Re: [PATCH v9 00/13] Introduce STM32 Firewall framework

[Alexandre TORGUE <alexandre.torgue@foss.st.com>]

Hi Gatien,

On 1/5/24 14:03, Gatien Chevallier wrote:
> Introduce STM32 Firewall framework for STM32MP1x and STM32MP2x
> platforms. STM32MP1x(ETZPC) and STM32MP2x(RIFSC) Firewall controllers
> register to the framework to offer firewall services such as access
> granting.
> 
> This series of patches is a new approach on the previous STM32 system
> bus, history is available here:
> https://lore.kernel.org/lkml/20230127164040.1047583/
> 
> The need for such framework arises from the fact that there are now
> multiple hardware firewalls implemented across multiple products.
> Drivers are shared between different products, using the same code.
> When it comes to firewalls, the purpose mostly stays the same: Protect
> hardware resources. But the implementation differs, and there are
> multiple types of firewalls: peripheral, memory, ...
> 
> Some hardware firewall controllers such as the RIFSC implemented on
> STM32MP2x platforms may require to take ownership of a resource before
> being able to use it, hence the requirement for firewall services to
> take/release the ownership of such resources.
> 
> On the other hand, hardware firewall configurations are becoming
> more and more complex. These mecanisms prevent platform crashes
> or other firewall-related incoveniences by denying access to some
> resources.
> 
> The stm32 firewall framework offers an API that is defined in
> firewall controllers drivers to best fit the specificity of each
> firewall.
> 
> For every peripherals protected by either the ETZPC or the RIFSC, the
> firewall framework checks the firewall controlelr registers to see if
> the peripheral's access is granted to the Linux kernel. If not, the
> peripheral is configured as secure, the node is marked populated,
> so that the driver is not probed for that device.
> 
> The firewall framework relies on the access-controller device tree
> binding. It is used by peripherals to reference a domain access
> controller. In this case a firewall controller. The bus uses the ID
> referenced by the access-controller property to know where to look
> in the firewall to get the security configuration for the peripheral.
> This allows a device tree description rather than a hardcoded peripheral
> table in the bus driver.
> 
> The STM32 ETZPC device is responsible for filtering accesses based on
> security level, or co-processor isolation for any resource connected
> to it.
> 
> The RIFSC is responsible for filtering accesses based on Compartment
> ID / security level / privilege level for any resource connected to
> it.
> 
> STM32MP13/15/25 SoC device tree files are updated in this series to
> implement this mecanism.
> 

...

After minor cosmetic fixes, series applied on stm32-next.
Seen with Arnd: it will be part on my next PR and will come through 
arm-soc tree.

Thanks
Alex