Re: [PATCH 1/7] dt-bindings: soc: st: document the RISAB firewall peripheral

[Krzysztof Kozlowski <krzk@kernel.org>]

On 19/02/2026 15:02, Gatien CHEVALLIER wrote:
> Just a small reintroduction of the issue:
> We need to provide three sets of information to the drivers of RISAx:
> - The registers of the RISAx device, handled through property "reg"
> - The global range of memory addresses protected by the RISAx devices
> (currently through the custom property "st,mem-map")
> - Each individual memory range protected, handled through property
> "memory-region" that points to children of "/reserved-memory". Memory
> regions may not cover the whole range covered by the RISAx.
> 
> To replace the custom property, I have explored a few ways:
> 
> 1) Describe the memory range covered by the memory firewall as a
> reserved memory: Cannot be done because, for the memory firewall
> covering the DDR, the reserved memory would overlap with the memory
> node used to describe the memory available for regular kernel use.
> The memory node represents part of the DDR in that case.

But isn't this the entire point of RISAB on main system memory? You want
to mark part of system memory one way or another. And now you say that
overlapping would be a problem.

You do understand you do not have to reserve the memory, right? You are
doing only your specific mapping for that region.

> 
> 	memory@80000000 {
> 		device_type = "memory";
> 		reg = <0x0 0x80000000 0x1 0x0>;
> 	};
> 
> 	reserved-memory {
> 		#address-cells = <2>;
> 		#size-cells = <2>;
> 		ranges;
> 
> 		risaf_range: risaf-range@80000000 {

There is no compatible here...

> 			reg = <0x0 0x80000000 0x0 0x80000000>;
> 			no-map;

And why no-mapping? Isn't the point of the block is to have it as main
system memory?

> 		};
> 	}
> 



Best regards,
Krzysztof