[PATCH] drm/nouveau: add lockdep annotations

[Marcin Slusarz <marcin.slusarz@gmail.com>]

1) Lockdep thinks all nouveau subdevs belong to the same class and can be
locked in arbitrary order, which is not true (at least in general case).
Tell it to distinguish subdevs by (o)class type.
2) DRM client can be locked under user client lock - tell lockdep to put DRM
client lock in a separate class.

Reported-by: Arend van Spriel <arend@broadcom.com>
Reported-by: Peter Hurley <peter@hurleysoftware.com>
Reported-by: Maarten Lankhorst <maarten.lankhorst@canonical.com>
Reported-by: Daniel J Blueman <daniel@quora.org>
Signed-off-by: Marcin Slusarz <marcin.slusarz@gmail.com>
Cc: stable@vger.kernel.org [3.7, but needs s/const ofuncs/ofuncs/ to build]
---
Lightly tested, only on NV4B and NVC1.
---
 drivers/gpu/drm/nouveau/core/core/subdev.c         | 2 +-
 drivers/gpu/drm/nouveau/core/include/core/object.h | 7 +++++--
 drivers/gpu/drm/nouveau/nouveau_drm.c              | 3 +++
 3 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/core/core/subdev.c b/drivers/gpu/drm/nouveau/core/core/subdev.c
index f74c30a..48f0637 100644
--- a/drivers/gpu/drm/nouveau/core/core/subdev.c
+++ b/drivers/gpu/drm/nouveau/core/core/subdev.c
@@ -99,7 +99,7 @@ nouveau_subdev_create_(struct nouveau_object *parent,
 	if (ret)
 		return ret;
 
-	mutex_init(&subdev->mutex);
+	__mutex_init(&subdev->mutex, subname, &oclass->lock_class_key);
 	subdev->name = subname;
 
 	if (parent) {
diff --git a/drivers/gpu/drm/nouveau/core/include/core/object.h b/drivers/gpu/drm/nouveau/core/include/core/object.h
index 6a90267..62e68ba 100644
--- a/drivers/gpu/drm/nouveau/core/include/core/object.h
+++ b/drivers/gpu/drm/nouveau/core/include/core/object.h
@@ -50,10 +50,13 @@ int  nouveau_object_fini(struct nouveau_object *, bool suspend);
 
 extern struct nouveau_ofuncs nouveau_object_ofuncs;
 
+/* Don't allocate dynamically, because lockdep needs lock_class_keys to be in
+ * ".data". */
 struct nouveau_oclass {
 	u32 handle;
-	struct nouveau_ofuncs *ofuncs;
-	struct nouveau_omthds *omthds;
+	struct nouveau_ofuncs * const ofuncs;
+	struct nouveau_omthds * const omthds;
+	struct lock_class_key lock_class_key;
 };
 
 #define nv_oclass(o)    nv_object(o)->oclass
diff --git a/drivers/gpu/drm/nouveau/nouveau_drm.c b/drivers/gpu/drm/nouveau/nouveau_drm.c
index ef1ad21..bc00587 100644
--- a/drivers/gpu/drm/nouveau/nouveau_drm.c
+++ b/drivers/gpu/drm/nouveau/nouveau_drm.c
@@ -245,6 +245,8 @@ static int nouveau_drm_probe(struct pci_dev *pdev,
 	return 0;
 }
 
+static struct lock_class_key drm_client_lock_class_key;
+
 static int
 nouveau_drm_load(struct drm_device *dev, unsigned long flags)
 {
@@ -256,6 +258,7 @@ nouveau_drm_load(struct drm_device *dev, unsigned long flags)
 	ret = nouveau_cli_create(pdev, "DRM", sizeof(*drm), (void**)&drm);
 	if (ret)
 		return ret;
+	lockdep_set_class(&drm->client.mutex, &drm_client_lock_class_key);
 
 	dev->dev_private = drm;
 	drm->dev = dev;
-- 
1.8.1