RE: [PATCH v6 2/2] clocksource: Add Intel Keem Bay timer support

[Sanil, Shruthi]

Hi Thomas

> -----Original Message-----
> From: Sanil, Shruthi
> Sent: Thursday, November 11, 2021 4:12 PM
> To: Thomas Gleixner <tglx@xxxxxxxxxxxxx>; daniel.lezcano@xxxxxxxxxx;
> robh+dt@xxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
> devicetree@xxxxxxxxxxxxxxx
> Cc: andriy.shevchenko@xxxxxxxxxxxxxxx; kris.pan@xxxxxxxxxxxxxxx;
> mgross@xxxxxxxxxxxxxxx; Thokala, Srikanth <srikanth.thokala@xxxxxxxxx>;
> Raja Subramanian, Lakshmi Bai <lakshmi.bai.raja.subramanian@xxxxxxxxx>;
> Sangannavar, Mallikarjunappa <mallikarjunappa.sangannavar@xxxxxxxxx>
> Subject: RE: [PATCH v6 2/2] clocksource: Add Intel Keem Bay timer support
> 
> > -----Original Message-----
> > From: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> > Sent: Monday, September 27, 2021 3:11 AM
> > To: Sanil, Shruthi <shruthi.sanil@xxxxxxxxx>;
> > daniel.lezcano@xxxxxxxxxx;
> > robh+dt@xxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
> > devicetree@xxxxxxxxxxxxxxx
> > Cc: andriy.shevchenko@xxxxxxxxxxxxxxx; kris.pan@xxxxxxxxxxxxxxx;
> > mgross@xxxxxxxxxxxxxxx; Thokala, Srikanth
> > <srikanth.thokala@xxxxxxxxx>; Raja Subramanian, Lakshmi Bai
> > <lakshmi.bai.raja.subramanian@xxxxxxxxx>;
> > Sangannavar, Mallikarjunappa <mallikarjunappa.sangannavar@xxxxxxxxx>;
> > Sanil, Shruthi <shruthi.sanil@xxxxxxxxx>
> > 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?
> 

Could you please help me with the above query?

Thanks,
Shruthi

> Thanks,
> Shruthi
> 
> >
> > Thanks,
> >
> >         tglx