coresight: etm4x: Update ETM4 driver to use Trace ID API

The trace ID API is now used to allocate trace IDs for ETM4.x / ETE
devices.

For perf sessions, these will be allocated on enable, and released on
disable.

For sysfs sessions, these will be allocated on enable, but only released
on reset. This allows the sysfs session to interrogate the Trace ID used
after the session is over - maintaining functional consistency with the
previous allocation scheme.

The trace ID will also be allocated on read of the mgmt/trctraceid file.
This ensures that if perf or sysfs read this before enabling trace, the
value will be the one used for the trace session.

Trace ID initialisation is removed from the _probe() function.

Signed-off-by: Mike Leach <mike.leach@linaro.org>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20230116124928.5440-6-mike.leach@linaro.org

1 files changed, 24 insertions, 3 deletions

diff --git a/drivers/hwtracing/coresight/coresight-etm4x-sysfs.c b/drivers/hwtracing/coresight/coresight-etm4x-sysfs.c
index 9cac848cffaf..5e62aa40ecd0 100644
--- a/drivers/hwtracing/coresight/coresight-etm4x-sysfs.c
+++ b/drivers/hwtracing/coresight/coresight-etm4x-sysfs.c
@@ -266,10 +266,11 @@ static ssize_t reset_store(struct device *dev,
 	config->vmid_mask0 = 0x0;
 	config->vmid_mask1 = 0x0;
 
-	drvdata->trcid = drvdata->cpu + 1;
-
 	spin_unlock(&drvdata->spinlock);
 
+	/* for sysfs - only release trace id when resetting */
+	etm4_release_trace_id(drvdata);
+
 	cscfg_csdev_reset_feats(to_coresight_device(dev));
 
 	return size;
@@ -2392,6 +2393,26 @@ static struct attribute *coresight_etmv4_attrs[] = {
 	NULL,
 };
 
+/*
+ * Trace ID allocated dynamically on enable - but also allocate on read
+ * in case sysfs or perf read before enable to ensure consistent metadata
+ * information for trace decode
+ */
+static ssize_t trctraceid_show(struct device *dev,
+			       struct device_attribute *attr,
+			       char *buf)
+{
+	int trace_id;
+	struct etmv4_drvdata *drvdata = dev_get_drvdata(dev->parent);
+
+	trace_id = etm4_read_alloc_trace_id(drvdata);
+	if (trace_id < 0)
+		return trace_id;
+
+	return sysfs_emit(buf, "0x%x\n", trace_id);
+}
+static DEVICE_ATTR_RO(trctraceid);
+
 struct etmv4_reg {
 	struct coresight_device *csdev;
 	u32 offset;
@@ -2528,7 +2549,7 @@ static struct attribute *coresight_etmv4_mgmt_attrs[] = {
 	coresight_etm4x_reg(trcpidr3, TRCPIDR3),
 	coresight_etm4x_reg(trcoslsr, TRCOSLSR),
 	coresight_etm4x_reg(trcconfig, TRCCONFIGR),
-	coresight_etm4x_reg(trctraceid, TRCTRACEIDR),
+	&dev_attr_trctraceid.attr,
 	coresight_etm4x_reg(trcdevarch, TRCDEVARCH),
 	NULL,
 };