linux-kernel - [PATCH 11/44] coresight: etb10: Fix handling of perf mode

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Date:   Thu, 20 Sep 2018 13:17:46 -0600
From:   Mathieu Poirier <mathieu.poirier@...aro.org>
To:     gregkh@...uxfoundation.org
Cc:     linux-kernel@...r.kernel.org
Subject: [PATCH 11/44] coresight: etb10: Fix handling of perf mode

From: Suzuki K Poulose <suzuki.poulose@....com>

If the ETB is already enabled in sysfs mode, the ETB reports
success even if a perf mode is requested. Fix this by checking
the requested mode.

Cc: Mathieu Poirier <mathieu.poirier@...aro.org>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
Signed-off-by: Mathieu Poirier <mathieu.poirier@...aro.org>
---
 drivers/hwtracing/coresight/coresight-etb10.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/hwtracing/coresight/coresight-etb10.c b/drivers/hwtracing/coresight/coresight-etb10.c
index 306119eaf16a..0dad8626bcfb 100644
--- a/drivers/hwtracing/coresight/coresight-etb10.c
+++ b/drivers/hwtracing/coresight/coresight-etb10.c
@@ -147,6 +147,10 @@ static int etb_enable(struct coresight_device *csdev, u32 mode)
 	if (val == CS_MODE_PERF)
 		return -EBUSY;
 
+	/* Don't let perf disturb sysFS sessions */
+	if (val == CS_MODE_SYSFS && mode == CS_MODE_PERF)
+		return -EBUSY;
+
 	/* Nothing to do, the tracer is already enabled. */
 	if (val == CS_MODE_SYSFS)
 		goto out;
-- 
2.7.4