linux-kernel - [PATCH 16/16] coresight: etm4x: Fix number of resources check for ETM 4.3 and above

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Date:   Wed, 16 Sep 2020 13:17:37 -0600
From:   Mathieu Poirier <mathieu.poirier@...aro.org>
To:     gregkh@...uxfoundation.org
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH 16/16] coresight: etm4x: Fix number of resources check for ETM 4.3 and above

From: Mike Leach <mike.leach@...aro.org>

The initialisation code checks TRCIDR4 to determine the number of resource
selectors available on the system. Since ETM v 4.3, the value 0 has a
different meaning. This patch takes into account this change.

Cc: stable@...r.kernel.org
Signed-off-by: Mike Leach <mike.leach@...aro.org>
[Removed '.' in patch title, added stable]
Signed-off-by: Mathieu Poirier <mathieu.poirier@...aro.org>
---
 drivers/hwtracing/coresight/coresight-etm4x.c | 8 +++++++-
 drivers/hwtracing/coresight/coresight-etm4x.h | 3 +++
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/hwtracing/coresight/coresight-etm4x.c b/drivers/hwtracing/coresight/coresight-etm4x.c
index b29ad4f7fac2..f5ab13aaecea 100644
--- a/drivers/hwtracing/coresight/coresight-etm4x.c
+++ b/drivers/hwtracing/coresight/coresight-etm4x.c
@@ -742,8 +742,14 @@ static void etm4_init_arch_data(void *info)
 	 * The number of resource pairs conveyed by the HW starts at 0, i.e a
 	 * value of 0x0 indicate 1 resource pair, 0x1 indicate two and so on.
 	 * As such add 1 to the value of NUMRSPAIR for a better representation.
+	 *
+	 * For ETM v4.3 and later, 0x0 means 0, and no pairs are available -
+	 * the default TRUE and FALSE resource selectors are omitted.
+	 * Otherwise for values 0x1 and above the number is N + 1 as per v4.2.
 	 */
-	drvdata->nr_resource = BMVAL(etmidr4, 16, 19) + 1;
+	drvdata->nr_resource = BMVAL(etmidr4, 16, 19);
+	if ((drvdata->arch < ETM4X_ARCH_4V3) || (drvdata->nr_resource > 0))
+		drvdata->nr_resource += 1;
 	/*
 	 * NUMSSCC, bits[23:20] the number of single-shot
 	 * comparator control for tracing. Read any status regs as these
diff --git a/drivers/hwtracing/coresight/coresight-etm4x.h b/drivers/hwtracing/coresight/coresight-etm4x.h
index 5259f96fd28a..eefc7371c6c4 100644
--- a/drivers/hwtracing/coresight/coresight-etm4x.h
+++ b/drivers/hwtracing/coresight/coresight-etm4x.h
@@ -200,6 +200,9 @@
 /* NS MON (EL3) mode never implemented */
 #define ETM_EXLEVEL_NS_VICTLR_MASK	GENMASK(22, 20)
 
+/* Interpretation of resource numbers change at ETM v4.3 architecture */
+#define ETM4X_ARCH_4V3	0x43
+
 /**
  * struct etmv4_config - configuration information related to an ETMv4
  * @mode:	Controls various modes supported by this ETM.
-- 
2.25.1