drm/radeon/kms: fix oops when set_base is call with no FB

Just do nothing if crct_set_base() is called with no FB.

The oops happens when the user switches between X & vt or in some case
when changing mode.
Signed-off-by: Jerome Glisse <jglisse@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/radeon/atombios_crtc.c

@@ -578,8 +578,11 @@ int atombios_crtc_set_base(struct drm_crtc *crtc, int x, int y,
 	uint64_t fb_location;
 	uint32_t fb_format, fb_pitch_pixels, tiling_flags;
 
-	if (!crtc->fb)
-		return -EINVAL;
+	/* no fb bound */
+	if (!crtc->fb) {
+		DRM_DEBUG("No FB bound\n");
+		return 0;
+	}
 
 	radeon_fb = to_radeon_framebuffer(crtc->fb);
 

drivers/gpu/drm/radeon/radeon_legacy_crtc.c

@@ -408,6 +408,11 @@ int radeon_crtc_set_base(struct drm_crtc *crtc, int x, int y,
 	uint32_t gen_cntl_reg, gen_cntl_val;
 
 	DRM_DEBUG("\n");
+	/* no fb bound */
+	if (!crtc->fb) {
+		DRM_DEBUG("No FB bound\n");
+		return 0;
+	}
 
 	radeon_fb = to_radeon_framebuffer(crtc->fb);