[v9,01/18] arm: make SWIOTLB available

Commit Message

Stefano Stabellini Oct. 25, 2013, 10:51 a.m. UTC

IOMMU_HELPER is needed because SWIOTLB calls iommu_is_span_boundary,
provided by lib/iommu_helper.c.

Signed-off-by: Stefano Stabellini <[e-mail]>
Reviewed-by: Konrad Rzeszutek Wilk <[e-mail]>
CC: [e-mail]
CC: [e-mail]


Changes in v8:
- use __phys_to_pfn and __pfn_to_phys.

Changes in v7:
- dma_mark_clean: empty implementation;
- in dma_capable use coherent_dma_mask if dma_mask hasn't been
  allocated.

Changes in v6:
- check for dev->dma_mask being NULL in dma_capable.

Changes in v5:
- implement dma_mark_clean using dmac_flush_range.

Changes in v3:
- dma_capable: do not treat dma_mask as a limit;
- remove SWIOTLB dependency on NEED_SG_DMA_LENGTH.
---
 arch/arm/Kconfig                   |    6 +++++
 arch/arm/include/asm/dma-mapping.h |   37 ++++++++++++++++++++++++++++++++++++
 2 files changed, 43 insertions(+), 0 deletions(-)

Comments

Stefano Stabellini Oct. 25, 2013, 11:08 a.m. UTC | #1

Russell,
this is the only patch that needs an ack at the moment.
As you commented on it before and I have already addressed your comments
few versions ago, unless you have any complaints I am going to add it to
linux-next and I am thinking of merging it during the next merge window.

On Fri, 25 Oct 2013, Stefano Stabellini wrote:
> IOMMU_HELPER is needed because SWIOTLB calls iommu_is_span_boundary,
> provided by lib/iommu_helper.c.
> 
> Signed-off-by: Stefano Stabellini <[e-mail]>
> Reviewed-by: Konrad Rzeszutek Wilk <[e-mail]>
> CC: [e-mail]
> CC: [e-mail]
> 
> 
> Changes in v8:
> - use __phys_to_pfn and __pfn_to_phys.
> 
> Changes in v7:
> - dma_mark_clean: empty implementation;
> - in dma_capable use coherent_dma_mask if dma_mask hasn't been
>   allocated.
> 
> Changes in v6:
> - check for dev->dma_mask being NULL in dma_capable.
> 
> Changes in v5:
> - implement dma_mark_clean using dmac_flush_range.
> 
> Changes in v3:
> - dma_capable: do not treat dma_mask as a limit;
> - remove SWIOTLB dependency on NEED_SG_DMA_LENGTH.
> ---
>  arch/arm/Kconfig                   |    6 +++++
