[PATCH] UIO: Allow a UIO driver to override the default pgprot when we mmap

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 <redacted>
---
 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

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

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:

quoted

For some devices the default behavior of pgprot_noncached is not
the correct flags for the address space.

=20
For what devices? Can you give a real world usecase where this is =

needed?

=20
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

=20

quoted

Provide a means for the
kernel side UIO driver to override the flags without having to
implement its own full mmap callback.
=20
Signed-off-by: Kumar Gala <redacted>
---
drivers/uio/uio.c          |    6 +++++-
include/linux/uio_driver.h |    2 ++
2 files changed, 7 insertions(+), 1 deletions(-)
=20

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)

quoted

=20
	vma->vm_flags |=3D VM_IO | VM_RESERVED;
=20
-	vma->vm_page_prot =3D pgprot_noncached(vma->vm_page_prot);
+	if (idev->info->mem[mi].set_pgprot)
+		vma->vm_page_prot =3D
+			=

idev->info->mem[mi].set_pgprot(vma->vm_page_prot);

quoted

+	else
+		vma->vm_page_prot =3D =

pgprot_noncached(vma->vm_page_prot);

quoted

=20
	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

quoted

 * @map:		for use by the UIO core only.
+ * @set_pgprot:		allow driver to override =

default(noncached) pgprot

quoted

 */
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);
};
=20
#define MAX_UIO_MAPS	5
--=20
1.7.3.4
=20
=20

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:

quoted

On Wed, Oct 12, 2011 at 09:43:36AM -0500, Kumar Gala wrote:

quoted

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