Re: [PATCHv7 3/5] common: dma-mapping: Introduce common remapping functions

Re: [PATCHv7 3/5] common: dma-mapping: Introduce common remapping functions

[James Hogan]

On 12 August 2014 00:40, Laura Abbott <lauraa@codeaurora.org> wrote:
>
> For architectures without coherent DMA, memory for DMA may
> need to be remapped with coherent attributes. Factor out
> the the remapping code from arm and put it in a
> common location to reduce code duplication.
>
> As part of this, the arm APIs are now migrated away from
> ioremap_page_range to the common APIs which use map_vm_area for remapping.
> This should be an equivalent change and using map_vm_area is more
> correct as ioremap_page_range is intended to bring in io addresses
> into the cpu space and not regular kernel managed memory.
>
> Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
> Signed-off-by: Laura Abbott <lauraa@codeaurora.org>

This commit in linux-next () breaks the build for metag:

drivers/base/dma-mapping.c: In function ‘dma_common_contiguous_remap’:
drivers/base/dma-mapping.c:294: error: implicit declaration of
function ‘dma_common_pages_remap’
drivers/base/dma-mapping.c:294: warning: assignment makes pointer from
integer without a cast
drivers/base/dma-mapping.c: At top level:
drivers/base/dma-mapping.c:308: error: conflicting types for
‘dma_common_pages_remap’
drivers/base/dma-mapping.c:294: error: previous implicit declaration
of ‘dma_common_pages_remap’ was here

Looks like metag isn't alone either:

$ git grep -L dma-mapping-common arch/*/include/asm/dma-mapping.h
arch/arc/include/asm/dma-mapping.h
arch/avr32/include/asm/dma-mapping.h
arch/blackfin/include/asm/dma-mapping.h
arch/c6x/include/asm/dma-mapping.h
arch/cris/include/asm/dma-mapping.h
arch/frv/include/asm/dma-mapping.h
arch/m68k/include/asm/dma-mapping.h
arch/metag/include/asm/dma-mapping.h
arch/mn10300/include/asm/dma-mapping.h
arch/parisc/include/asm/dma-mapping.h
arch/xtensa/include/asm/dma-mapping.h

I've checked a couple of these arches (blackfin, xtensa) which don't
include dma-mapping-common.h and their builds seem to be broken too.

