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 <jh...@codeaurora.org>
Cc: Bjorn Andersson <bjorn.anders...@sonymobile.com>
Cc: Andy Gross <agr...@codeaurora.org>
Signed-off-by: Lina Iyer <lina.i...@linaro.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
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
