Hello all,

I am using PPC 405 Walnut with 16M sdram. I got a question regarding the DCache setting in u-boot cpu/ppc4xx/start.S. I wrote the pseudo-code of start.S as below:

(In File cpu/ppc4xx/start.S) .globl _start _start: _start: clear and set up registers invalidate I and D caches Enable 128M cachable regions set up temporary stack in DCACHE sdram_init() (cpu/ppc4xx/sdram.c)

..........

I understand the code is trying to set up a stack in DCache. But I didn't get how the code makes it. Before calling sdram_init(), the stack pointer is CFG_INIT_RAM_ADDR = 0x40000000. I suppose this address is not a physical address and it refers to the address in the DCache. Is that right? But the CFG_INIT_RAM_ADDR is located in the address space of sdram. So is there any address translator in between DCache and CFG_INIT_RAM_ADDR? Or did I miss anything? I just couldn't figure out how the stack works in DCache... Can someone give me any clue? Thanks!

Frank

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