linux-kernel - Re: [PATCH v7 0/6] imx8mp: add support for the IMX AIPSTZ bridge

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Message-ID: <8db56c73-191e-48ec-9a28-cbb0da9a8a80@pengutronix.de>
Date: Thu, 3 Jul 2025 11:56:56 +0200
From: Ahmad Fatoum <a.fatoum@...gutronix.de>
To: Laurentiu Mihalcea <laurentiumihalcea111@...il.com>,
 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>,
 Daniel Baluta <daniel.baluta@....com>, Shengjiu Wang
 <shengjiu.wang@....com>, Frank Li <Frank.Li@....com>,
 Marco Felsch <m.felsch@...gutronix.de>,
 Marc Kleine-Budde <mkl@...gutronix.de>,
 Alexander Stein <alexander.stein@...tq-group.com>
Cc: devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org,
 Pengutronix Kernel Team <kernel@...gutronix.de>, imx@...ts.linux.dev
Subject: Re: [PATCH v7 0/6] imx8mp: add support for the IMX AIPSTZ bridge

Hello Laurentiu,

On 7/3/25 10:51, Laurentiu Mihalcea wrote:
> 
> 
> On 7/3/2025 11:11 AM, Ahmad Fatoum wrote:
>> Hello Laurentiu,
>>
>> On 10.06.25 18:01, Laurentiu Mihalcea wrote:
>>> From: Laurentiu Mihalcea <laurentiu.mihalcea@....com>
>>>
>>> The AIPSTZ bridge offers some security-related configurations which can
>>> be used to restrict master access to certain peripherals on the bridge.
>>>
>>> Normally, this could be done from a secure environment such as ATF before
>>> Linux boots but the configuration of AIPSTZ5 is lost each time the power
>>> domain is powered off and then powered on. Because of this, it has to be
>>> configured each time the power domain is turned on and before any master
>>> tries to access the peripherals (e.g: AP, CM7, DSP, on i.MX8MP).
>> Sorry if this has been asked before, but I hoped the cover letter or patch
>> 3/6 would explain if it were.
>>
>> What is the default configuration for the AIPSTZ before this series?
> 
> the default configuration is the reset configuration since AIPSTZ registers go
> back to their reset values during domain power cycling.
> 
>> I assume the SAIs under AIPS5 can be accessed by SDMA already, so why was
>> changing the AIPSTZ settings needed for the DSP to work?
> 
> AFAIK SDMA transactions to peripherals don't go through AIPS5. They use SPBA, which
> is why SDMA works even w/o this series. As for the DSP: transactions to peripherals go
> through AIPS5. With the reset configuration, the DSP is not allowed to access said peripherals,
> which is why this series was needed.

I see. Thanks for tackling this issue and your explanation.

Cheers,
Ahmad

> 

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