Cheers
James

> ---
>  arch/arm/mm/dma-mapping.c                | 57 +++++---------------------
>  drivers/base/dma-mapping.c               | 68 ++++++++++++++++++++++++++++++++
>  include/asm-generic/dma-mapping-common.h |  9 +++++
>  3 files changed, 86 insertions(+), 48 deletions(-)
>
> diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
> index 4c88935..f5190ac 100644
> --- a/arch/arm/mm/dma-mapping.c
> +++ b/arch/arm/mm/dma-mapping.c
> @@ -297,37 +297,19 @@ static void *
>  __dma_alloc_remap(struct page *page, size_t size, gfp_t gfp, pgprot_t prot,
>         const void *caller)
>  {
> -       struct vm_struct *area;
> -       unsigned long addr;
> -
>         /*
>          * DMA allocation can be mapped to user space, so lets
>          * set VM_USERMAP flags too.
>          */
> -       area = get_vm_area_caller(size, VM_ARM_DMA_CONSISTENT | VM_USERMAP,
> -                                 caller);
> -       if (!area)
> -               return NULL;
> -       addr = (unsigned long)area->addr;
> -       area->phys_addr = __pfn_to_phys(page_to_pfn(page));
> -
> -       if (ioremap_page_range(addr, addr + size, area->phys_addr, prot)) {
> -               vunmap((void *)addr);
> -               return NULL;
> -       }
> -       return (void *)addr;
> +       return dma_common_contiguous_remap(page, size,
> +                       VM_ARM_DMA_CONSISTENT | VM_USERMAP,
> +                       prot, caller);
>  }
>
>  static void __dma_free_remap(void *cpu_addr, size_t size)
>  {
> -       unsigned int flags = VM_ARM_DMA_CONSISTENT | VM_USERMAP;
> -       struct vm_struct *area = find_vm_area(cpu_addr);
> -       if (!area || (area->flags & flags) != flags) {
> -               WARN(1, "trying to free invalid coherent area: %p\n", cpu_addr);
> -               return;
> -       }
> -       unmap_kernel_range((unsigned long)cpu_addr, size);
> -       vunmap(cpu_addr);
> +       dma_common_free_remap(cpu_addr, size,
> +                       VM_ARM_DMA_CONSISTENT | VM_USERMAP);
>  }
>
>  #define DEFAULT_DMA_COHERENT_POOL_SIZE SZ_256K
> @@ -1261,29 +1243,8 @@ static void *
>  __iommu_alloc_remap(struct page **pages, size_t size, gfp_t gfp, pgprot_t prot,
>                     const void *caller)
>  {
> -       unsigned int i, nr_pages = PAGE_ALIGN(size) >> PAGE_SHIFT;
> -       struct vm_struct *area;
> -       unsigned long p;
> -
> -       area = get_vm_area_caller(size, VM_ARM_DMA_CONSISTENT | VM_USERMAP,
> -                                 caller);
> -       if (!area)
> -               return NULL;
> -
> -       area->pages = pages;
> -       area->nr_pages = nr_pages;
> -       p = (unsigned long)area->addr;
> -
> -       for (i = 0; i < nr_pages; i++) {
> -               phys_addr_t phys = __pfn_to_phys(page_to_pfn(pages[i]));
> -               if (ioremap_page_range(p, p + PAGE_SIZE, phys, prot))
> -                       goto err;
> -               p += PAGE_SIZE;
> -       }
> -       return area->addr;
> -err:
> -       unmap_kernel_range((unsigned long)area->addr, size);
> -       vunmap(area->addr);
> +       return dma_common_pages_remap(pages, size,
> +                       VM_ARM_DMA_CONSISTENT | VM_USERMAP, prot, caller);
>         return NULL;
>  }
>
> @@ -1491,8 +1452,8 @@ void arm_iommu_free_attrs(struct device *dev, size_t size, void *cpu_addr,
>         }
>
>         if (!dma_get_attr(DMA_ATTR_NO_KERNEL_MAPPING, attrs)) {
> -               unmap_kernel_range((unsigned long)cpu_addr, size);
> -               vunmap(cpu_addr);
> +               dma_common_free_remap(cpu_addr, size,
> +                       VM_ARM_DMA_CONSISTENT | VM_USERMAP);
>         }
>
>         __iommu_remove_mapping(dev, handle, size);
> diff --git a/drivers/base/dma-mapping.c b/drivers/base/dma-mapping.c
> index 6cd08e1..1bc46df 100644
> --- a/drivers/base/dma-mapping.c
> +++ b/drivers/base/dma-mapping.c
> @@ -10,6 +10,8 @@
>  #include <linux/dma-mapping.h>
>  #include <linux/export.h>
>  #include <linux/gfp.h>
> +#include <linux/slab.h>
> +#include <linux/vmalloc.h>
>  #include <asm-generic/dma-coherent.h>
>
>  /*
> @@ -267,3 +269,69 @@ int dma_common_mmap(struct device *dev, struct vm_area_struct *vma,
>         return ret;
>  }
>  EXPORT_SYMBOL(dma_common_mmap);
> +
> +/*
> + * remaps an allocated contiguous region into another vm_area.
> + * Cannot be used in non-sleeping contexts
> + */
> +
> +void *dma_common_contiguous_remap(struct page *page, size_t size,
> +                       unsigned long vm_flags,
> +                       pgprot_t prot, const void *caller)
> +{
> +       int i;
> +       struct page **pages;
> +       void *ptr;
> +       unsigned long pfn;
> +
> +       pages = kmalloc(sizeof(struct page *) << get_order(size), GFP_KERNEL);
> +       if (!pages)
> +               return NULL;
> +
> +       for (i = 0, pfn = page_to_pfn(page); i < (size >> PAGE_SHIFT); i++)
> +               pages[i] = pfn_to_page(pfn + i);
> +
> +       ptr = dma_common_pages_remap(pages, size, vm_flags, prot, caller);
> +
> +       kfree(pages);
> +
> +       return ptr;
> +}
> +
> +/*
> + * remaps an array of PAGE_SIZE pages into another vm_area
> + * Cannot be used in non-sleeping contexts
> + */
> +void *dma_common_pages_remap(struct page **pages, size_t size,
> +                       unsigned long vm_flags, pgprot_t prot,
> +                       const void *caller)
> +{
> +       struct vm_struct *area;
> +
> +       area = get_vm_area_caller(size, vm_flags, caller);
> +       if (!area)
> +               return NULL;
> +
> +       if (map_vm_area(area, prot, pages)) {
> +               vunmap(area->addr);
> +               return NULL;
> +       }
> +
> +       return area->addr;
> +}
> +
> +/*
> + * unmaps a range previously mapped by dma_common_*_remap
> + */
> +void dma_common_free_remap(void *cpu_addr, size_t size, unsigned long vm_flags)
> +{
> +       struct vm_struct *area = find_vm_area(cpu_addr);
> +
> +       if (!area || (area->flags & vm_flags) != vm_flags) {
> +               WARN(1, "trying to free invalid coherent area: %p\n", cpu_addr);
> +               return;
> +       }
> +
> +       unmap_kernel_range((unsigned long)cpu_addr, size);
> +       vunmap(cpu_addr);
> +}
> diff --git a/include/asm-generic/dma-mapping-common.h b/include/asm-generic/dma-mapping-common.h
> index de8bf89..a9fd248 100644
> --- a/include/asm-generic/dma-mapping-common.h
> +++ b/include/asm-generic/dma-mapping-common.h
> @@ -179,6 +179,15 @@ dma_sync_sg_for_device(struct device *dev, struct scatterlist *sg,
>  extern int dma_common_mmap(struct device *dev, struct vm_area_struct *vma,
>                            void *cpu_addr, dma_addr_t dma_addr, size_t size);
>
> +void *dma_common_contiguous_remap(struct page *page, size_t size,
> +                       unsigned long vm_flags,
> +                       pgprot_t prot, const void *caller);
> +
> +void *dma_common_pages_remap(struct page **pages, size_t size,
> +                       unsigned long vm_flags, pgprot_t prot,
> +                       const void *caller);
> +void dma_common_free_remap(void *cpu_addr, size_t size, unsigned long vm_flags);
> +
>  /**
>   * dma_mmap_attrs - map a coherent DMA allocation into user space
>   * @dev: valid struct device pointer, or NULL for ISA and EISA-like devices
> --
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> hosted by The Linux Foundation
>
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Re: [PATCHv7 3/5] common: dma-mapping: Introduce common remapping functions

