Re: [PATCH RESEND] dma-mapping: tidy up dma_parms default handling

Re: [PATCH RESEND] dma-mapping: tidy up dma_parms default handling

[Arnd Bergmann]

On Friday 09 January 2015 16:56:03 Robin Murphy wrote:
> 
> This one's a bit tricky to find a home for - I think technically it's 
> probably an IOMMU patch, but then the long-underlying problem doesn't
> seem to have blown up anything until arm64, and my motivation is to
> make bits of Juno work, which seems to nudge it towards arm64/arm-soc
> territory. Could anyone suggest which tree is most appropriate?

I have a set of patches touching various dma-mapping.h related bits
across architectures and in ARM in particular. Your patch fits into
that series, and I guess we could either have it in my asm-generic
tree or in Andrew Morton's mm tree. Possibly also arm-soc for practical
reasons, although it really doesn't belong in there.

	Arnd

Re: [PATCH RESEND] dma-mapping: tidy up dma_parms default handling

[Will Deacon]

On Fri, Jan 09, 2015 at 07:45:49PM +0000, Arnd Bergmann wrote:
> On Friday 09 January 2015 16:56:03 Robin Murphy wrote:
> > 
> > This one's a bit tricky to find a home for - I think technically it's 
> > probably an IOMMU patch, but then the long-underlying problem doesn't
> > seem to have blown up anything until arm64, and my motivation is to
> > make bits of Juno work, which seems to nudge it towards arm64/arm-soc
> > territory. Could anyone suggest which tree is most appropriate?
> 
> I have a set of patches touching various dma-mapping.h related bits
> across architectures and in ARM in particular. Your patch fits into
> that series, and I guess we could either have it in my asm-generic
> tree or in Andrew Morton's mm tree. Possibly also arm-soc for practical
> reasons, although it really doesn't belong in there.

I also have a couple of fixes for issues found by Laurent for tearing
down the IOMMU dma ops, so you could include those too.

I'll send them out this afternoon.

Will

Re: [PATCH RESEND] dma-mapping: tidy up dma_parms default handling

[Robin Murphy]

On 09/01/15 19:45, Arnd Bergmann wrote:
> On Friday 09 January 2015 16:56:03 Robin Murphy wrote:
>>
>> This one's a bit tricky to find a home for - I think technically it's
>> probably an IOMMU patch, but then the long-underlying problem doesn't
>> seem to have blown up anything until arm64, and my motivation is to
>> make bits of Juno work, which seems to nudge it towards arm64/arm-soc
>> territory. Could anyone suggest which tree is most appropriate?
>
> I have a set of patches touching various dma-mapping.h related bits
> across architectures and in ARM in particular. Your patch fits into
> that series, and I guess we could either have it in my asm-generic
> tree or in Andrew Morton's mm tree. Possibly also arm-soc for practical
> reasons, although it really doesn't belong in there.
>

Thanks Arnd, I'd agree asm-generic or mm sound the most sensible - If 
you're happy to carry this patch with your series that'd be really helpful.

Robin.

Re: [PATCH RESEND] dma-mapping: tidy up dma_parms default handling

[Marek Szyprowski]

Hello,

On 2015-01-09 17:56, Robin Murphy wrote:
> Many DMA controllers and other devices set max_segment_size to
> indicate their scatter-gather capability, but have no interest in
> segment_boundary_mask. However, the existence of a dma_parms structure
> precludes the use of any default value, leaving them as zeros (assuming
> a properly kzalloc'ed structure). If a well-behaved IOMMU (or SWIOTLB)
> then tries to respect this by ensuring a mapped segment does not cross
> a zero-byte boundary, hilarity ensues.
>
> Since zero is a nonsensical value for either parameter, treat it as an
> indicator for "default", as might be expected. In the process, clean up
> a bit by replacing the bare constants with slightly more meaningful
> macros and removing the superfluous "else" statements.
>
> Signed-off-by: Robin Murphy <robin.murphy-5wv7dgnIgG8@public.gmane.org>

Acked-by: Marek Szyprowski <m.szyprowski-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>

