[PATCH RFC v2 2/2] hwspinlock: qcom: Lock #7 is special lock, uses dynamic proc_id

Lina Iyer
2015-06-09T16:25:20Z

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.

Declare lock #7 as raw capable, so the hwspinlock framework would not
enfore acquiring a s/w spinlock before acquiring the hwspinlock.

Cc: Jeffrey Hugo <jhugo@codeaurora.org>
Cc: Bjorn Andersson <bjorn.andersson@sonymobile.com>
Cc: Andy Gross <agross@codeaurora.org>
Signed-off-by: Lina Iyer <lina.iyer@linaro.org>
---
drivers/hwspinlock/qcom_hwspinlock.c | 22 +++++++++++++++++-----
1 file changed, 17 insertions(+), 5 deletions(-)

diff --git a/drivers/hwspinlock/qcom_hwspinlock.c b/drivers/hwspinlock/qcom_hwspinlock.c
index 93b62e0..59278b0 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);
}
@@ -129,6 +139,8 @@ static int qcom_hwspinlock_probe(struct platform_device *pdev)
regmap, field);
}

+ bank->lock[QCOM_CPUIDLE_LOCK].hwcaps = HWL_CAP_ALLOW_RAW;
+
pm_runtime_enable(&pdev->dev);

ret = hwspin_lock_register(bank, &pdev->dev, &qcom_hwspinlock_ops,
--
2.1.4