>  arch/arm/include/asm/dma-mapping.h |   37 ++++++++++++++++++++++++++++++++++++
>  2 files changed, 43 insertions(+), 0 deletions(-)
> 
> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> index 1ad6fb6..b08374f 100644
> --- a/arch/arm/Kconfig
> +++ b/arch/arm/Kconfig
> @@ -1872,6 +1872,12 @@ config CC_STACKPROTECTOR
>  	  neutralized via a kernel panic.
>  	  This feature requires gcc version 4.2 or above.
>  
> +config SWIOTLB
> +	def_bool y
> +
> +config IOMMU_HELPER
> +	def_bool SWIOTLB
> +
>  config XEN_DOM0
>  	def_bool y
>  	depends on XEN
> diff --git a/arch/arm/include/asm/dma-mapping.h b/arch/arm/include/asm/dma-mapping.h
> index 5b579b9..01b5a3d 100644
> --- a/arch/arm/include/asm/dma-mapping.h
> +++ b/arch/arm/include/asm/dma-mapping.h
> @@ -10,6 +10,7 @@
>  
>  #include <asm-generic/dma-coherent.h>
>  #include <asm/memory.h>
> +#include <asm/cacheflush.h>
>  
>  #define DMA_ERROR_CODE	(~0)
>  extern struct dma_map_ops arm_dma_ops;
> @@ -86,6 +87,42 @@ static inline dma_addr_t virt_to_dma(struct device *dev, void *addr)
>  }
>  #endif
>  
> +static inline dma_addr_t phys_to_dma(struct device *dev, phys_addr_t paddr)
> +{
> +	unsigned int offset = paddr & ~PAGE_MASK;
> +	return pfn_to_dma(dev, __phys_to_pfn(paddr)) + offset;
> +}
> +
> +static inline phys_addr_t dma_to_phys(struct device *dev, dma_addr_t dev_addr)
> +{
> +	unsigned int offset = dev_addr & ~PAGE_MASK;
> +	return __pfn_to_phys(dma_to_pfn(dev, dev_addr)) + offset;
> +}
> +
> +static inline bool dma_capable(struct device *dev, dma_addr_t addr, size_t size)
> +{
> +	u64 limit, mask;
> +	
> +	if (dev->dma_mask)
> +		mask = *dev->dma_mask;
> +	else 
> +		mask = dev->coherent_dma_mask;
> +
> +	if (mask == 0)
> +		return 0;
> +
> +	limit = (mask + 1) & ~mask;
> +	if (limit && size > limit)
> +		return 0;
> +
> +	if ((addr | (addr + size - 1)) & ~mask)
> +		return 0;
> +
> +	return 1;
> +}
> +
> +static inline void dma_mark_clean(void *addr, size_t size) { }
> +
>  /*
>   * DMA errors are defined by all-bits-set in the DMA address.
>   */
> -- 
> 1.7.2.5
>

