linux-kernel - [PATCH] hwspinlock: qcom: Lock #7 is special lock, uses dynamic proc

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Message-Id: <1430499992-47944-1-git-send-email-lina.iyer@linaro.org>
Date:	Fri,  1 May 2015 11:06:32 -0600
From:	Lina Iyer <lina.iyer@...aro.org>
To:	ohad@...ery.com, s-anna@...com, Bjorn.Andersson@...ymobile.com,
	agross@...eaurora.org
Cc:	linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
	galak@...eaurora.org, jhugo@...eaurora.org,
	Lina Iyer <lina.iyer@...aro.org>,
	Bjorn Andersson <bjorn.andersson@...ymobile.com>
Subject: [PATCH] hwspinlock: qcom: Lock #7 is special lock, uses dynamic proc_id

Hwspinlocks are widely used between processors in an SoC, and also
between elevation levels within in the same processor.  QCOM SoC's use
hwspinlock to serialize entry into a low power mode when the context
switches from Linux to secure monitor.

Lock #7 has been assigned for this purpose. In order to differentiate
between one cpu core holding a lock while another cpu is contending for
the same lock, the proc id written into the lock is (128 + cpu id). This
makes it unique value among the cpu cores and therefore when a core
locks the hwspinlock, other cores would wait for the lock to be released
since they would have a different proc id.  This value is specific for
the lock #7 only.

Cc: Jeffrey Hugo <jhugo@...eaurora.org>
Cc: Bjorn Andersson <bjorn.andersson@...ymobile.com>
Cc: Andy Gross <agross@...eaurora.org>
Signed-off-by: Lina Iyer <lina.iyer@...aro.org>
---
 drivers/hwspinlock/qcom_hwspinlock.c | 20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/drivers/hwspinlock/qcom_hwspinlock.c b/drivers/hwspinlock/qcom_hwspinlock.c
index 93b62e0..043c62c 100644
--- a/drivers/hwspinlock/qcom_hwspinlock.c
+++ b/drivers/hwspinlock/qcom_hwspinlock.c
@@ -25,16 +25,26 @@
 
 #include "hwspinlock_internal.h"
 
-#define QCOM_MUTEX_APPS_PROC_ID	1
-#define QCOM_MUTEX_NUM_LOCKS	32
+#define QCOM_MUTEX_APPS_PROC_ID		1
+#define QCOM_MUTEX_CPUIDLE_OFFSET	128
+#define QCOM_CPUIDLE_LOCK		7
+#define QCOM_MUTEX_NUM_LOCKS		32
+
+static inline u32 __qcom_get_proc_id(struct hwspinlock *lock)
+{
+	return hwspin_lock_get_id(lock) == QCOM_CPUIDLE_LOCK ?
+			(QCOM_MUTEX_CPUIDLE_OFFSET + smp_processor_id()) :
+			QCOM_MUTEX_APPS_PROC_ID;
+}
 
 static int qcom_hwspinlock_trylock(struct hwspinlock *lock)
 {
 	struct regmap_field *field = lock->priv;
 	u32 lock_owner;
 	int ret;
+	u32 proc_id = __qcom_get_proc_id(lock);
 
-	ret = regmap_field_write(field, QCOM_MUTEX_APPS_PROC_ID);
+	ret = regmap_field_write(field, proc_id);
 	if (ret)
 		return ret;
 
@@ -42,7 +52,7 @@ static int qcom_hwspinlock_trylock(struct hwspinlock *lock)
 	if (ret)
 		return ret;
 
-	return lock_owner == QCOM_MUTEX_APPS_PROC_ID;
+	return lock_owner == proc_id;
 }
 
 static void qcom_hwspinlock_unlock(struct hwspinlock *lock)
@@ -57,7 +67,7 @@ static void qcom_hwspinlock_unlock(struct hwspinlock *lock)
 		return;
 	}
 
-	if (lock_owner != QCOM_MUTEX_APPS_PROC_ID) {
+	if (lock_owner != __qcom_get_proc_id(lock)) {
 		pr_err("%s: spinlock not owned by us (actual owner is %d)\n",
 				__func__, lock_owner);
 	}
-- 
2.1.4

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