Patchwork UIO: Allow a UIO driver to override the default pgprot when we mmap

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Submitter Kumar Gala
Date Oct. 12, 2011, 2:43 p.m.
Message ID <1318430616-20351-1-git-send-email-galak@kernel.crashing.org>
Download mbox | patch
Permalink /patch/119224/
State Not Applicable
Delegated to: Kumar Gala
Headers show

Comments

Kumar Gala - Oct. 12, 2011, 2:43 p.m.
For some devices the default behavior of pgprot_noncached is not
the correct flags for the address space.  Provide a means for the
kernel side UIO driver to override the flags without having to
implement its own full mmap callback.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
---
 drivers/uio/uio.c          |    6 +++++-
 include/linux/uio_driver.h |    2 ++
 2 files changed, 7 insertions(+), 1 deletions(-)
Hans J. Koch - Oct. 12, 2011, 3:35 p.m.
On Wed, Oct 12, 2011 at 09:43:36AM -0500, Kumar Gala wrote:
> For some devices the default behavior of pgprot_noncached is not
> the correct flags for the address space.

For what devices? Can you give a real world usecase where this is needed?

Thanks,
Hans

> Provide a means for the
> kernel side UIO driver to override the flags without having to
> implement its own full mmap callback.
> 
> Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
> ---
>  drivers/uio/uio.c          |    6 +++++-
>  include/linux/uio_driver.h |    2 ++
>  2 files changed, 7 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/uio/uio.c b/drivers/uio/uio.c
> index d2efe82..88f4444 100644
> --- a/drivers/uio/uio.c
> +++ b/drivers/uio/uio.c
> @@ -656,7 +656,11 @@ static int uio_mmap_physical(struct vm_area_struct *vma)
>  
>  	vma->vm_flags |= VM_IO | VM_RESERVED;
>  
> -	vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
> +	if (idev->info->mem[mi].set_pgprot)
> +		vma->vm_page_prot =
> +			idev->info->mem[mi].set_pgprot(vma->vm_page_prot);
> +	else
> +		vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
>  
>  	return remap_pfn_range(vma,
>  			       vma->vm_start,
> diff --git a/include/linux/uio_driver.h b/include/linux/uio_driver.h
> index 665517c..4c618cd 100644
> --- a/include/linux/uio_driver.h
> +++ b/include/linux/uio_driver.h
> @@ -28,6 +28,7 @@ struct uio_map;
>   * @memtype:		type of memory addr points to
>   * @internal_addr:	ioremap-ped version of addr, for driver internal use
>   * @map:		for use by the UIO core only.
> + * @set_pgprot:		allow driver to override default(noncached) pgprot
>   */
>  struct uio_mem {
>  	const char		*name;
> @@ -36,6 +37,7 @@ struct uio_mem {
>  	int			memtype;
>  	void __iomem		*internal_addr;
>  	struct uio_map		*map;
> +	pgprot_t (*set_pgprot)(pgprot_t prot);
>  };
>  
>  #define MAX_UIO_MAPS	5
> -- 
> 1.7.3.4
> 
>
Kumar Gala - Oct. 12, 2011, 4:08 p.m.
On Oct 12, 2011, at 10:35 AM, Hans J. Koch wrote:

> On Wed, Oct 12, 2011 at 09:43:36AM -0500, Kumar Gala wrote:
>> For some devices the default behavior of pgprot_noncached is not
>> the correct flags for the address space.
> 
> For what devices? Can you give a real world usecase where this is needed?
> 
> Thanks,
> Hans

In the Freescale Networking devices we have a coherent memory interface to our HW queuing system.  In that case we want to change the pgprot() to be cache-able instead of non-cached.

