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Date:   Fri, 29 Oct 2021 18:06:44 +0200
From:   Uwe =?utf-8?Q?Kleine-K=C3=B6nig?= <u.kleine-koenig@pengutronix.de>
To:     =?utf-8?Q?M=C3=A5rten?= Lindahl <marten.lindahl@axis.com>
Cc:     Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>,
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        linux-arm-kernel@lists.infradead.org,
        linux-samsung-soc@vger.kernel.org, linux-pwm@vger.kernel.org,
        kernel@axis.com
Subject: Re: [PATCH v3] pwm: pwm-samsung: Trigger manual update when
 disabling PWM
Message-ID: <20211029160644.vtaaxy2txszcjybn@pengutronix.de>
References: <20210909101042.17431-1-marten.lindahl@axis.com>
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On Thu, Sep 09, 2021 at 12:10:42PM +0200, M=E5rten Lindahl wrote:
> When duty-cycle is at full level (100%), the TCNTn and TCMPn registers
> needs to be flushed in order to disable the signal. The PWM manual does
> not say anything about this, but states that only clearing the TCON
> auto-reload bit should be needed, and this seems to be true when the PWM
> duty-cycle is not at full level. This can be observed on an Axis
> ARTPEC-8, by running:
>=20
>   echo <period> > pwm/period
>   echo <period> > pwm/duty_cycle
>   echo 1 > pwm/enable
>   echo 0 > pwm/enable
>=20
> Since the TCNTn and TCMPn registers are activated when enabling the PWM
> (setting TCON auto-reload bit), and are not touched when disabling the
> PWM, the double buffered auto-reload function seems to be still active.
> Lowering duty-cycle, and restoring it again in between the enabling and
> disabling, makes the disable work since it triggers a reload of the
> TCNTn and TCMPn registers.
>=20
> Fix this by securing a reload of the TCNTn and TCMPn registers when
> disabling the PWM and having a full duty-cycle.
>=20
> Signed-off-by: M=E5rten Lindahl <marten.lindahl@axis.com>

Acked-by: Uwe Kleine-K=F6nig <u.kleine-koenig@pengutronix.de>

Thanks
Uwe

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

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