MSS_SYS_spi_copy() runs with wrong frequency due to issue with mailbox_reg variable definition in mss_sys_services.c

[ChrRudel]

platform/drivers/mss/mss_sys_services/mss_sys_services.c

Line 1978 in 8b4b440

uint32_t * mailbox_reg;

There seems to be a bug in the HSS / bare-metal-library:
mailbox_reg needs to be declared as “volatile uint32_t * mailbox_reg;”, otherwise the read/modify/write cycle starting at line 2021 will lead to unpredictable values
In our case, this lead to the 17th byte of the MSS_SYS_SPI_COPY_CMD operation being corrupted.
This byte contains the options / clock frequency, which explains why we were seeing wrong frequencies and data corruption.

This is likely also the root cause for why this workaround is necessary:
polarfire-soc/hart-software-services@c058394

[nitindeshpande]

Thanks for reporting @ChrRudel. Will have this fixed soon.