On Thu, 2019-10-31 at 16:47 +0100, Christoph Hellwig wrote:
> On Thu, Oct 31, 2019 at 04:28:37PM +0100, Nicolas Saenz Julienne wrote:
> > Some architectures, notably ARM, are interested in tweaking this
> > depending on their runtime DMA addressing limitations.
> > 
> > Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
> > ---
> > 
> > Changes since RFC:
> >  - Rebased to v5.4-rc6, fixed arm64 code.
> > 
> > NOTE: This will only apply to linux-next, where 
> 
> missing end of the sentence.  But only applying to linux-next isn't
> going to help anyone..

Arrgh, excuse me, I meant to delete that line.

> > diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> > index 45c00a54909c..f716ea634804 100644
> > --- a/arch/arm64/mm/init.c
> > +++ b/arch/arm64/mm/init.c
> > @@ -20,6 +20,7 @@
> >  #include <linux/sort.h>
> >  #include <linux/of.h>
> >  #include <linux/of_fdt.h>
> > +#include <linux/dma-direct.h>
> >  #include <linux/dma-mapping.h>
> >  #include <linux/dma-contiguous.h>
> >  #include <linux/efi.h>
> > @@ -41,6 +42,8 @@
> >  #include <asm/tlb.h>
> >  #include <asm/alternative.h>
> >  
> > +#define ARM64_ZONE_DMA_BITS	30
> > +
> >  /*
> >   * We need to be able to catch inadvertent references to memstart_addr
> >   * that occur (potentially in generic code) before arm64_memblock_init()
> > @@ -424,6 +427,8 @@ void __init arm64_memblock_init(void)
> >  	else
> >  		arm64_dma_phys_limit = PHYS_MASK + 1;
> >  
> > +	zone_dma_bits = ARM64_ZONE_DMA_BITS;
> > +
> >  	reserve_crashkernel();
> 
> This actually adds a new limit, as there wasn't one before for arm64.

Well, as zone_dma_bits is only relevant in dma/direct when ZONE_DMA is defined
I figured it doesn't matter if the variable is set conditionally to ZONE_DMA or
not.