From: Philipp Rosenberger <p.rosenberger@kunbus.com>
To: Alexandre Belloni <alexandre.belloni@bootlin.com>
Cc: dan.carpenter@oracle.com, u.kleine-koenig@pengutronix.de,
biwen.li@nxp.com, lvb@xiphos.com, bruno.thomsen@gmail.com,
l.sanfilippo@kunbus.com, Alessandro Zummo <a.zummo@towertech.it>,
linux-rtc@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 2/2] rtc: pcf2127: Run a OTP refresh if not done before
Date: Thu, 14 Jan 2021 12:18:22 +0100 [thread overview]
Message-ID: <346be3d3-362e-b1a7-38eb-9e7a82e61ac7@kunbus.com> (raw)
In-Reply-To: <20210114111157.GC3654@piout.net>
On 14.01.21 12:11, Alexandre Belloni wrote:
> On 14/01/2021 11:30:37+0100, Philipp Rosenberger wrote:
>>>> + ret = regmap_set_bits(pcf2127->regmap, PCF2127_REG_CLKOUT,
>>>> + PCF2127_BIT_CLKOUT_OTPR);
>>>> + if (ret < 0) {
>>>> + dev_err(dev, "%s: OTP refresh (clkout_ctrl) failed.\n", __func__);
>>>
>>> Please drop this error message.
>>
>> If I return from the probe with an error, shouldn't there be an error
>> message? Or should I ignore the problem at all and don't return from the
>> probe?
>
> You can return from probe without an error message.
>
>>
>>>
>>>> + return ret;
>>>> + }
>>>> + msleep(100);
>>>
>>> Maybe this should be done just before setting the time. Or if you want
>>> to keep it in probe, then you could optimise by not waiting but ensuring
>>> the time between pcf2127_probe and the first pcf2127_rtc_set_time is
>>> more than 100ms.
>>>
>>
>> Doing it just before setting the time might be not the best way. The
>> watchdog might be used before the OTPR is done.
>>
>> From the PCF2129 manual:
>> | The OTP refresh (see Section 8.3.2 on page 13) should ideally be
>> | executed as the first instruction after start-up and also after a
>> | reset due to an oscillator stop.
>>
>> As I see it this should be done before setting up the watchdog as well. So
>> sleeping if the OTPR wasn't done before might be the most viable solution.
>> So I would check the OTPR and only if the OTPR is not set starting an OTPR
>> and then sleep 100ms.
>>
>
> Indeed, the remaining question is whether you should test OTPR or OSF.
> OSF states: "oscillator has stopped and chip reset has occurred since
> flag was last cleared" if OTPR is always 0 when OSF is 1, then OTPR is
> probably enough.
The datasheet is unclear about that. And I thought about that as well.
The OSF flag is and should only reset when the time is set. But if I
reboot or reload the driver without setting the time the OTRP would be
rerun. So I thought it would be best to only rely on the OTPR bit. If
someone has a better idea I'm open far that.
Best Regards,
Philipp
prev parent reply other threads:[~2021-01-14 11:19 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-13 11:27 [PATCH v2 0/2] rtc: pcf2127: proper initialization after power loss Philipp Rosenberger
2021-01-13 11:27 ` [PATCH v2 1/2] rtc: pcf2127: Disable Power-On Reset Override Philipp Rosenberger
2021-01-14 8:05 ` Uwe Kleine-König
2021-01-14 9:10 ` Philipp Rosenberger
2021-01-14 9:33 ` Alexandre Belloni
2021-01-14 10:43 ` Philipp Rosenberger
2021-01-14 10:53 ` Alexandre Belloni
2021-01-14 11:11 ` Philipp Rosenberger
2021-01-13 11:27 ` [PATCH v2 2/2] rtc: pcf2127: Run a OTP refresh if not done before Philipp Rosenberger
2021-01-14 8:06 ` Uwe Kleine-König
2021-01-14 9:15 ` Philipp Rosenberger
2021-01-14 9:50 ` Alexandre Belloni
2021-01-14 10:30 ` Philipp Rosenberger
2021-01-14 11:11 ` Alexandre Belloni
2021-01-14 11:18 ` Philipp Rosenberger [this message]
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