Re: [PATCH v3 5/6] ARM: dts: stm32: add ETZPC as a system bus for STM32MP15x boards - Uwe Kleine-König

From: "Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>
To: Gatien Chevallier <gatien.chevallier@foss.st.com>
Cc: Oleksii_Moisieiev@epam.com, gregkh@linuxfoundation.org,
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Subject: Re: [PATCH v3 5/6] ARM: dts: stm32: add ETZPC as a system bus for STM32MP15x boards
Date: Thu, 9 Feb 2023 08:51:44 +0100	[thread overview]
Message-ID: <20230209075144.cuw3xsxa6qgbttgq@pengutronix.de> (raw)
In-Reply-To: <20230127164040.1047583-6-gatien.chevallier@foss.st.com>

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Hello,

On Fri, Jan 27, 2023 at 05:40:39PM +0100, Gatien Chevallier wrote:
> The STM32 System Bus is an internal bus on which devices are connected.
> ETZPC is a peripheral overseeing the firewall bus that configures
> and control access to the peripherals connected on it.
> 
> For more information on which peripheral is securable, please read
> the STM32MP15 reference manual.

it might be naive, but I somehow expected that when showing at the
resulting commit with git show -b that the patch gets quite small.

Is it really intended that &etzpc (which has reg = <0x5c007000 0x400>;)
is the parent bus of the devices with feature-domains = <&etzpc XX>; even
though their addresses are out of &etzpc's range? Doesn't a bus usually
have a ranges property and a base address that matches its contained
devices?

Looking at imx6qdl.dtsi there is:

	aips1: bus@2000000 { /* AIPS1 */
		...
		reg = <0x02000000 0x100000>;
		ranges;

		spba-bus@2000000 {
			...
			reg = <0x02000000 0x40000>;
			...
		};

		...

		sdma: dma-controller@20ec000 {
			...
			reg = <0x020ec000 0x4000>;
			...
		};
	};

and the registers configuring the aips1 bus are (I think) in

                        aipstz@207c000 { /* AIPSTZ1 */
                                reg = <0x0207c000 0x4000>;
                        };

Maybe this change could be made less intrusive by using a similar setup
here?

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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