[V3,1/2] cpuidle: Simplify multiple driver support

Commit bf4d1b5ddb78f86078ac6ae0415802d5f0c68f92 brought the multiple driver
support. The code added a couple of new API to register the driver per cpu.
That led to some code complexity to handle the kernel config options when
the multiple driver support is enabled or not, which is not really necessary.
The code has to be compatible when the multiple driver support is not enabled,
and the multiple driver support has to be compatible with the old api.

This patch removes this API, which is not yet used by any driver but needed
for the HMP cpuidle drivers which will come soon, and replaces its usage
by a cpumask pointer in the cpuidle driver structure telling what cpus are
handled by the driver. That let the API cpuidle_[un]register_driver to be used
for the multiple driver support and also the cpuidle_[un]register functions,
added recently in the cpuidle framework.

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
---
[V3]
 - moved the kerneldoc and comments to a separate patch
[V2]:
 - fixed bad refcount check
 - inverted clockevent notify off order at unregister time

 drivers/cpuidle/cpuidle.c |    4 +-
 drivers/cpuidle/driver.c  |  196 ++++++++++++++++++---------------------------
 include/linux/cpuidle.h   |   21 ++---
 3 files changed, 93 insertions(+), 128 deletions(-)

On Thursday, June 06, 2013 01:40:30 PM Daniel Lezcano wrote:
> Commit bf4d1b5ddb78f86078ac6ae0415802d5f0c68f92 brought the multiple driver
> support. The code added a couple of new API to register the driver per cpu.
> That led to some code complexity to handle the kernel config options when
> the multiple driver support is enabled or not, which is not really necessary.
> The code has to be compatible when the multiple driver support is not enabled,
> and the multiple driver support has to be compatible with the old api.
> 
> This patch removes this API, which is not yet used by any driver but needed
> for the HMP cpuidle drivers which will come soon, and replaces its usage
> by a cpumask pointer in the cpuidle driver structure telling what cpus are
> handled by the driver. That let the API cpuidle_[un]register_driver to be used
> for the multiple driver support and also the cpuidle_[un]register functions,
> added recently in the cpuidle framework.
> 
> Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
> ---
> [V3]
>  - moved the kerneldoc and comments to a separate patch
> [V2]:
>  - fixed bad refcount check
>  - inverted clockevent notify off order at unregister time
> 
>  drivers/cpuidle/cpuidle.c |    4 +-
>  drivers/cpuidle/driver.c  |  196 ++++++++++++++++++---------------------------
>  include/linux/cpuidle.h   |   21 ++---
>  3 files changed, 93 insertions(+), 128 deletions(-)
> 
> diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
> index c3a93fe..fdc432f 100644
> --- a/drivers/cpuidle/cpuidle.c
> +++ b/drivers/cpuidle/cpuidle.c
> @@ -466,7 +466,7 @@ void cpuidle_unregister(struct cpuidle_driver *drv)
>  	int cpu;
>  	struct cpuidle_device *device;
>  
> -	for_each_possible_cpu(cpu) {
> +	for_each_cpu(cpu, drv->cpumask) {
>  		device = &per_cpu(cpuidle_dev, cpu);
>  		cpuidle_unregister_device(device);
>  	}
> @@ -498,7 +498,7 @@ int cpuidle_register(struct cpuidle_driver *drv,
>  		return ret;
>  	}
>  
> -	for_each_possible_cpu(cpu) {
> +	for_each_cpu(cpu, drv->cpumask) {
>  		device = &per_cpu(cpuidle_dev, cpu);
>  		device->cpu = cpu;
>  
> diff --git a/drivers/cpuidle/driver.c b/drivers/cpuidle/driver.c
> index 8dfaaae..745adae 100644
> --- a/drivers/cpuidle/driver.c
> +++ b/drivers/cpuidle/driver.c
> @@ -18,167 +18,138 @@
>  
>  DEFINE_SPINLOCK(cpuidle_driver_lock);
>  
> -static void __cpuidle_set_cpu_driver(struct cpuidle_driver *drv, int cpu);
> -static struct cpuidle_driver * __cpuidle_get_cpu_driver(int cpu);
> +#ifdef CONFIG_CPU_IDLE_MULTIPLE_DRIVERS
>  
> -static void cpuidle_setup_broadcast_timer(void *arg)
> +static DEFINE_PER_CPU(struct cpuidle_driver *, cpuidle_drivers);
> +
> +static struct cpuidle_driver *__cpuidle_get_cpu_driver(int cpu)
>  {
> -	int cpu = smp_processor_id();
> -	clockevents_notify((long)(arg), &cpu);
> +	return per_cpu(cpuidle_drivers, cpu);
>  }
>  
> -static void __cpuidle_driver_init(struct cpuidle_driver *drv, int cpu)
> +static inline int __cpuidle_set_driver(struct cpuidle_driver *drv)
>  {
> -	int i;
> -
> -	drv->refcnt = 0;
> +	int cpu;
>  
> -	for (i = drv->state_count - 1; i >= 0 ; i--) {
> +	for_each_cpu(cpu, drv->cpumask) {
>  
> -		if (!(drv->states[i].flags & CPUIDLE_FLAG_TIMER_STOP))
> -			continue;
> +		if (__cpuidle_get_cpu_driver(cpu))
> +			return -EBUSY;

