Re: Reorg of 32-bit dma code

[Benjamin Herrenschmidt <benh@kernel.crashing.org>]

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

> 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 !

>   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.

> 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 !

Ben.