linux-kernel - [PATCH 1/7] hwspinlock: Introduce refcount

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Message-ID: <20240516-hwspinlock-bust-v1-1-47a90a859238@quicinc.com>
Date: Thu, 16 May 2024 15:58:19 -0700
From: Chris Lew <quic_clew@...cinc.com>
To: Bjorn Andersson <andersson@...nel.org>,
        Baolin Wang
	<baolin.wang@...ux.alibaba.com>,
        Peter Zijlstra <peterz@...radead.org>,
        "Ingo
 Molnar" <mingo@...hat.com>, Will Deacon <will@...nel.org>,
        Waiman Long
	<longman@...hat.com>, Boqun Feng <boqun.feng@...il.com>,
        Jonathan Corbet
	<corbet@....net>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Rob Herring
	<robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley
	<conor+dt@...nel.org>,
        Manivannan Sadhasivam
	<manivannan.sadhasivam@...aro.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>
CC: <linux-remoteproc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-doc@...r.kernel.org>, <linux-arm-msm@...r.kernel.org>,
        <devicetree@...r.kernel.org>, Chris Lew <quic_clew@...cinc.com>,
        "Richard
 Maina" <quic_rmaina@...cinc.com>
Subject: [PATCH 1/7] hwspinlock: Introduce refcount

From: Richard Maina <quic_rmaina@...cinc.com>

Currently each device receives a dedicated hwspinlock that is not
accesible to other device drivers. In order to allow multiple consumers
access to the same hwspinlock, introduce a refcount to hwspinlock struct
and implement refcounting infrastructure.

Signed-off-by: Richard Maina <quic_rmaina@...cinc.com>
Signed-off-by: Chris Lew <quic_clew@...cinc.com>
---
 drivers/hwspinlock/hwspinlock_core.c     | 14 +++++++++-----
 drivers/hwspinlock/hwspinlock_internal.h |  2 ++
 2 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/drivers/hwspinlock/hwspinlock_core.c b/drivers/hwspinlock/hwspinlock_core.c
index 0c0a932c00f3..29b33072ff57 100644
--- a/drivers/hwspinlock/hwspinlock_core.c
+++ b/drivers/hwspinlock/hwspinlock_core.c
@@ -428,6 +428,7 @@ static int hwspin_lock_register_single(struct hwspinlock *hwlock, int id)
 	int ret;
 
 	mutex_lock(&hwspinlock_tree_lock);
+	hwlock->refcnt = 0;
 
 	ret = radix_tree_insert(&hwspinlock_tree, id, hwlock);
 	if (ret) {
@@ -671,6 +672,8 @@ static int __hwspin_lock_request(struct hwspinlock *hwlock)
 
 	ret = 0;
 
+	hwlock->refcnt++;
+
 	/* mark hwspinlock as used, should not fail */
 	tmp = radix_tree_tag_clear(&hwspinlock_tree, hwlock_to_id(hwlock),
 							HWSPINLOCK_UNUSED);
@@ -829,12 +832,13 @@ int hwspin_lock_free(struct hwspinlock *hwlock)
 	/* notify the underlying device that power is not needed */
 	pm_runtime_put(dev);
 
-	/* mark this hwspinlock as available */
-	tmp = radix_tree_tag_set(&hwspinlock_tree, hwlock_to_id(hwlock),
-							HWSPINLOCK_UNUSED);
+	if (--hwlock->refcnt == 0) {
+		/* mark this hwspinlock as available */
+		tmp = radix_tree_tag_set(&hwspinlock_tree, hwlock_to_id(hwlock), HWSPINLOCK_UNUSED);
 
-	/* sanity check (this shouldn't happen) */
-	WARN_ON(tmp != hwlock);
+		/* sanity check (this shouldn't happen) */
+		WARN_ON(tmp != hwlock);
+	}
 
 	module_put(dev->driver->owner);
 
diff --git a/drivers/hwspinlock/hwspinlock_internal.h b/drivers/hwspinlock/hwspinlock_internal.h
index 29892767bb7a..12f230b40693 100644
--- a/drivers/hwspinlock/hwspinlock_internal.h
+++ b/drivers/hwspinlock/hwspinlock_internal.h
@@ -35,11 +35,13 @@ struct hwspinlock_ops {
  * struct hwspinlock - this struct represents a single hwspinlock instance
  * @bank: the hwspinlock_device structure which owns this lock
  * @lock: initialized and used by hwspinlock core
+ * @refcnt: counter for the number of existing references to the hwspinlock
  * @priv: private data, owned by the underlying platform-specific hwspinlock drv
  */
 struct hwspinlock {
 	struct hwspinlock_device *bank;
 	spinlock_t lock;
+	unsigned int refcnt;
 	void *priv;
 };
 

-- 
2.25.1