I'm a bit concerned about this code.  I don't think it should just return here
leaving all of the already set pointers in that state.  It looks like it should
clear the previously assigned pointers and ideally clear the driver's cpumask
as well before returning the error (or let the caller clear the cpumask if
that's better).

>  
> -		drv->bctimer = 1;
> -		on_each_cpu_mask(get_cpu_mask(cpu), cpuidle_setup_broadcast_timer,
> -				 (void *)CLOCK_EVT_NOTIFY_BROADCAST_ON, 1);
> -		break;
> +		per_cpu(cpuidle_drivers, cpu) = drv;
>  	}
> +
> +	return 0;
>  }
>  
> -static int __cpuidle_register_driver(struct cpuidle_driver *drv, int cpu)
> +static inline void __cpuidle_unset_driver(struct cpuidle_driver *drv)
>  {
> -	if (!drv || !drv->state_count)
> -		return -EINVAL;
> -
> -	if (cpuidle_disabled())
> -		return -ENODEV;
> -
> -	if (__cpuidle_get_cpu_driver(cpu))
> -		return -EBUSY;
> +	int cpu;
>  
> -	__cpuidle_driver_init(drv, cpu);
> +	for_each_cpu(cpu, drv->cpumask) {
>  
> -	__cpuidle_set_cpu_driver(drv, cpu);
> +		if (drv != __cpuidle_get_cpu_driver(cpu))
> +			continue;
>  
> -	return 0;
> +		per_cpu(cpuidle_drivers, cpu) = NULL;
> +	}
>  }
>  
> -static void __cpuidle_unregister_driver(struct cpuidle_driver *drv, int cpu)
> -{
> -	if (drv != __cpuidle_get_cpu_driver(cpu))
> -		return;
> +#else
>  
> -	if (!WARN_ON(drv->refcnt > 0))
> -		__cpuidle_set_cpu_driver(NULL, cpu);
> +static struct cpuidle_driver *cpuidle_curr_driver;
>  
> -	if (drv->bctimer) {
> -		drv->bctimer = 0;
> -		on_each_cpu_mask(get_cpu_mask(cpu), cpuidle_setup_broadcast_timer,
> -				 (void *)CLOCK_EVT_NOTIFY_BROADCAST_OFF, 1);
> -	}
> +static inline struct cpuidle_driver *__cpuidle_get_cpu_driver(int cpu)
> +{
> +	return cpuidle_curr_driver;
>  }
>  
> -#ifdef CONFIG_CPU_IDLE_MULTIPLE_DRIVERS
> +static inline int __cpuidle_set_driver(struct cpuidle_driver *drv)
> +{
> +	if (cpuidle_curr_driver)
> +		return -EBUSY;
>  
> -static DEFINE_PER_CPU(struct cpuidle_driver *, cpuidle_drivers);
> +	cpuidle_curr_driver = drv;
>  
> -static void __cpuidle_set_cpu_driver(struct cpuidle_driver *drv, int cpu)
> -{
> -	per_cpu(cpuidle_drivers, cpu) = drv;
> +	return 0;
>  }
>  
> -static struct cpuidle_driver *__cpuidle_get_cpu_driver(int cpu)
