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

To: David Daney <ddaney.cavm@gmail.com>
Subject: Re: [PATCH RFT RESEND linux-next] mips: dma-mapping: support debug_dma_mapping_error
From: Shuah Khan <shuah.khan@hp.com>
Date: Fri, 26 Oct 2012 15:51:04 -0600
Cc: ralf@linux-mips.org, kyungmin.park@samsung.com, arnd@arndb.de, andrzej.p@samsung.com, m.szyprowski@samsung.com, linux-mips@linux-mips.org, LKML <linux-kernel@vger.kernel.org>, shuahkhan@gmail.com
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On Fri, 2012-10-26 at 13:07 -0700, David Daney wrote:
> On 10/26/2012 10:06 AM, Shuah Khan wrote:
> > 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@hp.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.
> 
> No, you have a false predicate here.
> 
> debug_dma_* *is* already mostly added.  The problem is that it is 
> incomplete.  That is the nature of the problem.  Your patch makes it 
> slightly better, but doesn't fully fix the problems.

Got it. Thanks. I would volunteer to look at fixing all the problems,
but unfortunately I don't have a MIPS box handy for a thorough testing
that would be necessary for such a change.

-- Shuah
> 
> 
> >
> > 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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