[PATCH V2] arm: mm: Remove hugetlb warning from Coherent DMA allocator

[PATCH V2] arm: mm: Remove hugetlb warning from Coherent DMA allocator

[Steve Capper]

The Coherant DMA allocator allocates pages of high order then splits
them up into smaller pages.

This splitting logic would run into problems if the allocator was
given compound pages. Thus the Coherant DMA allocator was originally
incompatible with compound pages existing and, by extension, huge
pages. A compile #error was put in place whenever huge pages were
enabled.

Compatibility with compound pages has since been introduced by the
following commit (which merely excludes GFP_COMP pages from being
requested by the coherant DMA allocator):
  ea2e705 ARM: 7172/1: dma: Drop GFP_COMP for DMA memory allocations

When huge page support was introduced to ARM, the compile #error in
dma-mapping.c was replaced by a #warning when it should have been
removed instead.

This patch removes the compile #warning in dma-mapping.c when huge
pages are enabled.

Signed-off-by: Steve Capper <steve.capper@linaro.org>
---
Changed in V2: commit message completely re-written to give a better
justification.
---
 arch/arm/mm/dma-mapping.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index f61a570..8edd1b5 100644
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -284,9 +284,6 @@ static void __dma_free_buffer(struct page *page, size_t size)
 }
 
 #ifdef CONFIG_MMU
-#ifdef CONFIG_HUGETLB_PAGE
-#warning ARM Coherent DMA allocator does not (yet) support huge TLB
-#endif
 
 static void *__alloc_from_contiguous(struct device *dev, size_t size,
 				     pgprot_t prot, struct page **ret_page,
-- 
1.8.1.4

[PATCH V2] arm: mm: Remove hugetlb warning from Coherent DMA allocator

[Steve Capper]

On Thu, Jan 16, 2014 at 10:07:43AM +0000, Steve Capper wrote:
> The Coherant DMA allocator allocates pages of high order then splits
> them up into smaller pages.
> 
> This splitting logic would run into problems if the allocator was
> given compound pages. Thus the Coherant DMA allocator was originally
> incompatible with compound pages existing and, by extension, huge
> pages. A compile #error was put in place whenever huge pages were
> enabled.
> 
> Compatibility with compound pages has since been introduced by the
> following commit (which merely excludes GFP_COMP pages from being
> requested by the coherant DMA allocator):
>   ea2e705 ARM: 7172/1: dma: Drop GFP_COMP for DMA memory allocations
> 
> When huge page support was introduced to ARM, the compile #error in
> dma-mapping.c was replaced by a #warning when it should have been
> removed instead.
> 
> This patch removes the compile #warning in dma-mapping.c when huge
> pages are enabled.
> 
> Signed-off-by: Steve Capper <steve.capper@linaro.org>
> ---
> Changed in V2: commit message completely re-written to give a better
> justification.
> ---
>  arch/arm/mm/dma-mapping.c | 3 ---
>  1 file changed, 3 deletions(-)

Would anyone object to this going into Russell's patch system?

Cheers,
-- 
Steve

[PATCH V2] arm: mm: Remove hugetlb warning from Coherent DMA allocator

[Russell King - ARM Linux]

On Tue, Feb 18, 2014 at 03:45:51PM +0000, Steve Capper wrote:
> On Thu, Jan 16, 2014 at 10:07:43AM +0000, Steve Capper wrote:
> > The Coherant DMA allocator allocates pages of high order then splits
> > them up into smaller pages.
> > 
> > This splitting logic would run into problems if the allocator was
> > given compound pages. Thus the Coherant DMA allocator was originally
> > incompatible with compound pages existing and, by extension, huge
> > pages. A compile #error was put in place whenever huge pages were
> > enabled.
> > 
> > Compatibility with compound pages has since been introduced by the
> > following commit (which merely excludes GFP_COMP pages from being
> > requested by the coherant DMA allocator):
> >   ea2e705 ARM: 7172/1: dma: Drop GFP_COMP for DMA memory allocations
> > 
> > When huge page support was introduced to ARM, the compile #error in
> > dma-mapping.c was replaced by a #warning when it should have been
> > removed instead.
> > 
> > This patch removes the compile #warning in dma-mapping.c when huge
> > pages are enabled.
> > 
> > Signed-off-by: Steve Capper <steve.capper@linaro.org>
> > ---
> > Changed in V2: commit message completely re-written to give a better
> > justification.
> > ---
> >  arch/arm/mm/dma-mapping.c | 3 ---
> >  1 file changed, 3 deletions(-)
> 
> Would anyone object to this going into Russell's patch system?

It's been a month, no one's objected, so please put it in the patch
system anyway, thanks.

-- 
FTTC broadband for 0.8mile line: 5.8Mbps down 500kbps up.  Estimation
in database were 13.1 to 19Mbit for a good line, about 7.5+ for a bad.
Estimate before purchase was "up to 13.2Mbit".

[PATCH V2] arm: mm: Remove hugetlb warning from Coherent DMA allocator

[Steve Capper]

On Tue, Feb 18, 2014 at 03:49:30PM +0000, Russell King - ARM Linux wrote:
> On Tue, Feb 18, 2014 at 03:45:51PM +0000, Steve Capper wrote:
> > On Thu, Jan 16, 2014 at 10:07:43AM +0000, Steve Capper wrote:
> > > The Coherant DMA allocator allocates pages of high order then splits
> > > them up into smaller pages.
> > > 
> > > This splitting logic would run into problems if the allocator was
> > > given compound pages. Thus the Coherant DMA allocator was originally
> > > incompatible with compound pages existing and, by extension, huge
> > > pages. A compile #error was put in place whenever huge pages were
> > > enabled.
> > > 
> > > Compatibility with compound pages has since been introduced by the
> > > following commit (which merely excludes GFP_COMP pages from being
> > > requested by the coherant DMA allocator):
> > >   ea2e705 ARM: 7172/1: dma: Drop GFP_COMP for DMA memory allocations
> > > 
> > > When huge page support was introduced to ARM, the compile #error in
> > > dma-mapping.c was replaced by a #warning when it should have been
> > > removed instead.
> > > 
> > > This patch removes the compile #warning in dma-mapping.c when huge
> > > pages are enabled.
> > > 
> > > Signed-off-by: Steve Capper <steve.capper@linaro.org>
> > > ---
> > > Changed in V2: commit message completely re-written to give a better
> > > justification.
> > > ---
> > >  arch/arm/mm/dma-mapping.c | 3 ---
> > >  1 file changed, 3 deletions(-)
> > 
> > Would anyone object to this going into Russell's patch system?
> 
> It's been a month, no one's objected, so please put it in the patch
> system anyway, thanks.
> 

Cheers, that's in as 7979/1.

-- 
Steve