linux-kernel - Re: [RESEND PATCH 0/7] Introduce bus domains controller framework

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Date:   Mon, 18 Mar 2019 10:43:43 +0000
From:   Sudeep Holla <sudeep.holla@....com>
To:     Benjamin Gaignard <benjamin.gaignard@...com>
Cc:     broonie@...nel.org, robh@...nel.org, arnd@...db.de,
        shawnguo@...nel.org, s.hauer@...gutronix.de, fabio.estevam@....com,
        benjamin.gaignard@...aro.org, loic.pallardy@...com,
        gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org,
        linux-imx@....com, kernel@...gutronix.de,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [RESEND PATCH 0/7] Introduce bus domains controller framework

On Mon, Mar 18, 2019 at 11:05:58AM +0100, Benjamin Gaignard wrote:
> Bus domains controllers allow to divided system on chip into multiple domains
> that can be used to select by who hardware blocks could be accessed.
> A domain could be a cluster of CPUs (or coprocessors), a range of addresses or
> a group of hardware blocks.
>
> Framework architecture is inspirated by pinctrl framework:
> - a default configuration could be applied before bind the driver
> - configurations could be apllied dynamically by drivers
> - device node provides the bus domains configurations
>
> An example of bus domains controller is STM32 ETZPC hardware block
> which got 3 domains:
> - secure: hardware blocks are only accessible by software running on trust
>   zone.
> - non-secure: hardware blocks are accessible by non-secure software (i.e.
>   linux kernel).
> - coprocessor: hardware blocks are only accessible by the corpocessor.
> Up to 94 hardware blocks of the soc could be managed by ETZPC and
> assigned to one of the three domains.
>

You fail to explain why do we need this in non-secure Linux ?
You need to have solid reasons as why this can't be done in secure
firmware. And yes I mean even on arm32. On platforms with such hardware
capabilities you will need some secure firmware to be running and these
things can be done there. I don't want this enabled for ARM64 at all,
firmware *has to deal* with this.

--
Regards,
Sudeep