[PATCH 4/5 v4] arc: Add our own implementation of fb_pgprotect()

From: Alexey Brodkin
Date: Thu Mar 24 2016 - 12:49:13 EST

During mmaping of frame-buffer pages to user-space
fb_protect() is called to set proper page settings.

In case of ARC we need to mark pages that are mmaped to
user as uncached because of 2 reasons:
* Huge amount of data if passing through data cache will
thrash cache a lot making cache almost useless for other
less traffic hungry processes.
* Data written by user in FB will be immediately available for
hardware (such as PGU etc) without requirements to flush data
cache regularly.

Signed-off-by: Alexey Brodkin <abrodkin@xxxxxxxxxxxx>
Cc: linux-snps-arc@xxxxxxxxxxxxxxxxxxx

Changes v3 -> v4:
* This change was introduced only in v4.

arch/arc/include/asm/fb.h | 19 +++++++++++++++++++
1 file changed, 19 insertions(+)
create mode 100644 arch/arc/include/asm/fb.h

diff --git a/arch/arc/include/asm/fb.h b/arch/arc/include/asm/fb.h
new file mode 100644
index 0000000..bd3f68c
--- /dev/null
+++ b/arch/arc/include/asm/fb.h
@@ -0,0 +1,19 @@
+#ifndef _ASM_FB_H_
+#define _ASM_FB_H_
+#include <linux/fb.h>
+#include <linux/fs.h>
+#include <asm/page.h>
+static inline void fb_pgprotect(struct file *file, struct vm_area_struct *vma,
+ unsigned long off)
+ vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
+static inline int fb_is_primary_device(struct fb_info *info)
+ return 0;
+#endif /* _ASM_FB_H_ */