linux-kernel - [PATCH v3 RESEND 02/10] coresight: core: add a new API to retrieve the helper device

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Message-Id: <20250714063109.591-3-jie.gan@oss.qualcomm.com>
Date: Mon, 14 Jul 2025 14:31:01 +0800
From: Jie Gan <jie.gan@....qualcomm.com>
To: Suzuki K Poulose <suzuki.poulose@....com>,
        Mike Leach <mike.leach@...aro.org>,
        James Clark <james.clark@...aro.org>, Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Tingwei Zhang <quic_tingweiz@...cinc.com>,
        Yuanfang Zhang <quic_yuanfang@...cinc.com>,
        Mao Jinlong <quic_jinlmao@...cinc.com>,
        Jie Gan <quic_jiegan@...cinc.com>
Cc: coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        devicetree@...r.kernel.org
Subject: [PATCH v3 RESEND 02/10] coresight: core: add a new API to retrieve the helper device

Retrieving the helper device of the specific coresight device based on
its helper_subtype because a single coresight device may has multiple types
of the helper devices.

Signed-off-by: Jie Gan <jie.gan@....qualcomm.com>
---
 drivers/hwtracing/coresight/coresight-core.c | 30 ++++++++++++++++++++
 drivers/hwtracing/coresight/coresight-priv.h |  2 ++
 2 files changed, 32 insertions(+)

diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c
index 5297a5ff7921..76e10c36a8a1 100644
--- a/drivers/hwtracing/coresight/coresight-core.c
+++ b/drivers/hwtracing/coresight/coresight-core.c
@@ -580,6 +580,36 @@ struct coresight_device *coresight_get_sink(struct coresight_path *path)
 }
 EXPORT_SYMBOL_GPL(coresight_get_sink);
 
+/**
+ * coresight_get_helper: find the helper device of the assigned csdev.
+ *
+ * @csdev: The csdev the helper device is conntected to.
+ * @type:  helper_subtype of the expected helper device.
+ *
+ * Retrieve the helper device for the specific csdev based on its
+ * helper_subtype.
+ *
+ * Return: the helper's csdev upon success or NULL for fail.
+ */
+struct coresight_device *coresight_get_helper(struct coresight_device *csdev,
+					      int type)
+{
+	int i;
+	struct coresight_device *helper;
+
+	for (i = 0; i < csdev->pdata->nr_outconns; ++i) {
+		helper = csdev->pdata->out_conns[i]->dest_dev;
+		if (!helper || !coresight_is_helper(helper))
+			continue;
+
+		if (helper->subtype.helper_subtype == type)
+			return helper;
+	}
+
+	return NULL;
+}
+EXPORT_SYMBOL_GPL(coresight_get_helper);
+
 /**
  * coresight_get_port_helper: get the in-port number of the helper device
  * that is connected to the csdev.
diff --git a/drivers/hwtracing/coresight/coresight-priv.h b/drivers/hwtracing/coresight/coresight-priv.h
index 07a5f03de81d..5b912eb60401 100644
--- a/drivers/hwtracing/coresight/coresight-priv.h
+++ b/drivers/hwtracing/coresight/coresight-priv.h
@@ -158,6 +158,8 @@ void coresight_path_assign_trace_id(struct coresight_path *path,
 				   enum cs_mode mode);
 int coresight_get_port_helper(struct coresight_device *csdev,
 			      struct coresight_device *helper);
+struct coresight_device *coresight_get_helper(struct coresight_device *csdev,
+					      int type);
 
 #if IS_ENABLED(CONFIG_CORESIGHT_SOURCE_ETM3X)
 int etm_readl_cp14(u32 off, unsigned int *val);
-- 
2.34.1