After enabling TrustZone various parts of the CAAM silicon become
inaccessible to non TrustZone contexts. The job-ring registers are designed
to allow non TrustZone contexts like Linux to still submit jobs to CAAM
even after TrustZone has been enabled.
The default job-ring permissions after the BootROM look like this for
job-ring zero.
ms=0x00008001 ls=0x00008001
The MS field is JRaMIDR_MS (job ring MID most significant).
Referring to "Security Reference Manual for i.MX 7Dual and 7Solo
Applications Processors, Rev. 0, 03/2017" section 8.10.4 we see that
JROWN_NS controls whether or not a job-ring is accessible from non
TrustZone.
Bit 15 (TrustZone) is the logical inverse of bit 3 hence the above value of
0x8001 shows that JROWN_NS=0 and TrustZone=1.
Clearly then as soon as TrustZone becomes active the job-ring registers are
no longer accessible from Linux, which is not what we want.
This patch explicitly sets all job-ring registers to JROWN_NS=1 (non
TrustZone) by default and to the Non-Secure MID 001. Both settings are
required to successfully assign a job-ring to non-secure mode. If a piece
of TrustZone firmware requires ownership of job-ring registers it can unset
the JROWN_NS bit itself.
This patch in conjunction with a modification of the Linux kernel to skip
HWRNG initialisation makes CAAM usable to Linux with TrustZone enabled.
Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Cc: Fabio Estevam <fabio.estevam@nxp.com>
Cc: Peng Fan <peng.fan@nxp.com>
Cc: Alex Porosanu <alexandru.porosanu@nxp.com>
Cc: Ruchika Gupta <ruchika.gupta@nxp.com>
Cc: Aneesh Bansal <aneesh.bansal@nxp.com>
Link: https://github.com/OP-TEE/optee_os/issues/1408
Link: https://tinyurl.com/yam5gv9a
Tested-by: Lukas Auer <lukas.auer@aisec.fraunhofer.de>
Bryan O'Donoghue
22191ac353