RE: This question may be simple for you, but it doesn't let me sleeping.

I have linux2.4.1 from Lineo runing on ppc8250, IMMR =
0xF0000000, in my driver function, I can directly access
0xF00xxxxx( internal memory area on PPC's chip), why?

A BAT is configured to map this region with addressing virtual == physical.
See function m8260_map_io in arch/ppc/kernel/m8260_setup.c

When passing a logical address pointer to BD's address
pointer that allocated by function kmalloc().

Memory should probably be uncached (as the IMMR is).
Use function m8260_cpm_hostalloc instead of kmalloc, then use __pa.
See for example arch/ppc/8260_io/fcc_enet.c

Regards,
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