linux-kernel - [PATCH v11 20/24] coresight: cti: increase reference count when enabling cti

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Message-Id: <20200915104116.16789-21-tingwei@codeaurora.org>
Date:   Tue, 15 Sep 2020 18:41:12 +0800
From:   Tingwei Zhang <tingwei@...eaurora.org>
To:     Mathieu Poirier <mathieu.poirier@...aro.org>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Mike Leach <mike.leach@...aro.org>
Cc:     Tingwei Zhang <tingwei@...eaurora.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Leo Yan <leo.yan@...aro.org>,
        Randy Dunlap <rdunlap@...radead.org>,
        Russell King <linux@...linux.org.uk>,
        Kim Phillips <kim.phillips@....com>,
        Mian Yousaf Kaukab <ykaukab@...e.de>, tsoni@...eaurora.org,
        Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>,
        Mao Jinlong <jinlmao@...eaurora.org>,
        coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v11 20/24] coresight: cti: increase reference count when enabling cti

CTI device is enabled when associated coresight device is enabled.
Increase the module and device reference count for CTI device
when it's enabled. This can prevent CTI device be removed or
module be unloaded when CTI device is enabled by an active trace
session.

Signed-off-by: Mike Leach <mike.leach@...aro.org>
Signed-off-by: Tingwei Zhang <tingwei@...eaurora.org>
Reviewed-by: Mathieu Poirier <mathieu.poirier@...aro.org>
---
 drivers/hwtracing/coresight/coresight.c | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight.c b/drivers/hwtracing/coresight/coresight.c
index 711beb92166a..546c97045afe 100644
--- a/drivers/hwtracing/coresight/coresight.c
+++ b/drivers/hwtracing/coresight/coresight.c
@@ -241,19 +241,30 @@ coresight_control_assoc_ectdev(struct coresight_device *csdev, bool enable)
 {
 	int ect_ret = 0;
 	struct coresight_device *ect_csdev = csdev->ect_dev;
+	struct module *mod;
 
 	if (!ect_csdev)
 		return 0;
 	if ((!ect_ops(ect_csdev)->enable) || (!ect_ops(ect_csdev)->disable))
 		return 0;
 
+	mod = ect_csdev->dev.parent->driver->owner;
 	if (enable) {
-		ect_ret = ect_ops(ect_csdev)->enable(ect_csdev);
-		if (!ect_ret)
-			csdev->ect_enabled = true;
+		if (try_module_get(mod)) {
+			ect_ret = ect_ops(ect_csdev)->enable(ect_csdev);
+			if (ect_ret) {
+				module_put(mod);
+			} else {
+				get_device(ect_csdev->dev.parent);
+				csdev->ect_enabled = true;
+			}
+		} else
+			ect_ret = -ENODEV;
 	} else {
 		if (csdev->ect_enabled) {
 			ect_ret = ect_ops(ect_csdev)->disable(ect_csdev);
+			put_device(ect_csdev->dev.parent);
+			module_put(mod);
 			csdev->ect_enabled = false;
 		}
 	}
-- 
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