drm: Don't update property values for atomic drivers

Atomic drivers only use the property value store for immutable (i.e.
can't be set by userspace, but the kernel can still adjust it)
properties. The only tricky part is the removal of the update in
drm_atomic_helper_update_legacy_modeset_state().

This was added in

commit 8c10342c (tag: topic/drm-misc-2015-07-28)
Author: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Date:   Mon Jul 27 13:24:29 2015 +0200

    drm/atomic: Update legacy DPMS state during modesets, v3.

by copying it from the i915 code, where it was originally added in

commit 68d34720
Author: Daniel Vetter <daniel.vetter@ffwll.ch>
Date:   Thu Sep 6 22:08:35 2012 +0200

    drm/i915: update dpms property in set_mode

for the legacy modeset code. The reason we needed this hack was that
i915 didn't yet set DRIVER_ATOMIC, and we checked for that instead of
the newer-ish drm_drv_uses_atomic_modeset(), which avoids such
troubles. With the correct feature checks this isn't needed anymore at
all.

Also make sure that drivers don't accidentally get this wrong by
making the exported version of drm_object_property_get_value() only
work for legacy drivers. Only gma500 uses it anyway.

v2: Fixup the uses_atomic_modeset() checks (Maarten)

Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20170725120137.1903-1-daniel.vetter@ffwll.ch

drivers/gpu/drm/drm_atomic_helper.c

@@ -921,16 +921,12 @@ drm_atomic_helper_update_legacy_modeset_state(struct drm_device *dev,
 		crtc = new_conn_state->crtc;
 		if ((!crtc && old_conn_state->crtc) ||
 		    (crtc && drm_atomic_crtc_needs_modeset(crtc->state))) {
-			struct drm_property *dpms_prop =
-				dev->mode_config.dpms_property;
 			int mode = DRM_MODE_DPMS_OFF;
 
 			if (crtc && crtc->state->active)
 				mode = DRM_MODE_DPMS_ON;
 
 			connector->dpms = mode;
-			drm_object_property_set_value(&connector->base,
-						      dpms_prop, mode);
 		}
 	}
 

drivers/gpu/drm/drm_connector.c

@@ -1225,8 +1225,7 @@ int drm_mode_connector_set_obj_prop(struct drm_mode_object *obj,
 	} else if (connector->funcs->set_property)
 		ret = connector->funcs->set_property(connector, property, value);
 
-	/* store the property value if successful */
-	if (!ret)
+	if (!ret && !drm_drv_uses_atomic_modeset(property->dev))
 		drm_object_property_set_value(&connector->base, property, value);
 	return ret;
 }

drivers/gpu/drm/drm_crtc.c

@@ -736,7 +736,7 @@ int drm_mode_crtc_set_obj_prop(struct drm_mode_object *obj,
 
 	if (crtc->funcs->set_property)
 		ret = crtc->funcs->set_property(crtc, property, value);
-	if (!ret)
+	if (!ret && !drm_drv_uses_atomic_modeset(property->dev))
 		drm_object_property_set_value(obj, property, value);
 
 	return ret;

drivers/gpu/drm/drm_mode_object.c

@@ -233,6 +233,9 @@ int drm_object_property_set_value(struct drm_mode_object *obj,
 {
 	int i;
 
+	WARN_ON(drm_drv_uses_atomic_modeset(property->dev) &&
+		!(property->flags & DRM_MODE_PROP_IMMUTABLE));
+
 	for (i = 0; i < obj->properties->count; i++) {
 		if (obj->properties->properties[i] == property) {
 			obj->properties->values[i] = val;
@@ -244,24 +247,7 @@ int drm_object_property_set_value(struct drm_mode_object *obj,
 }
 EXPORT_SYMBOL(drm_object_property_set_value);
 
-/**
- * drm_object_property_get_value - retrieve the value of a property
- * @obj: drm mode object to get property value from
- * @property: property to retrieve
- * @val: storage for the property value
- *
- * This function retrieves the softare state of the given property for the given
- * property. Since there is no driver callback to retrieve the current property
- * value this might be out of sync with the hardware, depending upon the driver
- * and property.
- *
- * Atomic drivers should never call this function directly, the core will read
- * out property values through the various ->atomic_get_property callbacks.
- *
- * Returns:
- * Zero on success, error code on failure.
- */
-int drm_object_property_get_value(struct drm_mode_object *obj,
+int __drm_object_property_get_value(struct drm_mode_object *obj,
 				  struct drm_property *property, uint64_t *val)
 {
 	int i;
@@ -284,6 +270,31 @@ int drm_object_property_get_value(struct drm_mode_object *obj,
 
 	return -EINVAL;
 }
+
+/**
+ * drm_object_property_get_value - retrieve the value of a property
+ * @obj: drm mode object to get property value from
+ * @property: property to retrieve
+ * @val: storage for the property value
+ *
+ * This function retrieves the softare state of the given property for the given
+ * property. Since there is no driver callback to retrieve the current property
+ * value this might be out of sync with the hardware, depending upon the driver
+ * and property.
+ *
+ * Atomic drivers should never call this function directly, the core will read
+ * out property values through the various ->atomic_get_property callbacks.
+ *
+ * Returns:
+ * Zero on success, error code on failure.
+ */
+int drm_object_property_get_value(struct drm_mode_object *obj,
+				  struct drm_property *property, uint64_t *val)
+{
+	WARN_ON(drm_drv_uses_atomic_modeset(property->dev));
+
+	return __drm_object_property_get_value(obj, property, val);
+}
 EXPORT_SYMBOL(drm_object_property_get_value);
 
 /* helper for getconnector and getproperties ioctls */
@@ -302,7 +313,7 @@ int drm_mode_object_get_properties(struct drm_mode_object *obj, bool atomic,
 			continue;
 
 		if (*arg_count_props > count) {
-			ret = drm_object_property_get_value(obj, prop, &val);
+			ret = __drm_object_property_get_value(obj, prop, &val);
 			if (ret)
 				return ret;
 

drivers/gpu/drm/drm_plane.c

@@ -448,7 +448,7 @@ int drm_mode_plane_set_obj_prop(struct drm_plane *plane,
 
 	if (plane->funcs->set_property)
 		ret = plane->funcs->set_property(plane, property, value);
-	if (!ret)
+	if (!ret && !drm_drv_uses_atomic_modeset(property->dev))
 		drm_object_property_set_value(obj, property, value);
 
 	return ret;