linux-kernel - Re: [PATCH v2 02/17] RTC: ds1307: Disable square wave and timers as default

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Message-ID: <CAHQ1cqGp9kDDWS0bVtTUayQBkKxC1FJNfjURfcjTvX732oauDQ@mail.gmail.com>
Date:	Tue, 21 Jun 2016 16:43:45 -0700
From:	Andrey Smirnov <andrew.smirnov@...il.com>
To:	Alexandre Belloni <alexandre.belloni@...e-electrons.com>
Cc:	rtc-linux@...glegroups.com,
	Alessandro Zummo <a.zummo@...ertech.it>,
	linux-kernel@...r.kernel.org, Chris Healy <cphealy@...il.com>
Subject: Re: [PATCH v2 02/17] RTC: ds1307: Disable square wave and timers as default

On Tue, Jun 21, 2016 at 2:17 PM, Alexandre Belloni
<alexandre.belloni@...e-electrons.com> wrote:
> On 21/06/2016 at 00:22:35 -0700, Andrey Smirnov wrote :
>> Disable square wave and timers as default for DS1337/39/41 and
>> DS3231. The rationale being that configuring a chip this way puts it
>> into a known state with lower power consumption. While it is not very
>> likely it is still possible that the code controlling RTCs that ran
>> before this driver configured it to produce square wave and left it in
>> such a state.
>>
>
> The main issue being that if it has been configured that way (from the
> bootloader for example). It is probably necessary for the board. There
> may be users of that clock and this patch definitively breaks them.
> The proper way of doing that is to add CCF support in the driver. See:
> http://patchwork.ozlabs.org/patch/576201/

Implementing CCF support would still break users who rely on this
particular behavior and they would still have to spend effort
modifying their boards' device tree blob, so doing it the way you
propose wouldn't really save those users from pain, it would just give
them a way out.

Unfortunately, I don't have a bandwidth to develop and test a feature
that I don't have a use-case for, so I'll drop this patch from v3.

Andrey