[Laura Abbott]

On 8/26/2014 3:05 AM, James Hogan wrote:
> On 12 August 2014 00:40, Laura Abbott <lauraa@codeaurora.org> wrote:
>>
>> For architectures without coherent DMA, memory for DMA may
>> need to be remapped with coherent attributes. Factor out
>> the the remapping code from arm and put it in a
>> common location to reduce code duplication.
>>
>> As part of this, the arm APIs are now migrated away from
>> ioremap_page_range to the common APIs which use map_vm_area for remapping.
>> This should be an equivalent change and using map_vm_area is more
>> correct as ioremap_page_range is intended to bring in io addresses
>> into the cpu space and not regular kernel managed memory.
>>
>> Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
>> Signed-off-by: Laura Abbott <lauraa@codeaurora.org>
> 
> This commit in linux-next () breaks the build for metag:
> 
> drivers/base/dma-mapping.c: In function ‘dma_common_contiguous_remap’:
> drivers/base/dma-mapping.c:294: error: implicit declaration of
> function ‘dma_common_pages_remap’
> drivers/base/dma-mapping.c:294: warning: assignment makes pointer from
> integer without a cast
> drivers/base/dma-mapping.c: At top level:
> drivers/base/dma-mapping.c:308: error: conflicting types for
> ‘dma_common_pages_remap’
> drivers/base/dma-mapping.c:294: error: previous implicit declaration
> of ‘dma_common_pages_remap’ was here
> 
> Looks like metag isn't alone either:
> 
> $ git grep -L dma-mapping-common arch/*/include/asm/dma-mapping.h
> arch/arc/include/asm/dma-mapping.h
> arch/avr32/include/asm/dma-mapping.h
> arch/blackfin/include/asm/dma-mapping.h
> arch/c6x/include/asm/dma-mapping.h
> arch/cris/include/asm/dma-mapping.h
> arch/frv/include/asm/dma-mapping.h
> arch/m68k/include/asm/dma-mapping.h
> arch/metag/include/asm/dma-mapping.h
> arch/mn10300/include/asm/dma-mapping.h
> arch/parisc/include/asm/dma-mapping.h
> arch/xtensa/include/asm/dma-mapping.h
> 
> I've checked a couple of these arches (blackfin, xtensa) which don't
> include dma-mapping-common.h and their builds seem to be broken too.
> 
> Cheers
> James
> 

