Commit ba026334 authored Apr 28, 2016 by Noralf Trønnes Committed by Daniel Vetter May 02, 2016

fbdev: fb_defio: Export fb_deferred_io_mmap



Export fb_deferred_io_mmap so drivers can change vma->vm_page_prot.
When the framebuffer memory is allocated using dma_alloc_writecombine()
instead of vmalloc(), I get cache syncing problems on ARM.
This solves it:

static int drm_fbdev_cma_deferred_io_mmap(struct fb_info *info,
					  struct vm_area_struct *vma)
{
	fb_deferred_io_mmap(info, vma);
	vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot);

	return 0;
}

Could this have been done in the core?
Drivers that don't set (struct fb_ops *)->fb_mmap, gets a call to
fb_pgprotect() at the end of the default fb_mmap implementation
(drivers/video/fbdev/core/fbmem.c). This is an architecture specific
function that on many platforms uses pgprot_writecombine(), but not on
all. And looking at some of the fb_mmap implementations, some of them
sets vm_page_prot to nocache for instance, so I think the safest bet is
to do this in the driver and not in the fbdev core. And we can't call
fb_pgprotect() from fb_deferred_io_mmap() either because we don't have
access to the file pointer that powerpc needs.

Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
Acked-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1461856717-6476-5-git-send-email-noralf@tronnes.org

parent eaa434de

drivers/video/fbdev/core/fb_defio.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -164,7 +164,7 @@ static const struct address_space_operations fb_deferred_io_aops = {
		.set_page_dirty = fb_deferred_io_set_page_dirty,
		};

		static int fb_deferred_io_mmap(struct fb_info info, struct vm_area_struct vma)
		int fb_deferred_io_mmap(struct fb_info info, struct vm_area_struct vma)
		{
		vma->vm_ops = &fb_deferred_io_vm_ops;
		vma->vm_flags \|= VM_DONTEXPAND \| VM_DONTDUMP;
		@@ -173,6 +173,7 @@ static int fb_deferred_io_mmap(struct fb_info info, struct vm_area_struct vma)
		vma->vm_private_data = info;
		return 0;
		}
		EXPORT_SYMBOL(fb_deferred_io_mmap);

		/* workqueue callback */
		static void fb_deferred_io_work(struct work_struct *work)

include/linux/fb.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -673,6 +673,7 @@ static inline void __fb_pad_aligned_buffer(u8 *dst, u32 d_pitch,
		}

		/* drivers/video/fb_defio.c */
		int fb_deferred_io_mmap(struct fb_info info, struct vm_area_struct vma);
		extern void fb_deferred_io_init(struct fb_info *info);
		extern void fb_deferred_io_open(struct fb_info *info,
		struct inode *inode,