The reason for the poor performance was not working SVID bus. Understand exactly what settings affect the enabling/disabling SVID bus failed to find out. The problem was solved by choosing another platform in spsFITs (Aspen Cove instead of Harcuvar). After that, the SVID bus started to work, we saw the clock signals (25 MHz), saw the exchange of data between the processor and the PMICs. Performance came in the expected frame :)