drm/udl: add cache flags definitions for udl_gem_object

By default set udl_gem_object as cacheable, but set WC flag when attaching
dmabuf. In udl_gem_mmap() update cache attributes based on the flags, similar
to exynos_drm_gem_mmap().

Signed-off-by: Haixia Shi <hshi@chromium.org>
Reviewed-by: Sonny Rao <sonnyrao@chromium.org>
Reviewed-by: Olof Johansson <olofj@chromium.org>
Reviewed-by: Stéphane Marchesin <marcheu@chromium.org>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/udl/udl_drv.h

@@ -25,6 +25,9 @@
 #define DRIVER_MINOR		0
 #define DRIVER_PATCHLEVEL	1
 
+#define UDL_BO_CACHEABLE		(1 << 0)
+#define UDL_BO_WC		(1 << 1)
+
 struct udl_device;
 
 struct urb_node {
@@ -69,6 +72,7 @@ struct udl_gem_object {
 	struct page **pages;
 	void *vmapping;
 	struct sg_table *sg;
+	unsigned int flags;
 };
 
 #define to_udl_bo(x) container_of(x, struct udl_gem_object, base)

drivers/gpu/drm/udl/udl_gem.c

@@ -25,6 +25,7 @@ struct udl_gem_object *udl_gem_alloc_object(struct drm_device *dev,
 		return NULL;
 	}
 
+	obj->flags = UDL_BO_CACHEABLE;
 	return obj;
 }
 
@@ -56,6 +57,23 @@ udl_gem_create(struct drm_file *file,
 	return 0;
 }
 
+static void update_vm_cache_attr(struct udl_gem_object *obj,
+				 struct vm_area_struct *vma)
+{
+	DRM_DEBUG_KMS("flags = 0x%x\n", obj->flags);
+
+	/* non-cacheable as default. */
+	if (obj->flags & UDL_BO_CACHEABLE) {
+		vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
+	} else if (obj->flags & UDL_BO_WC) {
+		vma->vm_page_prot =
+			pgprot_writecombine(vm_get_page_prot(vma->vm_flags));
+	} else {
+		vma->vm_page_prot =
+			pgprot_noncached(vm_get_page_prot(vma->vm_flags));
+	}
+}
+
 int udl_dumb_create(struct drm_file *file,
 		    struct drm_device *dev,
 		    struct drm_mode_create_dumb *args)
@@ -77,6 +95,8 @@ int udl_drm_gem_mmap(struct file *filp, struct vm_area_struct *vma)
 	vma->vm_flags &= ~VM_PFNMAP;
 	vma->vm_flags |= VM_MIXEDMAP;
 
+	update_vm_cache_attr(to_udl_bo(vma->vm_private_data), vma);
+
 	return ret;
 }
 
@@ -279,6 +299,7 @@ struct drm_gem_object *udl_gem_prime_import(struct drm_device *dev,
 	}
 
 	uobj->base.import_attach = attach;
+	uobj->flags = UDL_BO_WC;
 
 	return &uobj->base;