drm: Fix lack of CRTC disable for drm_crtc_helper_set_config(.fb=NULL)

Disabling the CRTC by setting its framebuffer to NULL, as used by
drm_framebuffer_cleanup(), was failing to pass the current framebuffer
to the crtc_func->disable callback. This is because of the dance within
drm_crtc_helper_set_config to pass the new_fb (NULL in this case) to the
drm_crtc_helper_set_mode with the currently attached fb as a parameter.
drm_crtc_helper_set_mode treats this as a no-op and the encoder is still
enabled. And so the current fb is forgotten before the call to
drm_helper_disable_unused_functions.

This patch treats disabling the CRTC as a simple special case rather
than adding further complexity into the configuration logic.

This fixes a pin-leak of the fb bo on Xserver close.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Dave Airlie <airlied@redhat.com>

1 files changed, 25 insertions, 2 deletions

diff --git a/drivers/gpu/drm/drm_crtc_helper.c b/drivers/gpu/drm/drm_crtc_helper.c
index 3969f7553fe7..d2619d72cece 100644
--- a/drivers/gpu/drm/drm_crtc_helper.c
+++ b/drivers/gpu/drm/drm_crtc_helper.c
@@ -456,6 +456,30 @@ done:
 EXPORT_SYMBOL(drm_crtc_helper_set_mode);
 
 
+static int
+drm_crtc_helper_disable(struct drm_crtc *crtc)
+{
+        struct drm_device *dev = crtc->dev;
+        struct drm_connector *connector;
+        struct drm_encoder *encoder;
+
+        /* Decouple all encoders and their attached connectors from this crtc */
+        list_for_each_entry(encoder, &dev->mode_config.encoder_list, head) {
+                if (encoder->crtc != crtc)
+                        continue;
+
+                list_for_each_entry(connector, &dev->mode_config.connector_list, head) {
+                        if (connector->encoder != encoder)
+                                continue;
+
+                        connector->encoder = NULL;
+                }
+        }
+
+        drm_helper_disable_unused_functions(dev);
+        return 0;
+}
+
 /**
  * drm_crtc_helper_set_config - set a new config from userspace
  * @crtc: CRTC to setup
@@ -510,8 +534,7 @@ int drm_crtc_helper_set_config(struct drm_mode_set *set)
                                 (int)set->num_connectors, set->x, set->y);
         } else {
                 DRM_DEBUG_KMS("[CRTC:%d] [NOFB]\n", set->crtc->base.id);
-                set->mode = NULL;
-                set->num_connectors = 0;
+                return drm_crtc_helper_disable(set->crtc);
         }
 
         dev = set->crtc->dev;