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Subject[PATCH v4 2/2] ARM: cpuidle: make arm_cpuidle_suspend() a bit more efficient
Date
Currently, we check cpuidle_ops.suspend every time when entering a
low-power idle state. But this check could be avoided in this hot path
by moving it into arm_cpuidle_read_ops() to reduce arm_cpuidle_suspend
overhead a bit.

Signed-off-by: Jisheng Zhang <jszhang@marvell.com>
---
arch/arm/kernel/cpuidle.c | 17 ++++++-----------
1 file changed, 6 insertions(+), 11 deletions(-)

diff --git a/arch/arm/kernel/cpuidle.c b/arch/arm/kernel/cpuidle.c
index 2129b29..7dccc96 100644
--- a/arch/arm/kernel/cpuidle.c
+++ b/arch/arm/kernel/cpuidle.c
@@ -47,18 +47,13 @@ int arm_cpuidle_simple_enter(struct cpuidle_device *dev,
* This function calls the underlying arch specific low level PM code as
* registered at the init time.
*
- * Returns -EOPNOTSUPP if no suspend callback is defined, the result of the
- * callback otherwise.
+ * Returns the result of the suspend callback.
*/
int arm_cpuidle_suspend(int index)
{
- int ret = -EOPNOTSUPP;
int cpu = smp_processor_id();

- if (cpuidle_ops[cpu].suspend)
- ret = cpuidle_ops[cpu].suspend(index);
-
- return ret;
+ return cpuidle_ops[cpu].suspend(index);
}

/**
@@ -92,8 +87,8 @@ static const struct cpuidle_ops *__init arm_cpuidle_get_ops(const char *method)
* process.
*
* Return 0 on sucess, -ENOENT if no 'enable-method' is defined, -EOPNOTSUPP if
- * no cpuidle_ops is registered for the 'enable-method', or if no init callback
- * is defined.
+ * no cpuidle_ops is registered for the 'enable-method', or if either init or
+ * suspend callback isn't defined.
*/
static int __init arm_cpuidle_read_ops(struct device_node *dn, int cpu)
{
@@ -111,8 +106,8 @@ static int __init arm_cpuidle_read_ops(struct device_node *dn, int cpu)
return -EOPNOTSUPP;
}

- if (!ops->init) {
- pr_warn("cpuidle_ops '%s': no init callback\n",
+ if (!ops->init || !ops->suspend) {
+ pr_warn("cpuidle_ops '%s': no init or suspend callback\n",
enable_method);
return -EOPNOTSUPP;
}
--
2.8.1
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