Re: [PATCH 38 of 39] IB/ipath - More changes to support InfiniPath on PowerPC 970 systems

[Benjamin Herrenschmidt <benh@kernel.crashing.org>]

> +#if defined(__powerpc__)
> +	/* There isn't a generic way to specify writethrough mappings */
> +	pgprot_val(vma->vm_page_prot) |= _PAGE_NO_CACHE;
> +	pgprot_val(vma->vm_page_prot) |= _PAGE_WRITETHRU;
> +	pgprot_val(vma->vm_page_prot) &= ~_PAGE_GUARDED;
> +#endif

I don't see any case where having both NO_CACHE and WRITE_THRU can be
legal... It's one or the other.

> +/**
> + * ipath_unordered_wc - indicate whether write combining is ordered
> + *
> + * PowerPC systems (at least those in the 970 processor family)
> + * write partially filled store buffers in address order, but will write
> + * completely filled store buffers in "random" order, and therefore must
> + * have serialization for correctness with current InfiniPath chips.
> + *
> + */
> +int ipath_unordered_wc(void)
> +{
> +	return 1;
> +}

How is the above providing any kind of serialisation ?

Ben.


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