Re: [PATCH v4 3/3] rtc: spacemit: default module when MFD_SPACEMIT_P1 is enabled

From: Alexandre Belloni <alexandre.belloni@bootlin.com>
To: Alex Elder <elder@riscstar.com>
Cc: Troy Mitchell <troy.mitchell@linux.spacemit.com>,
	Lee Jones <lee@kernel.org>, Yixun Lan <dlan@gentoo.org>,
	Andi Shyti <andi.shyti@kernel.org>,
	Liam Girdwood <lgirdwood@gmail.com>,
	Mark Brown <broonie@kernel.org>,
	linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org,
	spacemit@lists.linux.dev, linux-i2c@vger.kernel.org,
	linux-rtc@vger.kernel.org
Subject: Re: [PATCH v4 3/3] rtc: spacemit: default module when MFD_SPACEMIT_P1 is enabled
Date: Tue, 30 Dec 2025 01:51:42 +0100	[thread overview]
Message-ID: <20251230005142d1bfc6f7@mail.local> (raw)
In-Reply-To: <4c7c0f69-4732-4f62-970a-2a9273b3b5c7@riscstar.com>

On 29/12/2025 12:02:23-0600, Alex Elder wrote:
> On 12/25/25 10:53 AM, Alexandre Belloni wrote:
> > On 25/12/2025 15:46:33+0800, Troy Mitchell wrote:
> > > The RTC driver defaulted to the same value as MFD_SPACEMIT_P1, which
> > > caused it to be built-in automatically whenever the PMIC support was
> > > set to y.
> > > 
> > > This is not always desirable, as the RTC function is not required on
> > > all platforms using the SpacemiT P1 PMIC.
> > 
> > But then, can't people simply change the config? I don't feel like
> > this is an improvement.
> 
> It's not an improvement for people who want to use the SpacemiT
> P1 PMIC, but it's an improvement for all the other RISC-V builds
> using "defconfig" that would rather have that support be modular
> to avoid needlessly consuming resources.

But then, wouldn't MFD_SPACEMIT_P1 be simply not set or set to m ? So
this doesn't have any impact on other RISC-V builds while it makes
people using the SpacemiT P1 PMIC jump through hoops to be able to use
the RTC as this is a very uncommon way to set default values.

My point is:
 - other RISC-V platforms would simply not select MFD_SPACEMIT_P1 or
   have MFD_SPACEMIT_P1 set to m
 - having RTC_DRV_SPACEMIT_P1 built-in by default when MFD_SPACEMIT_P1
   is built-in doesn't really hurt any SpacemiT P1 users but would be
   the expectation of those using the RTC.
 - those wanting to optimise because they won't use the RTC, they can
   already simply unselect RTC_DRV_SPACEMIT_P1 or set it to m.

> 
> I haven't done any testing on this but it looks fine to me.
> 
> Acked-by: Alex Elder <elder@riscstar.com>
> 
> I think it's a small change worth merging.  I don't think
> doing so does any harm.  Your call or course, Alexandre.
> 
> 					-Alex
> 
> > > Signed-off-by: Troy Mitchell <troy.mitchell@linux.spacemit.com>
> > > ---
> > >   drivers/rtc/Kconfig | 2 +-
> > >   1 file changed, 1 insertion(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
> > > index 50dc779f7f983074df7882200c90f0df21d142f2..53866493e9bbaf35ff0de85cbfe43e8343eadc1e 100644
> > > --- a/drivers/rtc/Kconfig
> > > +++ b/drivers/rtc/Kconfig
> > > @@ -410,7 +410,7 @@ config RTC_DRV_SPACEMIT_P1
> > >   	tristate "SpacemiT P1 RTC"
> > >   	depends on ARCH_SPACEMIT || COMPILE_TEST
> > >   	depends on MFD_SPACEMIT_P1
> > > -	default MFD_SPACEMIT_P1
> > > +	default m if MFD_SPACEMIT_P1
> > >   	help
> > >   	  Enable support for the RTC function in the SpacemiT P1 PMIC.
> > >   	  This driver can also be built as a module, which will be called
> > > 
> > > -- 
> > > 2.52.0
> > > 
> > 
> 

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