On 2012?02?29? 20:35, Arnd Bergmann wrote:

On Monday 13 February 2012, Bill Carson wrote:

quoted

--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c

@@ -152,9 +152,6 @@ static struct arm_vmregion_head consistent_head = {
         .vm_end         = CONSISTENT_END,
  };

-#ifdef CONFIG_HUGETLB_PAGE
-#error ARM Coherent DMA allocator does not (yet) support huge TLB
-#endif

This one needs an explanation, too. What has changed that now allows
dma_alloc_coherent to work with CONFIG_HUGETLB_PAGE set that did not
work before?

AFAIK, __dma_alloc has the finest granularity at 4k page size even when
user requests 1M bytes memory.

but current hugetlb low level set_hugepte_at *ONLY*/*MUST* support 2M 
page mapping, so it can't be used to create huge dma mapping in a more
general way.

comments this error out doesn't mean that it could support huge page dma
mapping now with this patch, just shut up gcc when compiling.

Adding a single low level hook to create 1M page mapping can satisfy
the needs, but apparently that's out of hugetlb scope.
And it's on my TODO list :)

In general, please add a description with each patch you send, following
the instructions in Documentation/SubmittingPatches.

Thanks, I will follow the rules.

	Arnd

-- 
I am a slow learner
but I will keep trying to fight for my dreams!

--bill