From: "Uwe Kleine-König" <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, krzysztof.kozlowski+dt@linaro.org,
conor+dt@kernel.org, paul.walmsley@sifive.com,
palmer@dabbelt.com, aou@eecs.berkeley.edu,
thierry.reding@gmail.com, 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
Date: Mon, 8 Jan 2024 10:25:33 +0100 [thread overview]
Message-ID: <djdio3t54er4vqnjp4yjeoghopd5gdkybktvojzzvhs5ijxmwg@4db2hsmtoh6e> (raw)
In-Reply-To: <CAHh=Yk-9-M2G_cfdxLig2d0g1DucEytXhfFO5dp5HcDn+egWBw@mail.gmail.com>
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Hello Nylon,
On Mon, Jan 08, 2024 at 04:27:40PM +0800, Nylon Chen wrote:
> Uwe Kleine-König <u.kleine-koenig@pengutronix.de> 於 2023年12月12日 週二 上午4:50寫道：
> > 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_sifive_ddata *ddata,
> > >
> > > /* As scale <= 15 the shift operation cannot overflow. */
> > > num = (unsigned long long)NSEC_PER_SEC << (PWM_SIFIVE_CMPWIDTH + scale);
> > > - ddata->real_period = div64_ul(num, rate);
> > > + ddata->real_period = 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=1 pol=0 1739692/4032985)
> -> (ena=1 pol=0 1739630/4032985)
> root@unmatched:~# echo 120 >
> /sys/devices/platform/led-controller-1/leds/d12/brightness
> [ 709.817554] .apply is not idempotent (ena=1 pol=0 1897846/4032985)
> -> (ena=1 pol=0 1897784/4032985)
>
> 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.
>
> 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
--
Pengutronix e.K. | Uwe Kleine-König |
Industrial Linux Solutions | https://www.pengutronix.de/ |
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prev parent reply other threads:[~2024-01-08 9:44 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-24 10:19 [v5 0/2] Change PWM-controlled LED pin active mode and algorithm Nylon Chen
2023-10-24 10:19 ` [v5 1/2] riscv: dts: sifive: unleashed/unmatched: Remove PWM controlled LED's active-low properties Nylon Chen
2023-10-24 14:55 ` Conor Dooley
2023-10-25 9:32 ` Nylon Chen
2023-10-25 14:14 ` Conor Dooley
2023-10-27 8:54 ` Nylon Chen
2023-12-11 20:42 ` Uwe Kleine-König
2023-10-24 10:19 ` [v5 2/2] pwm: sifive: change the PWM controlled LED algorithm Nylon Chen
2023-11-09 7:02 ` Nylon Chen
2023-11-09 8:22 ` Krzysztof Kozlowski
2023-12-06 2:35 ` Nylon Chen
2023-12-11 20:49 ` Uwe Kleine-König
2024-01-08 8:27 ` Nylon Chen
2024-01-08 9:25 ` Uwe Kleine-König [this message]
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