intel_th: Make SOURCE devices children of the root device

The switch (GTH) does not directly interact with SOURCE type devices and
may not even be present (in host mode). To reflect this and avoid
inconsistencies between target and host mode, make SOURCE devices
descendant directly from the root (i.e. PCI) device. Their symlinks
will no longer appear under the switch device, but they can still
be found under intel_th bus.
Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>

drivers/hwtracing/intel_th/core.c

@@ -311,10 +311,10 @@ intel_th_device_alloc(struct intel_th *th, unsigned int type, const char *name,
 	struct device *parent;
 	struct intel_th_device *thdev;
 
-	if (type == INTEL_TH_SWITCH)
-		parent = th->dev;
-	else
+	if (type == INTEL_TH_OUTPUT)
 		parent = &th->hub->dev;
+	else
+		parent = th->dev;
 
 	thdev = kzalloc(sizeof(*thdev) + strlen(name) + 1, GFP_KERNEL);
 	if (!thdev)

drivers/hwtracing/intel_th/intel_th.h

@@ -172,6 +172,16 @@ struct intel_th_driver {
 #define to_intel_th_driver_or_null(_d)		\
 	((_d) ? to_intel_th_driver(_d) : NULL)
 
+/*
+ * Subdevice tree structure is as follows:
+ * + struct intel_th device (pci; dev_{get,set}_drvdata()
+ *   + struct intel_th_device INTEL_TH_SWITCH (GTH)
+ *     + struct intel_th_device INTEL_TH_OUTPUT (MSU, PTI)
+ *   + struct intel_th_device INTEL_TH_SOURCE (STH)
+ *
+ * In other words, INTEL_TH_OUTPUT devices are children of INTEL_TH_SWITCH;
+ * INTEL_TH_SWITCH and INTEL_TH_SOURCE are children of the intel_th device.
+ */
 static inline struct intel_th_device *
 to_intel_th_parent(struct intel_th_device *thdev)
 {
@@ -183,24 +193,12 @@ to_intel_th_parent(struct intel_th_device *thdev)
 	return to_intel_th_device(parent);
 }
 
-static inline struct intel_th_device *
-to_intel_th_hub(struct intel_th_device *thdev)
-{
-	/*
-	 * subdevice tree is flat: if this one is not a switch, its
-	 * parent must be
-	 */
-	if (thdev->type == INTEL_TH_SWITCH)
-		return thdev;
-
-	return to_intel_th_parent(thdev);
-}
-
 static inline struct intel_th *to_intel_th(struct intel_th_device *thdev)
 {
-	thdev = to_intel_th_hub(thdev);
+	if (thdev->type == INTEL_TH_OUTPUT)
+		thdev = to_intel_th_parent(thdev);
 
-	if (WARN_ON_ONCE(!thdev || thdev->type != INTEL_TH_SWITCH))
+	if (WARN_ON_ONCE(!thdev || thdev->type == INTEL_TH_OUTPUT))
 		return NULL;
 
 	return dev_get_drvdata(thdev->dev.parent);
@@ -254,6 +252,17 @@ struct intel_th {
 #endif
 };
 
+static inline struct intel_th_device *
+to_intel_th_hub(struct intel_th_device *thdev)
+{
+	if (thdev->type == INTEL_TH_SWITCH)
+		return thdev;
+	else if (thdev->type == INTEL_TH_OUTPUT)
+		return to_intel_th_parent(thdev);
+
+	return to_intel_th(thdev)->hub;
+}
+
 /*
  * Register windows
  */