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

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Date:   Thu, 9 Feb 2023 08:51:44 +0100
From:   Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
To:     Gatien Chevallier <gatien.chevallier@...s.st.com>
Cc:     Oleksii_Moisieiev@...m.com, gregkh@...uxfoundation.org,
        herbert@...dor.apana.org.au, davem@...emloft.net,
        robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org,
        alexandre.torgue@...s.st.com, vkoul@...nel.org, jic23@...nel.org,
        olivier.moysan@...s.st.com, arnaud.pouliquen@...s.st.com,
        mchehab@...nel.org, fabrice.gasnier@...s.st.com,
        ulf.hansson@...aro.org, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, linux-crypto@...r.kernel.org,
        devicetree@...r.kernel.org,
        linux-stm32@...md-mailman.stormreply.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        dmaengine@...r.kernel.org, linux-i2c@...r.kernel.org,
        linux-iio@...r.kernel.org, alsa-devel@...a-project.org,
        linux-media@...r.kernel.org, linux-mmc@...r.kernel.org,
        netdev@...r.kernel.org, linux-phy@...ts.infradead.org,
        linux-serial@...r.kernel.org, linux-spi@...r.kernel.org,
        linux-usb@...r.kernel.org, kernel@...gutronix.de
Subject: Re: [PATCH v3 5/6] ARM: dts: stm32: add ETZPC as a system bus for
 STM32MP15x boards

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@...0000 { /* AIPS1 */
		...
		reg = <0x02000000 0x100000>;
		ranges;

		spba-bus@...0000 {
			...
			reg = <0x02000000 0x40000>;
			...
		};

		...

		sdma: dma-controller@...c000 {
			...
			reg = <0x020ec000 0x4000>;
			...
		};
	};

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

                        aipstz@...c000 { /* 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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