TMDSCNCD263P: HsmClient_setFirewall hangs

Hi Tobias,

To understand the issue of HsmClient_setFirewall hanging, we will start with the bonus question that you had asked.

Tobias Jäggi said:

What is the Region Number parameter in the sysconfig MPU Region Configuration used for?

 Each MPU firewall module contains multiple region descriptor registers that define independent memory protection rules. These region descriptors are indexed by a region number (also called region ID or region index). Each region is an independent hardware protection descriptor with its own address range, privilege ID mask, and permission
attributes.

For the L2OCRAM_BANK0_SLV, there are 8 regions, out of which the region 0 is configured by default, by the HSMRt during secure boot init, to enable system operation.

(Image from TRM of System MPU/Firewalls Section)

Here, this OCRAM_BANK0 (0x70000000 - 0x7007FFFF) is very crucial for SIPC which is used in communication between HSM Client and HSM Server. All the parameters of the SIPC_Notify calls stay in this region. Thus, it is very crucial for M4FSS0 core to have access to this region to process any HsmClient request.

Now, when you try to add another firewall configuration on the same region 0 for L2OCRAM_BANK0_SLV, the existing configuration intialized by the HSMRt gets overwritten and thus, the access to the OCRAM is restricted for M4FSS0 core, as in the configuration, you have allowed only the R5FSS0_0 core. Thus, the HsmClient_setFirewall() function gets stuck.

The easy fix, would be to use a region number other than 0 (you can try 2), this would not overwrite the initialization done by the HSMRt. Now, the M4 core still retains its access to OCRAM and thus, HsmClient_setFirewall() executes without getting stuck.



Regards,
Naren