linux-kernel - Re: [PATCH 4/5] arm64: dts: imx8mp: convert 'aips5' to 'aipstz5'

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Message-ID: <20250227-monumental-whale-of-security-b1c84e-mkl@pengutronix.de>
Date: Thu, 27 Feb 2025 11:57:54 +0100
From: Marc Kleine-Budde <mkl@...gutronix.de>
To: Mihalcea Laurentiu <laurentiumihalcea111@...il.com>
Cc: Frank Li <Frank.li@....com>, Daniel Baluta <daniel.baluta@....com>, 
	Rob Herring <robh@...nel.org>, Conor Dooley <conor+dt@...nel.org>, devicetree@...r.kernel.org, 
	Fabio Estevam <festevam@...il.com>, Sascha Hauer <s.hauer@...gutronix.de>, 
	linux-kernel@...r.kernel.org, imx@...ts.linux.dev, 
	Pengutronix Kernel Team <kernel@...gutronix.de>, Krzysztof Kozlowski <krzk+dt@...nel.org>, 
	Shawn Guo <shawnguo@...nel.org>, Shengjiu Wang <shengjiu.wang@....com>, 
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 4/5] arm64: dts: imx8mp: convert 'aips5' to 'aipstz5'

On 25.02.2025 16:14:34, Mihalcea Laurentiu wrote:
> 
> On 21.02.2025 21:56, Frank Li wrote:
> > On Fri, Feb 21, 2025 at 02:19:08PM -0500, Laurentiu Mihalcea wrote:
> >> From: Laurentiu Mihalcea <laurentiu.mihalcea@....com>
> >>
> >> AIPS5 is actually AIPSTZ5 as it offers some security-related
> >> configurations. Since these configurations need to be applied before
> >> accessing any of the peripherals on the bus, it's better to make AIPSTZ5
> >> be their parent instead of keeping AIPS5 and adding a child node for
> >> AIPSTZ5. Also, because of the security configurations, the address space
> >> of the bus has to be changed to that of the configuration registers.
> > The orginal 0x30c0_0000..0x31200000 include 0x30df0000, why not map only
> > config address part in your drivers.
> >
> > Frank
> 
> 
> Any concerns/anything wrong with current approach?
> 
> 
> I find it a bit awkward to have the whole bus address space
> in the DT given that we're only interested in using the access
> controller register space.
> 
> 
> I'm fine with the approach you suggested but I don't see a
> reason for using it?

Looking at the "AIPS5 Memory Map" (page 34/35 in i.MX 8M Plus
Applications Processor Reference Manual, Rev. 3, 08/2024), the
AIPS5_Configuration is part of the AIPS5 bus. IMHO the bus is something
different than the bus configuration. Why not model it as part of the
bus?

> >> diff --git a/arch/arm64/boot/dts/freescale/imx8mp.dtsi b/arch/arm64/boot/dts/freescale/imx8mp.dtsi
> >> index e0d3b8cba221..a1d9b834d2da 100644
> >> --- a/arch/arm64/boot/dts/freescale/imx8mp.dtsi
> >> +++ b/arch/arm64/boot/dts/freescale/imx8mp.dtsi
> >> @@ -1399,11 +1399,13 @@ eqos: ethernet@...f0000 {
> >>  			};
> >>  		};
> >>
> >> -		aips5: bus@...00000 {
> >> -			compatible = "fsl,aips-bus", "simple-bus";
> >> -			reg = <0x30c00000 0x400000>;
> >> +		aips5: bus@...f0000 {
                       ^^^^^^^^^^^^
> >> +			compatible = "fsl,imx8mp-aipstz", "simple-bus";
> >> +			reg = <0x30df0000 0x10000>;
> >> +			power-domains = <&pgc_audio>;
> >>  			#address-cells = <1>;
> >>  			#size-cells = <1>;
> >> +			#access-controller-cells = <0>;
> >>  			ranges;
> >>
> >>  			spba-bus@...00000 {
                        ^^^^^^^^^^^^^^^^^

This looks very strange: The aips5 bus starts at 0x30df0000 and has a
child bus starting at 0x30c00000?

regards,
Marc

-- 
Pengutronix e.K.                 | Marc Kleine-Budde          |
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