[PATCH v2] coresight: etm3x: Fix cntr_val_show() to match cntr_val_store() behavior

[Kuan-Wei Chiu]

The cntr_val_show() function was intended to print the values of all
counters using a loop. However, due to a buffer overwrite issue with
sprintf(), it effectively only displayed the value of the last counter.

The companion function, cntr_val_store(), allows users to modify a
specific counter selected by 'cntr_idx'. To maintain consistency
between read and write operations and to align with the ETM4x driver
behavior, modify cntr_val_show() to report only the value of the
currently selected counter.

This change removes the loop and the "counter %d:" prefix, printing
only the hexadecimal value. It also adopts sysfs_emit() for standard
sysfs output formatting.

Fixes: a939fc5a71ad ("coresight-etm: add CoreSight ETM/PTM driver")
Signed-off-by: Kuan-Wei Chiu <visitorckw at gmail.com>
---
Build test only.

Changes in v2:
- Redesigned the fix to match cntr_val_store() logic (display only the
  currently selected counter) instead of attempting to list all
  counters.
- Removed the loop and the "counter %d:" prefix.
- Switched from sprintf() to sysfs_emit().
- Refactored control flow to use a single return point.

v1: https://lore.kernel.org/lkml/20251121002350.1166758-1-visitorckw@gmail.com/

 .../hwtracing/coresight/coresight-etm3x-sysfs.c   | 15 ++++-----------
 1 file changed, 4 insertions(+), 11 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-etm3x-sysfs.c b/drivers/hwtracing/coresight/coresight-etm3x-sysfs.c
index 762109307b86..a6a650331196 100644
--- a/drivers/hwtracing/coresight/coresight-etm3x-sysfs.c
+++ b/drivers/hwtracing/coresight/coresight-etm3x-sysfs.c
@@ -717,26 +717,19 @@ static DEVICE_ATTR_RW(cntr_rld_event);
 static ssize_t cntr_val_show(struct device *dev,
 			     struct device_attribute *attr, char *buf)
 {
-	int i, ret = 0;
 	u32 val;
 	struct etm_drvdata *drvdata = dev_get_drvdata(dev->parent);
 	struct etm_config *config = &drvdata->config;
 
 	if (!coresight_get_mode(drvdata->csdev)) {
 		spin_lock(&drvdata->spinlock);
-		for (i = 0; i < drvdata->nr_cntr; i++)
-			ret += sprintf(buf, "counter %d: %x\n",
-				       i, config->cntr_val[i]);
+		val = config->cntr_val[config->cntr_idx];
 		spin_unlock(&drvdata->spinlock);
-		return ret;
-	}
-
-	for (i = 0; i < drvdata->nr_cntr; i++) {
-		val = etm_readl(drvdata, ETMCNTVRn(i));
-		ret += sprintf(buf, "counter %d: %x\n", i, val);
+	} else {
+		val = etm_readl(drvdata, ETMCNTVRn(config->cntr_idx));
 	}
 
-	return ret;
+	return sysfs_emit(buf, "%x\n", val);
 }
 
 static ssize_t cntr_val_store(struct device *dev,
-- 
2.52.0.487.g5c8c507ade-goog