On Mon, Oct 16, 2023 at 02:02:39PM +0200, Gatien CHEVALLIER wrote:

Hi Rob,

On 10/12/23 17:30, Rob Herring wrote:

quoted

On Wed, Oct 11, 2023 at 10:49:58AM +0200, Gatien CHEVALLIER wrote:

quoted

Hi Rob,

On 10/10/23 20:42, Rob Herring wrote:

quoted

On Tue, Oct 10, 2023 at 02:57:18PM +0200, Gatien Chevallier wrote:

quoted

ETZPC is a firewall controller. Put all peripherals filtered by the
ETZPC as ETZPC subnodes and reference ETZPC as an
access-control-provider.

For more information on which peripheral is securable or supports MCU
isolation, please read the STM32MP15 reference manual.

Signed-off-by: Gatien Chevallier <gatien.chevallier@foss.st.com>
---

Changes in V6:
      	- Renamed access-controller to access-controllers
      	- Removal of access-control-provider property

Changes in V5:
      	- Renamed feature-domain* to access-control*

   arch/arm/boot/dts/st/stm32mp151.dtsi  | 2756 +++++++++++++------------
   arch/arm/boot/dts/st/stm32mp153.dtsi  |   52 +-
   arch/arm/boot/dts/st/stm32mp15xc.dtsi |   19 +-
   3 files changed, 1450 insertions(+), 1377 deletions(-)

This is not reviewable. Change the indentation and any non-functional
change in one patch and then actual changes in another.

Ok, I'll make it easier to read.

quoted

This is also an ABI break. Though I'm not sure it's avoidable. All the
devices below the ETZPC node won't probe on existing kernel. A
simple-bus fallback for ETZPC node should solve that.

I had one issue when trying with a simple-bus fallback that was the
drivers were probing even though the access rights aren't correct.
Hence the removal of the simple-bus compatible in the STM32MP25 patch.

But it worked before, right? So the difference is you have either added
new devices which need setup or your firmware changed how devices are
setup (or not setup). Certainly can't fix the latter case. You just need
to be explicit about what you are doing to users.

I should've specified it was during a test where I deliberately set
incorrect rights on a peripheral and enabled its node to see if the
firewall would allow the creation of the device.

quoted

quoted

Even though a node is tagged with the OF_POPULATED flag when checking
the access rights with the firewall controller, it seems that when
simple-bus is probing, there's no check of this flag.

It shouldn't. Those flags are for creating the devices (or not) and
removing only devices of_platform_populate() created.

About the "simple-bus" being a fallback, I think I understood why I saw
that the devices were created.

All devices under a node whose compatible is "simple-bus" are created
in of_platform_device_create_pdata(), called by
of_platform_default_populate_init() at arch_initcall level. This
before the firewall-controller has a chance to populate it's bus.

Therefore, when I flag nodes when populating the firewall-bus, the
devices are already created. The "simple-bus" mechanism is not a
fallback here as it precedes the driver probe.

Is there a safe way to safely remove/disable a device created this way?

There's 2 ways to handle this. Either controlling creating the device or 
controlling probing the device. The latter should just work with 
fw_devlink dependency. The former probably needs some adjustment to 
simple-pm-bus driver if you have 'simple-bus' compatible. You want it to 
probe on old kernels and not probe on new kernels with your firewall 
driver. Look at the commit history for simple-pm-bus. There was some 
discussion on it as well.

Devices that are under the firewall controller (simple-bus) node
should not be probed before it as they're child of it.

fw_devlink should take care of parent/child dependencies without any 
explicit handling of the access ctrl binding.

Rob