[PATCH v4 6/7] coresight: etm4x: Report whether the PMU counts the external outputs

[Amir Ayupov]

Some CPUs count the trace unit's external outputs as the PMU common
events TRCEXTOUT0-3 (0x4010-0x4013), which lets a configuration drive a
PMU event from trace unit events. Other CPUs, Neoverse N1 for example,
have no such events, and a feature relying on them would silently do
nothing there.

Detect at probe, on the trace unit's CPU, whether the PMU counts every
external output: the trace unit has an external output for each of its
events (caps.nr_event), and pmuv3_event_implemented() reports whether
the PMU implements TRCEXTOUTn. Only check ETE: per its specification, an
implemented TRCEXTOUTn event counts external output n, while whether that
output is also an external input is IMPLEMENTATION DEFINED.

Add a CS_CFG_MATCH_CAP_TRCEXTOUT capability match flag, set it on those
trace units, and show it in the feature's configfs 'matches' attribute.
With capabilities matched separately from the device class, a feature
that requires it only loads on those trace units.

Assisted-by: Devmate:Opus-5.5
Signed-off-by: Amir Ayupov <aaupov at fb.com>
---
 .../hwtracing/coresight/coresight-config.h    |  2 ++
 .../hwtracing/coresight/coresight-etm4x-cfg.c |  6 ++++-
 .../coresight/coresight-etm4x-core.c          | 26 +++++++++++++++++++
 drivers/hwtracing/coresight/coresight-etm4x.h |  3 +++
 .../coresight/coresight-syscfg-configfs.c     |  3 +++
 5 files changed, 39 insertions(+), 1 deletion(-)

diff --git a/drivers/hwtracing/coresight/coresight-config.h b/drivers/hwtracing/coresight/coresight-config.h
index 220bc54f8e5e1..4cf53230854d0 100644
--- a/drivers/hwtracing/coresight/coresight-config.h
+++ b/drivers/hwtracing/coresight/coresight-config.h
@@ -38,6 +38,8 @@
  * a device that matches one of its classes and has all of its capabilities.
  */
 #define CS_CFG_MATCH_CAP_MASK		GENMASK_U32(15, 8)
+/* the PMU counts the trace unit's external outputs as TRCEXTOUTn */
+#define CS_CFG_MATCH_CAP_TRCEXTOUT	BIT(8)
 
 /*
  * Limit number of presets in a configuration
diff --git a/drivers/hwtracing/coresight/coresight-etm4x-cfg.c b/drivers/hwtracing/coresight/coresight-etm4x-cfg.c
index 52cb036bb04b9..9e4dc5950c13d 100644
--- a/drivers/hwtracing/coresight/coresight-etm4x-cfg.c
+++ b/drivers/hwtracing/coresight/coresight-etm4x-cfg.c
@@ -176,9 +176,13 @@ static int etm4_cfg_load_feature(struct coresight_device *csdev,
 
 int etm4_cscfg_register(struct coresight_device *csdev)
 {
+	struct etmv4_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
 	struct cscfg_csdev_feat_ops ops;
+	u32 match_flags = CS_CFG_ETM4_MATCH_FLAGS;
 
 	ops.load_feat = &etm4_cfg_load_feature;
+	if (drvdata->caps.trcextout)
+		match_flags |= CS_CFG_MATCH_CAP_TRCEXTOUT;
 
-	return cscfg_register_csdev(csdev, CS_CFG_ETM4_MATCH_FLAGS, &ops);
+	return cscfg_register_csdev(csdev, match_flags, &ops);
 }
diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c
index af017bd8a5477..cb5fbb0279b88 100644
--- a/drivers/hwtracing/coresight/coresight-etm4x-core.c
+++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c
@@ -30,6 +30,7 @@
 #include <linux/uaccess.h>
 #include <linux/perf_event.h>
 #include <linux/perf/arm_pmu.h>
+#include <linux/perf/arm_pmuv3.h>
 #include <linux/platform_device.h>
 #include <linux/pm_runtime.h>
 #include <linux/property.h>
@@ -1399,6 +1400,29 @@ static void etm4_fixup_wrong_ccitmin(struct etmv4_caps *caps)
 	}
 }
 
+/*
+ * Whether the PMU counts each external output of this trace unit as
+ * TRCEXTOUTn. The trace unit has an external output for each of its events.
+ * Only ETE is checked: per its specification, an implemented TRCEXTOUTn event
+ * counts external output n.
+ *
+ * Must run on the CPU that owns the trace unit.
+ */
+static bool etm4_pmu_counts_extout(struct etmv4_drvdata *drvdata)
+{
+	int n;
+
+	if (!etm4x_is_ete(drvdata) || !drvdata->caps.nr_event)
+		return false;
+
+	for (n = 0; n < drvdata->caps.nr_event; n++) {
+		if (!pmuv3_event_implemented(ARMV8_PMUV3_PERFCTR_TRCEXTOUT0 + n))
+			return false;
+	}
+
+	return true;
+}
+
 static void etm4_init_arch_data(void *info)
 {
 	u32 etmidr0;
@@ -1562,6 +1586,8 @@ static void etm4_init_arch_data(void *info)
 	/* NUMCNTR, bits[30:28] number of counters available for tracing */
 	caps->nr_cntr = FIELD_GET(TRCIDR5_NUMCNTR_MASK, etmidr5);
 
+	caps->trcextout = etm4_pmu_counts_extout(drvdata);
+
 	coresight_clear_self_claim_tag_unlocked(csa);
 	etm4_cs_lock(drvdata, csa);
 	cpu_detect_trace_filtering(drvdata);
diff --git a/drivers/hwtracing/coresight/coresight-etm4x.h b/drivers/hwtracing/coresight/coresight-etm4x.h
index 5417280cdb274..33994ad4b2641 100644
--- a/drivers/hwtracing/coresight/coresight-etm4x.h
+++ b/drivers/hwtracing/coresight/coresight-etm4x.h
@@ -868,6 +868,8 @@ enum etm_impdef_type {
  * @lpoverride:	If the implementation can support low-power state over.
  * @skip_power_up: Indicates if an implementation can skip powering up
  *		   the trace unit.
+ * @trcextout:	The trace unit is an ETE whose PMU counts its external
+ *		outputs as TRCEXTOUTn.
  */
 struct etmv4_caps {
 	u8	nr_pe;
@@ -907,6 +909,7 @@ struct etmv4_caps {
 	bool	atbtrig : 1;
 	bool	lpoverride : 1;
 	bool	skip_power_up : 1;
+	bool	trcextout : 1;
 };
 
 /**
diff --git a/drivers/hwtracing/coresight/coresight-syscfg-configfs.c b/drivers/hwtracing/coresight/coresight-syscfg-configfs.c
index 2b40e556be872..7b3800138f625 100644
--- a/drivers/hwtracing/coresight/coresight-syscfg-configfs.c
+++ b/drivers/hwtracing/coresight/coresight-syscfg-configfs.c
@@ -250,6 +250,9 @@ static ssize_t cscfg_feat_matches_show(struct config_item *item, char *page)
 	if (match_flags & CS_CFG_MATCH_CLASS_SRC_ETM4)
 		used += scnprintf(page + used, PAGE_SIZE - used, "SRC_ETMV4 ");
 
+	if (match_flags & CS_CFG_MATCH_CAP_TRCEXTOUT)
+		used += scnprintf(page + used, PAGE_SIZE - used, "TRCEXTOUT ");
+
 	used += scnprintf(page + used, PAGE_SIZE - used, "\n");
 	return used;
 }
-- 
2.52.0