Linux/AM1808: am1808‘s upp driver problems

Part Number: AM1808

Tool/software: Linux

hi,

    i want to add uPP driver for am1080, because you have not provide the linux driver?

    i add the uPP driver refer to  https://e2echina.ti.com/question_answer/dsp_arm/omap_l1x/f/54/p/172062/512475?keyMatch=upp&tisearch=Search-CN-Everything

    then , i test the driver， I find i can't read the upp register effective, the value of all upp registers is always 0;

    then, i use the busybox's  devmem tools to read the register 0x01E16000 (uPP base address + 0, is the UPPID), the value is 0 as before:

    admin@localhost:/# busybox devmem 0x01E16000 32
    0x00000000

   I can read vpif registers effective:

    admin@localhost:/# busybox devmem 0x01E17000 32
    0x4C080A01

    i don't know why is that？？？ could you help me 。。。

thanks！