Stefano Stabellini Oct. 29, 2013, 4:41 a.m. UTC | #2

ping?

On Fri, 25 Oct 2013, Stefano Stabellini wrote:
> Russell,
> this is the only patch that needs an ack at the moment.
> As you commented on it before and I have already addressed your comments
> few versions ago, unless you have any complaints I am going to add it to
> linux-next and I am thinking of merging it during the next merge window.
> 
> On Fri, 25 Oct 2013, Stefano Stabellini wrote:
> > IOMMU_HELPER is needed because SWIOTLB calls iommu_is_span_boundary,
> > provided by lib/iommu_helper.c.
> > 
> > Signed-off-by: Stefano Stabellini <[e-mail]>
> > Reviewed-by: Konrad Rzeszutek Wilk <[e-mail]>
> > CC: [e-mail]
> > CC: [e-mail]
> > 
> > 
> > Changes in v8:
> > - use __phys_to_pfn and __pfn_to_phys.
> > 
> > Changes in v7:
> > - dma_mark_clean: empty implementation;
> > - in dma_capable use coherent_dma_mask if dma_mask hasn't been
> >   allocated.
> > 
> > Changes in v6:
> > - check for dev->dma_mask being NULL in dma_capable.
> > 
> > Changes in v5:
> > - implement dma_mark_clean using dmac_flush_range.
> > 
> > Changes in v3:
> > - dma_capable: do not treat dma_mask as a limit;
> > - remove SWIOTLB dependency on NEED_SG_DMA_LENGTH.
> > ---
> >  arch/arm/Kconfig                   |    6 +++++
> >  arch/arm/include/asm/dma-mapping.h |   37 ++++++++++++++++++++++++++++++++++++
> >  2 files changed, 43 insertions(+), 0 deletions(-)
> > 
> > diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> > index 1ad6fb6..b08374f 100644
> > --- a/arch/arm/Kconfig
> > +++ b/arch/arm/Kconfig
> > @@ -1872,6 +1872,12 @@ config CC_STACKPROTECTOR
> >  	  neutralized via a kernel panic.
> >  	  This feature requires gcc version 4.2 or above.
> >  
> > +config SWIOTLB
> > +	def_bool y
> > +
> > +config IOMMU_HELPER
> > +	def_bool SWIOTLB
> > +
> >  config XEN_DOM0
> >  	def_bool y
> >  	depends on XEN
> > diff --git a/arch/arm/include/asm/dma-mapping.h b/arch/arm/include/asm/dma-mapping.h
> > index 5b579b9..01b5a3d 100644
> > --- a/arch/arm/include/asm/dma-mapping.h
> > +++ b/arch/arm/include/asm/dma-mapping.h
> > @@ -10,6 +10,7 @@
> >  
> >  #include <asm-generic/dma-coherent.h>
> >  #include <asm/memory.h>
> > +#include <asm/cacheflush.h>
> >  
> >  #define DMA_ERROR_CODE	(~0)
> >  extern struct dma_map_ops arm_dma_ops;
> > @@ -86,6 +87,42 @@ static inline dma_addr_t virt_to_dma(struct device *dev, void *addr)
> >  }
> >  #endif
> >  
> > +static inline dma_addr_t phys_to_dma(struct device *dev, phys_addr_t paddr)
> > +{
> > +	unsigned int offset = paddr & ~PAGE_MASK;
> > +	return pfn_to_dma(dev, __phys_to_pfn(paddr)) + offset;
> > +}
> > +
> > +static inline phys_addr_t dma_to_phys(struct device *dev, dma_addr_t dev_addr)
> > +{
> > +	unsigned int offset = dev_addr & ~PAGE_MASK;
> > +	return __pfn_to_phys(dma_to_pfn(dev, dev_addr)) + offset;
> > +}
> > +
> > +static inline bool dma_capable(struct device *dev, dma_addr_t addr, size_t size)
> > +{
> > +	u64 limit, mask;
> > +	
> > +	if (dev->dma_mask)
> > +		mask = *dev->dma_mask;
> > +	else 
> > +		mask = dev->coherent_dma_mask;
> > +
> > +	if (mask == 0)
> > +		return 0;
> > +
> > +	limit = (mask + 1) & ~mask;
> > +	if (limit && size > limit)
> > +		return 0;
> > +
> > +	if ((addr | (addr + size - 1)) & ~mask)
> > +		return 0;
> > +
> > +	return 1;
> > +}
> > +
> > +static inline void dma_mark_clean(void *addr, size_t size) { }
> > +
> >  /*
> >   * DMA errors are defined by all-bits-set in the DMA address.
> >   */
> > -- 
> > 1.7.2.5
> > 
>

Konrad Rzeszutek Wilk Oct. 29, 2013, 2:20 p.m. UTC | #3

On Tue, Oct 29, 2013 at 04:41:40AM +0000, Stefano Stabellini wrote:
> ping?

You know you are pinging yourself, right ? :-)

