On Wed, 2011-10-12 at 16:08 -0500, Ayman El-Khashab wrote: > 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 ...
Did you try looking at what the dma_* functions do under the hood and call it directly (or reproducing it) ? Basically it boils down to using dcbf instructions to flush dirty data or dcbi to invalidate cache lines. Cheers, Ben. _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
