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

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

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@nxp.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

> 

-- 
Pengutronix e.K.                  |                             |
Steuerwalder Str. 21              | http://www.pengutronix.de/  |
31137 Hildesheim, Germany         | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686  | Fax:   +49-5121-206917-5555 |