linux-kernel - Re: [PATCH RFT RESEND linux-next] mips: dma-mapping: support debug_dma_mapping

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Date:	Fri, 26 Oct 2012 11:06:38 -0600
From:	Shuah Khan <shuah.khan@...com>
To:	David Daney <ddaney.cavm@...il.com>
Cc:	ralf@...ux-mips.org, kyungmin.park@...sung.com, arnd@...db.de,
	andrzej.p@...sung.com, m.szyprowski@...sung.com,
	linux-mips@...ux-mips.org, LKML <linux-kernel@...r.kernel.org>,
	shuahkhan@...il.com
Subject: Re: [PATCH RFT RESEND linux-next] mips: dma-mapping: support
 debug_dma_mapping_error

On Fri, 2012-10-26 at 09:45 -0700, David Daney wrote:
> On 10/26/2012 09:01 AM, Shuah Khan wrote:
> > Add support for debug_dma_mapping_error() call to avoid warning from
> > debug_dma_unmap() interface when it checks for mapping error checked
> > status. Without this patch, device driver failed to check map error
> > warning is generated.
> >
> > Signed-off-by: Shuah Khan <shuah.khan@...com>
> > ---
> >   arch/mips/include/asm/dma-mapping.h |    2 ++
> >   1 file changed, 2 insertions(+)
> >
> > diff --git a/arch/mips/include/asm/dma-mapping.h b/arch/mips/include/asm/dma-mapping.h
> > index be39a12..006b43e 100644
> > --- a/arch/mips/include/asm/dma-mapping.h
> > +++ b/arch/mips/include/asm/dma-mapping.h
> > @@ -40,6 +40,8 @@ static inline int dma_supported(struct device *dev, u64 mask)
> >   static inline int dma_mapping_error(struct device *dev, u64 mask)
> >   {
> >   	struct dma_map_ops *ops = get_dma_ops(dev);
> > +
> > +	debug_dma_mapping_error(dev, mask);
> >   	return ops->mapping_error(dev, mask);
> >   }
> >
> >
> 
> Although this is a start, I don't think it is sufficient.
> 
> As far as I can tell, there are many missing calls to debug_dma_*() in 
> the various MIPS commone and sub-architecture DMA code.
> 
> Really you (or someone) needs to look at *all* the functions in 
> arch/mips/asm/dma-mapping.h, and arch/mips/mm/dma-default.c and find 
> places missing a debug_dma_*().

Is it correct to assume that this patch is not needed on MIPS until
debug_dma interfaces get added to MIPS common and sub-architecture DMA
code. 

When I didn't see dma_map_page() in arch/mips/include/asm/dma-mapping.h
defined, and just an extern, I incorrectly assumed, it is getting picked
up from <asm-generic/dma-mapping-common.h>, hence the need for this
patch in the first place.

-- Shuah

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