> ---
>
> Hi, various maintainers from Git logs ;)
>
> This one's a bit tricky to find a home for - I think technically it's
> probably an IOMMU patch, but then the long-underlying problem doesn't
> seem to have blown up anything until arm64, and my motivation is to
> make bits of Juno work, which seems to nudge it towards arm64/arm-soc
> territory. Could anyone suggest which tree is most appropriate?
>
> Thanks,
> Robin.
>
>   include/linux/dma-mapping.h | 17 ++++++++++-------
>   1 file changed, 10 insertions(+), 7 deletions(-)
>
> diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
> index c3007cb..99ba736 100644
> --- a/include/linux/dma-mapping.h
> +++ b/include/linux/dma-mapping.h
> @@ -141,7 +141,9 @@ static inline void arch_teardown_dma_ops(struct device *dev) { }
>   
>   static inline unsigned int dma_get_max_seg_size(struct device *dev)
>   {
> -	return dev->dma_parms ? dev->dma_parms->max_segment_size : 65536;
> +	if (dev->dma_parms && dev->dma_parms->max_segment_size)
> +		return dev->dma_parms->max_segment_size;
> +	return SZ_64K;
>   }
>   
>   static inline unsigned int dma_set_max_seg_size(struct device *dev,
> @@ -150,14 +152,15 @@ static inline unsigned int dma_set_max_seg_size(struct device *dev,
>   	if (dev->dma_parms) {
>   		dev->dma_parms->max_segment_size = size;
>   		return 0;
> -	} else
> -		return -EIO;
> +	}
> +	return -EIO;
>   }
>   
>   static inline unsigned long dma_get_seg_boundary(struct device *dev)
>   {
> -	return dev->dma_parms ?
> -		dev->dma_parms->segment_boundary_mask : 0xffffffff;
> +	if (dev->dma_parms && dev->dma_parms->segment_boundary_mask)
> +		return dev->dma_parms->segment_boundary_mask;
> +	return DMA_BIT_MASK(32);
>   }
>   
>   static inline int dma_set_seg_boundary(struct device *dev, unsigned long mask)
> @@ -165,8 +168,8 @@ static inline int dma_set_seg_boundary(struct device *dev, unsigned long mask)
>   	if (dev->dma_parms) {
>   		dev->dma_parms->segment_boundary_mask = mask;
>   		return 0;
> -	} else
> -		return -EIO;
> +	}
> +	return -EIO;
>   }
>   
>   #ifndef dma_max_pfn

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland

Re: [PATCH RESEND] dma-mapping: tidy up dma_parms default handling

[Sumit Semwal]

Hi Robin,

On 13 January 2015 at 16:49, Marek Szyprowski <m.szyprowski@samsung.com> wrote:
> Hello,
>
> On 2015-01-09 17:56, Robin Murphy wrote:
>>
>> Many DMA controllers and other devices set max_segment_size to
>> indicate their scatter-gather capability, but have no interest in
>> segment_boundary_mask. However, the existence of a dma_parms structure
>> precludes the use of any default value, leaving them as zeros (assuming
>> a properly kzalloc'ed structure). If a well-behaved IOMMU (or SWIOTLB)
>> then tries to respect this by ensuring a mapped segment does not cross
>> a zero-byte boundary, hilarity ensues.
>>
>> Since zero is a nonsensical value for either parameter, treat it as an
>> indicator for "default", as might be expected. In the process, clean up
>> a bit by replacing the bare constants with slightly more meaningful
>> macros and removing the superfluous "else" statements.
>>
>> Signed-off-by: Robin Murphy <robin.murphy@arm.com>
>
>
> Acked-by: Marek Szyprowski <m.szyprowski@samsung.com>

