Re: [PATCH v2 05/10] pwm: ntxec: Add driver for PWM function in Netronix EC

From: Lee Jones <lee.jones@linaro.org>
To: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: "Jonathan Neuschäfer" <j.neuschaefer@gmx.net>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"Rob Herring" <robh+dt@kernel.org>,
	"Thierry Reding" <thierry.reding@gmail.com>,
	"Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>,
	"Alessandro Zummo" <a.zummo@towertech.it>,
	"Alexandre Belloni" <alexandre.belloni@bootlin.com>,
	"Shawn Guo" <shawnguo@kernel.org>,
	"Sascha Hauer" <s.hauer@pengutronix.de>,
	"Pengutronix Kernel Team" <kernel@pengutronix.de>,
	"Fabio Estevam" <festevam@gmail.com>,
	"NXP Linux Team" <linux-imx@nxp.com>,
	"Sam Ravnborg" <sam@ravnborg.org>,
	"Linus Walleij" <linus.walleij@linaro.org>,
	"Heiko Stuebner" <heiko.stuebner@theobroma-systems.com>,
	"Stephan Gerhold" <stephan@gerhold.net>,
	"Lubomir Rintel" <lkundrak@v3.sk>,
	"Mark Brown" <broonie@kernel.org>, allen <allen.chen@ite.com.tw>,
	"Mauro Carvalho Chehab" <mchehab+huawei@kernel.org>,
	"David S. Miller" <davem@davemloft.net>,
	"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
	"linux-pwm@vger.kernel.org" <linux-pwm@vger.kernel.org>,
	"linux-rtc@vger.kernel.org" <linux-rtc@vger.kernel.org>,
	"linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>,
	"Heiko Stuebner" <heiko@sntech.de>,
	"Josua Mayer" <josua.mayer@jm0.eu>,
	"Andreas Kemnade" <andreas@kemnade.info>,
	"Arnd Bergmann" <arnd@arndb.de>,
	"Daniel Palmer" <daniel@0x0f.com>
Subject: Re: [PATCH v2 05/10] pwm: ntxec: Add driver for PWM function in Netronix EC
Date: Tue, 8 Sep 2020 09:14:45 +0100	[thread overview]
Message-ID: <20200908081445.GC4400@dell> (raw)
In-Reply-To: <CAHp75VdUHoOyM3bObzhdfiqpne0AmSK_UakteTZxnjqJVrNV9A@mail.gmail.com>

On Sat, 05 Sep 2020, Andy Shevchenko wrote:

> On Saturday, September 5, 2020, Jonathan Neuschäfer <j.neuschaefer@gmx.net>
> wrote:
> 
> > The Netronix EC provides a PWM output which is used for the backlight
> > on some ebook readers. This patches adds a driver for the PWM output.
> >
> > Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
> > ---
> >
> > v2:
> > - Various grammar and style improvements, as suggested by Uwe Kleine-König,
> >   Lee Jones, and Alexandre Belloni
> > - Switch to regmap
> > - Prefix registers with NTXEC_REG_
> > - Add help text to the Kconfig option
> > - Use the .apply callback instead of the old API
> > - Add a #define for the time base (125ns)
> > - Don't change device state in .probe; this avoids multiple problems
> > - Rework division and overflow check logic to perform divisions in 32 bits
> > - Avoid setting duty cycle to zero, to work around a hardware quirk
> > ---
> >  drivers/pwm/Kconfig     |   8 ++
> >  drivers/pwm/Makefile    |   1 +
> >  drivers/pwm/pwm-ntxec.c | 160 ++++++++++++++++++++++++++++++++++++++++
> >  3 files changed, 169 insertions(+)
> >  create mode 100644 drivers/pwm/pwm-ntxec.c
> >
> > diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
> > index 7dbcf6973d335..7fd17c6cda95e 100644
> > --- a/drivers/pwm/Kconfig
> > +++ b/drivers/pwm/Kconfig
> > @@ -350,6 +350,14 @@ config PWM_MXS
> >           To compile this driver as a module, choose M here: the module
> >           will be called pwm-mxs.
> >
> > +config PWM_NTXEC
> > +       tristate "Netronix embedded controller PWM support"
> 
> 
> 
> 
> > +       depends on MFD_NTXEC && OF
> 
> 
> I don’t see need to reduce test coverage and use of the driver by sticking
> with OF. Actually it’s not used.

If the device is only known to boot with OF, then it's pointless
building it when !OF.  If you want to increase test coverage enable
COMPILE_TEST instead.

-- 
Lee Jones [李琼斯]
Senior Technical Lead - Developer Services
Linaro.org │ Open source software for Arm SoCs
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