drm/exynos: add exynos drm specific fb_mmap function

Changelog v3:

Passing the actual buffer size instead of vm_size to dma_mmap_attrs.

Changelog v2:

Extracting the private data from fb_info structure to obtain the exynos
gem buffer structure. Now, dma address is obtained from the exynos gem
buffer structure and not from smem_start. Also calling dma_mmap_attrs
(instead of dma_mmap_writecombine) with the same attributes used
during allocation.

Changelog v1:

This patch adds a exynos drm specific implementation of fb_mmap
which supports mapping a non-contiguous buffer to user space.

This new function does not assume that the frame buffer is contiguous
and calls dma_mmap_writecombine for mapping the buffer to user space.
dma_mmap_writecombine will be able to map a contiguous buffer as well
as non-contig buffer depending on whether an IOMMU mapping is created
for drm or not.
Signed-off-by: Prathyush K <prathyush.k@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>

drivers/gpu/drm/exynos/exynos_drm_fbdev.c

@@ -46,8 +46,38 @@ struct exynos_drm_fbdev {
 	struct exynos_drm_gem_obj	*exynos_gem_obj;
 };
 
+static int exynos_drm_fb_mmap(struct fb_info *info,
+			struct vm_area_struct *vma)
+{
+	struct drm_fb_helper *helper = info->par;
+	struct exynos_drm_fbdev *exynos_fbd = to_exynos_fbdev(helper);
+	struct exynos_drm_gem_obj *exynos_gem_obj = exynos_fbd->exynos_gem_obj;
+	struct exynos_drm_gem_buf *buffer = exynos_gem_obj->buffer;
+	unsigned long vm_size;
+	int ret;
+
+	DRM_DEBUG_KMS("%s\n", __func__);
+
+	vma->vm_flags |= VM_IO | VM_DONTEXPAND | VM_DONTDUMP;
+
+	vm_size = vma->vm_end - vma->vm_start;
+
+	if (vm_size > buffer->size)
+		return -EINVAL;
+
+	ret = dma_mmap_attrs(helper->dev->dev, vma, buffer->kvaddr,
+		buffer->dma_addr, buffer->size, &buffer->dma_attrs);
+	if (ret < 0) {
+		DRM_ERROR("failed to mmap.\n");
+		return ret;
+	}
+
+	return 0;
+}
+
 static struct fb_ops exynos_drm_fb_ops = {
 	.owner		= THIS_MODULE,
+	.fb_mmap        = exynos_drm_fb_mmap,
 	.fb_fillrect	= cfb_fillrect,
 	.fb_copyarea	= cfb_copyarea,
 	.fb_imageblit	= cfb_imageblit,