linux-kernel - Re: [PATCH 2/4] arm64: dts: imx8mp: convert 'aips5' to 'aipstz5'

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Message-ID: <20a3325e-d8be-4a1d-890d-bf112d170bcc@gmail.com>
Date: Wed, 29 Oct 2025 07:47:18 -0700
From: Laurentiu Mihalcea <laurentiumihalcea111@...il.com>
To: Krzysztof Kozlowski <krzk@...nel.org>, Rob Herring <robh@...nel.org>,
 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>,
 Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>
Cc: 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 2/4] arm64: dts: imx8mp: convert 'aips5' to 'aipstz5'


On 8/24/2025 4:29 AM, Krzysztof Kozlowski wrote:
> On 21/08/2025 12:56, 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.
>>
>> Finally, since AIPSTZ5 belongs to the AUDIOMIX power domain, add the
>> missing 'power-domains' property. The domain needs to be powered on before
>> attempting to configure the security-related registers.
>>
>> The DT node name is not changed to avoid potential issues with DTs in
>> which this node is referenced.
>>
>> Co-developed-by: Daniel Baluta <daniel.baluta@....com>
>> Signed-off-by: Daniel Baluta <daniel.baluta@....com>
>> Signed-off-by: Laurentiu Mihalcea <laurentiu.mihalcea@....com>
>> Reviewed-by: Frank Li <Frank.Li@....com>
> Where did it happen?


https://lore.kernel.org/lkml/Z+xY4wZ8ZFSOJhGS@lizhi-Precision-Tower-5810/ <https://lore.kernel.org/lkml/Z+xY4wZ8ZFSOJhGS@lizhi-Precision-Tower-5810/>


>
>> ---
>>  arch/arm64/boot/dts/freescale/imx8mp.dtsi | 10 ++++++----
>>  1 file changed, 6 insertions(+), 4 deletions(-)
>>
>> diff --git a/arch/arm64/boot/dts/freescale/imx8mp.dtsi b/arch/arm64/boot/dts/freescale/imx8mp.dtsi
>> index bb24dba7338e..b62bb821cf61 100644
>> --- a/arch/arm64/boot/dts/freescale/imx8mp.dtsi
>> +++ b/arch/arm64/boot/dts/freescale/imx8mp.dtsi
>> @@ -1396,12 +1396,14 @@ eqos: ethernet@...f0000 {
>>  			};
>>  		};
>>  
>> -		aips5: bus@...00000 {
>> -			compatible = "fsl,aips-bus", "simple-bus";
>
> This breaks all the users. I understood explanation as "it is better",
> no real reasons.


sorry, a rather poor choice of wording on my part....


the reason we're doing this change is because we need to configure the bridge's

security-related registers. If we don't, masters such as the DSP core won't be able to

access the peripherals connected to this bridge after the AUDIOMIX PD is turned off

and then on. The configuration needs to be done before any of the masters attempt to

perform transactions to the peripherals.


yes, this change is not ideal and we've had problems caused by this

(see https://lore.kernel.org/lkml/20250707234628.164151-2-laurentiumihalcea111@gmail.com/ <https://lore.kernel.org/lkml/20250707234628.164151-2-laurentiumihalcea111@gmail.com/>)

so if you have any suggestions that would be much appreciated.


>
> No, you cannot do that.
>
> Best regards,
> Krzysztof