Currently, three types of mem regions are supported: UIO_MEM_PHYS,
UIO_MEM_LOGICAL and UIO_MEM_VIRTUAL. Among these UIO_MEM_PHYS helps
UIO driver export physcial memory to user space as non-cacheable
user memory. Typcially memory-mapped registers of a device are exported
to user space as UIO_MEM_PHYS type mem region. The UIO_MEM_PHYS type
is not efficient if dma-capable devices are capable of maintaining coherency
with CPU caches.
This patch adds new type UIO_MEM_PHYS_CACHE for mem regions to enable
cacheable access to physical memory from user space.
Signed-off-by: Ankit Jindal <ankit.jindal@xxxxxxxxxx>
Signed-off-by: Tushar Jagad <tushar.jagad@xxxxxxxxxx>
---
drivers/uio/uio.c | 11 ++++++++---
include/linux/uio_driver.h | 1 +
2 files changed, 9 insertions(+), 3 deletions(-)
diff --git a/drivers/uio/uio.c b/drivers/uio/uio.c
index 97e6444..120a84b 100644
--- a/drivers/uio/uio.c
+++ b/drivers/uio/uio.c
@@ -644,7 +644,7 @@ static const struct vm_operations_struct uio_physical_vm_ops = {
#endif
};
-static int uio_mmap_physical(struct vm_area_struct *vma)
+static int uio_mmap_physical(struct vm_area_struct *vma, bool cacheable)
{
struct uio_device *idev = vma->vm_private_data;
int mi = uio_find_mem_index(vma);
@@ -659,7 +659,9 @@ static int uio_mmap_physical(struct vm_area_struct *vma)
return -EINVAL;
vma->vm_ops = &uio_physical_vm_ops;
- vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
+
+ if (!cacheable)
+ vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
/*
* We cannot use the vm_iomap_memory() helper here,
@@ -707,10 +709,13 @@ static int uio_mmap(struct file *filep, struct vm_area_struct *vma)
switch (idev->info->mem[mi].memtype) {
case UIO_MEM_PHYS:
- return uio_mmap_physical(vma);
+ return uio_mmap_physical(vma, false);
case UIO_MEM_LOGICAL:
case UIO_MEM_VIRTUAL:
return uio_mmap_logical(vma);
+ case UIO_MEM_PHYS_CACHE:
+ return uio_mmap_physical(vma, true);
+
default:
return -EINVAL;
}
diff --git a/include/linux/uio_driver.h b/include/linux/uio_driver.h
index 1ad4724..40ca3f3 100644
--- a/include/linux/uio_driver.h
+++ b/include/linux/uio_driver.h
@@ -118,6 +118,7 @@ extern void uio_event_notify(struct uio_info *info);
#define UIO_MEM_PHYS 1
#define UIO_MEM_LOGICAL 2
#define UIO_MEM_VIRTUAL 3
+#define UIO_MEM_PHYS_CACHE 4
/* defines for uio_port->porttype */
#define UIO_PORT_NONE 0
--
1.7.9.5
--
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