coresight: implementing 'cpu_id()' API

Other than plainly parsing the device tree there is no way to
know which CPU a tracer is affined to.  As such adding an
interface to lookup the CPU field enclosed in the etm_drvdata
structure that was initialised at boot time.
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/hwtracing/coresight/coresight-etm3x.c

@@ -315,6 +315,13 @@ static void etm_enable_hw(void *info)
 	dev_dbg(drvdata->dev, "cpu: %d enable smp call done\n", drvdata->cpu);
 }
 
+static int etm_cpu_id(struct coresight_device *csdev)
+{
+	struct etm_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
+
+	return drvdata->cpu;
+}
+
 static int etm_trace_id(struct coresight_device *csdev)
 {
 	struct etm_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
@@ -421,6 +428,7 @@ static void etm_disable(struct coresight_device *csdev)
 }
 
 static const struct coresight_ops_source etm_source_ops = {
+	.cpu_id		= etm_cpu_id,
 	.trace_id	= etm_trace_id,
 	.enable		= etm_enable,
 	.disable	= etm_disable,

drivers/hwtracing/coresight/coresight-etm4x.c

@@ -63,6 +63,13 @@ static bool etm4_arch_supported(u8 arch)
 	return true;
 }
 
+static int etm4_cpu_id(struct coresight_device *csdev)
+{
+	struct etmv4_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
+
+	return drvdata->cpu;
+}
+
 static int etm4_trace_id(struct coresight_device *csdev)
 {
 	struct etmv4_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
@@ -262,6 +269,7 @@ static void etm4_disable(struct coresight_device *csdev)
 }
 
 static const struct coresight_ops_source etm4_source_ops = {
+	.cpu_id		= etm4_cpu_id,
 	.trace_id	= etm4_trace_id,
 	.enable		= etm4_enable,
 	.disable	= etm4_disable,

include/linux/coresight.h

@@ -205,12 +205,15 @@ struct coresight_ops_link {
 /**
  * struct coresight_ops_source - basic operations for a source
  * Operations available for sources.
+ * @cpu_id:	returns the value of the CPU number this component
+ *		is associated to.
  * @trace_id:	returns the value of the component's trace ID as known
 		to the HW.
  * @enable:	enables tracing for a source.
  * @disable:	disables tracing for a source.
  */
 struct coresight_ops_source {
+	int (*cpu_id)(struct coresight_device *csdev);
 	int (*trace_id)(struct coresight_device *csdev);
 	int (*enable)(struct coresight_device *csdev);
 	void (*disable)(struct coresight_device *csdev);