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Date:   Mon, 29 Mar 2021 19:15:59 +0200
From:   Uwe =?utf-8?Q?Kleine-K=C3=B6nig?= <u.kleine-koenig@pengutronix.de>
To:     Clemens Gruber <clemens.gruber@pqgruber.com>
Cc:     linux-pwm@vger.kernel.org,
        Thierry Reding <thierry.reding@gmail.com>,
        Sven Van Asbroeck <TheSven73@gmail.com>,
        linux-kernel@vger.kernel.org, kernel@pengutronix.de
Subject: Re: [PATCH v6 6/7] pwm: pca9685: Restrict period change for
 prescaler users
Message-ID: <20210329171559.rfelpt42shlebct5@pengutronix.de>
References: <20210329125707.182732-1-clemens.gruber@pqgruber.com>
 <20210329125707.182732-6-clemens.gruber@pqgruber.com>
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On Mon, Mar 29, 2021 at 02:57:06PM +0200, Clemens Gruber wrote:
> @@ -330,14 +345,22 @@ static int pca9685_pwm_apply(struct pwm_chip *chip,=
 struct pwm_device *pwm,
> =20
>  	if (!state->enabled || duty < 1) {
>  		pca9685_pwm_set_duty(pca, pwm->hwpwm, 0);
> +		clear_bit(pwm->hwpwm, pca->prescaler_users);

Hmm, so if "my" channel runs at say

	.duty_cycle =3D 2539520 ns
	.period =3D 5079040 ns

and I call pwm_apply_state(mypwm, { .duty_cycle =3D 0, .period =3D 5079040,
enabled =3D true }); it might happen that another channel modifies the
period and I won't be able to return to the initial setting.

So I think it's sensible to only clear the user bit if the PWM is
disabled, but not if it is configured for duty_cycle =3D 0.

Does this make sense?

Best regards
Uwe

--=20
Pengutronix e.K.                           | Uwe Kleine-K=F6nig            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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