Question about linux boot procedure (head_64.S)

Hi ~

This is a boot flow of linux kernel under the arch/powerpc/kernel and I'm
using pasemi cpu.

__start  (in head_64.S)
  ---> __start_initialization_multiplatform (in head_64.S)
    ---> __boot_from_prom (in head_64.S)
       ---> prom_init ( in prom_init.c)
         ---> __start ???

And I don't understand where __start is called, because I can find __start
only in head_64.S.
If it calls __start in head_64.S, it's a recursive call.

Can anybody explain about this precedure ?

Thanks in advance.

HongWoo.