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

["Heiko Stübner" <heiko@sntech.de>]

Am Freitag, 19. September 2025, 01:57:57 Mitteleuropäische Sommerzeit schrieb 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.

yes, exactly
So patches for the other header peripherals welcome :-) .

But still it's nice to do it in steps like this one, as it makes reviewing easier.


Heiko