[PATCH v2 5/5] coresight: etm3x: fix inconsistencies with sysfs configration

[Yeoreum Yun]

The current ETM3x configuration via sysfs can lead to the following
inconsistencies:

  - If a configuration is modified via sysfs while a perf session is
    active, the running configuration may differ between before
    a sched-out and after a subsequent sched-in.

To resolve these inconsistencies, the configuration should be separated into:

  - active_config, which is applied configuration for the current session
  - config, which stores the settings configured via sysfs.

and apply configuration after taking a mode.

Signed-off-by: Yeoreum Yun <yeoreum.yun at arm.com>
---
 drivers/hwtracing/coresight/coresight-etm.h   |  2 ++
 .../coresight/coresight-etm3x-core.c          | 20 ++++++++++++-------
 2 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-etm.h b/drivers/hwtracing/coresight/coresight-etm.h
index 6fda26039db8..9ed5e2361be1 100644
--- a/drivers/hwtracing/coresight/coresight-etm.h
+++ b/drivers/hwtracing/coresight/coresight-etm.h
@@ -241,6 +241,7 @@ struct etm_config {
  * @boot_enable:true if we should start tracing at boot time.
  * @os_unlock:	true if access to management registers is allowed.
  * @traceid:	value of the current ID for this component.
+ * @active_config:	structure holding current running configuration parameters.
  * @config:	structure holding configuration parameters.
  */
 struct etm_drvdata {
@@ -256,6 +257,7 @@ struct etm_drvdata {
 	bool				boot_enable;
 	bool				os_unlock;
 	u32				traceid;
+	struct etm_config		active_config;
 	struct etm_config		config;
 };
 
diff --git a/drivers/hwtracing/coresight/coresight-etm3x-core.c b/drivers/hwtracing/coresight/coresight-etm3x-core.c
index b7e977defb1c..0afe2275aa27 100644
--- a/drivers/hwtracing/coresight/coresight-etm3x-core.c
+++ b/drivers/hwtracing/coresight/coresight-etm3x-core.c
@@ -308,7 +308,7 @@ void etm_config_trace_mode(struct etm_config *config)
 static int etm_parse_event_config(struct etm_drvdata *drvdata,
 				  struct perf_event *event)
 {
-	struct etm_config *config = &drvdata->config;
+	struct etm_config *config = &drvdata->active_config;
 	struct perf_event_attr *attr = &event->attr;
 	u8 ts_level;
 
@@ -368,7 +368,7 @@ static int etm_enable_hw(struct etm_drvdata *drvdata)
 	int i, rc;
 	u32 etmcr;
 	const struct etm_caps *caps = &drvdata->caps;
-	struct etm_config *config = &drvdata->config;
+	struct etm_config *config = &drvdata->active_config;
 	struct coresight_device *csdev = drvdata->csdev;
 
 	CS_UNLOCK(drvdata->csa.base);
@@ -442,24 +442,30 @@ static int etm_enable_hw(struct etm_drvdata *drvdata)
 
 struct etm_enable_arg {
 	struct etm_drvdata *drvdata;
+	u32 traceid;
 	int rc;
 };
 
 static void etm_enable_sysfs_smp_call(void *info)
 {
 	struct etm_enable_arg *arg = info;
+	struct etm_drvdata *drvdata;
 	struct coresight_device *csdev;
 
 	if (WARN_ON(!arg))
 		return;
 
-	csdev = arg->drvdata->csdev;
+	drvdata = arg->drvdata;
+	csdev = drvdata->csdev;
 	if (!coresight_take_mode(csdev, CS_MODE_SYSFS)) {
 		/* Someone is already using the tracer */
 		arg->rc = -EBUSY;
 		return;
 	}
 
+	drvdata->active_config = drvdata->config;
+	drvdata->traceid = arg->traceid;
+
 	arg->rc = etm_enable_hw(arg->drvdata);
 
 	/* The tracer didn't start */
@@ -514,14 +520,13 @@ static int etm_enable_sysfs(struct coresight_device *csdev, struct coresight_pat
 
 	spin_lock(&drvdata->spinlock);
 
-	drvdata->traceid = path->trace_id;
-
 	/*
 	 * Configure the ETM only if the CPU is online.  If it isn't online
 	 * hw configuration will take place on the local CPU during bring up.
 	 */
 	if (cpu_online(drvdata->cpu)) {
 		arg.drvdata = drvdata;
+		arg.traceid = path->trace_id;
 		ret = smp_call_function_single(drvdata->cpu,
 					       etm_enable_sysfs_smp_call, &arg, 1);
 		if (!ret)
@@ -564,7 +569,7 @@ static int etm_enable(struct coresight_device *csdev, struct perf_event *event,
 static void etm_disable_hw(struct etm_drvdata *drvdata)
 {
 	int i;
-	struct etm_config *config = &drvdata->config;
+	struct etm_config *config = &drvdata->active_config;
 	struct coresight_device *csdev = drvdata->csdev;
 
 	CS_UNLOCK(drvdata->csa.base);
@@ -882,7 +887,8 @@ static int etm_probe(struct amba_device *adev, const struct amba_id *id)
 	if (etm_arch_supported(drvdata->arch) == false)
 		return -EINVAL;
 
-	etm_set_default(&drvdata->config);
+	etm_set_default(&drvdata->active_config);
+	drvdata->config = drvdata->active_config;
 
 	pdata = coresight_get_platform_data(dev);
 	if (IS_ERR(pdata))
-- 
LEVI:{C3F47F37-75D8-414A-A8BA-3980EC8A46D7}