Re: [PATCH 2/2] arm64: dts: imx8mm: Add Crypto CAAM support

On Mon, Dec 9, 2019 at 10:23 AM Horia Geanta [off-list ref] wrote:

On 12/1/2019 12:52 AM, Adam Ford wrote:

quoted

The i.MX8M Mini supports the same crypto engine as what is in
the i.MX8MQ, but it is not currently present in the device tree,
because it may be resricted by security features.

What exactly are you referring to?

I don't know this hardware very well, but on a different platform, we
needed to make the crypto engines as disabled if they were being
accessed through secure operations which made it unavailable to Linux
without using some special barriers. I didn't have the special
hardware on the other platform that required it that way, so I can't
really explain it well.  I know on those special cases, because some
people were accessing these registers through other means, the devices
had to be marked as 'disabled' so to avoid breaking something.  Since
I wasn't sure if this was left out of the i.MX8M Mini on purpose, I
let this disabled just in case this hardware platform was also
affected in a similar and people wanting to use it could mark it as
'okay'

adam

quoted

This patch places in into the device tree and marks it as disabled,
but anyone not restricting the CAAM with secure mode functions
can mark it as enabled.

Even if - due to export control regulations - CAAM is "trimmed down",
it loses only the encryption capabilities (hashing etc. still working).

Again, please clarify what you mean by "secure mode functions",
"security features" etc.

Horia