linux-kernel - [PATCH v2 22/28] coresight: Add 'in_idle' argument to path enable/disable functions

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20250701-arm_cs_pm_fix_v3-v2-22-23ebb864fcc1@arm.com>
Date: Tue, 01 Jul 2025 15:53:47 +0100
From: Leo Yan <leo.yan@....com>
To: Suzuki K Poulose <suzuki.poulose@....com>, 
 Mike Leach <mike.leach@...aro.org>, James Clark <james.clark@...aro.org>, 
 Levi Yun <yeoreum.yun@....com>, 
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>, 
 Yabin Cui <yabinc@...gle.com>, Keita Morisaki <keyz@...gle.com>, 
 Yuanfang Zhang <quic_yuanfang@...cinc.com>
Cc: coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org, 
 linux-kernel@...r.kernel.org, Leo Yan <leo.yan@....com>
Subject: [PATCH v2 22/28] coresight: Add 'in_idle' argument to path
 enable/disable functions

Introduce an in_idle argument to the path enable and disable functions.
When set to true, it skips to touch the sink device. To avoid invoking
sink related helpers, the condition check is moved before the enable
helpers are called.

This is a preparation for managing the path during CPU idle.

Signed-off-by: Leo Yan <leo.yan@....com>
---
 drivers/hwtracing/coresight/coresight-core.c | 29 +++++++++++++++++++---------
 1 file changed, 20 insertions(+), 9 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c
index ef2a0de366d9b12b4f609027c8b67f690cf84558..b1c122d1c4164e3ca6f1aaad0bd24917032626be 100644
--- a/drivers/hwtracing/coresight/coresight-core.c
+++ b/drivers/hwtracing/coresight/coresight-core.c
@@ -477,7 +477,8 @@ static void coresight_restore_source(struct coresight_device *csdev)
  * disabled.
  */
 static void coresight_disable_path_from(struct coresight_path *path,
-					struct coresight_node *nd)
+					struct coresight_node *nd,
+					bool in_idle)
 {
 	u32 type;
 	struct coresight_device *csdev, *parent, *child;
@@ -500,6 +501,10 @@ static void coresight_disable_path_from(struct coresight_path *path,
 						CORESIGHT_DEV_TYPE_SINK :
 						CORESIGHT_DEV_TYPE_LINK;
 
+		/* To reduce latency, CPU idle does not touch the sink */
+		if (in_idle && type == CORESIGHT_DEV_TYPE_SINK)
+			continue;
+
 		switch (type) {
 		case CORESIGHT_DEV_TYPE_SINK:
 			coresight_disable_sink(csdev);
@@ -535,7 +540,7 @@ void coresight_disable_path(struct coresight_path *path)
 	if (coresight_is_percpu_source(source))
 		per_cpu(csdev_cpu_path, source->cpu) = NULL;
 
-	coresight_disable_path_from(path, NULL);
+	coresight_disable_path_from(path, NULL, false);
 }
 EXPORT_SYMBOL_GPL(coresight_disable_path);
 
@@ -559,7 +564,8 @@ static int coresight_enable_helpers(struct coresight_device *csdev,
 }
 
 static int _coresight_enable_path(struct coresight_path *path,
-				  enum cs_mode mode, void *sink_data)
+				  enum cs_mode mode, void *sink_data,
+				  bool in_idle)
 {
 	int ret = 0;
 	u32 type;
@@ -572,10 +578,6 @@ static int _coresight_enable_path(struct coresight_path *path,
 		csdev = nd->csdev;
 		type = csdev->type;
 
-		/* Enable all helpers adjacent to the path first */
-		ret = coresight_enable_helpers(csdev, mode, path);
-		if (ret)
-			goto err_disable_path;
 		/*
 		 * ETF devices are tricky... They can be a link or a sink,
 		 * depending on how they are configured.  If an ETF has been
@@ -587,6 +589,15 @@ static int _coresight_enable_path(struct coresight_path *path,
 						CORESIGHT_DEV_TYPE_SINK :
 						CORESIGHT_DEV_TYPE_LINK;
 
+		/* To reduce latency, CPU idle does not touch the sink */
+		if (in_idle && type == CORESIGHT_DEV_TYPE_SINK)
+			continue;
+
+		/* Enable all helpers adjacent to the path first */
+		ret = coresight_enable_helpers(csdev, mode, path);
+		if (ret)
+			goto err_disable_path;
+
 		switch (type) {
 		case CORESIGHT_DEV_TYPE_SINK:
 			ret = coresight_enable_sink(csdev, mode, sink_data);
@@ -622,7 +633,7 @@ static int _coresight_enable_path(struct coresight_path *path,
 err_disable_helpers:
 	coresight_disable_helpers(csdev, path);
 err_disable_path:
-	coresight_disable_path_from(path, nd);
+	coresight_disable_path_from(path, nd, false);
 	goto out;
 }
 
@@ -632,7 +643,7 @@ int coresight_enable_path(struct coresight_path *path, enum cs_mode mode,
 	int ret;
 	struct coresight_device *source;
 
-	ret = _coresight_enable_path(path, mode, sink_data);
+	ret = _coresight_enable_path(path, mode, sink_data, false);
 	if (ret)
 		return ret;
 

-- 
2.34.1