APPLE_SPI_IE_FIFO
reg_write(spi, APPLE_SPI_IE_FIFO, 0);
u32 fifo = reg_read(spi, APPLE_SPI_IF_FIFO) & reg_read(spi, APPLE_SPI_IE_FIFO);
reg_write(spi, APPLE_SPI_IE_FIFO, 0);
reg_write(spi, APPLE_SPI_IE_FIFO, fifo_bit);
reg_write(spi, APPLE_SPI_IE_FIFO, 0);