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Subject: Re: [PATCH 4/4] rtc: s3c: Fix RTC read on first boot
To:     Sam Protsenko <semen.protsenko@linaro.org>,
        Alexandre Belloni <alexandre.belloni@bootlin.com>
Cc:     Alessandro Zummo <a.zummo@towertech.it>, linux-rtc@vger.kernel.org,
        Linux Samsung SOC <linux-samsung-soc@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
References: <20211019131724.3109-1-semen.protsenko@linaro.org>
 <20211019131724.3109-5-semen.protsenko@linaro.org>
 <YW7o4iVhJNmv/ea6@piout.net>
 <CAPLW+4nWvMWfz32WmcDZ=X78jVREMUAOD1Z7SefxH--p8F+NXA@mail.gmail.com>
From:   Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Message-ID: <754ac854-f1ca-2e93-f8fa-92dd332a44b9@canonical.com>
Date:   Tue, 19 Oct 2021 18:19:45 +0200
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On 19/10/2021 18:04, Sam Protsenko wrote:
> On Tue, 19 Oct 2021 at 18:48, Alexandre Belloni
> <alexandre.belloni@bootlin.com> wrote:
>>
>> On 19/10/2021 16:17:24+0300, Sam Protsenko wrote:
>>> On first RTC boot it has the month register value set to 0.
>>> Unconditional subtracting of 1 subsequently in s3c_rtc_gettime() leads
>>> to the next error message in kernel log:
>>>
>>>     hctosys: unable to read the hardware clock
>>>
>>> That happens in s3c_rtc_probe() when trying to register the RTC, which
>>> in turn tries to read and validate the time. Initialize RTC date/time
>>> registers to valid values in probe function on the first boot to prevent
>>> such errors.
>>>
>>
>> No, never ever do that, the time is bogus and it has to stay this way,
>> else userspace can't know whether the time on the RTC is the actual wall
>> time or just some random value that you have set from the driver.
>>
> 
> Thought about that, but that error message looked distracting and not
> very helpful in understanding what's actually going on. Anyway, can
> you please drop this patch from series (and maybe [PATCH 3/4] too) and
> apply the rest?
> 

Please give it some time for review. Pinging after few hours is too fast.

Best regards,
Krzysztof