L2 cache functions and physical to virtual mappings

[Ben Gray]

Hi,

     I've been working on the OMAP4430 chip (Pandaboard) which uses the 
ARM PL310 L2 cache controller.  I've written basic support for it, but 
when it comes to mapping it back into cpu_l2cache_??? functions I hit a 
problem in that these functions take a virtual address rather than a 
physical address.

     The PL310 is a PIPT cache and naturally all cache maintenance 
operations use physical addresses. AFAICT the OMAP4430 doesn't use the 
nice cp15 instructions for flushing L2 caches (i.e. "mcr    p15, 1, r0, 
c15, c9, 0"), instead operations are performed by writing to registers 
within the controller.

     So I guess I'm just after some advice on the best way to get around 
this, I came up with the following options but none are particularly neat.


        1. Create a compile time #define which indicates the type of l2 
cache, i.e. pseudo-code

             #if defined(L2_CACHE_PHYS_ADDR)
                 for (adr= buf & (PAGE_SIZE - 1); adr < len; adr += 
PAGE_SIZE)
                     cpu_l2cache_wb_range(pmap_extract(pmap, buf), 
PAGE_SIZE);
             #else
cpu_l2cache_wb_range(buf, len);
             #endif


        2. Perform the virtual to physical translation in the 
cpu_l2cache_xxx() functions using pmap_extract().  But I think this will 
require the pmap pointer to be passed to the cpu_l2cache_xxx() 
functions, therefore changing the current API.


        3.Perform the virtual to physical translation in the 
cpu_l2cache_xxx() functions as above, but use the "CP15 c7, Virtual 
Address to Physical Address translation operations" to do the translation.


     Any advice would be greatly appreciated.

Cheers,
Ben.