linux-kernel - Re: [PATCH v2 1/2] rtc: add pcf85053a

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Message-ID: <ZUf4czmwLEqKpM28@arch-bow>
Date:   Sun, 5 Nov 2023 17:17:55 -0300
From:   Carlos Menin <menin@...losaurelio.net>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     linux-rtc@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-hwmon@...r.kernel.org,
        Alessandro Zummo <a.zummo@...ertech.it>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Jean Delvare <jdelvare@...e.com>,
        Sergio Prado <sergio.prado@...abworks.com>,
        menin@...losaurelio.net
Subject: Re: [PATCH v2 1/2] rtc: add pcf85053a

On Fri, Nov 03, 2023 at 07:09:27AM -0700, Guenter Roeck wrote:
> On 11/3/23 05:51, Carlos Menin wrote:
> > Add support for NXP's PCF85053A RTC chip.
> > 
> > Signed-off-by: Carlos Menin <menin@...losaurelio.net>
> > Reviewed-by: Sergio Prado <sergio.prado@...abworks.com>
> > ---
> 
> [ ... ]
> 
> > +static int pcf85053a_bvl_to_mv(unsigned int bvl)
> > +{
> > +	long mv_table[] = {
> > +		1700,
> > +		1900,
> > +		2100,
> > +		2300,
> > +		2500,
> > +		2700,
> > +		2900,
> > +		3100,
> 
> How are those numbers determined ? The datasheet gives voltage ranges.
> I'd have assumed that the center of those ranges is chosen, but for the
> most part it is the maximum, except for 2900 which is a bit above center
> and 3100 for "> 3.0V". Not that I care too much, but it seems to me that
> using the center voltage for each range would be more consistent.
> 

I just used numbers that would result in the same step between levels
(200 mV) at the same time they would fit in the ranges, but I agree
that using the center of the ranges makes sense. In this case which
values would you suggest for <= 1.7 and > 3.0 ?

> > +static int pcf85053a_hwmon_register(struct device *dev, const char *name)
> > +{
> > +	struct pcf85053a *pcf85053a = dev_get_drvdata(dev);
> > +	struct device *hwmon_dev;
> > +
> > +	hwmon_dev = devm_hwmon_device_register_with_info(dev, name, pcf85053a,
> > +							 &pcf85053a_hwmon_chip_info,
> > +							 0);
> 
> This won't compile if CONFIG_HWMON=n or if CONFIG_RTC_DRV_PCF85053A=y and
> CONFIG_HWMON=m.
> 
> Guenter
> 

I will add dependencies in the Kconfig file.

Thanks for reviewing,
Carlos