intel_th: Support Host Debugger mode of operation

This patch adds a 'host_mode' module option to enable host-driven
operational mode in the driver. In this mode, the driver does not
perform trace configuration or enable trace capture, but still
provides all the means necessary for software trace sources to
write their data to the Trace Hub. This means that the debug host
takes care of all the configuration and enabling and we do not
interfere.

Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>

1 files changed, 18 insertions, 8 deletions

diff --git a/drivers/hwtracing/intel_th/core.c b/drivers/hwtracing/intel_th/core.c
index 79e19627b99f..cdd9b3b26195 100644
--- a/drivers/hwtracing/intel_th/core.c
+++ b/drivers/hwtracing/intel_th/core.c
@@ -29,6 +29,9 @@
 #include "intel_th.h"
 #include "debug.h"
 
+static bool host_mode __read_mostly;
+module_param(host_mode, bool, 0444);
+
 static DEFINE_IDA(intel_th_ida);
 
 static int intel_th_match(struct device *dev, struct device_driver *driver)
@@ -527,14 +530,19 @@ static int intel_th_populate(struct intel_th *th, struct resource *devres,
 {
 	struct resource res[3];
 	unsigned int req = 0;
-	int i, err;
+	int src, dst, err;
 
 	/* create devices for each intel_th_subdevice */
-	for (i = 0; i < ARRAY_SIZE(intel_th_subdevices); i++) {
-		struct intel_th_subdevice *subdev = &intel_th_subdevices[i];
+	for (src = 0, dst = 0; src < ARRAY_SIZE(intel_th_subdevices); src++) {
+		const struct intel_th_subdevice *subdev =
+			&intel_th_subdevices[src];
 		struct intel_th_device *thdev;
 		int r;
 
+		/* only allow SOURCE and SWITCH devices in host mode */
+		if (host_mode && subdev->type == INTEL_TH_OUTPUT)
+			continue;
+
 		thdev = intel_th_device_alloc(th, subdev->type, subdev->name,
 					      subdev->id);
 		if (!thdev) {
@@ -577,10 +585,12 @@ static int intel_th_populate(struct intel_th *th, struct resource *devres,
 		}
 
 		if (subdev->type == INTEL_TH_OUTPUT) {
-			thdev->dev.devt = MKDEV(th->major, i);
+			thdev->dev.devt = MKDEV(th->major, dst);
 			thdev->output.type = subdev->otype;
 			thdev->output.port = -1;
 			thdev->output.scratchpad = subdev->scrpd;
+		} else if (subdev->type == INTEL_TH_SWITCH) {
+			thdev->host_mode = host_mode;
 		}
 
 		err = device_add(&thdev->dev);
@@ -597,14 +607,14 @@ static int intel_th_populate(struct intel_th *th, struct resource *devres,
 				req++;
 		}
 
-		th->thdev[i] = thdev;
+		th->thdev[dst++] = thdev;
 	}
 
 	return 0;
 
 kill_subdevs:
-	for (i-- ; i >= 0; i--)
-		intel_th_device_remove(th->thdev[i]);
+	for (; dst >= 0; dst--)
+		intel_th_device_remove(th->thdev[dst]);
 
 	return err;
 }
@@ -717,7 +727,7 @@ void intel_th_free(struct intel_th *th)
 
 	intel_th_request_hub_module_flush(th);
 	for (i = 0; i < TH_SUBDEVICE_MAX; i++)
-		if (th->thdev[i] != th->hub)
+		if (th->thdev[i] && th->thdev[i] != th->hub)
 			intel_th_device_remove(th->thdev[i]);
 
 	intel_th_device_remove(th->hub);