From: Nylon Chen <nylon.chen@sifive.com>
To: "Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>
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 2/3] pwm: sifive: change the PWM algorithm
Date: Fri, 12 Apr 2024 10:07:12 +0800 [thread overview]
Message-ID: <CAHh=Yk-WmzJe0vb+noX8Gb13BL2SOB=MwSB=F9nH_G-j9zi1Lw@mail.gmail.com> (raw)
In-Reply-To: <CAHh=Yk8MXy73d8M1J5bVu4spDMbjQDneVTqA=Ts=SGPDO7PXMQ@mail.gmail.com>
Nylon Chen <nylon.chen@sifive.com> 於 2024年4月2日 週二 上午10:08寫道：
>
> Uwe Kleine-König <u.kleine-koenig@pengutronix.de> 於 2024年3月19日 週二 上午2:16寫道：
> >
> > On Thu, Feb 22, 2024 at 04:12:30PM +0800, Nylon Chen wrote:
> > > The `frac` variable represents the pulse inactive time, and the result
> > > of this algorithm is the pulse active time.
> > > Therefore, we must reverse the result.
> > >
> > > The reference is SiFive FU740-C000 Manual[0]
> > >
> > > Link: https://sifive.cdn.prismic.io/sifive/1a82e600-1f93-4f41-b2d8-86ed8b16acba_fu740-c000-manual-v1p6.pdf [0]
> > >
> > > Co-developed-by: Zong Li <zong.li@sifive.com>
> > > Signed-off-by: Zong Li <zong.li@sifive.com>
> > > Co-developed-by: Vincent Chen <vincent.chen@sifive.com>
> > > Signed-off-by: Vincent Chen <vincent.chen@sifive.com>
> > > Signed-off-by: Nylon Chen <nylon.chen@sifive.com>
> > > ---
> > > drivers/pwm/pwm-sifive.c | 10 ++++++----
> > > 1 file changed, 6 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/drivers/pwm/pwm-sifive.c b/drivers/pwm/pwm-sifive.c
> > > index eabddb7c7820..a586cfe4191b 100644
> > > --- a/drivers/pwm/pwm-sifive.c
> > > +++ b/drivers/pwm/pwm-sifive.c
> > > @@ -110,9 +110,10 @@ static int pwm_sifive_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
> > > struct pwm_state *state)
> > > {
> > > struct pwm_sifive_ddata *ddata = pwm_sifive_chip_to_ddata(chip);
> > > - u32 duty, val;
> > > + u32 duty, val, inactive;
> > >
> > > - duty = readl(ddata->regs + PWM_SIFIVE_PWMCMP(pwm->hwpwm));
> > > + inactive = readl(ddata->regs + PWM_SIFIVE_PWMCMP(pwm->hwpwm));
> > > + duty = (1U << PWM_SIFIVE_CMPWIDTH) - 1 - inactive;
> > >
> > > state->enabled = duty > 0;
> > >
> > > @@ -123,7 +124,7 @@ static int pwm_sifive_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
> > > state->period = ddata->real_period;
> > > state->duty_cycle =
> > > (u64)duty * ddata->real_period >> PWM_SIFIVE_CMPWIDTH;
> > > - state->polarity = PWM_POLARITY_INVERSED;
> > > + state->polarity = PWM_POLARITY_NORMAL;
> > >
> > > return 0;
> > > }
> > > @@ -139,7 +140,7 @@ static int pwm_sifive_apply(struct pwm_chip *chip, struct pwm_device *pwm,
> > > int ret = 0;
> > > u32 frac;
> > >
> > > - if (state->polarity != PWM_POLARITY_INVERSED)
> > > + if (state->polarity != PWM_POLARITY_NORMAL)
> > > return -EINVAL;
> > >
> > > cur_state = pwm->state;
> > > @@ -159,6 +160,7 @@ static int pwm_sifive_apply(struct pwm_chip *chip, struct pwm_device *pwm,
> > > frac = DIV64_U64_ROUND_CLOSEST(num, state->period);
Hi Uwe,
> > > /* The hardware cannot generate a 100% duty cycle */
Do you mean that if the inference is correct, this comment should be modified?
> >
> > Is this still true now that we know that PWM_SIFIVE_PWMCMP is the
> > inactive time in a period? If you fix that, the same claim in the header
> > of the driver needs adaption, too.
> I believe the statement is true, but I don't know which part the
> driver header file refers to.
> >
> > > frac = min(frac, (1U << PWM_SIFIVE_CMPWIDTH) - 1);
> > > + frac = (1U << PWM_SIFIVE_CMPWIDTH) - 1 - frac;
> >
> > I like the additional variable in pwm_sifive_get_state(). Can you please
> > add one here, too?
> got it
> >
> > > mutex_lock(&ddata->lock);
> > > if (state->period != ddata->approx_period) {
> >
> Thank you for taking the time to help me review my implementation.
>
> Nylon
> > Best regards
> > Uwe
> >
> > --
> > Pengutronix e.K. | Uwe Kleine-König |
> > Industrial Linux Solutions | https://www.pengutronix.de/ |
next prev parent reply other threads:[~2024-04-12 2:07 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 [this message]
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
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