Thanks for the report. Would you mind giving the following patch
a test (this is theoretical only but I think it should work)

-----8<------

From 81c9a5504cbc1d72ff1df084d48502b248cd79d0 Mon Sep 17 00:00:00 2001
From: Laura Abbott <lauraa@codeaurora.org>
Date: Tue, 26 Aug 2014 09:50:49 -0700
Subject: [PATCH] common: dma-mapping: Swap function order

Fix the order of dma_common_contiguous_remap and
dma_common_pages_remap to avoid function declaration errors:

drivers/base/dma-mapping.c: In function 'dma_common_contiguous_remap':
drivers/base/dma-mapping.c:294: error: implicit declaration of
function 'dma_common_pages_remap'
drivers/base/dma-mapping.c:294: warning: assignment makes pointer from
integer without a cast
drivers/base/dma-mapping.c: At top level:
drivers/base/dma-mapping.c:308: error: conflicting types for
'dma_common_pages_remap'
drivers/base/dma-mapping.c:294: error: previous implicit declaration
of 'dma_common_pages_remap' was here

Change-Id: I65db739114e8f5816a24a279a2ff1a6dc92e2b83
Reported-by: James Hogan <james.hogan@imgtec.com>
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Laura Abbott <lauraa@codeaurora.org>
---
 drivers/base/dma-mapping.c | 44 ++++++++++++++++++++++----------------------
 1 file changed, 22 insertions(+), 22 deletions(-)

diff --git a/drivers/base/dma-mapping.c b/drivers/base/dma-mapping.c
index 1bc46df..056fd46 100644
--- a/drivers/base/dma-mapping.c
+++ b/drivers/base/dma-mapping.c
@@ -271,6 +271,28 @@ int dma_common_mmap(struct device *dev, struct vm_area_struct *vma,
 EXPORT_SYMBOL(dma_common_mmap);
 
 /*
+ * remaps an array of PAGE_SIZE pages into another vm_area
+ * Cannot be used in non-sleeping contexts
+ */
+void *dma_common_pages_remap(struct page **pages, size_t size,
+			unsigned long vm_flags, pgprot_t prot,
+			const void *caller)
+{
+	struct vm_struct *area;
+
+	area = get_vm_area_caller(size, vm_flags, caller);
+	if (!area)
+		return NULL;
+
+	if (map_vm_area(area, prot, pages)) {
+		vunmap(area->addr);
+		return NULL;
+	}
+
+	return area->addr;
+}
+
+/*
  * remaps an allocated contiguous region into another vm_area.
  * Cannot be used in non-sleeping contexts
  */
@@ -299,28 +321,6 @@ void *dma_common_contiguous_remap(struct page *page, size_t size,
 }
 
 /*
- * remaps an array of PAGE_SIZE pages into another vm_area
- * Cannot be used in non-sleeping contexts
- */
-void *dma_common_pages_remap(struct page **pages, size_t size,
-			unsigned long vm_flags, pgprot_t prot,
-			const void *caller)
-{
-	struct vm_struct *area;
-
-	area = get_vm_area_caller(size, vm_flags, caller);
-	if (!area)
-		return NULL;
-
-	if (map_vm_area(area, prot, pages)) {
-		vunmap(area->addr);
-		return NULL;
-	}
-
-	return area->addr;
-}
-
-/*
  * unmaps a range previously mapped by dma_common_*_remap
  */
 void dma_common_free_remap(void *cpu_addr, size_t size, unsigned long vm_flags)
-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
hosted by The Linux Foundation

-- 
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
hosted by The Linux Foundation

Re: [PATCHv7 3/5] common: dma-mapping: Introduce common remapping functions

[James Hogan]

