From:   Peng Fan <peng.fan@nxp.com>
To:     Daniel Lezcano <daniel.lezcano@linaro.org>,
        "Peng Fan (OSS)" <peng.fan@oss.nxp.com>,
        "tglx@linutronix.de" <tglx@linutronix.de>,
        "shawnguo@kernel.org" <shawnguo@kernel.org>,
        "s.hauer@pengutronix.de" <s.hauer@pengutronix.de>
CC:     "kernel@pengutronix.de" <kernel@pengutronix.de>,
        "festevam@gmail.com" <festevam@gmail.com>,
        dl-linux-imx <linux-imx@nxp.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-arm-kernel@lists.infradead.org" 
        <linux-arm-kernel@lists.infradead.org>,
        "van.freenix@gmail.com" <van.freenix@gmail.com>
Subject: RE: [PATCH 2/2] clocksource: timer-imx-sysctr: set cpumask to
 cpu_possible_mask
Thread-Topic: [PATCH 2/2] clocksource: timer-imx-sysctr: set cpumask to
 cpu_possible_mask
Thread-Index: AQHX5rIpXvvERj8j10espZggT53Quawe/42AgATgKoA=
Date:   Sun, 5 Dec 2021 12:53:51 +0000
Message-ID: <DU0PR04MB9417992CCF80CAA4CF78F8EF886C9@DU0PR04MB9417.eurprd04.prod.outlook.com>
References: <20211201125030.2307746-1-peng.fan@oss.nxp.com>
 <20211201125030.2307746-2-peng.fan@oss.nxp.com>
 <80578aa9-35dd-02ca-fb07-5895991572e2@linaro.org>
In-Reply-To: <80578aa9-35dd-02ca-fb07-5895991572e2@linaro.org>
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> Subject: Re: [PATCH 2/2] clocksource: timer-imx-sysctr: set cpumask to
> cpu_possible_mask
>=20
> On 01/12/2021 13:50, Peng Fan (OSS) wrote:
> > From: Peng Fan <peng.fan@nxp.com>
> >
> > Actually we have CLOCK_EVT_FEAT_DYNIRQ, the irq affinity will be
> > runtime changed and no issue. But the system counter timer is not tied
> > to CPU0, so use cpu_possible_mask here.
>=20
> Did you mean:
>=20
> "There is no reason to tie the system counter timer to CPU0, change its
> affinity to cpu_possible_mask.
>=20
> Moreover, the timer has the flag CLOCK_EVT_FEAT_DYNIRQ set, changing to
> cpu_possibl_mask will reduce the number of wakeups related to the system
> timer"

The syctr interrupt could be set affinity to any cores in the SoC. Default =
affinity
is set to cpu 0.

This timer will be used as broadcast timer on all the i.MX SoCs. Because DY=
NIRQ
flag set, the core time framework will runtime set the interrupt affinity t=
o the cores
that needs to wake up and the cpumask will runtime set to the core that wil=
l be
wake up. So even the sysctr initialization use cpumask 0, there is no issue=
,
the current patch is just use cpu_possible_mask to show the fact that the
timer supports routed to all the cpu cores and nothing else.

Thanks,
Peng.

>=20
> ?
>=20
> Note you may want to explain why 'there is no reason'
>=20
>=20
> > Signed-off-by: Peng Fan <peng.fan@nxp.com>
> > ---
> >  drivers/clocksource/timer-imx-sysctr.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/clocksource/timer-imx-sysctr.c
> > b/drivers/clocksource/timer-imx-sysctr.c
> > index 2b309af11266..55a8e198d2a1 100644
> > --- a/drivers/clocksource/timer-imx-sysctr.c
> > +++ b/drivers/clocksource/timer-imx-sysctr.c
> > @@ -119,7 +119,7 @@ static struct timer_of to_sysctr =3D {
> >
> >  static void __init sysctr_clockevent_init(void)  {
> > -	to_sysctr.clkevt.cpumask =3D cpumask_of(0);
> > +	to_sysctr.clkevt.cpumask =3D cpu_possible_mask;
> >
> >  	clockevents_config_and_register(&to_sysctr.clkevt,
> >  					timer_of_rate(&to_sysctr),
> >
>=20
>=20
> --
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