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SubjectRE: [PATCH v6 2/2] clocksource: Add Intel Keem Bay timer support
Date
> -----Original Message-----
> From: Thomas Gleixner <tglx@linutronix.de>
> Sent: Monday, September 27, 2021 3:11 AM
> To: Sanil, Shruthi <shruthi.sanil@intel.com>; daniel.lezcano@linaro.org;
> robh+dt@kernel.org; linux-kernel@vger.kernel.org;
> devicetree@vger.kernel.org
> Cc: andriy.shevchenko@linux.intel.com; kris.pan@linux.intel.com;
> mgross@linux.intel.com; Thokala, Srikanth <srikanth.thokala@intel.com>;
> Raja Subramanian, Lakshmi Bai <lakshmi.bai.raja.subramanian@intel.com>;
> Sangannavar, Mallikarjunappa <mallikarjunappa.sangannavar@intel.com>;
> Sanil, Shruthi <shruthi.sanil@intel.com>
> Subject: Re: [PATCH v6 2/2] clocksource: Add Intel Keem Bay timer support
>
> On Tue, Sep 07 2021 at 00:06, shruthi sanil wrote:
> > +
> > +/* Provides a unique ID for each timer */ static
> > +DEFINE_IDA(keembay_timer_ida);
>
> > +
> > + timer_id = ida_alloc(&keembay_timer_ida, GFP_KERNEL);
> > + if (timer_id < 0) {
> > + ret = timer_id;
> > + goto err_keembay_ce_to_free;
> > + }
>
> May I ask what the purpose of the IDA, which is backed by a full blown
> xarray, is here?
>
> AFAICT all you want is a unique number for the timer name for up to 8
> timers.
>
> > + timer_name = kasprintf(GFP_KERNEL, "keembay_timer%d",
> timer_id);
>
> So what's wrong about:
>
> static unsigned int keembay_timer_id;
>
> timer_name = kasprintf(GFP_KERNEL, "keembay_timer%d",
> keembay_timer_id++);
>
> Hmm?

Yes, we had initially implemented it in the similar way,
but in the course of review it got changed to use IDA.

>
> > +
> > + clockevents_config_and_register(&keembay_ce_to->clkevt,
> > + timer_of_rate(keembay_ce_to),
> > + 1,
> > + U32_MAX);
>
> Aside of that what's the point of registering more than one of those timers as
> clock event? The core will only use one and the rest is just going to use
> memory for no value.

Instead of
keembay_ce_to->clkevt.cpumask = cpumask_of(0);
can I update it as
keembay_ce_to->clkevt.cpumask = cpu_possible_mask;
so that each timer would be associated with different cores?

Thanks,
Shruthi

>
> Thanks,
>
> tglx

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