On 26/08/14 17:58, Laura Abbott wrote:
> On 8/26/2014 3:05 AM, James Hogan wrote:
>> On 12 August 2014 00:40, Laura Abbott <lauraa@codeaurora.org> wrote:
>>>
>>> For architectures without coherent DMA, memory for DMA may
>>> need to be remapped with coherent attributes. Factor out
>>> the the remapping code from arm and put it in a
>>> common location to reduce code duplication.
>>>
>>> As part of this, the arm APIs are now migrated away from
>>> ioremap_page_range to the common APIs which use map_vm_area for remapping.
>>> This should be an equivalent change and using map_vm_area is more
>>> correct as ioremap_page_range is intended to bring in io addresses
>>> into the cpu space and not regular kernel managed memory.
>>>
>>> Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
>>> Signed-off-by: Laura Abbott <lauraa@codeaurora.org>
>>
>> This commit in linux-next () breaks the build for metag:
>>
>> drivers/base/dma-mapping.c: In function ‘dma_common_contiguous_remap’:
>> drivers/base/dma-mapping.c:294: error: implicit declaration of
>> function ‘dma_common_pages_remap’
>> drivers/base/dma-mapping.c:294: warning: assignment makes pointer from
>> integer without a cast
>> drivers/base/dma-mapping.c: At top level:
>> drivers/base/dma-mapping.c:308: error: conflicting types for
>> ‘dma_common_pages_remap’
>> drivers/base/dma-mapping.c:294: error: previous implicit declaration
>> of ‘dma_common_pages_remap’ was here
>>
>> Looks like metag isn't alone either:
>>
>> $ git grep -L dma-mapping-common arch/*/include/asm/dma-mapping.h
>> arch/arc/include/asm/dma-mapping.h
>> arch/avr32/include/asm/dma-mapping.h
>> arch/blackfin/include/asm/dma-mapping.h
>> arch/c6x/include/asm/dma-mapping.h
>> arch/cris/include/asm/dma-mapping.h
>> arch/frv/include/asm/dma-mapping.h
>> arch/m68k/include/asm/dma-mapping.h
>> arch/metag/include/asm/dma-mapping.h
>> arch/mn10300/include/asm/dma-mapping.h
>> arch/parisc/include/asm/dma-mapping.h
>> arch/xtensa/include/asm/dma-mapping.h
>>
>> I've checked a couple of these arches (blackfin, xtensa) which don't
>> include dma-mapping-common.h and their builds seem to be broken too.
>>
>> Cheers
>> James
>>
> 
> Thanks for the report. Would you mind giving the following patch
> a test (this is theoretical only but I think it should work)

It certainly fixes the build for metag.

Thanks
James

> 
> -----8<------
> 
> From 81c9a5504cbc1d72ff1df084d48502b248cd79d0 Mon Sep 17 00:00:00 2001
> From: Laura Abbott <lauraa@codeaurora.org>
> Date: Tue, 26 Aug 2014 09:50:49 -0700
> Subject: [PATCH] common: dma-mapping: Swap function order
> 
> Fix the order of dma_common_contiguous_remap and
> dma_common_pages_remap to avoid function declaration errors:
> 
> drivers/base/dma-mapping.c: In function 'dma_common_contiguous_remap':
> drivers/base/dma-mapping.c:294: error: implicit declaration of
> function 'dma_common_pages_remap'
> drivers/base/dma-mapping.c:294: warning: assignment makes pointer from
> integer without a cast
> drivers/base/dma-mapping.c: At top level:
> drivers/base/dma-mapping.c:308: error: conflicting types for
> 'dma_common_pages_remap'
> drivers/base/dma-mapping.c:294: error: previous implicit declaration
> of 'dma_common_pages_remap' was here
> 
> Change-Id: I65db739114e8f5816a24a279a2ff1a6dc92e2b83
> Reported-by: James Hogan <james.hogan@imgtec.com>
> Reported-by: kbuild test robot <fengguang.wu@intel.com>
> Signed-off-by: Laura Abbott <lauraa@codeaurora.org>
> ---
>  drivers/base/dma-mapping.c | 44 ++++++++++++++++++++++----------------------
>  1 file changed, 22 insertions(+), 22 deletions(-)
> 
> diff --git a/drivers/base/dma-mapping.c b/drivers/base/dma-mapping.c
> index 1bc46df..056fd46 100644
> --- a/drivers/base/dma-mapping.c
> +++ b/drivers/base/dma-mapping.c
> @@ -271,6 +271,28 @@ int dma_common_mmap(struct device *dev, struct vm_area_struct *vma,
>  EXPORT_SYMBOL(dma_common_mmap);
>  
>  /*
> + * remaps an array of PAGE_SIZE pages into another vm_area
> + * Cannot be used in non-sleeping contexts
> + */
> +void *dma_common_pages_remap(struct page **pages, size_t size,
> +			unsigned long vm_flags, pgprot_t prot,
> +			const void *caller)
> +{
> +	struct vm_struct *area;
> +
> +	area = get_vm_area_caller(size, vm_flags, caller);
> +	if (!area)
> +		return NULL;
> +
> +	if (map_vm_area(area, prot, pages)) {
> +		vunmap(area->addr);
> +		return NULL;
> +	}
> +
> +	return area->addr;
> +}
> +
> +/*
>   * remaps an allocated contiguous region into another vm_area.
>   * Cannot be used in non-sleeping contexts
>   */
> @@ -299,28 +321,6 @@ void *dma_common_contiguous_remap(struct page *page, size_t size,
>  }
>  
>  /*
> - * remaps an array of PAGE_SIZE pages into another vm_area
> - * Cannot be used in non-sleeping contexts
> - */
> -void *dma_common_pages_remap(struct page **pages, size_t size,
> -			unsigned long vm_flags, pgprot_t prot,
> -			const void *caller)
> -{
> -	struct vm_struct *area;
> -
> -	area = get_vm_area_caller(size, vm_flags, caller);
> -	if (!area)
> -		return NULL;
> -
> -	if (map_vm_area(area, prot, pages)) {
> -		vunmap(area->addr);
> -		return NULL;
> -	}
> -
> -	return area->addr;
> -}
> -
> -/*
>   * unmaps a range previously mapped by dma_common_*_remap
>   */
>  void dma_common_free_remap(void *cpu_addr, size_t size, unsigned long vm_flags)
> 

