linux-kernel - [PATCH] coresight: etm4x: Allow configuring cycle count threshold

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Message-ID: <20231019082357.1505047-1-wnhuang@google.com>
Date:   Thu, 19 Oct 2023 16:23:57 +0800
From:   Wei-Ning Huang <wnhuang@...gle.com>
To:     linux-arm-kernel@...ts.infradead.org, coresight@...ts.linaro.org,
        suzuki.poulose@....com, james.clark@....com, leo.yan@...aro.org
Cc:     linux-kernel@...r.kernel.org, Wei-Ning Huang <wnhuang@...gle.com>
Subject: [PATCH] coresight: etm4x: Allow configuring cycle count threshold

Allow userspace to configure cycle count threshold through
perf_event_attr config. The last high 12-bit of config value is used to
store the cycle count threshold.

Signed-off-by: Wei-Ning Huang <wnhuang@...gle.com>
---
 drivers/hwtracing/coresight/coresight-etm4x-core.c |  6 +++++-
 include/linux/coresight-pmu.h                      | 14 ++++++++------
 tools/include/linux/coresight-pmu.h                | 14 ++++++++------
 3 files changed, 21 insertions(+), 13 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c
index 77b0271ce6eb..155441668b4a 100644
--- a/drivers/hwtracing/coresight/coresight-etm4x-core.c
+++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c
@@ -645,6 +645,7 @@ static int etm4_parse_event_config(struct coresight_device *csdev,
 	struct perf_event_attr *attr = &event->attr;
 	unsigned long cfg_hash;
 	int preset;
+	u64 cyc_threadhold;
 
 	/* Clear configuration from previous run */
 	memset(config, 0, sizeof(struct etmv4_config));
@@ -667,7 +668,10 @@ static int etm4_parse_event_config(struct coresight_device *csdev,
 	if (attr->config & BIT(ETM_OPT_CYCACC)) {
 		config->cfg |= TRCCONFIGR_CCI;
 		/* TRM: Must program this for cycacc to work */
-		config->ccctlr = ETM_CYC_THRESHOLD_DEFAULT;
+		cyc_threshold = ((attr->config >> ETM_OPT_CYC_THRESHOLD_SHIFT) &
+				 ETM_OPT_CYC_THRESHOLD_MASK;
+		config->ccctlr = cyc_threshold ? cyc_threshold :
+				 ETM_CYC_THRESHOLD_DEFAULT;
 	}
 	if (attr->config & BIT(ETM_OPT_TS)) {
 		/*
diff --git a/include/linux/coresight-pmu.h b/include/linux/coresight-pmu.h
index 51ac441a37c3..14f48658ff1c 100644
--- a/include/linux/coresight-pmu.h
+++ b/include/linux/coresight-pmu.h
@@ -29,12 +29,14 @@
  * ETMv3.5/PTM doesn't define ETMCR config bits with prefix "ETM3_" and
  * directly use below macros as config bits.
  */
-#define ETM_OPT_BRANCH_BROADCAST 8
-#define ETM_OPT_CYCACC		12
-#define ETM_OPT_CTXTID		14
-#define ETM_OPT_CTXTID2		15
-#define ETM_OPT_TS		28
-#define ETM_OPT_RETSTK		29
+#define ETM_OPT_BRANCH_BROADCAST	8
+#define ETM_OPT_CYCACC			12
+#define ETM_OPT_CTXTID			14
+#define ETM_OPT_CTXTID2			15
+#define ETM_OPT_TS			28
+#define ETM_OPT_RETSTK			29
+#define ETM_OPT_CYC_THRESHOLD_SHIFT	52
+#define ETM_OPT_CYC_THRESHOLD_MASK	0xfff
 
 /* ETMv4 CONFIGR programming bits for the ETM OPTs */
 #define ETM4_CFG_BIT_BB         3
diff --git a/tools/include/linux/coresight-pmu.h b/tools/include/linux/coresight-pmu.h
index 51ac441a37c3..14f48658ff1c 100644
--- a/tools/include/linux/coresight-pmu.h
+++ b/tools/include/linux/coresight-pmu.h
@@ -29,12 +29,14 @@
  * ETMv3.5/PTM doesn't define ETMCR config bits with prefix "ETM3_" and
  * directly use below macros as config bits.
  */
-#define ETM_OPT_BRANCH_BROADCAST 8
-#define ETM_OPT_CYCACC		12
-#define ETM_OPT_CTXTID		14
-#define ETM_OPT_CTXTID2		15
-#define ETM_OPT_TS		28
-#define ETM_OPT_RETSTK		29
+#define ETM_OPT_BRANCH_BROADCAST	8
+#define ETM_OPT_CYCACC			12
+#define ETM_OPT_CTXTID			14
+#define ETM_OPT_CTXTID2			15
+#define ETM_OPT_TS			28
+#define ETM_OPT_RETSTK			29
+#define ETM_OPT_CYC_THRESHOLD_SHIFT	52
+#define ETM_OPT_CYC_THRESHOLD_MASK	0xfff
 
 /* ETMv4 CONFIGR programming bits for the ETM OPTs */
 #define ETM4_CFG_BIT_BB         3
-- 
2.42.0.655.g421f12c284-goog