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SubjectRe: [patch] x86, voyager: fix ioremap_nocache()
James Bottomley wrote:
> Here's another piece of the x86 API that's designed to be cached. The
> dma_declare_coherent_memory() usually represents behind bridge memory
> that's fully participatory in the coherence model.
>
> Making it uncached damages the utility of this memory because doing
> cacheline sized burst cycles when needed to it is far faster than
> individual byte/word/quad writes.
>
> Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
>
> ---
>
> diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c
> index 388b113..df83ffd 100644
> --- a/arch/x86/kernel/pci-dma.c
> +++ b/arch/x86/kernel/pci-dma.c
> @@ -214,7 +214,7 @@ int dma_declare_coherent_memory(struct device *dev, dma_addr_t bus_addr,
>
> /* FIXME: this routine just ignores DMA_MEMORY_INCLUDES_CHILDREN */
>
> - mem_base = ioremap(bus_addr, size);
> + mem_base = ioremap_cache(bus_addr, size);
> if (!mem_base)
> goto out;

Surely the change in semantics will find other places to creep out like
this?

I would rather change drivers to use ioremap_nocache(), and leave the
API as-is.

Isn't there Yet More Breakage in lib/iomap.c, given these new semantics?

if (flags & IORESOURCE_MEM) {
if (flags & IORESOURCE_CACHEABLE)
return ioremap(start, len);
return ioremap_nocache(start, len);
}

Any driver using pci_iomap() (libata, and others) is affected.

I disagree with this semantics change. A number of code places _and
drivers_ GET IT RIGHT, and these are all broken now?

Jeff





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