From: "Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>
To: Nylon Chen <nylon.chen@sifive.com>
Cc: linux-riscv@lists.infradead.org, devicetree@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-pwm@vger.kernel.org,
conor@kernel.org, robh+dt@kernel.org,
krzysztof.kozlowski+dt@linaro.org, palmer@dabbelt.com,
paul.walmsley@sifive.com, aou@eecs.berkeley.edu,
thierry.reding@gmail.com, vincent.chen@sifive.com,
zong.li@sifive.com, nylon7717@gmail.com
Subject: Re: [PATCH v9 3/3] pwm: sifive: Fix the error in the idempotent test within the pwm_apply_state_debug function
Date: Fri, 12 Apr 2024 09:05:32 +0200 [thread overview]
Message-ID: <xf6ympnaljfjztptb5w5qdpuluckptozdz5a7gtuycsev32ngr@x2ovibqv6evr> (raw)
In-Reply-To: <CAHh=Yk92=hp+kaTJWL13_jwJ5gzAAi8gbRF=Ns9=yq2trRUQEg@mail.gmail.com>
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On Tue, Apr 02, 2024 at 10:01:39AM +0800, Nylon Chen wrote:
> Uwe Kleine-König <u.kleine-koenig@pengutronix.de> 於 2024年3月19日 週二 上午2:17寫道：
> >
> > Hello,
> >
> > On Thu, Feb 22, 2024 at 04:12:31PM +0800, Nylon Chen wrote:
> > > 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.
> > >
> > > e.g.
> > > $ echo 110 > /sys/devices/platform/led-controller-1/leds/d12/brightness
> > > $ .apply is not idempotent (ena=1 pol=0 1739692/4032985) -> (ena=1 pol=0 1739630/4032985)
> > >
> > > Co-developed-by: Zong Li <zong.li@sifive.com>
> > > Signed-off-by: Zong Li <zong.li@sifive.com>
> > > Signed-off-by: Nylon Chen <nylon.chen@sifive.com>
> > > ---
> > > drivers/pwm/pwm-sifive.c | 2 +-
> > > 1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/pwm/pwm-sifive.c b/drivers/pwm/pwm-sifive.c
> > > index a586cfe4191b..bebcbebacccd 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);
> > > dev_dbg(ddata->chip.dev,
> > > "New real_period = %u ns\n", ddata->real_period);
> > > }
> Hi Uwe
> >
> > pwm_sifive_apply has a DIV64_U64_ROUND_CLOSEST(). I wonder if that needs
> > adaption, too?!
> According to my experiments, no adjustment is necessary.
Did you enable PWM_DEBUG and tested with something like:
seq 5000 100000 | while read p; do echo p > /sys/class/pwm/pwmchipX/pwmY/period; done
and then verified that this test didn't result in kernel messages about
wrong settings?
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:[~2024-04-12 7:05 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-22 8:12 [PATCH v9 0/3] Change PWM-controlled LED pin active mode and algorithm Nylon Chen
2024-02-22 8:12 ` [PATCH v9 1/3] riscv: dts: sifive: unleashed/unmatched: Remove PWM controlled LED's active-low properties Nylon Chen
2024-02-22 8:12 ` [PATCH v9 2/3] pwm: sifive: change the PWM algorithm Nylon Chen
2024-03-18 18:16 ` Uwe Kleine-König
2024-04-02 2:08 ` Nylon Chen
2024-04-12 2:07 ` Nylon Chen
2024-04-12 7:01 ` Uwe Kleine-König
2024-02-22 8:12 ` [PATCH v9 3/3] pwm: sifive: Fix the error in the idempotent test within the pwm_apply_state_debug function Nylon Chen
2024-03-18 18:17 ` Uwe Kleine-König
2024-04-02 2:01 ` Nylon Chen
2024-04-12 7:05 ` Uwe Kleine-König [this message]
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