linux-kernel - Re: [PATCH 1/5] ARM: dts: lpc32xx: add bus surfix for simple-bus

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Message-ID: <aRdfR89CNvk7QRm8@lizhi-Precision-Tower-5810>
Date: Fri, 14 Nov 2025 11:56:39 -0500
From: Frank Li <Frank.li@....com>
To: Vladimir Zapolskiy <vz@...ia.com>
Cc: Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Piotr Wojtaszczyk <piotr.wojtaszczyk@...esys.com>,
	"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" <devicetree@...r.kernel.org>,
	"moderated list:ARM/LPC32XX SOC SUPPORT" <linux-arm-kernel@...ts.infradead.org>,
	open list <linux-kernel@...r.kernel.org>, imx@...ts.linux.dev
Subject: Re: [PATCH 1/5] ARM: dts: lpc32xx: add bus surfix for simple-bus

On Fri, Nov 14, 2025 at 06:44:03PM +0200, Vladimir Zapolskiy wrote:
> On 11/14/25 18:19, Frank Li wrote:
> > On Fri, Nov 14, 2025 at 01:55:50AM +0200, Vladimir Zapolskiy wrote:
> > > Hi Frank.
> > >
> > > On 10/29/25 22:27, Frank Li wrote:
> > > > add bus surfix for simple-bus to fix below CHECK_DTBS warnings:
> > >
> > > typo in the subject and in the commit message above, s/surfix/suffix/
> > >
> > > > arm/boot/dts/nxp/lpc/lpc3250-ea3250.dtb: usb (simple-bus): $nodename:0: 'usb' does not match '^([a-z][a-z0-9\\-]+-bus|bus|localbus|soc|axi|ahb|apb)(@.+)?$'
> > > >           from schema $id: http://devicetree.org/schemas/simple-bus.yaml#
> > > >
> > > > Signed-off-by: Frank Li <Frank.Li@....com>
> > > > ---
> > > >    arch/arm/boot/dts/nxp/lpc/lpc32xx.dtsi | 6 +++---
> > > >    1 file changed, 3 insertions(+), 3 deletions(-)
> > > >
> > > > diff --git a/arch/arm/boot/dts/nxp/lpc/lpc32xx.dtsi b/arch/arm/boot/dts/nxp/lpc/lpc32xx.dtsi
> > > > index 2236901a00313..9790b0a1d6537 100644
> > > > --- a/arch/arm/boot/dts/nxp/lpc/lpc32xx.dtsi
> > > > +++ b/arch/arm/boot/dts/nxp/lpc/lpc32xx.dtsi
> > > > @@ -86,7 +86,7 @@ dma: dma-controller@...00000 {
> > > >    			#dma-cells = <2>;
> > > >    		};
> > > > -		usb {
> > > > +		usb-bus {
> > >
> > > Device nodes under "usb" should be just elevated, the "simple-bus" here
> > > was used only to group some controllers together.
> > >
> > > >    			#address-cells = <1>;
> > > >    			#size-cells = <1>;
> > > >    			compatible = "simple-bus";
> > > > @@ -307,14 +307,14 @@ mpwm: pwm@...e8000 {
> > > >    			};
> > > >    		};
> > > > -		fab {
> > > > +		fab-bus {
> > >
> > > FAB shall find its place in the AXI/AHB/APB/... list, isn't it?
> >
> > what's FAB means? It is too short and hard to find exact information
> > from google?
>
> You may find UM10326 "LPC32x0 and LPC32x0/01 User manual" document online,
> LPC32xx is an old and simple SoC.
>
> FAB stands for Fast Access Bus, it's a bus behind AHB to FAB bridge, you
> may get an overview from "Fig 3. LPC32x0 block diagram, AHB matrix view",
> and "Table 4. Peripheral devices on the LPC32x0" lists all FAB peripherals.
>
> So, FAB is very similar to APB functionally, could it be just another
> name of APB?.. Likely we won't know for sure.
>
> I'd suggest to send a change, which adds "fab" to the list of permitted
> device tree node names with a "simple-bus" compatible. Or let me know,
> and I'll do it myself whenever I find a minute for it...

If only use by NXP, I think it is not easy to add it. There are too much
similar vendor specific bus name in other Soc.

It is local in https://github.com/devicetree-org/dt-schema.git
dt-schema/dtschema/schemas

    pattern: '^([a-z][a-z0-9\-]+-bus|bus|localbus|soc|axi|ahb|apb)(@.+)?$'

Most likely Rob prefer use prefix.

Anyway, you can try if you want.

Frank
>
> > > >    			#address-cells = <1>;
> > > >    			#size-cells = <1>;
> > > >    			compatible = "simple-bus";
> > > >    			ranges = <0x20000000 0x20000000 0x30000000>;
> > > >    			/* System Control Block */
> > > > -			scb {
> > > > +			scb-bus {
> > > >    				compatible = "simple-bus";
> > > >    				ranges = <0x0 0x40004000 0x00001000>;
> > > >    				#address-cells = <1>;
> > >
> > > Here "simple-bus" is also unjustified...
>
> --
> Best wishes,
> Vladimir
>