AX_SPI_RX_FBCAR
u32 avail_bytes = ax_spi_read(xspi, AX_SPI_RX_FBCAR);
while (ax_spi_read(xspi, AX_SPI_RX_FBCAR) > 0 && safety_words-- > 0)
while (ax_spi_read(xspi, AX_SPI_RX_FBCAR) > 0 && drain_limit-- > 0)
rx_count_reg = ax_spi_read(xspi, AX_SPI_RX_FBCAR);