro@...tes.org>,
        Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>,
        David Woodhouse <dwmw2@...radead.org>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Nicholas Piggin <npiggin@...il.com>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>,
        Ricardo Neri <ricardo.neri@...el.com>,
        iommu@...ts.linux-foundation.org, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 15/29] x86/hpet: Add helper function
 hpet_set_comparator_periodic()

On Sat, May 14, 2022 at 10:17:38AM +0200, Thomas Gleixner wrote:
> On Fri, May 13 2022 at 14:19, Ricardo Neri wrote:
> > On Fri, May 06, 2022 at 11:41:13PM +0200, Thomas Gleixner wrote:
> >> The argument about not bloating the code
> >> with an "obvious???" function which is quite small is slightly beyond my
> >> comprehension level.
> >
> > That obvious function would look like this:
> >
> > void hpet_set_comparator_one_shot(int channel, u32 delta)
> > {
> > 	u32 count;
> >
> > 	count = hpet_readl(HPET_COUNTER);
> > 	count += delta;
> > 	hpet_writel(count, HPET_Tn_CMP(channel));
> > }
> 
> This function only works reliably when the delta is large. See
> hpet_clkevt_set_next_event().

That is a good point. One more reason to not have a
hpet_set_comparator_one_shot(), IMO.

Thanks and BR,
Ricardo