Re: [PATCH v7 06/19] rtc: sun6i: Add support for RTCs without external LOSCs

From: Icenowy Zheng <icenowy@aosc.io>
To: Maxime Ripard <maxime@cerno.tech>
Cc: Andre Przywara <andre.przywara@arm.com>,
	Chen-Yu Tsai <wens@csie.org>,
	Jernej Skrabec <jernej.skrabec@gmail.com>,
	Rob Herring <robh@kernel.org>,
	Samuel Holland <samuel@sholland.org>,
	linux-arm-kernel@lists.infradead.org,
	linux-sunxi@googlegroups.com, linux-sunxi@lists.linux.dev,
	linux-kernel@vger.kernel.org, Ondrej Jirman <megous@megous.com>,
	Alessandro Zummo <a.zummo@towertech.it>,
	Alexandre Belloni <alexandre.belloni@bootlin.com>,
	linux-rtc@vger.kernel.org
Subject: Re: [PATCH v7 06/19] rtc: sun6i: Add support for RTCs without external LOSCs
Date: Thu, 29 Jul 2021 21:04:21 +0800	[thread overview]
Message-ID: <E4567E12-60C1-4DF5-89D6-C93DC3152D4F@aosc.io> (raw)
In-Reply-To: <20210729103228.prdav7eobi52y3ny@gilmour>

于 2021年7月29日 GMT+08:00 下午6:32:28, Maxime Ripard <maxime@cerno.tech> 写到:
>On Thu, Jul 29, 2021 at 04:04:10PM +0800, Icenowy Zheng wrote:
>> 在 2021-06-16星期三的 11:14 +0200，Maxime Ripard写道：
>> > Hi,
>> > 
>> > On Tue, Jun 15, 2021 at 12:06:23PM +0100, Andre Przywara wrote:
>> > > Some newer Allwinner RTCs (for instance the one in the H616 SoC)
>> > > lack
>> > > a pin for an external 32768 Hz oscillator. As a consequence, this
>> > > LOSC
>> > > can't be selected as the RTC clock source, and we must rely on the
>> > > internal RC oscillator.
>> > > To allow additions of clocks to the RTC node, add a feature bit to
>> > > ignore
>> > > any provided clocks for now (the current code would think this is
>> > > the
>> > > external LOSC). Later DTs and code can then for instance add the
>> > > PLL
>> > > based clock input, and older kernel won't get confused.
>> > > 
>> > > Signed-off-by: Andre Przywara <andre.przywara@arm.com>
>> > 
>> > Honestly, I don't really know if it's worth it at this point.
>> > 
>> > If we sums this up:
>> > 
>> >  - The RTC has 2 features that we use, mostly centered around 2
>> >    registers set plus a global one
>> > 
>> >  - Those 2 features are programmed in a completely different way
>> > 
>> >  - Even the common part is different, given the discussion around the
>> >    clocks that we have.
>> > 
>> > What is there to share in that driver aside from the probe, and maybe
>> > the interrupt handling? Instead of complicating this further with
>> > more
>> > special case that you were (rightfully) complaining about, shouldn't
>> > we
>> > just acknowledge the fact that it's a completely separate design and
>> > should be treated as such, with a completely separate driver?
>> 
>> I think our problem is just that we're having a single driver for both
>> functionalities (clock manager and RTC).
>> 
>> Personally I don't think we should have seperated driver for clock
>> managers, although I am fine with seperated RTC driver for linear days.
>
>Why do you think it's a bad idea to have the RTC and clocks in the same
>driver?

Well you really misread, I'm just thinking we shouldn't have a new driver
from scratch. As we're going to have a single sun6i-rtc, please allow H616
and R329 to enter it.

>
>Maxime