Hello,
On Friday, August 12, 2011 5:01 PM Arnd Bergmann wrote:
On Friday 12 August 2011, Marek Szyprowski wrote:
@@ -82,16 +103,16 @@ static struct page *__dma_alloc_buffer(struct device
*dev,
size_t size, gfp_t gf
if (mask < 0xffffffffULL) gfp |= GFP_DMA;
- page = alloc_pages(gfp, order);
- if (!page)
return NULL;- /*
* Now split the huge page and free the excess pages
* Allocate contiguous memory
- split_page(page, order);
- for (p = page + (size >> PAGE_SHIFT), e = page + (1 << order); p < e;
p++)
__free_page(p);
- if (cma_available())
page = dma_alloc_from_contiguous(dev, count, order);- else
page = __dma_alloc_system_pages(count, gfp, order);- if (!page)
return NULL;Why do you need the fallback here? I would assume that CMA now has to be
available
on ARMv6 and up to work at all. When you allocate from
__dma_alloc_system_pages(),
wouldn't that necessarily fail in the dma_remap_area() stage?
It is not a fallback - I've just merged 2 cases together (CMA case and coheren/nommu arch). I agree that such mixed code might be confusing.
- if (arch_is_coherent() || nommu()) {
- if (arch_is_coherent() || nommu() ||
(cma_available() && !(gfp & GFP_ATOMIC))) {/** Allocate from system or CMA pages*/dma_remap_area(page, size, area->prot);Similarly with coherent and nommu. It seems to me that lumping too many cases together creates extra complexity here.
How about something like
if (arch_is_coherent() || nommu()) ret = alloc_simple_buffer(); else if (arch_is_v4_v5()) ret = alloc_remap(); else if (gfp & GFP_ATOMIC) ret = alloc_from_pool(); else ret = alloc_from_contiguous();
This also allows a natural conversion to dma_map_ops when we get there.
Ok. Is it ok to enable CMA permanently for ARMv6+? If CMA is left conditional the dma pool code will be much more complicated, because it will need to support both CMA and non-CMA cases.
/* reserve any platform specific memblock areas */ if (mdesc->reserve) mdesc->reserve();
- dma_coherent_reserve();
- dma_contiguous_reserve();
- memblock_analyze(); memblock_dump_all();
}
Since we can handle most allocations using CMA on ARMv6+, I would think that we can have a much smaller reserved area. Have you tried changing dma_coherent_reserve() to allocate out of the contiguous area instead of wasting a full 2MB section of memory?
I will move the reserved pool directly into CMA area, so it can be shrunk below 2MiB.
Best regards