How to handle cache when I allocate phys memory?

[Ayman El-Khashab]

I'm using the 460sx (440 core) so no snooping here.  What
I've done is reserved the top of memory for my driver.  My
driver can read/write the memory and I can mmap it just
fine.  The problem is I want to enable caching on the mmap
for performance but I don't know / can't figure out how to
tell the kernel to sync the cache after it gets dma data
from the device or after i put data into it from user space.
I know how to do it from regular devices, but not when I've
allocated the physical memory myself.  I suppose what I am
looking for is something akin to dma_sync_single cpu/device.

In my device driver, I am allocating the memory like this, 
in this case the buffer is about 512MB.

 vma->vm_flags |= VM_LOCKED | VM_RESERVED;

 /* map the physical area into one buffer */
 rc = remap_pfn_range(vma, vma->vm_start, 
                         (PHYS_MEM_ADDR)>>PAGE_SHIFT, 
                         len, vma->vm_page_prot);

Is this going to give me the best performance, or is there
something more I can do?

Failing that, what is the best way to do this (i need a very
large contiguous buffer).  it runs in batch mode, so it
DMAs, stops, cpu reads, cpu writes, repeat ...

thanks
ayman