> 
> On Fri, 25 Oct 2013, Stefano Stabellini wrote:
> > Russell,
> > this is the only patch that needs an ack at the moment.
> > As you commented on it before and I have already addressed your comments
> > few versions ago, unless you have any complaints I am going to add it to
> > linux-next and I am thinking of merging it during the next merge window.
> > 
> > On Fri, 25 Oct 2013, Stefano Stabellini wrote:
> > > IOMMU_HELPER is needed because SWIOTLB calls iommu_is_span_boundary,
> > > provided by lib/iommu_helper.c.
> > > 
> > > Signed-off-by: Stefano Stabellini <[e-mail]>
> > > Reviewed-by: Konrad Rzeszutek Wilk <[e-mail]>
> > > CC: [e-mail]
> > > CC: [e-mail]
> > > 
> > > 
> > > Changes in v8:
> > > - use __phys_to_pfn and __pfn_to_phys.
> > > 
> > > Changes in v7:
> > > - dma_mark_clean: empty implementation;
> > > - in dma_capable use coherent_dma_mask if dma_mask hasn't been
> > >   allocated.
> > > 
> > > Changes in v6:
> > > - check for dev->dma_mask being NULL in dma_capable.
> > > 
> > > Changes in v5:
> > > - implement dma_mark_clean using dmac_flush_range.
> > > 
> > > Changes in v3:
> > > - dma_capable: do not treat dma_mask as a limit;
> > > - remove SWIOTLB dependency on NEED_SG_DMA_LENGTH.
> > > ---
> > >  arch/arm/Kconfig                   |    6 +++++
> > >  arch/arm/include/asm/dma-mapping.h |   37 ++++++++++++++++++++++++++++++++++++
> > >  2 files changed, 43 insertions(+), 0 deletions(-)
> > > 
> > > diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> > > index 1ad6fb6..b08374f 100644
> > > --- a/arch/arm/Kconfig
> > > +++ b/arch/arm/Kconfig
> > > @@ -1872,6 +1872,12 @@ config CC_STACKPROTECTOR
> > >  	  neutralized via a kernel panic.
> > >  	  This feature requires gcc version 4.2 or above.
> > >  
> > > +config SWIOTLB
> > > +	def_bool y
> > > +
> > > +config IOMMU_HELPER
> > > +	def_bool SWIOTLB
> > > +
> > >  config XEN_DOM0
> > >  	def_bool y
> > >  	depends on XEN
> > > diff --git a/arch/arm/include/asm/dma-mapping.h b/arch/arm/include/asm/dma-mapping.h
> > > index 5b579b9..01b5a3d 100644
> > > --- a/arch/arm/include/asm/dma-mapping.h
> > > +++ b/arch/arm/include/asm/dma-mapping.h
> > > @@ -10,6 +10,7 @@
> > >  
> > >  #include <asm-generic/dma-coherent.h>
> > >  #include <asm/memory.h>
> > > +#include <asm/cacheflush.h>
> > >  
> > >  #define DMA_ERROR_CODE	(~0)
> > >  extern struct dma_map_ops arm_dma_ops;
> > > @@ -86,6 +87,42 @@ static inline dma_addr_t virt_to_dma(struct device *dev, void *addr)
> > >  }
> > >  #endif
> > >  
> > > +static inline dma_addr_t phys_to_dma(struct device *dev, phys_addr_t paddr)
> > > +{
> > > +	unsigned int offset = paddr & ~PAGE_MASK;
> > > +	return pfn_to_dma(dev, __phys_to_pfn(paddr)) + offset;
> > > +}
> > > +
> > > +static inline phys_addr_t dma_to_phys(struct device *dev, dma_addr_t dev_addr)
> > > +{
> > > +	unsigned int offset = dev_addr & ~PAGE_MASK;
> > > +	return __pfn_to_phys(dma_to_pfn(dev, dev_addr)) + offset;
> > > +}
> > > +
> > > +static inline bool dma_capable(struct device *dev, dma_addr_t addr, size_t size)
> > > +{
> > > +	u64 limit, mask;
> > > +	
> > > +	if (dev->dma_mask)
> > > +		mask = *dev->dma_mask;
> > > +	else 
> > > +		mask = dev->coherent_dma_mask;
> > > +
> > > +	if (mask == 0)
> > > +		return 0;
> > > +
> > > +	limit = (mask + 1) & ~mask;
> > > +	if (limit && size > limit)
> > > +		return 0;
> > > +
> > > +	if ((addr | (addr + size - 1)) & ~mask)
> > > +		return 0;
> > > +
> > > +	return 1;
> > > +}
> > > +
> > > +static inline void dma_mark_clean(void *addr, size_t size) { }
> > > +
> > >  /*
> > >   * DMA errors are defined by all-bits-set in the DMA address.
> > >   */
> > > -- 
> > > 1.7.2.5
> > > 
> >

Russell King - ARM Linux Oct. 29, 2013, 2:26 p.m. UTC | #4

On Tue, Oct 29, 2013 at 10:20:23AM -0400, Konrad Rzeszutek Wilk wrote:
> On Tue, Oct 29, 2013 at 04:41:40AM +0000, Stefano Stabellini wrote:
> > ping?
> 
> You know you are pinging yourself, right ? :-)

And the patch was only Cc'd.  I'm starting to read stuff which isn't
flagged as having me in the To: line with less priority in recent times.

