Please refer to the QorIQ LS1043A Reference Manual, 30.1.4 QuadSPI boot initialization sequence:
"QSPI_A_CS0 is used for boot initialization. QSPI is only accessed in 1-bit mode and at low speed for RCW/PBI fetch. PBI can reconfigure the QSPI to either higher frequency or 2-/4-bit mode as required for the QSPI boot to occur faster."
The SPI clocking is fully configurable and all 4 modes are supported - refer to the QorIQ LS1043A Reference Manual, 34.4.3 Clock and Transfer Attributes Register (In Master Mode) (SPI_CTARn).
Please refer to the QorIQ LS1043A Reference Manual, 30.1.4 QuadSPI boot initialization sequence:
"QSPI_A_CS0 is used for boot initialization. QSPI is only accessed in 1-bit mode and at low speed for RCW/PBI fetch.
PBI can reconfigure the QSPI to either higher frequency or 2-/4-bit mode as required for the QSPI boot to occur faster."