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Date:   Sat, 17 Apr 2021 17:50:09 +0200
From:   Uwe =?utf-8?Q?Kleine-K=C3=B6nig?= <u.kleine-koenig@pengutronix.de>
To:     Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@toshiba.co.jp>
Cc:     Rob Herring <robh+dt@kernel.org>,
        Thierry Reding <thierry.reding@gmail.com>,
        Lee Jones <lee.jones@linaro.org>, devicetree@vger.kernel.org,
        linux-pwm@vger.kernel.org, punit1.agrawal@toshiba.co.jp,
        yuji2.ishikawa@toshiba.co.jp, linux-arm-kernel@lists.infradead.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v4 2/2] pwm: visconti: Add Toshiba Visconti SoC PWM
 support
Message-ID: <20210417155009.vnqxx3fn2yjzp3qc@pengutronix.de>
References: <20210409230837.1919744-1-nobuhiro1.iwamatsu@toshiba.co.jp>
 <20210409230837.1919744-3-nobuhiro1.iwamatsu@toshiba.co.jp>
 <20210410135321.oissremqropvrpd3@pengutronix.de>
 <20210412025536.i5chpp6sighunvfx@toshiba.co.jp>
 <20210412070232.6q3cgqvuj53p4cmi@pengutronix.de>
 <20210416080721.oa7xdvu22w2b2rkf@toshiba.co.jp>
 <20210416094426.x4gyw3drp2fcwczs@pengutronix.de>
 <20210416121523.c34trzsrlcjuzirl@toshiba.co.jp>
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Hello Nobuhiro,

On Fri, Apr 16, 2021 at 09:15:23PM +0900, Nobuhiro Iwamatsu wrote:
> > > > For me the critical (and only) difference between "off" and
> > > > "duty cycle =3D 0" is that when a new configuration is to be applie=
d. In
> > > > the "off" state a new period can (and should) start immediately, wh=
ile
> > > > with "duty_cycle =3D 0" the rising edge should be delayed until the
> > > > currently running period is over.[1]
> > > >=20
> > > > So the thing to do here (IMHO) is:
> > > >=20
> > > > Iff with PIPGM_PCSR =3D 0 configuring a new setting (that is finali=
zed
> > > > with writing a non-zero value to PIPGM_PCSR) completes the currently
> > > > running period, then always assume the PWM as enabled.
> > >=20
> > > Yes, this device works that way.
> >=20
> > OK, then please use
> >=20
> > 	state->enabled =3D true
> >=20
> > unconditionally in visconti_pwm_get_state().
>=20
> Please let me check.
> If I unconditionally add 'state->enabled =3D true' to visconti_pwm_get_st=
ate(),
> state->enabled is set to true because visconti_pwm_get_state() is called =
when
> the device is created (this is when I write the device number to the expo=
rt of
> /sys/class/pwm/pwmchip0 ).
> And since PIPGM_PCSR is 0 in this state, the pulse by PWM is not output.

A PWM that is currently configured with .enabled =3D true and .duty_cycle
=3D 0 doesn't have a pulse, so this is fine.

> However, I think this means that the device is working as this driver.

I don't understand this sentence.

Best regards
Uwe

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

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