Re: [PATCH kernel v3 1/2] dma: Allow mixing bypass and mapped DMA operation

[Alexey Kardashevskiy]

On 29/10/2020 04:22, Christoph Hellwig wrote:
> On Wed, Oct 28, 2020 at 06:00:29PM +1100, Alexey Kardashevskiy wrote:
> > At the moment we allow bypassing DMA ops only when we can do this for
> > the entire RAM. However there are configs with mixed type memory
> > where we could still allow bypassing IOMMU in most cases;
> > POWERPC with persistent memory is one example.
> >
> > This adds an arch hook to determine where bypass can still work and
> > we invoke direct DMA API. The following patch checks the bus limit
> > on POWERPC to allow or disallow direct mapping.
> >
> > This adds a CONFIG_ARCH_HAS_DMA_SET_MASK config option to make arch_xxxx
> > hooks no-op by default.
> >
> > Signed-off-by: Alexey Kardashevskiy <aik@xxxxxxxxx>
> > ---
> >   kernel/dma/mapping.c | 24 ++++++++++++++++++++----
> >   kernel/dma/Kconfig   |  4 ++++
> >   2 files changed, 24 insertions(+), 4 deletions(-)
> >
> > diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
> > index 51bb8fa8eb89..a0bc9eb876ed 100644
> > --- a/kernel/dma/mapping.c
> > +++ b/kernel/dma/mapping.c
> > @@ -137,6 +137,18 @@ static inline bool dma_map_direct(struct device *dev,
> >   	return dma_go_direct(dev, *dev->dma_mask, ops);
> >   }
> >   
> > +#ifdef CONFIG_ARCH_HAS_DMA_MAP_DIRECT
> > +bool arch_dma_map_page_direct(struct device *dev, phys_addr_t addr);
> > +bool arch_dma_unmap_page_direct(struct device *dev, dma_addr_t dma_handle);
> > +bool arch_dma_map_sg_direct(struct device *dev, struct scatterlist *sg, int nents);
> > +bool arch_dma_unmap_sg_direct(struct device *dev, struct scatterlist *sg, int nents);
> > +#else
> > +#define arch_dma_map_page_direct(d, a) (0)
> > +#define arch_dma_unmap_page_direct(d, a) (0)
> > +#define arch_dma_map_sg_direct(d, s, n) (0)
> > +#define arch_dma_unmap_sg_direct(d, s, n) (0)
> > +#endif
>
> A bunch of overly long lines here.  Except for that this looks ok to me.
> If you want me to queue up the series I can just fix it up.

I thought 100 is the new limit since 
https://lkml.org/lkml/2020/5/29/1038 (yeah that mentioned some Christoph 
:) ) and having these multiline does not make a huge difference but feel 
free fixing them up.

Are you going to take both patches? Do you need mpe's ack? Thanks,


--
Alexey