linux-kernel - [PATCH v4 06/13] coresight: Interpret ETMv3 config with ATTR_CFG_GET

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Message-Id: <20251112-james-cs-syncfreq-v4-6-165ba21401dc@linaro.org>
Date: Wed, 12 Nov 2025 15:22:12 +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>
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 v4 06/13] coresight: Interpret ETMv3 config with
 ATTR_CFG_GET_FLD()

Currently we're programming attr->config directly into ETMCR after some
validation. This obscures which fields are being used, and also makes it
impossible to move fields around or use other configN fields in the
future.

Improve it by only reading the fields that are valid and then setting
the appropriate ETMCR bits based on each one.

The ETMCR_CTXID_SIZE part can be removed as it was never a valid option
because it's not in ETM3X_SUPPORTED_OPTIONS.

Signed-off-by: James Clark <james.clark@...aro.org>
---
 drivers/hwtracing/coresight/coresight-etm3x-core.c | 24 ++++++++++++----------
 1 file changed, 13 insertions(+), 11 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-etm3x-core.c b/drivers/hwtracing/coresight/coresight-etm3x-core.c
index a5e809589d3e..4511fc2f8d72 100644
--- a/drivers/hwtracing/coresight/coresight-etm3x-core.c
+++ b/drivers/hwtracing/coresight/coresight-etm3x-core.c
@@ -28,6 +28,7 @@
 #include <linux/uaccess.h>
 #include <linux/clk.h>
 #include <linux/perf_event.h>
+#include <linux/perf/arm_pmu.h>
 #include <asm/sections.h>
 
 #include "coresight-etm.h"
@@ -339,21 +340,22 @@ static int etm_parse_event_config(struct etm_drvdata *drvdata,
 	if (attr->config & ~ETM3X_SUPPORTED_OPTIONS)
 		return -EINVAL;
 
-	config->ctrl = attr->config;
+	config->ctrl = 0;
 
-	/* Don't trace contextID when runs in non-root PID namespace */
-	if (!task_is_in_init_pid_ns(current))
-		config->ctrl &= ~ETMCR_CTXID_SIZE;
+	if (ATTR_CFG_GET_FLD(attr, cycacc))
+		config->ctrl |= ETMCR_CYC_ACC;
+
+	if (ATTR_CFG_GET_FLD(attr, timestamp))
+		config->ctrl |= ETMCR_TIMESTAMP_EN;
 
 	/*
-	 * Possible to have cores with PTM (supports ret stack) and ETM
-	 * (never has ret stack) on the same SoC. So if we have a request
-	 * for return stack that can't be honoured on this core then
-	 * clear the bit - trace will still continue normally
+	 * Possible to have cores with PTM (supports ret stack) and ETM (never
+	 * has ret stack) on the same SoC. So only enable when it can be honored
+	 * - trace will still continue normally otherwise.
 	 */
-	if ((config->ctrl & ETMCR_RETURN_STACK) &&
-	    !(drvdata->etmccer & ETMCCER_RETSTACK))
-		config->ctrl &= ~ETMCR_RETURN_STACK;
+	if (ATTR_CFG_GET_FLD(attr, retstack) &&
+	    (drvdata->etmccer & ETMCCER_RETSTACK))
+		config->ctrl |= ETMCR_RETURN_STACK;
 
 	return 0;
 }

-- 
2.34.1