linux-kernel - [PATCH 8/8] coresight: cti: Refactor cti_reg32

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Message-Id: <20260209-arm_coresight_cti_refactor_v1-v1-8-db71ab4d200b@arm.com>
Date: Mon, 09 Feb 2026 18:01:18 +0000
From: Leo Yan <leo.yan@....com>
To: Suzuki K Poulose <suzuki.poulose@....com>, 
 Mike Leach <mike.leach@....com>, James Clark <james.clark@...aro.org>, 
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>, 
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
 Mathieu Poirier <mathieu.poirier@...aro.org>, 
 Tingwei Zhang <quic_tingwei@...cinc.com>, 
 Yingchao Deng <yingchao.deng@....qualcomm.com>, 
 Jie Gan <jie.gan@....qualcomm.com>
Cc: coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org, 
 linux-kernel@...r.kernel.org, Leo Yan <leo.yan@....com>
Subject: [PATCH 8/8] coresight: cti: Refactor cti_reg32_{show|store}()

Return an error for any negative offset.  Since the cached value is used
to store user config, it is not updated when reading back the register
in cti_reg32_show().

Signed-off-by: Leo Yan <leo.yan@....com>
---
 drivers/hwtracing/coresight/coresight-cti-sysfs.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-cti-sysfs.c b/drivers/hwtracing/coresight/coresight-cti-sysfs.c
index 9ef44956ebdc7781717d773fa014165989df2048..baac2a5dd467032fafbc6523d8885de59cb2665b 100644
--- a/drivers/hwtracing/coresight/coresight-cti-sysfs.c
+++ b/drivers/hwtracing/coresight/coresight-cti-sysfs.c
@@ -252,14 +252,14 @@ static ssize_t cti_reg32_show(struct device *dev, char *buf,
 	struct cti_drvdata *drvdata = dev_get_drvdata(dev->parent);
 	struct cti_config *config = &drvdata->config;
 
+	if (reg_offset < 0)
+		return -EINVAL;
+
 	scoped_guard(raw_spinlock_irqsave, &drvdata->spinlock) {
-		if ((reg_offset >= 0) && cti_is_active(config)) {
+		if (cti_is_active(config))
 			val = cti_read_single_reg(drvdata, reg_offset);
-			if (pcached_val)
-				*pcached_val = val;
-		} else if (pcached_val) {
+		else if (pcached_val)
 			val = *pcached_val;
-		}
 	}
 
 	return sprintf(buf, "%#x\n", val);
@@ -280,13 +280,16 @@ static ssize_t cti_reg32_store(struct device *dev, const char *buf,
 	if (kstrtoul(buf, 0, &val))
 		return -EINVAL;
 
+	if (reg_offset < 0)
+		return -EINVAL;
+
 	scoped_guard(raw_spinlock_irqsave, &drvdata->spinlock) {
 		/* local store */
 		if (pcached_val)
 			*pcached_val = (u32)val;
 
 		/* write through if offset and enabled */
-		if ((reg_offset >= 0) && cti_is_active(config))
+		if (cti_is_active(config))
 			cti_write_single_reg(drvdata, reg_offset, val);
 	}
 

-- 
2.34.1