coresight: tmc: make sysFS and Perf mode mutually exclusive

The sysFS and Perf access methods can't be allowed to interfere
with one another.  As such introducing guards to access
functions that prevents moving forward if a TMC is already
being used.

Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 58 insertions, 2 deletions

diff --git a/drivers/hwtracing/coresight/coresight-tmc-etf.c b/drivers/hwtracing/coresight/coresight-tmc-etf.c
index b5e5e6ac67eb..b11c52be54a9 100644
--- a/drivers/hwtracing/coresight/coresight-tmc-etf.c
+++ b/drivers/hwtracing/coresight/coresight-tmc-etf.c
@@ -111,7 +111,7 @@ static void tmc_etf_disable_hw(struct tmc_drvdata *drvdata)
 	CS_LOCK(drvdata->base);
 }
 
-static int tmc_enable_etf_sink(struct coresight_device *csdev, u32 mode)
+static int tmc_enable_etf_sink_sysfs(struct coresight_device *csdev, u32 mode)
 {
 	int ret = 0;
 	bool used = false;
@@ -185,6 +185,54 @@ out:
 	return ret;
 }
 
+static int tmc_enable_etf_sink_perf(struct coresight_device *csdev, u32 mode)
+{
+	int ret = 0;
+	long val;
+	unsigned long flags;
+	struct tmc_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
+
+	 /* This shouldn't be happening */
+	if (WARN_ON(mode != CS_MODE_PERF))
+		return -EINVAL;
+
+	spin_lock_irqsave(&drvdata->spinlock, flags);
+	if (drvdata->reading) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	val = local_xchg(&drvdata->mode, mode);
+	/*
+	 * In Perf mode there can be only one writer per sink.  There
+	 * is also no need to continue if the ETB/ETR is already operated
+	 * from sysFS.
+	 */
+	if (val != CS_MODE_DISABLED) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	tmc_etb_enable_hw(drvdata);
+out:
+	spin_unlock_irqrestore(&drvdata->spinlock, flags);
+
+	return ret;
+}
+
+static int tmc_enable_etf_sink(struct coresight_device *csdev, u32 mode)
+{
+	switch (mode) {
+	case CS_MODE_SYSFS:
+		return tmc_enable_etf_sink_sysfs(csdev, mode);
+	case CS_MODE_PERF:
+		return tmc_enable_etf_sink_perf(csdev, mode);
+	}
+
+	/* We shouldn't be here */
+	return -EINVAL;
+}
+
 static void tmc_disable_etf_sink(struct coresight_device *csdev)
 {
 	long val;
@@ -267,6 +315,7 @@ const struct coresight_ops tmc_etf_cs_ops = {
 
 int tmc_read_prepare_etb(struct tmc_drvdata *drvdata)
 {
+	long val;
 	enum tmc_mode mode;
 	int ret = 0;
 	unsigned long flags;
@@ -290,6 +339,13 @@ int tmc_read_prepare_etb(struct tmc_drvdata *drvdata)
 		goto out;
 	}
 
+	val = local_read(&drvdata->mode);
+	/* Don't interfere if operated from Perf */
+	if (val == CS_MODE_PERF) {
+		ret = -EINVAL;
+		goto out;
+	}
+
 	/* If drvdata::buf is NULL the trace data has been read already */
 	if (drvdata->buf == NULL) {
 		ret = -EINVAL;
@@ -297,7 +353,7 @@ int tmc_read_prepare_etb(struct tmc_drvdata *drvdata)
 	}
 
 	/* Disable the TMC if need be */
-	if (local_read(&drvdata->mode) == CS_MODE_SYSFS)
+	if (val == CS_MODE_SYSFS)
 		tmc_etb_disable_hw(drvdata);
 
 	drvdata->reading = true;