https://www.kernel.org/doc/Documentation/blackfin/bfin-spi-notes.txt says in mode0 you are using, the CS will be manipulated by the hardware, instead of our driver code, so could you try to use mode 3? If limited by hardware character and you can't use the mode 3, use the GPIO cs instead, take line ".chip_select = GPIO_PF10 + MAX_CTRL_CS," in arch/blackfin/mach-bf537/boards/stamp.c as example.
If none of this above works please attach your userspace code too.