[PATCH 2/4] coresight/etm4x: remove redundant usage of drvdata->spinlock

[Yeoreum Yun]

Remove redundant usage of drvdata->spinlock in  etm4_starting/dying_cpu()
by preventing cpu hotplug while enabling etm4x via sysfs since
 - perf and sysfs enable method are serialized by csdev->mode
 - etm4_starting/dying_cpu() aren't called concurrently with
   etm4_enable_perf/sysfs() because they're called in cpu offline status.
 - while etm4x_enable_sysfs(), config isn't altered since csdev->mode
   isn't DISABLED.

Signed-off-by: Yeoreum Yun <yeoreum.yun at arm.com>
---
 .../coresight/coresight-etm4x-core.c          | 20 +++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c
index 86893115df17..5c9475b44194 100644
--- a/drivers/hwtracing/coresight/coresight-etm4x-core.c
+++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c
@@ -799,16 +799,21 @@ static int etm4_enable_sysfs(struct coresight_device *csdev)
 	unsigned long cfg_hash;
 	int ret, preset;
 
+	cpus_read_lock();
+
+	if (cpu_is_offline(drvdata->cpu)) {
+		ret = -EPERM;
+		goto unlock_sysfs_enable;
+	}
+
 	/* enable any config activated by configfs */
 	cscfg_config_sysfs_get_active_cfg(&cfg_hash, &preset);
 	if (cfg_hash) {
 		ret = cscfg_csdev_enable_active_config(csdev, cfg_hash, preset);
 		if (ret)
-			return ret;
+			goto unlock_sysfs_enable;
 	}
 
-	raw_spin_lock(&drvdata->spinlock);
-
 	/* sysfs needs to read and allocate a trace ID */
 	ret = etm4_read_alloc_trace_id(drvdata);
 	if (ret < 0)
@@ -830,10 +835,11 @@ static int etm4_enable_sysfs(struct coresight_device *csdev)
 		etm4_release_trace_id(drvdata);
 
 unlock_sysfs_enable:
-	raw_spin_unlock(&drvdata->spinlock);
+	cpus_read_unlock();
 
 	if (!ret)
 		dev_dbg(&csdev->dev, "ETM tracing enabled\n");
+
 	return ret;
 }
 
@@ -977,7 +983,6 @@ static void etm4_disable_sysfs(struct coresight_device *csdev)
 	 * DYING hotplug callback is serviced by the ETM driver.
 	 */
 	cpus_read_lock();
-	raw_spin_lock(&drvdata->spinlock);
 
 	/*
 	 * Executing etm4_disable_hw on the cpu whose ETM is being disabled
@@ -985,7 +990,6 @@ static void etm4_disable_sysfs(struct coresight_device *csdev)
 	 */
 	smp_call_function_single(drvdata->cpu, etm4_disable_hw, drvdata, 1);
 
-	raw_spin_unlock(&drvdata->spinlock);
 	cpus_read_unlock();
 
 	/*
@@ -1663,13 +1667,11 @@ static int etm4_starting_cpu(unsigned int cpu)
 	if (!etmdrvdata[cpu])
 		return 0;
 
-	raw_spin_lock(&etmdrvdata[cpu]->spinlock);
 	if (!etmdrvdata[cpu]->os_unlock)
 		etm4_os_unlock(etmdrvdata[cpu]);
 
 	if (coresight_get_mode(etmdrvdata[cpu]->csdev))
 		etm4_enable_hw(etmdrvdata[cpu]);
-	raw_spin_unlock(&etmdrvdata[cpu]->spinlock);
 	return 0;
 }
 
@@ -1678,10 +1680,8 @@ static int etm4_dying_cpu(unsigned int cpu)
 	if (!etmdrvdata[cpu])
 		return 0;
 
-	raw_spin_lock(&etmdrvdata[cpu]->spinlock);
 	if (coresight_get_mode(etmdrvdata[cpu]->csdev))
 		etm4_disable_hw(etmdrvdata[cpu]);
-	raw_spin_unlock(&etmdrvdata[cpu]->spinlock);
 	return 0;
 }
 
-- 
LEVI:{C3F47F37-75D8-414A-A8BA-3980EC8A46D7}