Re: [PATCH] m68k: merge the mmu and non-mmu versions of checksum.h

[Greg Ungerer]

Hi Christoph,

Christoph Hellwig wrote:
> On Wed, Jun 17, 2009 at 05:11:15PM +1000, Greg Ungerer wrote:
> > +#ifdef CONFIG_MMU
> >  /*
> >   *	This is a version of ip_compute_csum() optimized for IP headers,
> >   *	which always checksum on 4 octet boundaries.
> > @@ -59,6 +61,9 @@ static inline __sum16 ip_fast_csum(const void *iph, unsigned int ihl)
> >  		 : "memory");
> >  	return (__force __sum16)~sum;
> >  }
> > +#else
> > +__sum16 ip_fast_csum(const void *iph, unsigned int ihl);
> > +#endif
>
> Any good reason this is inline for all mmu processors and out of line
> for nommu, independent of the actual cpu variant?

I don't recall of the simple (and thus non-mmu) m68k variants
support all the instructions used in this optimized version.
I will check that. It might be that this is mis-placed and
is actually conditional on the CPU type.

The C code version is significantly bigger, I think that is why
it was not inlined here (see arch/m68knommu/lib/checksum.c)


> >  static inline __sum16 csum_fold(__wsum sum)
> >  {
> >  	unsigned int tmp = (__force u32)sum;
> > +#ifdef CONFIG_COLDFIRE
> > +	tmp = (tmp & 0xffff) + (tmp >> 16);
> > +	tmp = (tmp & 0xffff) + (tmp >> 16);
> > +	return (__force __sum16)~tmp;
> > +#else
> >  	__asm__("swap %1\n\t"
> >  		"addw %1, %0\n\t"
> >  		"clrw %1\n\t"
> > @@ -74,6 +84,7 @@ static inline __sum16 csum_fold(__wsum sum)
> >  		: "=&d" (sum), "=&d" (tmp)
> >  		: "0" (sum), "1" (tmp));
> >  	return (__force __sum16)~sum;
> > +#endif
> >  }
>
> I think this would be cleaner by having totally separate functions
> for both cases, e.g.
>
> #ifdef CONFIG_COLDFIRE
> static inline __sum16 csum_fold(__wsum sum)
> {
> 	unsigned int tmp = (__force u32)sum;
>
> 	tmp = (tmp & 0xffff) + (tmp >> 16);
> 	tmp = (tmp & 0xffff) + (tmp >> 16);
>
> 	return (__force __sum16)~tmp;
> }
> #else
> ...
> #endif

Ok, I will change that.

Thanks
Greg


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Greg Ungerer  --  Principal Engineer        EMAIL:     gerg@xxxxxxxxxxxx
SnapGear Group, McAfee                      PHONE:       +61 7 3435 2888
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