drm/repaper: Use framebuffer dma-buf helpers

Replace dma_buf_begin_cpu_access() with drm_gem_fb_begin_cpu_access();
same for _end_cpu_access(). Remove some boiler-plate code. No functional
changes.
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Noralf Trønnes <noralf@tronnes.org>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20210716140801.1215-7-tzimmermann@suse.de

drivers/gpu/drm/tiny/repaper.c

@@ -14,7 +14,6 @@
  */
 
 #include <linux/delay.h>
-#include <linux/dma-buf.h>
 #include <linux/gpio/consumer.h>
 #include <linux/module.h>
 #include <linux/property.h>
@@ -532,7 +531,6 @@ static void repaper_gray8_to_mono_reversed(u8 *buf, u32 width, u32 height)
 static int repaper_fb_dirty(struct drm_framebuffer *fb)
 {
 	struct drm_gem_cma_object *cma_obj = drm_fb_cma_get_gem_obj(fb, 0);
-	struct dma_buf_attachment *import_attach = cma_obj->base.import_attach;
 	struct repaper_epd *epd = drm_to_epd(fb->dev);
 	struct drm_rect clip;
 	int idx, ret = 0;
@@ -558,21 +556,13 @@ static int repaper_fb_dirty(struct drm_framebuffer *fb)
 		goto out_exit;
 	}
 
-	if (import_attach) {
-		ret = dma_buf_begin_cpu_access(import_attach->dmabuf,
-					       DMA_FROM_DEVICE);
-		if (ret)
-			goto out_free;
-	}
+	ret = drm_gem_fb_begin_cpu_access(fb, DMA_FROM_DEVICE);
+	if (ret)
+		goto out_free;
 
 	drm_fb_xrgb8888_to_gray8(buf, cma_obj->vaddr, fb, &clip);
 
-	if (import_attach) {
-		ret = dma_buf_end_cpu_access(import_attach->dmabuf,
-					     DMA_FROM_DEVICE);
-		if (ret)
-			goto out_free;
-	}
+	drm_gem_fb_end_cpu_access(fb, DMA_FROM_DEVICE);
 
 	repaper_gray8_to_mono_reversed(buf, fb->width, fb->height);