Process ID in SMPU for MPC5745R

raghurajappa · ‎04-05-2019

For MPC5745R, from the features file, I see that this SMPU does not support Process ID. Is there a reason for this??

#define FEATURE_SMPU_HAS_PROCESS_IDENTIFIER (0U)

How do I configure regions and which processes can access the region if it is not supported?? There must be some alternative way to use the SMPU?

Thank you.

davidtosenovjan · ‎04-05-2019

Hi,

some implementation of SMPU does not have Process ID. It has been removed because it is redundant to CMPU if the core has this sub-unit.

Process ID is either supported by SMPU or CMPU. Specifically MPC5745R has this feature present in CMPU.

raghurajappa · ‎04-07-2019

Hi David,

In case of the MPC5745R, there exists an SMPU and a CMPU unit and using the CMPU we can load/monitor the Process ID. This is now my understanding. How can I use the CMPU for managing processes and the SMPU in a collaborative way to manage the regions, then? Rephrasing the question --> How can I use the CMPU and SMPU together to protect memory??

Kind Regards,
Raghu

davidtosenovjan · ‎04-08-2019

I am attaching screenshots from AN4658, it explains it quite well, I think

raghurajappa · ‎04-08-2019

Hi David,

I was just reading this. Now i understand the concept better. So the CMPU will manage local core related memory and SMPU will control system level memory. Now I am a little confused in protecting memory using CMPU and SMPU in tandem. Let's say, there are 2 software components (SW1 and SW2).I am aware I can save the data related to SW1 can be mapped to either the local d_mem or the m_data in the sram. Let's say I map SW1 data to CMPU, then I can handle the memory protection by defining process IDs for the CMPU of the particular core. But if within SW1, there are functions that access the peripheral, then this data would still be in the SRAM, right? Now if the SW1 is only allowed to write those peripheral registers only during the process ID-x, then how can I manage that??

Basically, I am looking for an example which uses the CMPU and the SMPU in tandem. As far as I am aware, there are no examples or even driver blocks that show the usage of CMPU (individually) and SMPU, together. If you have come across something I can use as a reference, that would be appreciated.

Kind regards,

Raghu