linux-kernel - [PATCH v2 24/27] coresight: tmc-etr: Relax collection of trace from sysfs mode

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Date:   Tue,  1 May 2018 10:10:54 +0100
From:   Suzuki K Poulose <suzuki.poulose@....com>
To:     linux-arm-kernel@...ts.infradead.org
Cc:     linux-kernel@...r.kernel.org, mathieu.poirier@...aro.org,
        mike.leach@...aro.org, robert.walker@....com, mark.rutland@....com,
        will.deacon@....com, robin.murphy@....com, sudeep.holla@....com,
        frowand.list@...il.com, robh@...nel.org, john.horley@....com,
        Suzuki K Poulose <suzuki.poulose@....com>
Subject: [PATCH v2 24/27] coresight: tmc-etr: Relax collection of trace from sysfs mode

Since the ETR now uses mode specific buffers, we can reliably
provide the trace data captured in sysfs mode, even when the ETR
is operating in PERF mode.

Cc: Mathieu Poirier <mathieu.poirier@...aro.org>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
---
 drivers/hwtracing/coresight/coresight-tmc-etr.c | 14 ++++++--------
 1 file changed, 6 insertions(+), 8 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c b/drivers/hwtracing/coresight/coresight-tmc-etr.c
index a35a12f..7551272 100644
--- a/drivers/hwtracing/coresight/coresight-tmc-etr.c
+++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c
@@ -1439,19 +1439,17 @@ int tmc_read_prepare_etr(struct tmc_drvdata *drvdata)
 		goto out;
 	}
 
-	/* Don't interfere if operated from Perf */
-	if (drvdata->mode == CS_MODE_PERF) {
-		ret = -EINVAL;
-		goto out;
-	}
-
-	/* If sysfs_buf is NULL the trace data has been read already */
+	/*
+	 * We can safely allow reads even if the ETR is operating in PERF mode,
+	 * since the sysfs session is captured in mode specific data.
+	 * If drvdata::sysfs_data is NULL the trace data has been read already.
+	 */
 	if (!drvdata->sysfs_buf) {
 		ret = -EINVAL;
 		goto out;
 	}
 
-	/* Disable the TMC if we are trying to read from a running session */
+	/* Disable the TMC if we are trying to read from a running session. */
 	if (drvdata->mode == CS_MODE_SYSFS)
 		tmc_etr_disable_hw(drvdata);
 
-- 
2.7.4