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Shared QSPI on i.Mx7-ULP

Question asked by Quentin Cabrol on Aug 19, 2019
Latest reply on Sep 2, 2019 by CarlosCasillas
Branched to a new discussion

Hello NXP team,


I had a question regarding the shared access to the QSPI memory on i.Mx7-ULP platform.


For this architecture, QSPI is used to store the M4 firmware that is loaded at startup.

The QSPI is flashed from u-boot or Linux runtime on A7 and then program is loaded by M4 upon restart.


What we would like is to use an address space of the qspi as a log (512ko or so) with the M4 writing to it in a circular buffer fashion and the A7 retrieving this log at Linux runtime. This is to avoid the overhead of having the A7 interrogating the M4 to retrieve the last logged data via eRPC.


qspi and sema42 examples are provided for the M4 side, so having the core writing at the end of the QSPI space shall hopefully not be too difficult.


Though, I could not find information regarding how this is handled from the Yocto side.

- Is it possible to lock/free that resource so to access read/write to a defined QSPI addresses space from both core in a secure fashion?

- How does the A7 handles the SEMA42 within Yocto ? 

- ... Or shall that be arbitrated via the RDC instead ?


Thank you in advance for your help.