Re: Reorg of 32-bit dma code

On Feb 6, 2008, at 7:26 PM, Benjamin Herrenschmidt wrote:

On Wed, 2008-02-06 at 18:32 -0600, Becky Bruce wrote:

quoted

I've been looking at converting 32-bit powerpc's DMA code over to the
64-bit method, where there is a dma_ops structure inside archdata
that tells us which operations a device should use for DMA.  I'll be
needing this shortly because I need to implement swiotlb to deal with
PCI and large amounts of RAM on 32-bit systems that support 36-bit
physical addressing. (Yes, I know.  Fun for me.  Woohoo.)

Anyway, I have an initial booting first pass, and wanted to get some
feedback.  What I've done at this point is to make dma_64 common to  
both
architectures (will rename it when I send a real patch...).  The
dma_direct_* functions have been changed to work on both 32/64, and  
the
old dma_* functionality in dma-mapping.h has been removed.   For  
now, to
avoid whacking on every 32-bit platform, the get_dma_ops() function  
has
been changed to return &dma_direct_ops if the device pointer exists  
but
the dma_ops field is NULL.   I'm not sure if this needs to be  
ifdef'd for
64-bit?

I'd prefer so yes.

Can you explain why?  Got no issue with doing this, but its good to  
know hy.

quoted

I've copied a bit of code over from pci_64.c into pci_common.c -  
some of
it isn't in use yet but will be once I start doing actual setup in  
the
platform code. pcibios_setup_new_device() becomes common as well.

Cool !

quoted

 I've
also temporarily hacked the 32-bit code to set archdata.dma_data to
PCI_DRAM_OFFSET, so we can eliminate the use of virt_to_bus() and  
instead
use the 64-bit method, which gets rid of some ugly ifdefs in the  
dma code.

Ok.

quoted

That's really about it - the preliminary patch is below - clearly  
it will
need some cleanup, but I wanted to post early and often.  Any  
feedback or
suggestions on cleaning this up are greatly appreciated.

I'll have a look asap, thanks for doing this !

Also, any ideas on how to handle setting dev->archdata for non-PCI  
devices would be welcome.

- k