Re: [PATCH 1/1] s390/dma: provide proper ARCH_ZONE_DMA_BITS value

[Halil Pasic <pasic@linux.ibm.com>]

On Fri, 19 Jul 2019 08:32:49 +0200
Heiko Carstens <heiko.carstens@de.ibm.com> wrote:

> On Thu, Jul 18, 2019 at 07:21:20PM +0200, Halil Pasic wrote:
> > On s390 ZONE_DMA is up to 2G, i.e. ARCH_ZONE_DMA_BITS should be 31 bits.
> > The current value is 24 and makes __dma_direct_alloc_pages() take a
> > wrong turn first (but __dma_direct_alloc_pages() recovers then).
> > 
> > Let's correct ARCH_ZONE_DMA_BITS value and avoid wrong turns.
> > 
> > Signed-off-by: Halil Pasic <pasic@linux.ibm.com>
> > Reported-by: Petr Tesarik <ptesarik@suse.cz>
> > Fixes: c61e9637340e ("dma-direct: add support for allocation from
> > ZONE_DMA and ZONE_DMA32")
> 
> Please don't add linebreaks to "Fixes:" tags.
> 

Will remember that, thanks! I was not aware of the rule and checkpatch
did not complain. 

> > ---
> >  arch/s390/include/asm/dma.h | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/arch/s390/include/asm/dma.h b/arch/s390/include/asm/dma.h
> > index 6f26f35d4a71..3b0329665b13 100644
> > --- a/arch/s390/include/asm/dma.h
> > +++ b/arch/s390/include/asm/dma.h
> > @@ -10,6 +10,7 @@
> >   * by the 31 bit heritage.
> >   */
> >  #define MAX_DMA_ADDRESS         0x80000000
> > +#define ARCH_ZONE_DMA_BITS      31
> 
> powerpc has this in arch/powerpc/include/asm/page.h. This really
> should be consistently defined in the same header file across
> architectures.
> 
> Christoph, what is the preferred header file for this definition?
> 
> I'd also rather say it would be better to move the #ifndef ARCH_ZONE_DMA_BITS
> check to a common code header file instead of having it in a C file, and
> make it more obvious in which header file architectures should/can override
> the default, no?

+1

I will wait for Christoph's answer with a respin. Thanks for having a
look.

Regards,
Halil