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Subject: [PATCH 02/11] cxl/core: Refactor a cxl_lock_class() out of
 cxl_nested_lock()
From:   Dan Williams <dan.j.williams@intel.com>
To:     gregkh@linuxfoundation.org, rafael.j.wysocki@intel.com
Cc:     Alison Schofield <alison.schofield@intel.com>,
        Vishal Verma <vishal.l.verma@intel.com>,
        Ira Weiny <ira.weiny@intel.com>,
        Ben Widawsky <ben.widawsky@intel.com>,
        linux-kernel@vger.kernel.org, linux-cxl@vger.kernel.org,
        nvdimm@lists.linux.dev
Date:   Mon, 28 Feb 2022 18:49:00 -0800
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In preparation for upleveling device_lock() lockdep annotation support into
the core, provide a helper to retrieve the lock class. This lock_class
will be used with device_set_lock_class() to idenify the CXL nested
locking rules.

Cc: Alison Schofield <alison.schofield@intel.com>
Cc: Vishal Verma <vishal.l.verma@intel.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Ben Widawsky <ben.widawsky@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
 drivers/cxl/cxl.h |   19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
index 5486fb6aebd4..ca8a61a623b7 100644
--- a/drivers/cxl/cxl.h
+++ b/drivers/cxl/cxl.h
@@ -509,13 +509,12 @@ enum cxl_lock_class {
 	 */
 };
 
-static inline void cxl_nested_lock(struct device *dev)
+static inline int cxl_lock_class(struct device *dev)
 {
 	if (is_cxl_port(dev)) {
 		struct cxl_port *port = to_cxl_port(dev);
 
-		mutex_lock_nested(&dev->lockdep_mutex,
-				  CXL_PORT_LOCK + port->depth);
+		return CXL_PORT_LOCK + port->depth;
 	} else if (is_cxl_decoder(dev)) {
 		struct cxl_port *port = to_cxl_port(dev->parent);
 
@@ -523,14 +522,18 @@ static inline void cxl_nested_lock(struct device *dev)
 		 * A decoder is the immediate child of a port, so set
 		 * its lock class equal to other child device siblings.
 		 */
-		mutex_lock_nested(&dev->lockdep_mutex,
-				  CXL_PORT_LOCK + port->depth + 1);
+		return CXL_PORT_LOCK + port->depth + 1;
 	} else if (is_cxl_nvdimm_bridge(dev))
-		mutex_lock_nested(&dev->lockdep_mutex, CXL_NVDIMM_BRIDGE_LOCK);
+		return CXL_NVDIMM_BRIDGE_LOCK;
 	else if (is_cxl_nvdimm(dev))
-		mutex_lock_nested(&dev->lockdep_mutex, CXL_NVDIMM_LOCK);
+		return CXL_NVDIMM_LOCK;
 	else
-		mutex_lock_nested(&dev->lockdep_mutex, CXL_ANON_LOCK);
+		return CXL_ANON_LOCK;
+}
+
+static inline void cxl_nested_lock(struct device *dev)
+{
+	mutex_lock_nested(&dev->lockdep_mutex, cxl_lock_class(dev));
 }
 
 static inline void cxl_nested_unlock(struct device *dev)