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authorBaolin Wang <baolin.wang@linaro.org>2018-04-08 06:06:57 +0300
committerBjorn Andersson <bjorn.andersson@linaro.org>2018-04-18 00:49:21 +0300
commit1e6c06a7e88c251d8a30271ad5206fbd967a4576 (patch)
tree42921ec0798d2d306cec575c10f7b9317cac9b56
parent66742b19e5e0d01297d355cc445d4920b648821b (diff)
downloadlinux-1e6c06a7e88c251d8a30271ad5206fbd967a4576.tar.xz
hwspinlock: Introduce one new mode for hwspinlock
In some scenarios, user need do some time-consuming or sleepable operations under the hardware spinlock protection for synchronization between the multiple subsystems. For example, there is one PMIC efuse on Spreadtrum platform, which need to be accessed under one hardware lock. But during the hardware lock protection, the efuse operation is time-consuming to almost 5 ms, so we can not disable the interrupts or preemption so long in this case. Thus we can introduce one new mode to indicate that we just acquire the hardware lock and do not disable interrupts or preemption, meanwhile we should force user to protect the hardware lock with mutex or spinlock to avoid dead-lock. Signed-off-by: Baolin Wang <baolin.wang@linaro.org> Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
-rw-r--r--drivers/hwspinlock/hwspinlock_core.c34
-rw-r--r--include/linux/hwspinlock.h58
2 files changed, 85 insertions, 7 deletions
diff --git a/drivers/hwspinlock/hwspinlock_core.c b/drivers/hwspinlock/hwspinlock_core.c
index f4a59f5631e4..5278d0560a4a 100644
--- a/drivers/hwspinlock/hwspinlock_core.c
+++ b/drivers/hwspinlock/hwspinlock_core.c
@@ -71,10 +71,16 @@ static DEFINE_MUTEX(hwspinlock_tree_lock);
* This function attempts to lock an hwspinlock, and will immediately
* fail if the hwspinlock is already taken.
*
- * Upon a successful return from this function, preemption (and possibly
- * interrupts) is disabled, so the caller must not sleep, and is advised to
- * release the hwspinlock as soon as possible. This is required in order to
- * minimize remote cores polling on the hardware interconnect.
+ * Caution: If the mode is HWLOCK_RAW, that means user must protect the routine
+ * of getting hardware lock with mutex or spinlock. Since in some scenarios,
+ * user need some time-consuming or sleepable operations under the hardware
+ * lock, they need one sleepable lock (like mutex) to protect the operations.
+ *
+ * If the mode is not HWLOCK_RAW, upon a successful return from this function,
+ * preemption (and possibly interrupts) is disabled, so the caller must not
+ * sleep, and is advised to release the hwspinlock as soon as possible. This is
+ * required in order to minimize remote cores polling on the hardware
+ * interconnect.
*
* The user decides whether local interrupts are disabled or not, and if yes,
* whether he wants their previous state to be saved. It is up to the user
@@ -113,6 +119,9 @@ int __hwspin_trylock(struct hwspinlock *hwlock, int mode, unsigned long *flags)
case HWLOCK_IRQ:
ret = spin_trylock_irq(&hwlock->lock);
break;
+ case HWLOCK_RAW:
+ ret = 1;
+ break;
default:
ret = spin_trylock(&hwlock->lock);
break;
@@ -134,6 +143,9 @@ int __hwspin_trylock(struct hwspinlock *hwlock, int mode, unsigned long *flags)
case HWLOCK_IRQ:
spin_unlock_irq(&hwlock->lock);
break;
+ case HWLOCK_RAW:
+ /* Nothing to do */
+ break;
default:
spin_unlock(&hwlock->lock);
break;
@@ -170,9 +182,14 @@ EXPORT_SYMBOL_GPL(__hwspin_trylock);
* is already taken, the function will busy loop waiting for it to
* be released, but give up after @timeout msecs have elapsed.
*
- * Upon a successful return from this function, preemption is disabled
- * (and possibly local interrupts, too), so the caller must not sleep,
- * and is advised to release the hwspinlock as soon as possible.
+ * Caution: If the mode is HWLOCK_RAW, that means user must protect the routine
+ * of getting hardware lock with mutex or spinlock. Since in some scenarios,
+ * user need some time-consuming or sleepable operations under the hardware
+ * lock, they need one sleepable lock (like mutex) to protect the operations.