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Re: [PATCHv7 3/5] common: dma-mapping: Introduce common remapping functions

[Mark Salter]

On Tue, 2014-08-26 at 09:58 -0700, Laura Abbott wrote:
> On 8/26/2014 3:05 AM, James Hogan wrote:
> > On 12 August 2014 00:40, Laura Abbott <lauraa@codeaurora.org> wrote:
> >>
> >> For architectures without coherent DMA, memory for DMA may
> >> need to be remapped with coherent attributes. Factor out
> >> the the remapping code from arm and put it in a
> >> common location to reduce code duplication.
> >>
> >> As part of this, the arm APIs are now migrated away from
> >> ioremap_page_range to the common APIs which use map_vm_area for remapping.
> >> This should be an equivalent change and using map_vm_area is more
> >> correct as ioremap_page_range is intended to bring in io addresses
> >> into the cpu space and not regular kernel managed memory.
> >>
> >> Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
> >> Signed-off-by: Laura Abbott <lauraa@codeaurora.org>
> > 
> > This commit in linux-next () breaks the build for metag:
> > 
> > drivers/base/dma-mapping.c: In function ‘dma_common_contiguous_remap’:
> > drivers/base/dma-mapping.c:294: error: implicit declaration of
> > function ‘dma_common_pages_remap’
> > drivers/base/dma-mapping.c:294: warning: assignment makes pointer from
> > integer without a cast
> > drivers/base/dma-mapping.c: At top level:
> > drivers/base/dma-mapping.c:308: error: conflicting types for
> > ‘dma_common_pages_remap’
> > drivers/base/dma-mapping.c:294: error: previous implicit declaration
> > of ‘dma_common_pages_remap’ was here
> > 
> > Looks like metag isn't alone either:
> > 
> > $ git grep -L dma-mapping-common arch/*/include/asm/dma-mapping.h
> > arch/arc/include/asm/dma-mapping.h
> > arch/avr32/include/asm/dma-mapping.h
> > arch/blackfin/include/asm/dma-mapping.h
> > arch/c6x/include/asm/dma-mapping.h
> > arch/cris/include/asm/dma-mapping.h
> > arch/frv/include/asm/dma-mapping.h
> > arch/m68k/include/asm/dma-mapping.h
> > arch/metag/include/asm/dma-mapping.h
> > arch/mn10300/include/asm/dma-mapping.h
> > arch/parisc/include/asm/dma-mapping.h
> > arch/xtensa/include/asm/dma-mapping.h
> > 
> > I've checked a couple of these arches (blackfin, xtensa) which don't
> > include dma-mapping-common.h and their builds seem to be broken too.
> > 
> > Cheers
> > James
> > 
> 
> Thanks for the report. Would you mind giving the following patch
> a test (this is theoretical only but I think it should work)

There's a further problem with c6x (no  MMU):

drivers/built-in.o: In function `dma_common_pages_remap':
(.text+0x220c4): undefined reference to `get_vm_area_caller'
drivers/built-in.o: In function `dma_common_pages_remap':
(.text+0x22108): undefined reference to `map_vm_area'
drivers/built-in.o: In function `dma_common_free_remap':
(.text+0x22278): undefined reference to `find_vm_area'



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