> > On Fri, 25 Oct 2013, Stefano Stabellini wrote:
> > > Russell,
> > > this is the only patch that needs an ack at the moment.
> > > As you commented on it before and I have already addressed your comments
> > > few versions ago, unless you have any complaints I am going to add it to
> > > linux-next and I am thinking of merging it during the next merge window.
> > > 
> > > On Fri, 25 Oct 2013, Stefano Stabellini wrote:
> > > > IOMMU_HELPER is needed because SWIOTLB calls iommu_is_span_boundary,
> > > > provided by lib/iommu_helper.c.
> > > > 
> > > > Signed-off-by: Stefano Stabellini <[e-mail]>
> > > > Reviewed-by: Konrad Rzeszutek Wilk <[e-mail]>
> > > > CC: [e-mail]
> > > > CC: [e-mail]
> > > > 
> > > > 
> > > > Changes in v8:
> > > > - use __phys_to_pfn and __pfn_to_phys.
> > > > 
> > > > Changes in v7:
> > > > - dma_mark_clean: empty implementation;
> > > > - in dma_capable use coherent_dma_mask if dma_mask hasn't been
> > > >   allocated.
> > > > 
> > > > Changes in v6:
> > > > - check for dev->dma_mask being NULL in dma_capable.
> > > > 
> > > > Changes in v5:
> > > > - implement dma_mark_clean using dmac_flush_range.
> > > > 
> > > > Changes in v3:
> > > > - dma_capable: do not treat dma_mask as a limit;
> > > > - remove SWIOTLB dependency on NEED_SG_DMA_LENGTH.
> > > > ---
> > > >  arch/arm/Kconfig                   |    6 +++++
> > > >  arch/arm/include/asm/dma-mapping.h |   37 ++++++++++++++++++++++++++++++++++++
> > > >  2 files changed, 43 insertions(+), 0 deletions(-)
> > > > 
> > > > diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> > > > index 1ad6fb6..b08374f 100644
> > > > --- a/arch/arm/Kconfig
> > > > +++ b/arch/arm/Kconfig
> > > > @@ -1872,6 +1872,12 @@ config CC_STACKPROTECTOR
> > > >  	  neutralized via a kernel panic.
> > > >  	  This feature requires gcc version 4.2 or above.
> > > >  
> > > > +config SWIOTLB
> > > > +	def_bool y
> > > > +
> > > > +config IOMMU_HELPER
> > > > +	def_bool SWIOTLB
> > > > +
> > > >  config XEN_DOM0
> > > >  	def_bool y
> > > >  	depends on XEN
> > > > diff --git a/arch/arm/include/asm/dma-mapping.h b/arch/arm/include/asm/dma-mapping.h
> > > > index 5b579b9..01b5a3d 100644
> > > > --- a/arch/arm/include/asm/dma-mapping.h
> > > > +++ b/arch/arm/include/asm/dma-mapping.h
> > > > @@ -10,6 +10,7 @@
> > > >  
> > > >  #include <asm-generic/dma-coherent.h>
> > > >  #include <asm/memory.h>
> > > > +#include <asm/cacheflush.h>

Why does this need to be here?  Your'e not adding anything which
needs it.

> > > > +static inline dma_addr_t phys_to_dma(struct device *dev, phys_addr_t paddr)
> > > > +{
> > > > +	unsigned int offset = paddr & ~PAGE_MASK;
> > > > +	return pfn_to_dma(dev, __phys_to_pfn(paddr)) + offset;
> > > > +}
> > > > +
> > > > +static inline phys_addr_t dma_to_phys(struct device *dev, dma_addr_t dev_addr)
> > > > +{
> > > > +	unsigned int offset = dev_addr & ~PAGE_MASK;
> > > > +	return __pfn_to_phys(dma_to_pfn(dev, dev_addr)) + offset;
> > > > +}

These look fine.

