drm/mipi-dbi: Fix source-buffer address in mipi_dbi_buf_copy

Set the source-buffer address after mapping the buffer into the
kernel's address space. Makes MIPI DBI helpers work again.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Fixes: c47160d8ed ("drm/mipi-dbi: Remove dependency on GEM CMA helper library")
Reviewed-by: Noralf Trønnes <noralf@tronnes.org>
Reported-by: Noralf Trønnes <noralf@tronnes.org>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20220111132634.18302-1-tzimmermann@suse.de
(cherry picked from commit 9d31993451)
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>

drivers/gpu/drm/drm_mipi_dbi.c

@@ -209,11 +209,11 @@ int mipi_dbi_buf_copy(void *dst, struct drm_framebuffer *fb,
 	ret = drm_gem_fb_begin_cpu_access(fb, DMA_FROM_DEVICE);
 	if (ret)
 		return ret;
-	src = data[0].vaddr; /* TODO: Use mapping abstraction properly */
 
 	ret = drm_gem_fb_vmap(fb, map, data);
 	if (ret)
 		goto out_drm_gem_fb_end_cpu_access;
+	src = data[0].vaddr; /* TODO: Use mapping abstraction properly */
 
 	switch (fb->format->format) {
 	case DRM_FORMAT_RGB565: