Message-ID: <20250331141513.GA2684092-robh@kernel.org>
Date: Mon, 31 Mar 2025 09:15:13 -0500
From: Rob Herring <robh@...nel.org>
To: Mihalcea Laurentiu <laurentiumihalcea111@...il.com>
Cc: Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>, Shawn Guo <shawnguo@...nel.org>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Fabio Estevam <festevam@...il.com>,
	Daniel Baluta <daniel.baluta@....com>,
	Shengjiu Wang <shengjiu.wang@....com>, Frank Li <Frank.li@....com>,
	Marco Felsch <m.felsch@...gutronix.de>,
	Marc Kleine-Budde <mkl@...gutronix.de>,
	Pengutronix Kernel Team <kernel@...gutronix.de>,
	devicetree@...r.kernel.org, imx@...ts.linux.dev,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/5] dt-bindings: bus: add documentation for the IMX
 AIPSTZ bridge

On Fri, Mar 28, 2025 at 02:34:11PM +0200, Mihalcea Laurentiu wrote:
> 
> On 25.03.2025 05:23, Rob Herring wrote:
> > On Mon, Mar 24, 2025 at 12:25:52PM -0400, Laurentiu Mihalcea wrote:
> >> From: Laurentiu Mihalcea <laurentiu.mihalcea@....com>
> >>
> >> Add documentation for IMX AIPSTZ bridge.
> >>
> >> Co-developed-by: Daniel Baluta <daniel.baluta@....com>
> >> Signed-off-by: Daniel Baluta <daniel.baluta@....com>
> >> Signed-off-by: Laurentiu Mihalcea <laurentiu.mihalcea@....com>
> >> ---
> >>  .../bindings/bus/fsl,imx8mp-aipstz.yaml       | 107 ++++++++++++++++++
> >>  1 file changed, 107 insertions(+)
> >>  create mode 100644 Documentation/devicetree/bindings/bus/fsl,imx8mp-aipstz.yaml
> >>
> >> diff --git a/Documentation/devicetree/bindings/bus/fsl,imx8mp-aipstz.yaml b/Documentation/devicetree/bindings/bus/fsl,imx8mp-aipstz.yaml
> >> new file mode 100644
> >> index 000000000000..c0427dfcdaca
> >> --- /dev/null
> >> +++ b/Documentation/devicetree/bindings/bus/fsl,imx8mp-aipstz.yaml
> >> @@ -0,0 +1,107 @@
> >> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> >> +%YAML 1.2
> >> +---
> >> +$id: http://devicetree.org/schemas/bus/fsl,imx8mp-aipstz.yaml#
> >> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> >> +
> >> +title: Secure AHB to IP Slave bus (AIPSTZ) bridge
> >> +
> >> +description:
> >> +  The secure AIPS bridge (AIPSTZ) acts as a bridge for AHB masters
> >> +  issuing transactions to IP Slave peripherals. Additionally, this module
> >> +  offers access control configurations meant to restrict which peripherals
> >> +  a master can access.
> > Wrap at 80 chars.
> 
> 
> fix in v4, thx
> 
> 
> >
> >> +
> >> +maintainers:
> >> +  - Laurentiu Mihalcea <laurentiu.mihalcea@....com>
> >> +
> >> +properties:
> >> +  compatible:
> >> +    const: fsl,imx8mp-aipstz
> >> +
> >> +  reg:
> >> +    maxItems: 2
> >> +
> >> +  reg-names:
> >> +    items:
> >> +      - const: bus
> >> +      - const: ac
> >> +
> >> +  power-domains:
> >> +    maxItems: 1
> >> +
> >> +  "#address-cells":
> >> +    const: 1
> >> +
> >> +  "#size-cells":
> >> +    const: 1
> >> +
> >> +  "#access-controller-cells":
> >> +    const: 0
> > With 0 cells, how do you identify which device it is?
> 
> 
> we don't atm. We're relying on the default configuration.

Then you don't really need the property at all. However, if you ever 
need the non-default and configure it, adding it or changing it later is 
an ABI issue. So better to define it correctly sooner rather than later.

> 
> 
> we don't have any APIs for AC configuration so I left the
> 
> cell number to 0 thinking that the cell number might depend
> 
> on the API.
> 
> 
> if need be, I can set it to the value I was initially thinking of in v4.
> 
> 
> >
> >> +
> >> +  ranges: true
> >> +
> >> +# borrowed from simple-bus.yaml, no additional requirements for children
> >> +patternProperties:
> >> +  "@(0|[1-9a-f][0-9a-f]*)$":
> >> +    type: object
> >> +    additionalProperties: true
> >> +    properties:
> >> +      reg:
> >> +        items:
> >> +          minItems: 2
> >> +          maxItems: 4
> >> +        minItems: 1
> >> +        maxItems: 1024
> >> +      ranges:
> >> +        oneOf:
> >> +          - items:
> >> +              minItems: 3
> >> +              maxItems: 7
> >> +            minItems: 1
> >> +            maxItems: 1024
> >> +          - $ref: /schemas/types.yaml#/definitions/flag
> >> +    anyOf:
> >> +      - required:
> >> +          - reg
> >> +      - required:
> >> +          - ranges
> >> +
> >> +required:
> >> +  - compatible
> >> +  - reg
> >> +  - reg-names
> >> +  - power-domains
> >> +  - "#address-cells"
> >> +  - "#size-cells"
> >> +  - "#access-controller-cells"
> >> +  - ranges
> >> +
> >> +additionalProperties: false
> >> +
> >> +examples:
> >> +  - |
> >> +    #include <dt-bindings/clock/imx8mp-clock.h>
> >> +    #include <dt-bindings/interrupt-controller/arm-gic.h>
> >> +
> >> +    bus@...00000 {
> >> +        compatible = "fsl,imx8mp-aipstz";
> >> +        reg = <0x30c00000 0x400000>, <0x30df0000 0x10000>;
> > It doesn't look like you have any registers in the 1st entry, but they 
> > are child devices? Then you should use ranges and drop it here:
> >
> > ranges = <0x0 0x30c00000 0x400000>;
> 
> 
> I guess this would mean switching from global addresses (current way) to
> 
> bus-relative addresses for the child devices. This wasn't my intent.
> 
> 
> I wonder if we could just switch to V2 in which we just use the bridge's AC
> 
> configuration space and an empty 'ranges':
> 
> 
> aips5: bus@...f0000 {
> 
>     compatible = "fsl,imx8mp-aipstz";
> 
>     reg = <0x30df0000 0x10000>;
> 
>     /* some more properties here */
> 
>     ranges;
> 
> };
> 
> 
> or as Marco just suggested use
> 
> 
> ranges = <0x30c00000 0x30c00000 0x400000>;
> 
> 
> instead of an empty 'ranges' to restrict the bus size.
> 
> 
> Personally, I'm fine with both approaches but what's your opinion on this?

The latter restricting the size is my preference.

Rob

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