[PATCH 1/5] uio: Add new UIO_MEM_PHYS_CACHE type for mem regions

[ankit.jindal@linaro.org (Ankit Jindal)]

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 useful if dma-capable devices are capable of maintaining coherency
with CPU caches becasue we can allow cacheable access to memory shared
between such devices and user space.

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@linaro.org>
Signed-off-by: Tushar Jagad <tushar.jagad@linaro.org>
---
 drivers/uio/uio.c          |   22 +++++++++++++---------
 include/linux/uio_driver.h |    7 ++++---
 2 files changed, 17 insertions(+), 12 deletions(-)

diff --git a/drivers/uio/uio.c b/drivers/uio/uio.c
index a673e5b..ff5b6c0 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,
@@ -706,13 +708,15 @@ 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);
-		case UIO_MEM_LOGICAL:
-		case UIO_MEM_VIRTUAL:
-			return uio_mmap_logical(vma);
-		default:
-			return -EINVAL;
+	case UIO_MEM_PHYS:
+		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..f6ea5bc 100644
--- a/include/linux/uio_driver.h
+++ b/include/linux/uio_driver.h
@@ -114,10 +114,11 @@ extern void uio_event_notify(struct uio_info *info);
 #define UIO_IRQ_NONE	0
 
 /* defines for uio_mem->memtype */
-#define UIO_MEM_NONE	0
-#define UIO_MEM_PHYS	1
+#define UIO_MEM_NONE		0
+#define UIO_MEM_PHYS		1
 #define UIO_MEM_LOGICAL	2
-#define UIO_MEM_VIRTUAL 3
+#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