+ *
+ * If the mode is not HWLOCK_RAW, upon a successful return from this function,
+ * preemption is disabled (and possibly local interrupts, too), so the caller
+ * must not sleep, and is advised to release the hwspinlock as soon as possible.
* This is required in order to minimize remote cores polling on the
* hardware interconnect.
*
@@ -266,6 +283,9 @@ void __hwspin_unlock(struct hwspinlock *hwlock, int mode, unsigned long *flags)
case HWLOCK_IRQ:
spin_unlock_irq(&hwlock->lock);
break;
+ case HWLOCK_RAW:
+ /* Nothing to do */
+ break;
default:
spin_unlock(&hwlock->lock);
break;
diff --git a/include/linux/hwspinlock.h b/include/linux/hwspinlock.h
index 859d673d98c8..fe450ee58d55 100644
--- a/include/linux/hwspinlock.h
+++ b/include/linux/hwspinlock.h
@@ -24,6 +24,7 @@
/* hwspinlock mode argument */
#define HWLOCK_IRQSTATE 0x01 /* Disable interrupts, save state */
#define HWLOCK_IRQ 0x02 /* Disable interrupts, don't save state */
+#define HWLOCK_RAW 0x03
struct device;
struct device_node;
@@ -176,6 +177,25 @@ static inline int hwspin_trylock_irq(struct hwspinlock *hwlock)
}
/**
+ * hwspin_trylock_raw() - attempt to lock a specific hwspinlock
+ * @hwlock: an hwspinlock which we want to trylock
+ *
+ * This function attempts to lock an hwspinlock, and will immediately fail
+ * if the hwspinlock is already taken.
+ *
+ * Caution: User must protect the routine of getting hardware lock with mutex
+ * or spinlock to avoid dead-lock, that will let user can do some time-consuming
+ * or sleepable operations under the hardware lock.
+ *
+ * Returns 0 if we successfully locked the hwspinlock, -EBUSY if
+ * the hwspinlock was already taken, and -EINVAL if @hwlock is invalid.
+ */
+static inline int hwspin_trylock_raw(struct hwspinlock *hwlock)
+{
+ return __hwspin_trylock(hwlock, HWLOCK_RAW, NULL);
+}
+
+/**
* hwspin_trylock() - attempt to lock a specific hwspinlock
* @hwlock: an hwspinlock which we want to trylock
*
@@ -243,6 +263,29 @@ int hwspin_lock_timeout_irq(struct hwspinlock *hwlock, unsigned int to)
}
/**
+ * hwspin_lock_timeout_raw() - lock an hwspinlock with timeout limit
+ * @hwlock: the hwspinlock to be locked
+ * @to: timeout value in msecs
+ *
+ * This function locks the underlying @hwlock. If the @hwlock
+ * is already taken, the function will busy loop waiting for it to
+ * be released, but give up when @timeout msecs have elapsed.
+ *
+ * Caution: User must protect the routine of getting hardware lock with mutex
+ * or spinlock to avoid dead-lock, that will let user can do some time-consuming
+ * or sleepable operations under the hardware lock.
+ *
+ * Returns 0 when the @hwlock was successfully taken, and an appropriate
+ * error code otherwise (most notably an -ETIMEDOUT if the @hwlock is still
+ * busy after @timeout msecs). The function will never sleep.
+ */
+static inline
+int hwspin_lock_timeout_raw(struct hwspinlock *hwlock, unsigned int to)
+{
+ return __hwspin_lock_timeout(hwlock, to, HWLOCK_RAW, NULL);
+}
+
+/**
* hwspin_lock_timeout() - lock an hwspinlock with timeout limit
* @hwlock: the hwspinlock to be locked
* @to: timeout value in msecs
@@ -302,6 +345,21 @@ static inline void hwspin_unlock_irq(struct hwspinlock *hwlock)
}
/**
+ * hwspin_unlock_raw() - unlock hwspinlock
+ * @hwlock: a previously-acquired hwspinlock which we want to unlock
+ *
+ * This function will unlock a specific hwspinlock.
+ *
+ * @hwlock must be already locked (e.g. by hwspin_trylock()) before calling
+ * this function: it is a bug to call unlock on a @hwlock that is already
+ * unlocked.
+ */
+static inline void hwspin_unlock_raw(struct hwspinlock *hwlock)
+{
+ __hwspin_unlock(hwlock, HWLOCK_RAW, NULL);
+}
+
+/**
* hwspin_unlock() - unlock hwspinlock
* @hwlock: a previously-acquired hwspinlock which we want to unlock
*