Please feel free to add my
Reviewed-by: Sumit Semwal <sumit.semwal@linaro.org>
>
>> ---
>>
>> Hi, various maintainers from Git logs ;)
>>
>> This one's a bit tricky to find a home for - I think technically it's
>> probably an IOMMU patch, but then the long-underlying problem doesn't
>> seem to have blown up anything until arm64, and my motivation is to
>> make bits of Juno work, which seems to nudge it towards arm64/arm-soc
>> territory. Could anyone suggest which tree is most appropriate?
>>
>> Thanks,
>> Robin.
>>
>>
>>   include/linux/dma-mapping.h | 17 ++++++++++-------
>>   1 file changed, 10 insertions(+), 7 deletions(-)
>>
>> diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
>> index c3007cb..99ba736 100644
>> --- a/include/linux/dma-mapping.h
>> +++ b/include/linux/dma-mapping.h
>> @@ -141,7 +141,9 @@ static inline void arch_teardown_dma_ops(struct device
>> *dev) { }
>>     static inline unsigned int dma_get_max_seg_size(struct device *dev)
>>   {
>> -       return dev->dma_parms ? dev->dma_parms->max_segment_size : 65536;
>> +       if (dev->dma_parms && dev->dma_parms->max_segment_size)
>> +               return dev->dma_parms->max_segment_size;
>> +       return SZ_64K;
>>   }
>>     static inline unsigned int dma_set_max_seg_size(struct device *dev,
>> @@ -150,14 +152,15 @@ static inline unsigned int
>> dma_set_max_seg_size(struct device *dev,
>>         if (dev->dma_parms) {
>>                 dev->dma_parms->max_segment_size = size;
>>                 return 0;
>> -       } else
>> -               return -EIO;
>> +       }
>> +       return -EIO;
>>   }
>>     static inline unsigned long dma_get_seg_boundary(struct device *dev)
>>   {
>> -       return dev->dma_parms ?
>> -               dev->dma_parms->segment_boundary_mask : 0xffffffff;
>> +       if (dev->dma_parms && dev->dma_parms->segment_boundary_mask)
>> +               return dev->dma_parms->segment_boundary_mask;
>> +       return DMA_BIT_MASK(32);
>>   }
>>     static inline int dma_set_seg_boundary(struct device *dev, unsigned
>> long mask)
>> @@ -165,8 +168,8 @@ static inline int dma_set_seg_boundary(struct device
>> *dev, unsigned long mask)
>>         if (dev->dma_parms) {
>>                 dev->dma_parms->segment_boundary_mask = mask;
>>                 return 0;
>> -       } else
>> -               return -EIO;
>> +       }
>> +       return -EIO;
>>   }
>>     #ifndef dma_max_pfn
>
>
> Best regards
> --
> Marek Szyprowski, PhD
> Samsung R&D Institute Poland
>
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at  http://www.tux.org/lkml/

-- 
Thanks and regards,

Sumit Semwal
Kernel Team Lead - Linaro Mobile Group
Linaro.org │ Open source software for ARM SoCs

[PATCH RESEND] dma-mapping: tidy up dma_parms default handling

[Robin Murphy]

Many DMA controllers and other devices set max_segment_size to
indicate their scatter-gather capability, but have no interest in
segment_boundary_mask. However, the existence of a dma_parms structure
precludes the use of any default value, leaving them as zeros (assuming
a properly kzalloc'ed structure). If a well-behaved IOMMU (or SWIOTLB)
then tries to respect this by ensuring a mapped segment does not cross
a zero-byte boundary, hilarity ensues.

Since zero is a nonsensical value for either parameter, treat it as an
indicator for "default", as might be expected. In the process, clean up
a bit by replacing the bare constants with slightly more meaningful
macros and removing the superfluous "else" statements.

Signed-off-by: Robin Murphy <robin.murphy-5wv7dgnIgG8@public.gmane.org>
---

Hi, various maintainers from Git logs ;)

This one's a bit tricky to find a home for - I think technically it's 
probably an IOMMU patch, but then the long-underlying problem doesn't
seem to have blown up anything until arm64, and my motivation is to
make bits of Juno work, which seems to nudge it towards arm64/arm-soc
territory. Could anyone suggest which tree is most appropriate?

Thanks,
Robin.

 include/linux/dma-mapping.h | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index c3007cb..99ba736 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -141,7 +141,9 @@ static inline void arch_teardown_dma_ops(struct device *dev) { }
 
 static inline unsigned int dma_get_max_seg_size(struct device *dev)
 {
-	return dev->dma_parms ? dev->dma_parms->max_segment_size : 65536;
+	if (dev->dma_parms && dev->dma_parms->max_segment_size)
+		return dev->dma_parms->max_segment_size;
+	return SZ_64K;
 }
 
 static inline unsigned int dma_set_max_seg_size(struct device *dev,
@@ -150,14 +152,15 @@ static inline unsigned int dma_set_max_seg_size(struct device *dev,
 	if (dev->dma_parms) {
 		dev->dma_parms->max_segment_size = size;
 		return 0;
-	} else
-		return -EIO;
+	}
+	return -EIO;
 }
 
 static inline unsigned long dma_get_seg_boundary(struct device *dev)
 {
-	return dev->dma_parms ?
-		dev->dma_parms->segment_boundary_mask : 0xffffffff;
+	if (dev->dma_parms && dev->dma_parms->segment_boundary_mask)
+		return dev->dma_parms->segment_boundary_mask;
+	return DMA_BIT_MASK(32);
 }
 
 static inline int dma_set_seg_boundary(struct device *dev, unsigned long mask)
@@ -165,8 +168,8 @@ static inline int dma_set_seg_boundary(struct device *dev, unsigned long mask)
 	if (dev->dma_parms) {
 		dev->dma_parms->segment_boundary_mask = mask;
 		return 0;
-	} else
-		return -EIO;
+	}
+	return -EIO;
 }
 
 #ifndef dma_max_pfn
-- 
1.9.1