[RV64imac] Context switch exception on HiFive unleashed board

[Nenad Obradović]

Hi,

I wanted to run RTEMS on HiFive Unleashed (rv64imac/imafdc) from QSPI memory.
Since I want to boot RTEMS from QSPI memory I placed PLL settings and
DDR timing training from SiFive first stage bootloader into RTEMS
booting procedure.

Booting procedure passes RTEMS linkersets initialization, but it fails
in the first context switch.
Store conditional instruction triggers the Store/AMO fault exception.
Instruction "CLEAR_RESERVATIONS a2" that is actually sw.c zero, zero,
(a2) triggers that fault (placed in riscv-context-switch.S line 139).
Register a2 holds and address somewhere in RAM memory that should be
unprotected.

Store should be done on normal R/W memory placed in RAM. I do not
configure any type of physical memory protection for the CPU.

Is there any way to check existing memory protection configuration on
RISCV (registers readout or something like that)?

Is there anything else that could trigger store conditional
instruction to fail that way except PMP?


Best regards,
Nenad