drm: add logging for RMFB ioctl

We already have logging for ADDFB2. Add some logging for RMFB as
well.

This can be handy when trying to find out why a CRTC gets magically
disabled.

v2: make log message more explicit, add log messages to
drm_framebuffer_remove (Daniel)

Signed-off-by: Simon Ser <contact@emersion.fr>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Acked-by: Pekka Paalanen <pekka.paalanen@collabora.com>
Link: https://patchwork.freedesktop.org/patch/msgid/EghsoRDcn1SJV0nxVqRCisPd7v0627yLZbBjn4A8Yg@cp3-web-048.plabs.ch

drivers/gpu/drm/drm_framebuffer.c

@@ -404,6 +404,9 @@ static void drm_mode_rmfb_work_fn(struct work_struct *w)
 		struct drm_framebuffer *fb =
 			list_first_entry(&arg->fbs, typeof(*fb), filp_head);
 
+		drm_dbg_kms(fb->dev,
+			    "Removing [FB:%d] from all active usage due to RMFB ioctl\n",
+			    fb->base.id);
 		list_del_init(&fb->filp_head);
 		drm_framebuffer_remove(fb);
 	}
@@ -981,6 +984,10 @@ static int atomic_remove_fb(struct drm_framebuffer *fb)
 		if (plane->state->fb != fb)
 			continue;
 
+		drm_dbg_kms(dev,
+			    "Disabling [PLANE:%d:%s] because [FB:%d] is removed\n",
+			    plane->base.id, plane->name, fb->base.id);
+
 		plane_state = drm_atomic_get_plane_state(state, plane);
 		if (IS_ERR(plane_state)) {
 			ret = PTR_ERR(plane_state);
@@ -990,6 +997,11 @@ static int atomic_remove_fb(struct drm_framebuffer *fb)
 		if (disable_crtcs && plane_state->crtc->primary == plane) {
 			struct drm_crtc_state *crtc_state;
 
+			drm_dbg_kms(dev,
+				    "Disabling [CRTC:%d:%s] because [FB:%d] is removed\n",
+				    plane_state->crtc->base.id,
+				    plane_state->crtc->name, fb->base.id);
+
 			crtc_state = drm_atomic_get_existing_crtc_state(state, plane_state->crtc);
 
 			ret = drm_atomic_add_affected_connectors(state, plane_state->crtc);
@@ -1052,15 +1064,23 @@ static void legacy_remove_fb(struct drm_framebuffer *fb)
 	/* remove from any CRTC */
 	drm_for_each_crtc(crtc, dev) {
 		if (crtc->primary->fb == fb) {
+			drm_dbg_kms(dev,
+				    "Disabling [CRTC:%d:%s] because [FB:%d] is removed\n",
+				    crtc->base.id, crtc->name, fb->base.id);
+
 			/* should turn off the crtc */
 			if (drm_crtc_force_disable(crtc))
 				DRM_ERROR("failed to reset crtc %p when fb was deleted\n", crtc);
 		}
 	}
 
 	drm_for_each_plane(plane, dev) {
-		if (plane->fb == fb)
+		if (plane->fb == fb) {
+			drm_dbg_kms(dev,
+				    "Disabling [PLANE:%d:%s] because [FB:%d] is removed\n",
+				    plane->base.id, plane->name, fb->base.id);
 			drm_plane_force_disable(plane);
+		}
 	}
 	drm_modeset_unlock_all(dev);
 }