[PATCH v12 01/14] coresight: etm4x: read-back TRCSEQSTR at disabling and prohibit modifying seq_state while enabling.

[Yeoreum Yun <yeoreum.yun@arm.com>]

TRCSEQSTR can be changed by the ETM while a session is active. Its value
therefore needs to be preserved when a sysfs session is disabled so that
users can read the current sequence state after the session ends.

This means that any changes made to TRCSEQSTR while the sysfs-session is active
would be lost when the session is disabled.

Copy the TRCSEQSTR value when disabling a sysfs session, and prohibit
modifying seq_state while the session is active.

Suggested-by: Mike Leach <mike.leach@arm.com>
Signed-off-by: Yeoreum Yun <yeoreum.yun@arm.com>
---
 drivers/hwtracing/coresight/coresight-etm4x-core.c  | 4 ++++
 drivers/hwtracing/coresight/coresight-etm4x-sysfs.c | 2 ++
 2 files changed, 6 insertions(+)

diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c
index 2247ad55d444..9ca03a5913a3 100644
--- a/drivers/hwtracing/coresight/coresight-etm4x-core.c
+++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c
@@ -1073,6 +1073,10 @@ static void etm4_disable_hw(struct etmv4_drvdata *drvdata)
 			etm4x_relaxed_read32(csa, TRCCNTVRn(i));
 	}
 
+	/* read back the sequence state */
+	if (drvdata->nrseqstate)
+		config->seq_state = etm4x_relaxed_read32(csa, TRCSEQSTR);
+
 	coresight_disclaim_device_unlocked(csdev);
 	etm4_cs_lock(drvdata, csa);
 
diff --git a/drivers/hwtracing/coresight/coresight-etm4x-sysfs.c b/drivers/hwtracing/coresight/coresight-etm4x-sysfs.c
index cc6cdd3ae29d..db3cf4ad6806 100644
--- a/drivers/hwtracing/coresight/coresight-etm4x-sysfs.c
+++ b/drivers/hwtracing/coresight/coresight-etm4x-sysfs.c
@@ -1437,6 +1437,8 @@ static ssize_t seq_state_store(struct device *dev,
 		return -EINVAL;
 	if (val >= drvdata->nrseqstate)
 		return -EINVAL;
+	if (IS_ERR_OR_NULL(drvdata) || coresight_get_mode(drvdata->csdev))
+		return -EBUSY;
 
 	config->seq_state = val;
 	return size;

-- 
2.43.0