linux-kernel - Re: [v5 2/2] pwm: sifive: change the PWM controlled LED algorithm

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Date:   Thu, 9 Nov 2023 15:02:18 +0800
From:   Nylon Chen <nylon.chen@...ive.com>
To:     linux-pwm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-riscv@...ts.infradead.org, devicetree@...r.kernel.org,
        robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org,
        conor+dt@...nel.org, paul.walmsley@...ive.com, palmer@...belt.com,
        aou@...s.berkeley.edu, thierry.reding@...il.com,
        u.kleine-koenig@...gutronix.de, emil.renner.berthing@...onical.com,
        vincent.chen@...ive.com
Cc:     greentime.hu@...ive.com, zong.li@...ive.com, nylon7717@...il.com
Subject: Re: [v5 2/2] pwm: sifive: change the PWM controlled LED algorithm

Hi, Ping on the series.

Uwe, is there anything more I can do to push the process forward?

Nylon Chen <nylon.chen@...ive.com> 於 2023年10月24日 週二 下午6:19寫道：

>
> 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]
>
> Signed-off-by: Nylon Chen <nylon.chen@...ive.com>
> Signed-off-by: Vincent Chen <vincent.chen@...ive.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..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);
>         dev_dbg(ddata->chip.dev,
>                 "New real_period = %u ns\n", ddata->real_period);
>  }
> @@ -121,13 +121,14 @@ static int pwm_sifive_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
>                 state->enabled = false;
>
>         state->period = ddata->real_period;
> +
> +       duty = (1U << PWM_SIFIVE_CMPWIDTH) - 1 - duty;
>         state->duty_cycle =
>                 (u64)duty * ddata->real_period >> PWM_SIFIVE_CMPWIDTH;
> -       state->polarity = PWM_POLARITY_INVERSED;
> +       state->polarity = PWM_POLARITY_NORMAL;
>
>         return 0;
>  }
> -
>  static int pwm_sifive_apply(struct pwm_chip *chip, struct pwm_device *pwm,
>                             const struct pwm_state *state)
>  {
> @@ -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;
> @@ -158,6 +159,7 @@ static int pwm_sifive_apply(struct pwm_chip *chip, struct pwm_device *pwm,
>         num = (u64)duty_cycle * (1U << PWM_SIFIVE_CMPWIDTH);
>         frac = DIV64_U64_ROUND_CLOSEST(num, state->period);
>         /* The hardware cannot generate a 100% duty cycle */
> +       frac = (1U << PWM_SIFIVE_CMPWIDTH) - 1 - frac;
>         frac = min(frac, (1U << PWM_SIFIVE_CMPWIDTH) - 1);
>
>         mutex_lock(&ddata->lock);
> --
> 2.42.0
>