> > > > +static inline bool dma_capable(struct device *dev, dma_addr_t addr, size_t size)
> > > > +{
> > > > +	u64 limit, mask;
> > > > +	
> > > > +	if (dev->dma_mask)
> > > > +		mask = *dev->dma_mask;
> > > > +	else 
> > > > +		mask = dev->coherent_dma_mask;

This looks like a hack.  Either we want to use the streaming mask or
the coherent mask as appropriate for the caller.  That should be a choice
the caller makes, not the implementation of this behind the callers back.

> > > > +
> > > > +	if (mask == 0)
> > > > +		return 0;
> > > > +
> > > > +	limit = (mask + 1) & ~mask;
> > > > +	if (limit && size > limit)
> > > > +		return 0;
> > > > +
> > > > +	if ((addr | (addr + size - 1)) & ~mask)
> > > > +		return 0;
> > > > +
> > > > +	return 1;
> > > > +}

The remainder looks fine to me.

Stefano Stabellini Oct. 29, 2013, 5:24 p.m. UTC | #5

On Tue, 29 Oct 2013, Russell King - ARM Linux wrote:
> On Tue, Oct 29, 2013 at 10:20:23AM -0400, Konrad Rzeszutek Wilk wrote:
> > On Tue, Oct 29, 2013 at 04:41:40AM +0000, Stefano Stabellini wrote:
> > > ping?
> > 
> > You know you are pinging yourself, right ? :-)
> 
> And the patch was only Cc'd.  I'm starting to read stuff which isn't
> flagged as having me in the To: line with less priority in recent times.

good to know


> > > On Fri, 25 Oct 2013, Stefano Stabellini wrote:
> > > > Russell,
> > > > this is the only patch that needs an ack at the moment.
> > > > As you commented on it before and I have already addressed your comments
> > > > few versions ago, unless you have any complaints I am going to add it to
> > > > linux-next and I am thinking of merging it during the next merge window.
> > > > 
> > > > On Fri, 25 Oct 2013, Stefano Stabellini wrote:
> > > > > IOMMU_HELPER is needed because SWIOTLB calls iommu_is_span_boundary,
> > > > > provided by lib/iommu_helper.c.
> > > > > 
> > > > > Signed-off-by: Stefano Stabellini <[e-mail]>
> > > > > Reviewed-by: Konrad Rzeszutek Wilk <[e-mail]>
> > > > > CC: [e-mail]
> > > > > CC: [e-mail]
> > > > > 
> > > > > 
> > > > > Changes in v8:
> > > > > - use __phys_to_pfn and __pfn_to_phys.
> > > > > 
> > > > > Changes in v7:
> > > > > - dma_mark_clean: empty implementation;
> > > > > - in dma_capable use coherent_dma_mask if dma_mask hasn't been
> > > > >   allocated.
> > > > > 
> > > > > Changes in v6:
> > > > > - check for dev->dma_mask being NULL in dma_capable.
> > > > > 
> > > > > Changes in v5:
> > > > > - implement dma_mark_clean using dmac_flush_range.
> > > > > 
> > > > > Changes in v3:
> > > > > - dma_capable: do not treat dma_mask as a limit;
> > > > > - remove SWIOTLB dependency on NEED_SG_DMA_LENGTH.
> > > > > ---
> > > > >  arch/arm/Kconfig                   |    6 +++++
> > > > >  arch/arm/include/asm/dma-mapping.h |   37 ++++++++++++++++++++++++++++++++++++
> > > > >  2 files changed, 43 insertions(+), 0 deletions(-)
> > > > > 
> > > > > diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> > > > > index 1ad6fb6..b08374f 100644
> > > > > --- a/arch/arm/Kconfig
> > > > > +++ b/arch/arm/Kconfig
> > > > > @@ -1872,6 +1872,12 @@ config CC_STACKPROTECTOR
> > > > >  	  neutralized via a kernel panic.
> > > > >  	  This feature requires gcc version 4.2 or above.
> > > > >  
> > > > > +config SWIOTLB
> > > > > +	def_bool y
> > > > > +
> > > > > +config IOMMU_HELPER
> > > > > +	def_bool SWIOTLB
> > > > > +
> > > > >  config XEN_DOM0
> > > > >  	def_bool y
> > > > >  	depends on XEN
> > > > > diff --git a/arch/arm/include/asm/dma-mapping.h b/arch/arm/include/asm/dma-mapping.h
> > > > > index 5b579b9..01b5a3d 100644
> > > > > --- a/arch/arm/include/asm/dma-mapping.h
> > > > > +++ b/arch/arm/include/asm/dma-mapping.h
> > > > > @@ -10,6 +10,7 @@
> > > > >  
> > > > >  #include <asm-generic/dma-coherent.h>
> > > > >  #include <asm/memory.h>
> > > > > +#include <asm/cacheflush.h>
> 
> Why does this need to be here?  Your'e not adding anything which
> needs it.

