Re: Secure resources in device trees

On Wed, 2015-01-21 at 16:21 +0000, Rob Herring wrote:

quoted

* Not possible to identify whether a device is shared or not between
the secure and non-secure worlds.

Typically, sharing requires a peripheral to be designed to be shared
like PL330 or MMU-400. I have seen some h/w with locking registers so
2 different cores/OSs can share an i2c bus. You could do something
like that for Trustzone as well I suppose. That's not really secure,
but allows shared access. I think it is generally a limited number of
peripherals which are shared.

Interestingly enough, the most common case for a shared peripheral is a
keypad/keyboard for secure PIN entry. A secure-programmable-only filter
like TZC-400 can be used to change the "designation" of a AXI master
connected to it.

Pawel

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