linux-kernel - [PATCH v6 04/13] coresight: Hide unused ETMv3 format attributes

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Message-Id: <20251119-james-cs-syncfreq-v6-4-740d24a29e51@linaro.org>
Date: Wed, 19 Nov 2025 16:18:00 +0000
From: James Clark <james.clark@...aro.org>
To: Suzuki K Poulose <suzuki.poulose@....com>, 
 Mike Leach <mike.leach@...aro.org>, 
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>, 
 Jonathan Corbet <corbet@....net>, Leo Yan <leo.yan@....com>, 
 Randy Dunlap <rdunlap@...radead.org>
Cc: coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org, 
 linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org, 
 James Clark <james.clark@...aro.org>
Subject: [PATCH v6 04/13] coresight: Hide unused ETMv3 format attributes

ETMv3 only has a few attributes, and setting unused ones results in an
error, so hide them to begin with.

Signed-off-by: James Clark <james.clark@...aro.org>
---
 drivers/hwtracing/coresight/coresight-etm-perf.c | 37 +++++++++++++-----------
 1 file changed, 20 insertions(+), 17 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-etm-perf.c b/drivers/hwtracing/coresight/coresight-etm-perf.c
index 17afa0f4cdee..3805282b97e8 100644
--- a/drivers/hwtracing/coresight/coresight-etm-perf.c
+++ b/drivers/hwtracing/coresight/coresight-etm-perf.c
@@ -50,27 +50,23 @@ struct etm_ctxt {
 static DEFINE_PER_CPU(struct etm_ctxt, etm_ctxt);
 static DEFINE_PER_CPU(struct coresight_device *, csdev_src);
 
-/*
- * The PMU formats were orignally for ETMv3.5/PTM's ETMCR 'config';
- * now take them as general formats and apply on all ETMs.
- */
-PMU_FORMAT_ATTR(branch_broadcast, "config:"__stringify(ETM_OPT_BRANCH_BROADCAST));
 PMU_FORMAT_ATTR(cycacc,		"config:" __stringify(ETM_OPT_CYCACC));
-/* contextid1 enables tracing CONTEXTIDR_EL1 for ETMv4 */
-PMU_FORMAT_ATTR(contextid1,	"config:" __stringify(ETM_OPT_CTXTID));
-/* contextid2 enables tracing CONTEXTIDR_EL2 for ETMv4 */
-PMU_FORMAT_ATTR(contextid2,	"config:" __stringify(ETM_OPT_CTXTID2));
 PMU_FORMAT_ATTR(timestamp,	"config:" __stringify(ETM_OPT_TS));
 PMU_FORMAT_ATTR(retstack,	"config:" __stringify(ETM_OPT_RETSTK));
+PMU_FORMAT_ATTR(sinkid,		"config2:0-31");
+
+#if IS_ENABLED(CONFIG_CORESIGHT_SOURCE_ETM4X)
+PMU_FORMAT_ATTR(branch_broadcast, "config:"__stringify(ETM_OPT_BRANCH_BROADCAST));
+/* contextid1 enables tracing CONTEXTIDR_EL1*/
+PMU_FORMAT_ATTR(contextid1,	"config:" __stringify(ETM_OPT_CTXTID));
+/* contextid2 enables tracing CONTEXTIDR_EL2*/
+PMU_FORMAT_ATTR(contextid2,	"config:" __stringify(ETM_OPT_CTXTID2));
 /* preset - if sink ID is used as a configuration selector */
 PMU_FORMAT_ATTR(preset,		"config:0-3");
-/* Sink ID - same for all ETMs */
-PMU_FORMAT_ATTR(sinkid,		"config2:0-31");
 /* config ID - set if a system configuration is selected */
 PMU_FORMAT_ATTR(configid,	"config2:32-63");
 PMU_FORMAT_ATTR(cc_threshold,	"config3:0-11");
 
-
 /*
  * contextid always traces the "PID".  The PID is in CONTEXTIDR_EL1
  * when the kernel is running at EL1; when the kernel is at EL2,
@@ -82,27 +78,34 @@ static ssize_t format_attr_contextid_show(struct device *dev,
 {
 	int pid_fmt = ETM_OPT_CTXTID;
 
-#if IS_ENABLED(CONFIG_CORESIGHT_SOURCE_ETM4X)
 	pid_fmt = is_kernel_in_hyp_mode() ? ETM_OPT_CTXTID2 : ETM_OPT_CTXTID;
-#endif
 	return sprintf(page, "config:%d\n", pid_fmt);
 }
 
 static struct device_attribute format_attr_contextid =
 	__ATTR(contextid, 0444, format_attr_contextid_show, NULL);
+#endif
 
+/*
+ * ETMv3 only uses the first 3 attributes for programming itself (see
+ * ETM3X_SUPPORTED_OPTIONS). Sink ID is also supported for selecting a
+ * sink in both, but not used for configuring the ETM. The remaining
+ * attributes are ETMv4 specific.
+ */
 static struct attribute *etm_config_formats_attr[] = {
 	&format_attr_cycacc.attr,
-	&format_attr_contextid.attr,
-	&format_attr_contextid1.attr,
-	&format_attr_contextid2.attr,
 	&format_attr_timestamp.attr,
 	&format_attr_retstack.attr,
 	&format_attr_sinkid.attr,
+#if IS_ENABLED(CONFIG_CORESIGHT_SOURCE_ETM4X)
+	&format_attr_contextid.attr,
+	&format_attr_contextid1.attr,
+	&format_attr_contextid2.attr,
 	&format_attr_preset.attr,
 	&format_attr_configid.attr,
 	&format_attr_branch_broadcast.attr,
 	&format_attr_cc_threshold.attr,
+#endif
 	NULL,
 };
 

-- 
2.34.1