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Date: Mon, 8 Jan 2024 10:25:33 +0100
From: Uwe =?utf-8?Q?Kleine-K=C3=B6nig?= <u.kleine-koenig@pengutronix.de>
To: Nylon Chen <nylon.chen@sifive.com>
Cc: linux-pwm@vger.kernel.org, linux-kernel@vger.kernel.org, 
	linux-riscv@lists.infradead.org, devicetree@vger.kernel.org, robh+dt@kernel.org, 
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	emil.renner.berthing@canonical.com, vincent.chen@sifive.com, greentime.hu@sifive.com, 
	zong.li@sifive.com, nylon7717@gmail.com
Subject: Re: [v5 2/2] pwm: sifive: change the PWM controlled LED algorithm
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Hello Nylon,

On Mon, Jan 08, 2024 at 04:27:40PM +0800, Nylon Chen wrote:
> Uwe Kleine-K=C3=B6nig <u.kleine-koenig@pengutronix.de> =E6=96=BC 2023=E5=
=B9=B412=E6=9C=8812=E6=97=A5 =E9=80=B1=E4=BA=8C =E4=B8=8A=E5=8D=884:50=E5=
=AF=AB=E9=81=93=EF=BC=9A
> > On Tue, Oct 24, 2023 at 06:19:02PM +0800, Nylon Chen wrote:
> > > diff --git a/drivers/pwm/pwm-sifive.c b/drivers/pwm/pwm-sifive.c
> > > index eabddb7c7820..353c2342fbf1 100644
> > > --- a/drivers/pwm/pwm-sifive.c
> > > +++ b/drivers/pwm/pwm-sifive.c
> > > @@ -101,7 +101,7 @@ static void pwm_sifive_update_clock(struct pwm_si=
five_ddata *ddata,
> > >
> > >       /* As scale <=3D 15 the shift operation cannot overflow. */
> > >       num =3D (unsigned long long)NSEC_PER_SEC << (PWM_SIFIVE_CMPWIDT=
H + scale);
> > > -     ddata->real_period =3D div64_ul(num, rate);
> > > +     ddata->real_period =3D DIV_ROUND_UP_ULL(num, rate);
> >
> > It's unclear to me, why you changed that.
> Because there is a gap in idempotent tests.
> e.g.
> root@unmatched:~# echo 110 >
> /sys/devices/platform/led-controller-1/leds/d12/brightness
> [  706.987712] .apply is not idempotent (ena=3D1 pol=3D0 1739692/4032985)
> -> (ena=3D1 pol=3D0 1739630/4032985)
> root@unmatched:~# echo 120 >
> /sys/devices/platform/led-controller-1/leds/d12/brightness
> [  709.817554] .apply is not idempotent (ena=3D1 pol=3D0 1897846/4032985)
> -> (ena=3D1 pol=3D0 1897784/4032985)
>=20
> Round the result to the nearest whole number. This ensures that
> real_period is always a reasonable integer that is not lower than the
> actual value.
>=20
> After modification, idempotent errors can be avoided.

That's very welcome, however I think this should be a separate change.

I'll think about the rest of your changes when you send a new patch.

Best regards
Uwe

--=20
Pengutronix e.K.                           | Uwe Kleine-K=C3=B6nig         =
   |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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