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

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Message-ID: <87pmkgsf31.ffs@tglx>
Date:   Sat, 14 May 2022 10:17:38 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
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 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().

Thanks,

        tglx