Sources for the serial clock generation can be either from the CLKIN, SCLK0, or a DAI pin source.
When CLKIN is chosen as input clock in PCG, the clock source bits (PCG_SYNCx.CLKx_CLKINSEL, PCG_SYNCx.CLKx_CLKINSEL) determine whether the clock source is SYS_CLKIN0 or SYS_CLKIN1.
The "CLKxSRC" bit in the "PCG_SYNCx" register is used to select the SCLK as clock source.