intel_th: Allow forcing host mode through drvdata

Some devices can only operate in host mode, so we need means of
communicating this to the core driver on per-device basis. This
adds a flag to drvdata to signal host-only capability to the core.
Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>

drivers/hwtracing/intel_th/core.c

@@ -630,7 +630,8 @@ intel_th_subdevice_alloc(struct intel_th *th,
 		thdev->output.port = -1;
 		thdev->output.scratchpad = subdev->scrpd;
 	} else if (subdev->type == INTEL_TH_SWITCH) {
-		thdev->host_mode = host_mode;
+		thdev->host_mode =
+			INTEL_TH_CAP(th, host_mode_only) ? true : host_mode;
 		th->hub = thdev;
 	}
 
@@ -729,7 +730,8 @@ static int intel_th_populate(struct intel_th *th)
 		struct intel_th_device *thdev;
 
 		/* only allow SOURCE and SWITCH devices in host mode */
-		if (host_mode && subdev->type == INTEL_TH_OUTPUT)
+		if ((INTEL_TH_CAP(th, host_mode_only) || host_mode) &&
+		    subdev->type == INTEL_TH_OUTPUT)
 			continue;
 
 		/*

drivers/hwtracing/intel_th/intel_th.h

@@ -42,9 +42,11 @@ struct intel_th_output {
 /**
  * struct intel_th_drvdata - describes hardware capabilities and quirks
  * @tscu_enable:	device needs SW to enable time stamping unit
+ * @host_mode_only:	device can only operate in 'host debugger' mode
  */
 struct intel_th_drvdata {
-	unsigned int	tscu_enable        : 1;
+	unsigned int	tscu_enable        : 1,
+			host_mode_only     : 1;
 };
 
 #define INTEL_TH_CAP(_th, _cap) ((_th)->drvdata ? (_th)->drvdata->_cap : 0)