From: m.szyprowski@samsung•com (Marek Szyprowski)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH] ARM: dma: Drop __GFP_COMP for iommu dma memory allocations
Date: Fri, 21 Jun 2013 11:33:40 +0200 [thread overview]
Message-ID: <51C41DF4.4090802@samsung.com> (raw)
In-Reply-To: <51C2FDE0.4060206@cogentembedded.com>
Hello,
On 6/20/2013 3:04 PM, Sergei Shtylyov wrote:
> Hello.
>
> On 20-06-2013 16:31, Richard Zhao wrote:
>
>> __iommu_alloc_buffer wants to split pages after allocation in order to
>> reduce the memory footprint. This does not work well with __GFP_COMP
>> pages, so drop this flag before allocation
>
>> One failure example is snd_malloc_dev_pages call dma_alloc_coherent with
>> __GFP_COMP.
>
>> Signed-off-by: Richard Zhao <rizhao@nvidia•com>
>> ---
>> arch/arm/mm/dma-mapping.c | 9 +++++++++
>> 1 file changed, 9 insertions(+)
>
>> diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
>> index ef3e0f3..f7efffd 100644
>> --- a/arch/arm/mm/dma-mapping.c
>> +++ b/arch/arm/mm/dma-mapping.c
>> @@ -1314,6 +1314,15 @@ static void *arm_iommu_alloc_attrs(struct
>> device *dev, size_t size,
>> if (gfp & GFP_ATOMIC)
>> return __iommu_alloc_atomic(dev, size, handle);
>>
>> + /*
>> + * Following is a work-around (a.k.a. hack) to prevent pages
>> + * with __GFP_COMP being passed to split_page() which cannot
>> + * handle them. The real problem is that this flag probably
>> + * should be 0 on ARM as it is not supported on this
>> + * platform; see CONFIG_HUGETLBFS.
>> + */
>> + gfp &= ~(__GFP_COMP);
>
> Hm, what exactly is the sense you meant in using ()?
I think that those parentheses come from the first patch, which disabled
__GFP_COMP
in dma-mapping allocations: 3611553ef98 ("[AVR32] Drop GFP_COMP for DMA
memory
allocations"). I would like to take this patch to the dma-mapping tree
together with
other changes related to iommu integration code.
Best regards
--
Marek Szyprowski
Samsung R&D Institute Poland
next prev parent reply other threads:[~2013-06-21 9:33 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-06-20 12:31 [PATCH] ARM: dma: Drop __GFP_COMP for iommu dma memory allocations Richard Zhao
2013-06-20 13:04 ` Sergei Shtylyov
2013-06-20 13:40 ` Richard Zhao
2013-06-20 14:35 ` Hiroshi Doyu
2013-06-21 4:52 ` Richard Zhao
2013-06-21 9:33 ` Marek Szyprowski [this message]
2013-06-21 11:04 ` Richard Zhao
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