Re: [PATCH 0/3] STM32 Extended TrustZone Protection driver

From: Benjamin Gaignard
Date: Tue Feb 27 2018 - 14:17:06 EST


2018-02-27 18:11 GMT+01:00 Mark Rutland <mark.rutland@xxxxxxx>:
> On Tue, Feb 27, 2018 at 03:09:23PM +0100, Benjamin Gaignard wrote:
>> On early boot stages STM32MP1 platform is able to dedicate some hardware blocks
>> to a secure OS running in TrustZone.
>> We need to avoid using those hardware blocks on non-secure context (i.e. kernel)
>> because read/write access will all be discarded.
>>
>> Extended TrustZone Protection driver register itself as listener of
>> BUS_NOTIFY_BIND_DRIVER and check, given the device address, if the hardware block
>> could be used in a Linux context. If not it returns NOTIFY_BAD to driver core
>> to stop driver probing.
>
> Huh?
>
> If these devices are not usable from the non-secure side, why are they
> not removed form the DT (or marked disabled)?
>
> In other cases, where resources are carved out for the secure side (e.g.
> DRAM carveouts), that's how we handle things.
>

That true you can parse and disable a device a boot time but if DT doesn't
exactly reflect etzpc status bits we will in trouble when try to get access to
the device.
Changing the DT is a software protection while etzpc is an hardware protection
so we need to check it anyway.

Benjamin


> Mark.
>
>>
>> NOTE: patches 2 and 3 should be applied only on
>> git://git.kernel.org/pub/scm/linux/kernel/git/atorgue/stm32.git stm32-next
>> but until this patch: https://lkml.org/lkml/2018/2/26/386
>> find it way to mailine KBuild will complain about them.
>>
>> Benjamin Gaignard (3):
>> driver core: check notifier_call_chain return value
>> dt-bindings: stm32: Add bindings for Extended TrustZone Protection
>> ARM: mach-stm32: Add Extended TrustZone Protection driver
>>
>> .../bindings/arm/stm32/st,stm32mp1-etzpc.txt | 13 ++
>> arch/arm/mach-stm32/Kconfig | 7 +
>> arch/arm/mach-stm32/Makefile | 1 +
>> arch/arm/mach-stm32/stm32-etzpc.c | 252 +++++++++++++++++++++
>> drivers/base/dd.c | 9 +-
>> 5 files changed, 279 insertions(+), 3 deletions(-)
>> create mode 100644 Documentation/devicetree/bindings/arm/stm32/st,stm32mp1-etzpc.txt
>> create mode 100644 arch/arm/mach-stm32/stm32-etzpc.c
>>
>> --
>> 2.15.0
>>