Re: [PATCH 1/2] arm64: dts: rockchip: correct uart mux for Radxa ZERO3

[FUKAUMI Naoki]

Hi Heiko, Ed,

On 9/19/25 01:18, Heiko Stübner wrote:
> Am Donnerstag, 18. September 2025, 17:23:04 Mitteleuropäische Sommerzeit schrieb Ed W:
> > On 18/09/2025 05:53, FUKAUMI Naoki wrote:
> > > Hi Ed,
> > >
> > > Thank you very much for your work.
> > >
> > > On 9/17/25 20:49, Ed Wildgoose wrote:
> > > > The rk3566 has multiplexed pins and the uarts can be moved to a choice
> > > > of 2 pin groups. The default rk356x-base.dtsi appears to default to mux0
> > > > for all uarts, however, specific hardware might choose to implement
> > > > alternatives
> > > >
> > > > The Radxa zero 3 shows that is uses M1 for uarts:
> > > > - uart4
> > > > - uart5
> > > > - uart9
> > > >
> > > > These aren't normally enabled, but we should at least correct the
> > > > default pinctrl definitions. Without these changes there will be
> > > > conflicts with mmc0/mmc1, leading to the SD or eMMC going missing.
> > >
> > > Sorry, but why do we need these definitions for disabled nodes?
> > >
> > > Or why don't we do similar definitions for nodes other than uart?
> > > For example, PWM12, I2S3, and SPI3 also use M1. Are they not related to SD/eMMC and therefore
> > > don't need to be defined?
> > >
> > > If users want to use UARTs on pin headers, they will refer to the correct documentation[1] to
> > > determine which pins are UARTs and will of course write the correct pinctrl definition.
> > >
> > > [1] https://docs.radxa.com/en/zero/zero3/hardware-design/hardware-interface#gpio-interface
> > >
> > > Best regards,
> >
> >
> > Personally, and I'm saying this as a user who is technical enough to fix the definitions, it took me
> > quite a few days to figure out what was wrong with the definitions and understand the intricate tree
> > of dtsi includes, to finally figure out why I couldn't just do a "status = "okay";" to enable the
> > UARTs... (which is roughly what is shown in several radxa supplied overlays to enable uarts on
> > various boards)
> >
> > So my vote would be to correctly define all the hardware for a given board. Then users can simply do
> > a status="okay" to enable and off they go.
>
> And I'd agree with that argument. Setting up the needed pinctrl settings
> for the peripherals described in the device documentation
> ( https://docs.radxa.com/en/zero/zero3/hardware-design/hardware-interface#gpio-interface )
>
> is the sensible thing to do. While keeping the peripherals itself disabled
> and for the user to decide which peripheral to enable.

I'm not strongly opposed to this policy, but I thought if you're going 
to do this, you should do it for everything, not just UARTs.

Best regards,

--
FUKAUMI Naoki
Radxa Computer (Shenzhen) Co., Ltd.

> Heiko