linux-kernel - Re: [PATCH 2/4] rtc: s3c: Add time range

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Message-ID: <CAPLW+4k26qZDug4JkuPaM_gZMgz8LPg7GHe-5C7zKzEGtzdp=g@mail.gmail.com>
Date:   Tue, 19 Oct 2021 22:12:09 +0300
From:   Sam Protsenko <semen.protsenko@...aro.org>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>
Cc:     Alessandro Zummo <a.zummo@...ertech.it>, linux-rtc@...r.kernel.org,
        Linux Samsung SOC <linux-samsung-soc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>
Subject: Re: [PATCH 2/4] rtc: s3c: Add time range

On Tue, 19 Oct 2021 at 20:48, Alexandre Belloni
<alexandre.belloni@...tlin.com> wrote:
>
> On 19/10/2021 19:35:26+0300, Sam Protsenko wrote:
> > On Tue, 19 Oct 2021 at 19:22, Krzysztof Kozlowski
> > <krzysztof.kozlowski@...onical.com> wrote:
> > >
> > > On 19/10/2021 18:17, Krzysztof Kozlowski wrote:
> > > > On 19/10/2021 15:17, Sam Protsenko wrote:
> > > >> This RTC driver only accepts dates from 2000 to 2099 year. It starts
> > > >> counting from 2000 to avoid Y2K problem,
> > > >
> > > > 1. Where is the minimum (2000) year set in the RTC driver?
> > >
> > > Ah, indeed. I found it now in the driver.
> > >
> > > >
> > > >> and S3C RTC only supports 100
> > > >
> > > > On some of the devices 100, on some 1000, therefore, no. This does not
> > > > look correct.
> > >
> > > That part of sentence is still incorrect, but change itself makes sense.
> > > Driver does not support <2000.
> > >
> >
> > Driver itself does not allow setting year >= 2100:
> >
> > <<<<<<<<<<<<<<<<<<<< cut here >>>>>>>>>>>>>>>>>>>
> >     if (year < 0 || year >= 100) {
> >         dev_err(dev, "rtc only supports 100 years\n");
> >         return -EINVAL;
> >     }
> > <<<<<<<<<<<<<<<<<<<< cut here >>>>>>>>>>>>>>>>>>>
> >
> > Devices might allow it, so the commit message phrasing is incorrect
> > and should be replaced, yes. But the code should be correct. Should I
> > send v2 with fixed commit message?
> >
>
> It would be better to pass the proper values because else nobody will
> ever come back and fix it (hence why I didn't move that driver to
> devm_rtc_register_device yet).
>

Krzysztof, do you have by chance the doc for different SoCs supported
by S3C RTC driver? I can implement proper values for min/max range for
each SoC, as Alexandre asked, by adding those to driver data. But I
need max year register value (100, 1000, etc) for each of those chips:

  - "samsung,s3c2410-rtc"
  - "samsung,s3c2416-rtc"
  - "samsung,s3c2443-rtc"
  - "samsung,s3c6410-rtc"
  - "samsung,exynos3250-rtc"

For example Exynos850 TRM states that BCDYEAR register has [11:0] bits
for holding the year value in BCD format, so it's 10^(12/4)=1000 years
max.

> --
> Alexandre Belloni, co-owner and COO, Bootlin
> Embedded Linux and Kernel engineering
> https://bootlin.com