- k

> 
>> Provide a means for the
>> kernel side UIO driver to override the flags without having to
>> implement its own full mmap callback.
>> 
>> Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
>> ---
>> drivers/uio/uio.c          |    6 +++++-
>> include/linux/uio_driver.h |    2 ++
>> 2 files changed, 7 insertions(+), 1 deletions(-)
>> 
>> diff --git a/drivers/uio/uio.c b/drivers/uio/uio.c
>> index d2efe82..88f4444 100644
>> --- a/drivers/uio/uio.c
>> +++ b/drivers/uio/uio.c
>> @@ -656,7 +656,11 @@ static int uio_mmap_physical(struct vm_area_struct *vma)
>> 
>> 	vma->vm_flags |= VM_IO | VM_RESERVED;
>> 
>> -	vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
>> +	if (idev->info->mem[mi].set_pgprot)
>> +		vma->vm_page_prot =
>> +			idev->info->mem[mi].set_pgprot(vma->vm_page_prot);
>> +	else
>> +		vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
>> 
>> 	return remap_pfn_range(vma,
>> 			       vma->vm_start,
>> diff --git a/include/linux/uio_driver.h b/include/linux/uio_driver.h
>> index 665517c..4c618cd 100644
>> --- a/include/linux/uio_driver.h
>> +++ b/include/linux/uio_driver.h
>> @@ -28,6 +28,7 @@ struct uio_map;
>>  * @memtype:		type of memory addr points to
>>  * @internal_addr:	ioremap-ped version of addr, for driver internal use
>>  * @map:		for use by the UIO core only.
>> + * @set_pgprot:		allow driver to override default(noncached) pgprot
>>  */
>> struct uio_mem {
>> 	const char		*name;
>> @@ -36,6 +37,7 @@ struct uio_mem {
>> 	int			memtype;
>> 	void __iomem		*internal_addr;
>> 	struct uio_map		*map;
>> +	pgprot_t (*set_pgprot)(pgprot_t prot);
>> };
>> 
>> #define MAX_UIO_MAPS	5
>> -- 
>> 1.7.3.4
>> 
>>
Hans J. Koch - Oct. 12, 2011, 4:20 p.m.
On Wed, Oct 12, 2011 at 11:08:20AM -0500, Kumar Gala wrote:
> 
> On Oct 12, 2011, at 10:35 AM, Hans J. Koch wrote:
> 
> > On Wed, Oct 12, 2011 at 09:43:36AM -0500, Kumar Gala wrote:
> >> For some devices the default behavior of pgprot_noncached is not
> >> the correct flags for the address space.
> > 
> > For what devices? Can you give a real world usecase where this is needed?
> > 
> > Thanks,
> > Hans
> 
> In the Freescale Networking devices we have a coherent memory interface to our HW queuing system.  In that case we want to change the pgprot() to be cache-able instead of non-cached.

Could you please post the kernel part of that driver?

Thanks,
Hans

Patch

diff --git a/drivers/uio/uio.c b/drivers/uio/uio.c
index d2efe82..88f4444 100644
--- a/drivers/uio/uio.c
+++ b/drivers/uio/uio.c
@@ -656,7 +656,11 @@  static int uio_mmap_physical(struct vm_area_struct *vma)
 
 	vma->vm_flags |= VM_IO | VM_RESERVED;
 
-	vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
+	if (idev->info->mem[mi].set_pgprot)
+		vma->vm_page_prot =
+			idev->info->mem[mi].set_pgprot(vma->vm_page_prot);
+	else
+		vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
 
 	return remap_pfn_range(vma,
 			       vma->vm_start,
diff --git a/include/linux/uio_driver.h b/include/linux/uio_driver.h
index 665517c..4c618cd 100644
--- a/include/linux/uio_driver.h
+++ b/include/linux/uio_driver.h
@@ -28,6 +28,7 @@  struct uio_map;
  * @memtype:		type of memory addr points to
  * @internal_addr:	ioremap-ped version of addr, for driver internal use
  * @map:		for use by the UIO core only.
+ * @set_pgprot:		allow driver to override default(noncached) pgprot
  */
 struct uio_mem {
 	const char		*name;
@@ -36,6 +37,7 @@  struct uio_mem {
 	int			memtype;
 	void __iomem		*internal_addr;
 	struct uio_map		*map;
+	pgprot_t (*set_pgprot)(pgprot_t prot);
 };
 
 #define MAX_UIO_MAPS	5