[PATCH] coresight-tmc: stop disabling tmc when flush timeout

[Yuanfang Zhang <quic_yuanfang@quicinc.com>]

When multiple ETMs are enabled simultaneously, the time required
to complete a flush in the process of reading the TMC device node
may exceed the default wait time of 100us. If the TMC capture is
stopped while any ETM has not completed its flush, it can cause
the corresponding CPU to hang.
Fix the by checking the TMCReady bit after the flush. If TMCReady
bit is set, TraceCaptEn bit can be clear; otherwise, return directly
and stop the TMC read.

Signed-off-by: Yuanfang Zhang <quic_yuanfang@quicinc.com>
---
 drivers/hwtracing/coresight/coresight-tmc-etf.c | 17 +++++++++++++++--
 drivers/hwtracing/coresight/coresight-tmc-etr.c | 22 +++++++++++++++++-----
 2 files changed, 32 insertions(+), 7 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-tmc-etf.c b/drivers/hwtracing/coresight/coresight-tmc-etf.c
index d4f641cd9de69488fe3d1c1dc9b5a9eafb55ed59..bded290c42891d782344d9a6e63ebdbed6719133 100644
--- a/drivers/hwtracing/coresight/coresight-tmc-etf.c
+++ b/drivers/hwtracing/coresight/coresight-tmc-etf.c
@@ -80,11 +80,21 @@ static void tmc_etb_dump_hw(struct tmc_drvdata *drvdata)
 	return;
 }
 
-static void __tmc_etb_disable_hw(struct tmc_drvdata *drvdata)
+static int __tmc_etb_disable_hw(struct tmc_drvdata *drvdata)
 {
+	int rc;
+
 	CS_UNLOCK(drvdata->base);
 
 	tmc_flush_and_stop(drvdata);
+
+	rc = tmc_wait_for_tmcready(drvdata);
+	if (rc) {
+		dev_err(&drvdata->csdev->dev,
+			"Failed to disable : TMC is not ready\n");
+		CS_LOCK(drvdata->base);
+		return rc;
+	}
 	/*
 	 * When operating in sysFS mode the content of the buffer needs to be
 	 * read before the TMC is disabled.
@@ -94,6 +104,7 @@ static void __tmc_etb_disable_hw(struct tmc_drvdata *drvdata)
 	tmc_disable_hw(drvdata);
 
 	CS_LOCK(drvdata->base);
+	return 0;
 }
 
 static void tmc_etb_disable_hw(struct tmc_drvdata *drvdata)
@@ -650,7 +661,9 @@ int tmc_read_prepare_etb(struct tmc_drvdata *drvdata)
 			ret = -EINVAL;
 			goto out;
 		}
-		__tmc_etb_disable_hw(drvdata);
+		ret = __tmc_etb_disable_hw(drvdata);
+		if (ret)
+			goto out;
 	}
 
 	drvdata->reading = true;
diff --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c b/drivers/hwtracing/coresight/coresight-tmc-etr.c
index a48bb85d0e7f44a25b813f3c828cc3d705d16012..63a1f7501562fa0b5c2fe6ea53dce4d82842bec3 100644
--- a/drivers/hwtracing/coresight/coresight-tmc-etr.c
+++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c
@@ -1135,11 +1135,21 @@ static void tmc_etr_sync_sysfs_buf(struct tmc_drvdata *drvdata)
 	}
 }
 
-static void __tmc_etr_disable_hw(struct tmc_drvdata *drvdata)
+static int __tmc_etr_disable_hw(struct tmc_drvdata *drvdata)
 {
+	int rc;
+
 	CS_UNLOCK(drvdata->base);
 
 	tmc_flush_and_stop(drvdata);
+
+	rc = tmc_wait_for_tmcready(drvdata);
+	if (rc) {
+		dev_err(&drvdata->csdev->dev,
+			"Failed to disable : TMC is not ready\n");
+		CS_LOCK(drvdata->base);
+		return rc;
+	}
 	/*
 	 * When operating in sysFS mode the content of the buffer needs to be
 	 * read before the TMC is disabled.
@@ -1150,7 +1160,7 @@ static void __tmc_etr_disable_hw(struct tmc_drvdata *drvdata)
 	tmc_disable_hw(drvdata);
 
 	CS_LOCK(drvdata->base);
-
+	return 0;
 }
 
 void tmc_etr_disable_hw(struct tmc_drvdata *drvdata)
@@ -1779,9 +1789,11 @@ int tmc_read_prepare_etr(struct tmc_drvdata *drvdata)
 	}
 
 	/* Disable the TMC if we are trying to read from a running session. */
-	if (coresight_get_mode(drvdata->csdev) == CS_MODE_SYSFS)
-		__tmc_etr_disable_hw(drvdata);
-
+	if (coresight_get_mode(drvdata->csdev) == CS_MODE_SYSFS) {
+		ret = __tmc_etr_disable_hw(drvdata);
+		if (ret)
+			goto out;
+	}
 	drvdata->reading = true;
 out:
 	spin_unlock_irqrestore(&drvdata->spinlock, flags);

---
base-commit: fac04efc5c793dccbd07e2d59af9f90b7fc0dca4
change-id: 20250103-fix_cpu_hung-b5a95179ada4

Best regards,
-- 
Yuanfang Zhang <quic_yuanfang@quicinc.com>