drm/tegra: Properly cleanup and zero out resources

When the DRM driver is unloaded, all the associated resources must be
cleaned up and zeroed out. This is necessary because of the architecture
of the Tegra DRM driver, where not all subdrivers are unloaded along
with the DRM driver. Therefore device-managed managed won't be freed and
memory cannot be assumed to have been cleared (because it hasn't been
reallocated using kzalloc()) by the time the DRM driver is reloaded. It
is therefore necessary to zero out the structures to prevent strange
errors (such as slab corruptions) from occurring.

Signed-off-by: Thierry Reding <treding@nvidia.com>

drivers/gpu/drm/tegra/dc.c

@@ -93,8 +93,11 @@ static int tegra_plane_disable(struct drm_plane *plane)
 
 static void tegra_plane_destroy(struct drm_plane *plane)
 {
+	struct tegra_plane *p = to_tegra_plane(plane);
+
 	tegra_plane_disable(plane);
 	drm_plane_cleanup(plane);
+	kfree(p);
 }
 
 static const struct drm_plane_funcs tegra_plane_funcs = {
@@ -120,7 +123,7 @@ static int tegra_dc_add_planes(struct drm_device *drm, struct tegra_dc *dc)
 	for (i = 0; i < 2; i++) {
 		struct tegra_plane *plane;
 
-		plane = devm_kzalloc(drm->dev, sizeof(*plane), GFP_KERNEL);
+		plane = kzalloc(sizeof(*plane), GFP_KERNEL);
 		if (!plane)
 			return -ENOMEM;
 
@@ -129,9 +132,11 @@ static int tegra_dc_add_planes(struct drm_device *drm, struct tegra_dc *dc)
 		err = drm_plane_init(drm, &plane->base, 1 << dc->pipe,
 				     &tegra_plane_funcs, plane_formats,
 				     ARRAY_SIZE(plane_formats), false);
-		if (err < 0)
+		if (err < 0) {
+			kfree(plane);
 			return err;
 		}
+	}
 
 	return 0;
 }
@@ -251,14 +256,26 @@ static int tegra_dc_page_flip(struct drm_crtc *crtc, struct drm_framebuffer *fb,
 	return 0;
 }
 
+static void drm_crtc_clear(struct drm_crtc *crtc)
+{
+	memset(crtc, 0, sizeof(*crtc));
+}
+
+static void tegra_dc_destroy(struct drm_crtc *crtc)
+{
+	drm_crtc_cleanup(crtc);
+	drm_crtc_clear(crtc);
+}
+
 static const struct drm_crtc_funcs tegra_crtc_funcs = {
 	.page_flip = tegra_dc_page_flip,
 	.set_config = drm_crtc_helper_set_config,
-	.destroy = drm_crtc_cleanup,
+	.destroy = tegra_dc_destroy,
 };
 
 static void tegra_crtc_disable(struct drm_crtc *crtc)
 {
+	struct tegra_dc *dc = to_tegra_dc(crtc);
 	struct drm_device *drm = crtc->dev;
 	struct drm_plane *plane;
 
@@ -273,6 +290,8 @@ static void tegra_crtc_disable(struct drm_crtc *crtc)
 			}
 		}
 	}
+
+	drm_vblank_off(drm, dc->pipe);
 }
 
 static bool tegra_crtc_mode_fixup(struct drm_crtc *crtc,

drivers/gpu/drm/tegra/drm.c

@@ -72,13 +72,13 @@ static int tegra_drm_unload(struct drm_device *drm)
 
 	drm_kms_helper_poll_fini(drm);
 	tegra_drm_fb_exit(drm);
+	drm_vblank_cleanup(drm);
+	drm_mode_config_cleanup(drm);
 
 	err = host1x_device_exit(device);
 	if (err < 0)
 		return err;
 
-	drm_mode_config_cleanup(drm);
-
 	return 0;
 }
 

drivers/gpu/drm/tegra/output.c

@@ -79,10 +79,16 @@ tegra_connector_detect(struct drm_connector *connector, bool force)
 	return status;
 }
 
+static void drm_connector_clear(struct drm_connector *connector)
+{
+	memset(connector, 0, sizeof(*connector));
+}
+
 static void tegra_connector_destroy(struct drm_connector *connector)
 {
 	drm_sysfs_connector_remove(connector);
 	drm_connector_cleanup(connector);
+	drm_connector_clear(connector);
 }
 
 static const struct drm_connector_funcs connector_funcs = {
@@ -92,9 +98,15 @@ static const struct drm_connector_funcs connector_funcs = {
 	.destroy = tegra_connector_destroy,
 };
 
+static void drm_encoder_clear(struct drm_encoder *encoder)
+{
+	memset(encoder, 0, sizeof(*encoder));
+}
+
 static void tegra_encoder_destroy(struct drm_encoder *encoder)
 {
 	drm_encoder_cleanup(encoder);
+	drm_encoder_clear(encoder);
 }
 
 static const struct drm_encoder_funcs encoder_funcs = {