drm: Add drm_atomic_set_mode_for_crtc

Add a new helper, to be used later for blob property management, that
sets the mode for a CRTC state, as well as updating the CRTC enable/active
state at the same time.

v2: Do not touch active/mode_changed in CRTC state. Document return
    value. Remove stray drm_atomic_set_mode_prop_for_crtc declaration.

v3: Remove i915 changes, and leave it directly bashing crtc_state->mode
    for the meantime.
Signed-off-by: Daniel Stone <daniels@collabora.com>
Tested-by: Sean Paul <seanpaul@chromium.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/drm_atomic.c

@@ -289,6 +289,42 @@ drm_atomic_get_crtc_state(struct drm_atomic_state *state,
 }
 EXPORT_SYMBOL(drm_atomic_get_crtc_state);
 
+/**
+ * drm_atomic_set_mode_for_crtc - set mode for CRTC
+ * @state: the CRTC whose incoming state to update
+ * @mode: kernel-internal mode to use for the CRTC, or NULL to disable
+ *
+ * Set a mode (originating from the kernel) on the desired CRTC state. Does
+ * not change any other state properties, including enable, active, or
+ * mode_changed.
+ *
+ * RETURNS:
+ * Zero on success, error code on failure. Cannot return -EDEADLK.
+ */
+int drm_atomic_set_mode_for_crtc(struct drm_crtc_state *state,
+				 struct drm_display_mode *mode)
+{
+	/* Early return for no change. */
+	if (mode && memcmp(&state->mode, mode, sizeof(*mode)) == 0)
+		return 0;
+
+	if (mode) {
+		drm_mode_copy(&state->mode, mode);
+		state->enable = true;
+		DRM_DEBUG_ATOMIC("Set [MODE:%s] for CRTC state %p\n",
+				 mode->name, state);
+	} else {
+		memset(&state->mode, 0, sizeof(state->mode));
+		state->enable = false;
+		DRM_DEBUG_ATOMIC("Set [NOMODE] for CRTC state %p\n",
+				 state);
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL(drm_atomic_set_mode_for_crtc);
+
+
 /**
  * drm_atomic_crtc_set_property - set property on CRTC
  * @crtc: the drm CRTC to set a property on

drivers/gpu/drm/drm_atomic_helper.c

@@ -1607,7 +1607,10 @@ int drm_atomic_helper_set_config(struct drm_mode_set *set)
 		WARN_ON(set->fb);
 		WARN_ON(set->num_connectors);
 
-		crtc_state->enable = false;
+		ret = drm_atomic_set_mode_for_crtc(crtc_state, NULL);
+		if (ret != 0)
+			goto fail;
+
 		crtc_state->active = false;
 
 		ret = drm_atomic_set_crtc_for_plane(primary_state, NULL);
@@ -1622,9 +1625,11 @@ int drm_atomic_helper_set_config(struct drm_mode_set *set)
 	WARN_ON(!set->fb);
 	WARN_ON(!set->num_connectors);
 
-	crtc_state->enable = true;
+	ret = drm_atomic_set_mode_for_crtc(crtc_state, set->mode);
+	if (ret != 0)
+		goto fail;
+
 	crtc_state->active = true;
-	drm_mode_copy(&crtc_state->mode, set->mode);
 
 	ret = drm_atomic_set_crtc_for_plane(primary_state, crtc);
 	if (ret != 0)

drivers/gpu/drm/drm_crtc_helper.c

@@ -937,10 +937,11 @@ int drm_helper_crtc_mode_set(struct drm_crtc *crtc, struct drm_display_mode *mod
 			crtc_state->crtc = crtc;
 	}
 
-	crtc_state->enable = true;
 	crtc_state->planes_changed = true;
 	crtc_state->mode_changed = true;
-	drm_mode_copy(&crtc_state->mode, mode);
+	ret = drm_atomic_set_mode_for_crtc(crtc_state, mode);
+	if (ret)
+		goto out;
 	drm_mode_copy(&crtc_state->adjusted_mode, adjusted_mode);
 
 	if (crtc_funcs->atomic_check) {

include/drm/drm_atomic.h

@@ -109,6 +109,9 @@ drm_atomic_get_existing_connector_state(struct drm_atomic_state *state,
 	return state->connector_states[index];
 }
 
+int __must_check
+drm_atomic_set_mode_for_crtc(struct drm_crtc_state *state,
+			     struct drm_display_mode *mode);
 int __must_check
 drm_atomic_set_crtc_for_plane(struct drm_plane_state *plane_state,
 			      struct drm_crtc *crtc);