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


------------------------------------------------------------------------
Greg Ungerer -- Principal Engineer EMAIL: gerg@snapgear.com
SnapGear Group, McAfee PHONE: +61 7 3435 2888
825 Stanley St, FAX: +61 7 3891 3630
Woolloongabba, QLD, 4102, Australia WEB: http://www.SnapGear.com


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