Re: [RFC PATCH 2/7] dma-mapping: replace set_arch_dma_coherent_ops with arch_setup_dma_ops

[Will Deacon <will.deacon-5wv7dgnIgG8@public.gmane.org>]

On Mon, Sep 01, 2014 at 03:27:30PM +0100, Arnd Bergmann wrote:
> On Friday 29 August 2014 16:54:25 Will Deacon wrote:
> > set_arch_dma_coherent_ops is called from of_dma_configure in order to
> > swizzle the architectural dma-mapping functions over to a cache-coherent
> > implementation. This is currently implemented only for ARM.
> > 
> > In anticipation of re-using this mechanism for IOMMU-backed dma-mapping
> > ops too, this patch replaces the function with a broader
> > arch_setup_dma_ops callback which is also responsible for setting the
> > DMA mask and offset as well as selecting the correct mapping functions.
> > 
> > A further advantage of this split is that it nicely isolates the
> > of-specific code from the dma-mapping code, allowing potential reuse by
> > other buses (e.g. PCI) in the future.
> > 
> > Signed-off-by: Will Deacon <will.deacon-5wv7dgnIgG8@public.gmane.org>
> 
> Looks good, just one tiny comment
> 
> > ---
> >  arch/arm/include/asm/dma-mapping.h | 20 ++++++++++++++----
> >  drivers/of/platform.c              | 42 ++++++++++----------------------------
> >  include/linux/dma-mapping.h        |  8 +++-----
> >  3 files changed, 30 insertions(+), 40 deletions(-)
> > 
> > diff --git a/arch/arm/include/asm/dma-mapping.h b/arch/arm/include/asm/dma-mapping.h
> > index c45b61a4b4a5..936125ef3f3f 100644
> > --- a/arch/arm/include/asm/dma-mapping.h
> > +++ b/arch/arm/include/asm/dma-mapping.h
> > @@ -121,12 +121,24 @@ static inline unsigned long dma_max_pfn(struct device *dev)
> >  }
> >  #define dma_max_pfn(dev) dma_max_pfn(dev)
> >  
> > -static inline int set_arch_dma_coherent_ops(struct device *dev)
> > +static inline void arch_setup_dma_ops(struct device *dev, u64 mask,
> > +                                     unsigned long offset, bool coherent)
> >  {
> > -       set_dma_ops(dev, &arm_coherent_dma_ops);
> > -       return 0;
> > +       dev->coherent_dma_mask = mask;
> > +
> > +       /*
> > +        * Set dma_mask to coherent_dma_mask by default if the architecture
> > +        * code has not set it.
> > +        */
> > +       if (!dev->dma_mask)
> > +               dev->dma_mask = &dev->coherent_dma_mask;
> > +
> 
> We are in architecture specific code here, and we know that this
> architecture has not set up the dev->dma_mask pointer, so we can
> remove the 'if (!dev->dma_mask)'

Good point; I'll fix it.

Thanks,

Will