Legacy of a previous iteration of the patch. I'll remove it.


> > > > > +static inline dma_addr_t phys_to_dma(struct device *dev, phys_addr_t paddr)
> > > > > +{
> > > > > +	unsigned int offset = paddr & ~PAGE_MASK;
> > > > > +	return pfn_to_dma(dev, __phys_to_pfn(paddr)) + offset;
> > > > > +}
> > > > > +
> > > > > +static inline phys_addr_t dma_to_phys(struct device *dev, dma_addr_t dev_addr)
> > > > > +{
> > > > > +	unsigned int offset = dev_addr & ~PAGE_MASK;
> > > > > +	return __pfn_to_phys(dma_to_pfn(dev, dev_addr)) + offset;
> > > > > +}
> 
> These look fine.
> 
> > > > > +static inline bool dma_capable(struct device *dev, dma_addr_t addr, size_t size)
> > > > > +{
> > > > > +	u64 limit, mask;
> > > > > +	
> > > > > +	if (dev->dma_mask)
> > > > > +		mask = *dev->dma_mask;
> > > > > +	else 
> > > > > +		mask = dev->coherent_dma_mask;
> 
> This looks like a hack.  Either we want to use the streaming mask or
> the coherent mask as appropriate for the caller.  That should be a choice
> the caller makes, not the implementation of this behind the callers back.

How should I choose?
Admittedly this is a workaround because some drivers (including Calxeda
xgmac) don't set the dma_mask when they should:

http://marc.info/?l=linux-arm-kernel&m=138082570519601&w=2

I am happy to reduce this to:

if (dev->dma_mask)
    mask = *dev->dma_mask;

even though it means that xgmac & co won't be dma_capable.


> > > > > +
> > > > > +	if (mask == 0)
> > > > > +		return 0;
> > > > > +
> > > > > +	limit = (mask + 1) & ~mask;
> > > > > +	if (limit && size > limit)
> > > > > +		return 0;
> > > > > +
> > > > > +	if ((addr | (addr + size - 1)) & ~mask)
> > > > > +		return 0;
> > > > > +
> > > > > +	return 1;
> > > > > +}
> 
> The remainder looks fine to me.
>

Russell King - ARM Linux Oct. 29, 2013, 6:01 p.m. UTC | #6

On Tue, Oct 29, 2013 at 05:24:50PM +0000, Stefano Stabellini wrote:
> On Tue, 29 Oct 2013, Russell King - ARM Linux wrote:
> > This looks like a hack.  Either we want to use the streaming mask or
> > the coherent mask as appropriate for the caller.  That should be a choice
> > the caller makes, not the implementation of this behind the callers back.
> 
> How should I choose?
> Admittedly this is a workaround because some drivers (including Calxeda
> xgmac) don't set the dma_mask when they should:
> 
> http://marc.info/?l=linux-arm-kernel&m=138082570519601&w=2
> 
> I am happy to reduce this to:
> 
> if (dev->dma_mask)
>     mask = *dev->dma_mask;
> 
> even though it means that xgmac & co won't be dma_capable.

