linux-kernel - [PATCH v3 1/3] coresight: Update timeout functions to allow return of test register value

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Message-Id: <20241218230118.999859-2-mike.leach@linaro.org>
Date: Wed, 18 Dec 2024 23:01:16 +0000
From: Mike Leach <mike.leach@...aro.org>
To: linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	coresight@...ts.linaro.org
Cc: james.clark@...aro.org,
	mike.leach@...aro.org,
	suzuki.poulose@....com,
	alexander.shishkin@...ux.intel.com
Subject: [PATCH v3 1/3] coresight: Update timeout functions to allow return of test register value

Current coresight_timeout function spins on a bit on a test register,
till bit value achieved or timeout hit.

Add another function to return the full value of the register being
tested.

Signed-off-by: Mike Leach <mike.leach@...aro.org>
---
 drivers/hwtracing/coresight/coresight-core.c | 50 +++++++++++++++-----
 include/linux/coresight.h                    |  2 +
 2 files changed, 41 insertions(+), 11 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c
index 0a9380350fb5..595f7ec0782f 100644
--- a/drivers/hwtracing/coresight/coresight-core.c
+++ b/drivers/hwtracing/coresight/coresight-core.c
@@ -1092,32 +1092,37 @@ static void coresight_remove_conns(struct coresight_device *csdev)
 }
 
 /**
- * coresight_timeout - loop until a bit has changed to a specific register
- *			state.
+ * coresight_timeout_retval - loop until a bit has changed to a specific register
+ *			      state. Optionally return final register value
  * @csa: coresight device access for the device
  * @offset: Offset of the register from the base of the device.
  * @position: the position of the bit of interest.
  * @value: the value the bit should have.
+ * @rval: if not NULL, return the last read value of the register being tested.
  *
  * Return: 0 as soon as the bit has taken the desired state or -EAGAIN if
  * TIMEOUT_US has elapsed, which ever happens first.
  */
-int coresight_timeout(struct csdev_access *csa, u32 offset,
-		      int position, int value)
+int coresight_timeout_retval(struct csdev_access *csa, u32 offset,
+			     int position, int value, u32 *rval)
 {
-	int i;
-	u32 val;
+	int i, rc = -EAGAIN;
+	u32 val = 0;
 
 	for (i = TIMEOUT_US; i > 0; i--) {
 		val = csdev_access_read32(csa, offset);
 		/* waiting on the bit to go from 0 to 1 */
 		if (value) {
-			if (val & BIT(position))
-				return 0;
+			if (val & BIT(position)) {
+				rc = 0;
+				goto return_rval;
+			}
 		/* waiting on the bit to go from 1 to 0 */
 		} else {
-			if (!(val & BIT(position)))
-				return 0;
+			if (!(val & BIT(position))) {
+				rc = 0;
+				goto return_rval;
+			}
 		}
 
 		/*
@@ -1129,7 +1134,30 @@ int coresight_timeout(struct csdev_access *csa, u32 offset,
 			udelay(1);
 	}
 
-	return -EAGAIN;
+return_rval:
+	/* return the register value used when terminating the test */
+	if (rval)
+		*rval = val;
+
+	return rc;
+}
+EXPORT_SYMBOL_GPL(coresight_timeout_retval);
+
+/**
+ * coresight_timeout - loop until a bit has changed to a specific register
+ *		       state
+ * @csa: coresight device access for the device
+ * @offset: Offset of the register from the base of the device.
+ * @position: the position of the bit of interest.
+ * @value: the value the bit should have.
+ *
+ * Return: 0 as soon as the bit has taken the desired state or -EAGAIN if
+ * TIMEOUT_US has elapsed, which ever happens first.
+ */
+int coresight_timeout(struct csdev_access *csa, u32 offset,
+		      int position, int value)
+{
+	return coresight_timeout_retval(csa, offset, position, value, NULL);
 }
 EXPORT_SYMBOL_GPL(coresight_timeout);
 
diff --git a/include/linux/coresight.h b/include/linux/coresight.h
index 17276965ff1d..cb3592d2803c 100644
--- a/include/linux/coresight.h
+++ b/include/linux/coresight.h
@@ -649,6 +649,8 @@ extern int coresight_enable_sysfs(struct coresight_device *csdev);
 extern void coresight_disable_sysfs(struct coresight_device *csdev);
 extern int coresight_timeout(struct csdev_access *csa, u32 offset,
 			     int position, int value);
+extern int coresight_timeout_retval(struct csdev_access *csa, u32 offset,
+				    int position, int value, u32 *rval);
 
 extern int coresight_claim_device(struct coresight_device *csdev);
 extern int coresight_claim_device_unlocked(struct coresight_device *csdev);
-- 
2.25.1