From: "Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>
To: Paul Cercueil <paul@crapouillou.net>
Cc: Thierry Reding <thierry.reding@gmail.com>,
od@zcrc.me, linux-pwm@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 6/7] pwm: jz4740: Make PWM start with the active part
Date: Fri, 9 Aug 2019 19:10:58 +0200 [thread overview]
Message-ID: <20190809171058.gothydohec6qx7hu@pengutronix.de> (raw)
In-Reply-To: <20190809123031.24219-7-paul@crapouillou.net>
On Fri, Aug 09, 2019 at 02:30:30PM +0200, Paul Cercueil wrote:
> The PWM will always start with the inactive part. To counter that,
> when PWM is enabled we switch the configured polarity, and use
> 'period - duty + 1' as the real duty.
Where does the + 1 come from? This looks wrong. (So if duty=0 is
requested you use duty = period + 1?)
>
> Signed-off-by: Paul Cercueil <paul@crapouillou.net>
> ---
> drivers/pwm/pwm-jz4740.c | 22 +++++++++++++---------
> 1 file changed, 13 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/pwm/pwm-jz4740.c b/drivers/pwm/pwm-jz4740.c
> index 85e2110aae4f..8df898429d47 100644
> --- a/drivers/pwm/pwm-jz4740.c
> +++ b/drivers/pwm/pwm-jz4740.c
> @@ -121,6 +121,7 @@ static int jz4740_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
> *parent_clk = clk_get_parent(clk);
> unsigned long rate, parent_rate, period, duty;
> unsigned long long tmp;
> + bool polarity_inversed;
> int ret;
>
> parent_rate = clk_get_rate(parent_clk);
> @@ -183,24 +184,27 @@ static int jz4740_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
> /* Reset counter to 0 */
> regmap_write(jz4740->map, TCU_REG_TCNTc(pwm->hwpwm), 0);
>
> - /* Set duty */
> - regmap_write(jz4740->map, TCU_REG_TDHRc(pwm->hwpwm), duty);
> -
> /* Set period */
> regmap_write(jz4740->map, TCU_REG_TDFRc(pwm->hwpwm), period);
>
> + /*
> + * The PWM will always start with the inactive part. To counter that,
> + * when PWM is enabled we switch the configured polarity, and use
> + * 'period - duty + 1' as the real duty.
> + */
> +
> + /* Set duty */
> + regmap_write(jz4740->map, TCU_REG_TDHRc(pwm->hwpwm), period - duty + 1);
> +
Before you set duty first, then period, now you do it the other way
round. Is there a good reason?
> /* Set polarity */
> - switch (state->polarity) {
> - case PWM_POLARITY_NORMAL:
> + polarity_inversed = state->polarity == PWM_POLARITY_INVERSED;
> + if (!polarity_inversed ^ state->enabled)
Why does state->enabled suddenly matter here?
> regmap_update_bits(jz4740->map, TCU_REG_TCSRc(pwm->hwpwm),
> TCU_TCSR_PWM_INITL_HIGH, 0);
> - break;
> - case PWM_POLARITY_INVERSED:
> + else
> regmap_update_bits(jz4740->map, TCU_REG_TCSRc(pwm->hwpwm),
> TCU_TCSR_PWM_INITL_HIGH,
> TCU_TCSR_PWM_INITL_HIGH);
> - break;
> - }
>
> if (state->enabled)
> jz4740_pwm_enable(chip, pwm);
Best regards
Uwe
--
Pengutronix e.K. | Uwe Kleine-König |
Industrial Linux Solutions | http://www.pengutronix.de/ |
next prev parent reply other threads:[~2019-08-09 17:11 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-09 12:30 [PATCH 0/7] pwm: jz4740: Driver update Paul Cercueil
2019-08-09 12:30 ` [PATCH 1/7] pwm: jz4740: Obtain regmap from parent node Paul Cercueil
2019-08-09 16:51 ` Uwe Kleine-König
2019-08-09 17:04 ` Paul Cercueil
2019-08-12 6:18 ` Uwe Kleine-König
2019-08-09 12:30 ` [PATCH 2/7] pwm: jz4740: Use clocks from TCU driver Paul Cercueil
2019-08-09 16:55 ` Uwe Kleine-König
2019-08-09 12:30 ` [PATCH 3/7] pwm: jz4740: Drop dependency on MACH_INGENIC Paul Cercueil
2019-08-09 16:41 ` Uwe Kleine-König
2019-08-09 21:40 ` Paul Cercueil
2019-08-12 6:09 ` Uwe Kleine-König
2019-08-09 12:30 ` [PATCH 4/7] pwm: jz4740: Improve algorithm of clock calculation Paul Cercueil
2019-08-09 17:05 ` Uwe Kleine-König
2019-08-09 17:14 ` Paul Cercueil
2019-08-12 6:15 ` Uwe Kleine-König
2019-08-12 20:43 ` Paul Cercueil
2019-08-12 21:48 ` Uwe Kleine-König
2019-08-12 22:25 ` Paul Cercueil
[not found] ` <1565648183.2007.3@crapouillou.net>
2019-08-13 5:27 ` Uwe Kleine-König
2019-08-13 11:01 ` Paul Cercueil
2019-08-13 12:33 ` Uwe Kleine-König
2019-08-13 12:47 ` Paul Cercueil
2019-08-13 14:09 ` Uwe Kleine-König
2019-08-14 16:10 ` Paul Cercueil
2019-08-14 17:32 ` Uwe Kleine-König
2019-10-21 12:47 ` Paul Cercueil
2020-02-12 7:29 ` About rounding in the clk framework [Was: Re: [PATCH 4/7] pwm: jz4740: Improve algorithm of clock calculation] Uwe Kleine-König
2020-04-14 9:24 ` Uwe Kleine-König
2020-12-21 13:57 ` Uwe Kleine-König
2019-08-09 12:30 ` [PATCH 5/7] pwm: jz4740: Allow selection of PWM channels 0 and 1 Paul Cercueil
2019-08-09 12:30 ` [PATCH 6/7] pwm: jz4740: Make PWM start with the active part Paul Cercueil
2019-08-09 17:10 ` Uwe Kleine-König [this message]
2019-08-09 17:33 ` Paul Cercueil
2019-08-12 5:55 ` Uwe Kleine-König
2019-08-12 20:50 ` Paul Cercueil
2019-08-12 21:58 ` Uwe Kleine-König
2019-09-20 22:52 ` Thierry Reding
2019-08-09 12:30 ` [PATCH 7/7] pwm: jz4740: document known limitations Paul Cercueil
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