Well, if xgmac (there's two in the kernel tree so I'm not sure which
you're referring to) is using DMA of any kind, it really ought to be
setting a DMA mask via the standard functions - in todays kernel,
that is dma_set_mask() for the streaming mask and dma_set_coherent_mask()
for the coherent mask.  The appropriate mask which the driver is aware
of for the hardware should be set here.

In the case that a driver needs to call both, and the kernel has my
patch set applied, dma_set_mask_and_coherent() can be used to set both
at the same time.

dma_set_mask() (and dma_set_mask_and_coherent) will fail if storage for
the DMA mask has not been allocated previously - iow, if the dev->dma_mask
pointer is NULL.  The allocation of this storage is the responsibility
of the struct device creator, and the struct device creator should
initialise the DMA masks to a sensible default for the type of bus.

I provide one last call in my patch set - a method that drivers can
coerce the DMA mask to whatever they desire irrespective of whether
the DMA mask allocation has been setup.  This is provided as a way to
mark the drivers which are doing this and to ensure that drivers do
this in a safe manner - we've had drivers setting it to static storage
in module space if it isn't previously set, which is a problem if the
module ever gets unloaded.

So... what I'm saying is please fix xgmac to use the DMA API properly
rather than working around such problems. :)

Patch

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 1ad6fb6..b08374f 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1872,6 +1872,12 @@  config CC_STACKPROTECTOR
 	  neutralized via a kernel panic.
 	  This feature requires gcc version 4.2 or above.
 
+config SWIOTLB
+	def_bool y
+
+config IOMMU_HELPER
+	def_bool SWIOTLB
+
 config XEN_DOM0
 	def_bool y
 	depends on XEN
diff --git a/arch/arm/include/asm/dma-mapping.h b/arch/arm/include/asm/dma-mapping.h
index 5b579b9..01b5a3d 100644
--- a/arch/arm/include/asm/dma-mapping.h
+++ b/arch/arm/include/asm/dma-mapping.h
@@ -10,6 +10,7 @@ 
 
 #include <asm-generic/dma-coherent.h>
 #include <asm/memory.h>
+#include <asm/cacheflush.h>
 
 #define DMA_ERROR_CODE	(~0)
 extern struct dma_map_ops arm_dma_ops;
@@ -86,6 +87,42 @@  static inline dma_addr_t virt_to_dma(struct device *dev, void *addr)
 }
 #endif
 
+static inline dma_addr_t phys_to_dma(struct device *dev, phys_addr_t paddr)
+{
+	unsigned int offset = paddr & ~PAGE_MASK;
+	return pfn_to_dma(dev, __phys_to_pfn(paddr)) + offset;
+}
+
+static inline phys_addr_t dma_to_phys(struct device *dev, dma_addr_t dev_addr)
+{
+	unsigned int offset = dev_addr & ~PAGE_MASK;
+	return __pfn_to_phys(dma_to_pfn(dev, dev_addr)) + offset;
+}
+
+static inline bool dma_capable(struct device *dev, dma_addr_t addr, size_t size)
+{
+	u64 limit, mask;
+	
+	if (dev->dma_mask)
+		mask = *dev->dma_mask;
+	else 
+		mask = dev->coherent_dma_mask;
+
+	if (mask == 0)
+		return 0;
+
+	limit = (mask + 1) & ~mask;
+	if (limit && size > limit)
+		return 0;
+
+	if ((addr | (addr + size - 1)) & ~mask)
+		return 0;
+
+	return 1;
+}
+
+static inline void dma_mark_clean(void *addr, size_t size) { }
+
 /*
  * DMA errors are defined by all-bits-set in the DMA address.
  */