2014-05-20 오전 4:59, Michal Nazarewicz 쓴 글:
On Sun, May 18 2014, Joonsoo Kim wrote:
I think that this problem is originated from atomic_pool_init().
If configured coherent_pool size is larger than default cma size,
it can be failed even if this patch is applied.
The coherent_pool size (atomic_pool.size) should be restricted smaller than cma size.
This is another issue, however I think the default atomic pool size is too small.
Only one port of USB host needs at most 256Kbytes coherent memory (according to the USB host spec).
If a platform has several ports, it needs more than 1MB.
Therefore the default atomic pool size should be at least 1MB.
How about below patch?
It uses fallback allocation if CMA is failed.
Yes, I thought about it, but __dma_alloc uses similar code:
else if (!IS_ENABLED(CONFIG_DMA_CMA))
addr = __alloc_remap_buffer(dev, size, gfp, prot, &page, caller);
else
addr = __alloc_from_contiguous(dev, size, prot, &page, caller);
so it probably needs to be changed as well.
If CMA option is not selected, __alloc_from_contiguous would not be called.
We don't need to the fallback allocation.
And if CMA option is selected and initialized correctly,
the cma allocation can fail in case of no-CMA-memory situation.
I thinks in that case we don't need to the fallback allocation also,
because it is normal case.
Therefore I think the restriction of CMA size option and make CMA work can cover every cases.
I think below patch is also good choice.
If both of you, Michal and Joonsoo, do not agree with me, please inform me.
I will make a patch including option restriction and fallback allocation.
-----------------8<---------------------
diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index 6b00be1..2909ab9 100644
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -379,7 +379,7 @@ static int __init atomic_pool_init(void)
unsigned long *bitmap;
struct page *page;
struct page **pages;
- void *ptr;
+ void *ptr = NULL;
int bitmap_size = BITS_TO_LONGS(nr_pages) * sizeof(long);
bitmap = kzalloc(bitmap_size, GFP_KERNEL);
@@ -393,7 +393,7 @@ static int __init atomic_pool_init(void)
if (IS_ENABLED(CONFIG_DMA_CMA))
ptr = __alloc_from_contiguous(NULL, pool->size, prot, &page,
atomic_pool_init);
- else
+ if (!ptr)
ptr = __alloc_remap_buffer(NULL, pool->size, gfp, prot, &page,
atomic_pool_init);
if (ptr) {
--
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