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Date:   Fri, 13 Jan 2023 19:39:01 +0100
From:   Uwe =?utf-8?Q?Kleine-K=C3=B6nig?= <u.kleine-koenig@pengutronix.de>
To:     Sasha Finkelstein <fnkl.kernel@gmail.com>
Cc:     thierry.reding@gmail.com, robh+dt@kernel.org,
        krzysztof.kozlowski+dt@linaro.org, marcan@marcan.st,
        sven@svenpeter.dev, alyssa@rosenzweig.io, asahi@lists.linux.dev,
        linux-arm-kernel@lists.infradead.org, linux-pwm@vger.kernel.org,
        devicetree@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v6 2/5] pwm: Add Apple PWM controller
Message-ID: <20230113183901.gt5vdmidprxbzzer@pengutronix.de>
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On Fri, Jan 13, 2023 at 09:25:08PM +0300, Sasha Finkelstein wrote:
> On Wed, 11 Jan 2023 at 02:06, Uwe Kleine-K=F6nig
> <u.kleine-koenig@pengutronix.de> wrote:
> > > + * Limitations:
> > > + * - The writes to cycle registers are shadowed until a write to
> > > + *   the control register.
> > > + * - If both OFF_CYCLES and ON_CYCLES are set to 0, the output
> > > + *   is a constant off signal.
> >
> > How does the PWM behave with *APPLE_PWM_CTRLAPPLE_PWM_CTRL =3D 0?
> > (typically: drives constant low)
> >
> APPLE_PWM_CTRL =3D 0 implies that the APPLE_CTRL_ENABLE bit is set low, w=
hich
> turns off the pwm signal (constant low). I do not think that it is
> necessary to explicitly
> specify that case in the comments.

This is an information that I want to have available. Ideally easily
greppable by using the format that other drivers use for that, too.
(The command I usually use is:

	sed -rn '/Limitations:/,/\*\/?$/p' drivers/pwm/*.c

so if you make sure your info is added accordingly that would be good.)

This is useful to answer questions like: Can I reasonably expect that a
disabled PWM respects the configured polarity.

> > Can you please rename such that the (maybe new) name for APPLE_PWM_CTRL
> > is a prefix for the (maybe new) APPLE_CTRL_ENABLE and the other register
> > bit definitions?
> To make sure, you want the register named APPLE_PWM_CTRL, and the bits na=
med
> APPLE_PWM_CTRL_ENABLE, APPLE_PWM_CTRL_MODE and so on?

Yes.

Best regards
Uwe

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

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