[U-Boot-Users] CFG_INIT_DCACHE_CS

[yu]

Hello. Everyone.
Now I am trying to port ppcboot to a simple custom board,
with ppc405cr, 32M RAM, 4M EEPROM, JTAG, UART.

I can not understand some Marcos in the header file include/configs/xxx.h.

#define CFG_INIT_DCACHE_CS      4      /*  use cs # 4 for data cache 
memory    */

there is no OCM in 405CR, so ppcboot needs data cache for initial stacks 
and data.
but what does the "chip  select" mean?

As I know, chip select should be used on some peripheral devices, like 
Flash, NVRAM,
why is it needed for data cache which is inside the CPU core?

Is the CS only a concept inside ppcboot?     or  something according to 
the  hardware?

thanks a lot in advance.

maoyuan