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Date:   Mon, 23 Nov 2020 22:31:05 +0100
From:   Jonathan =?utf-8?Q?Neusch=C3=A4fer?= <j.neuschaefer@gmx.net>
To:     Alexandre Belloni <alexandre.belloni@bootlin.com>
Cc:     Jonathan =?utf-8?Q?Neusch=C3=A4fer?= <j.neuschaefer@gmx.net>,
        linux-kernel@vger.kernel.org, Lee Jones <lee.jones@linaro.org>,
        Rob Herring <robh+dt@kernel.org>,
        Thierry Reding <thierry.reding@gmail.com>,
        Uwe =?utf-8?Q?Kleine-K=C3=B6nig?= 
        <u.kleine-koenig@pengutronix.de>,
        Alessandro Zummo <a.zummo@towertech.it>,
        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, linux-pwm@vger.kernel.org,
        linux-rtc@vger.kernel.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>,
        Andy Shevchenko <andy.shevchenko@gmail.com>
Subject: Re: [PATCH v4 5/7] rtc: New driver for RTC in Netronix embedded
 controller
Message-ID: <20201123213105.GC456020@latitude>
References: <20201122222739.1455132-1-j.neuschaefer@gmx.net>
 <20201122222739.1455132-6-j.neuschaefer@gmx.net>
 <20201122231054.GH348979@piout.net>
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On Mon, Nov 23, 2020 at 12:10:54AM +0100, Alexandre Belloni wrote:
> Hi,
>=20
> On 22/11/2020 23:27:37+0100, Jonathan Neusch=C3=A4fer wrote:
> > With this driver, mainline Linux can keep its time and date in sync with
> > the vendor kernel.
> >=20
> > Advanced functionality like alarm and automatic power-on is not yet
> > supported.
> >=20
> > Signed-off-by: Jonathan Neusch=C3=A4fer <j.neuschaefer@gmx.net>
> Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
>=20
> However, two comments below:
>=20
> > +static int ntxec_set_time(struct device *dev, struct rtc_time *tm)
> > +{
> > +	struct ntxec_rtc *rtc =3D dev_get_drvdata(dev);
> > +	int res =3D 0;
> > +
> > +	/*
> > +	 * To avoid time overflows while we're writing the full date/time,
> > +	 * set the seconds field to zero before doing anything else. For the
> > +	 * next 59 seconds (plus however long it takes until the RTC's next
> > +	 * update of the second field), the seconds field will not overflow
> > +	 * into the other fields.
> > +	 */
> > +	res =3D regmap_write(rtc->ec->regmap, NTXEC_REG_WRITE_SECOND, ntxec_r=
eg8(0));
> > +	if (res)
> > +		return res;
> > +
> > +	res =3D regmap_write(rtc->ec->regmap, NTXEC_REG_WRITE_YEAR, ntxec_reg=
8(tm->tm_year - 100));
> > +	if (res)
> > +		return res;
> > +
> > +	res =3D regmap_write(rtc->ec->regmap, NTXEC_REG_WRITE_MONTH, ntxec_re=
g8(tm->tm_mon + 1));
> > +	if (res)
> > +		return res;
> > +
> > +	res =3D regmap_write(rtc->ec->regmap, NTXEC_REG_WRITE_DAY, ntxec_reg8=
(tm->tm_mday));
> > +	if (res)
> > +		return res;
> > +
> > +	res =3D regmap_write(rtc->ec->regmap, NTXEC_REG_WRITE_HOUR, ntxec_reg=
8(tm->tm_hour));
> > +	if (res)
> > +		return res;
> > +
> > +	res =3D regmap_write(rtc->ec->regmap, NTXEC_REG_WRITE_MINUTE, ntxec_r=
eg8(tm->tm_min));
> > +	if (res)
> > +		return res;
> > +
> > +	return regmap_write(rtc->ec->regmap, NTXEC_REG_WRITE_SECOND, ntxec_re=
g8(tm->tm_sec));
>=20
> Couldn't you do a regmap_block_write or a regmap_multi_reg_write which
> would be more efficient as they would be locking the regmap only once.

I can't find regmap_block_write anywhere, but regmap_multi_reg_write
looks like a good approach to simplify the code here.


[...]
> Note that this won't compile after
> https://git.kernel.org/pub/scm/linux/kernel/git/abelloni/linux.git/commit=
/?id=3Dfdcfd854333be5b30377dc5daa9cd0fa1643a979
>=20
> We can solve that with immutable branches though.

Thanks for the heads-up. Please let me know if/when there is any action
that I need to take here.


Jonathan

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