> +static inline void __cpuidle_unset_driver(struct cpuidle_driver *drv)
>  {
> -	return per_cpu(cpuidle_drivers, cpu);
> +	if (drv == cpuidle_curr_driver)
> +		cpuidle_curr_driver = NULL;
>  }
>  
> -static void __cpuidle_unregister_all_cpu_driver(struct cpuidle_driver *drv)
> +#endif
> +
> +static void cpuidle_setup_broadcast_timer(void *arg)
>  {
> -	int cpu;
> -	for_each_present_cpu(cpu)
> -		__cpuidle_unregister_driver(drv, cpu);
> +	int cpu = smp_processor_id();
> +	clockevents_notify((long)(arg), &cpu);
>  }
>  
> -static int __cpuidle_register_all_cpu_driver(struct cpuidle_driver *drv)
> +static int __cpuidle_driver_init(struct cpuidle_driver *drv)
>  {
> -	int ret = 0;
> -	int i, cpu;
> +	int i;
>  
> -	for_each_present_cpu(cpu) {
> -		ret = __cpuidle_register_driver(drv, cpu);
> -		if (ret)
> -			break;
> -	}
> +	drv->refcnt = 0;
>  
> -	if (ret)
> -		for_each_present_cpu(i) {
> -			if (i == cpu)
> -				break;
> -			__cpuidle_unregister_driver(drv, i);
> -		}
> +	if (!drv->cpumask)
> +		drv->cpumask = (struct cpumask *)cpu_possible_mask;
>  
> +	for (i = drv->state_count - 1; i >= 0 ; i--) {
>  
> -	return ret;
> +		if (!(drv->states[i].flags & CPUIDLE_FLAG_TIMER_STOP))
> +			continue;
> +
> +		drv->bctimer = 1;
> +		break;
> +	}
> +
> +	return 0;
>  }
>  
> -int cpuidle_register_cpu_driver(struct cpuidle_driver *drv, int cpu)
> +static int __cpuidle_register_driver(struct cpuidle_driver *drv)
>  {
>  	int ret;
>  
> -	spin_lock(&cpuidle_driver_lock);
> -	ret = __cpuidle_register_driver(drv, cpu);
> -	spin_unlock(&cpuidle_driver_lock);
> +	if (!drv || !drv->state_count)
> +		return -EINVAL;
>  
> -	return ret;
> -}
> +	if (cpuidle_disabled())
> +		return -ENODEV;
>  
> -void cpuidle_unregister_cpu_driver(struct cpuidle_driver *drv, int cpu)
> -{
> -	spin_lock(&cpuidle_driver_lock);
> -	__cpuidle_unregister_driver(drv, cpu);
> -	spin_unlock(&cpuidle_driver_lock);
> -}
> +	ret = __cpuidle_driver_init(drv);
> +	if (ret)
> +		return ret;
>  
> -/**
> - * cpuidle_register_driver - registers a driver
> - * @drv: the driver
> - */
> -int cpuidle_register_driver(struct cpuidle_driver *drv)
> -{
> -	int ret;
> +	ret = __cpuidle_set_driver(drv);
> +	if (ret)
> +		return ret;
>  
> -	spin_lock(&cpuidle_driver_lock);
> -	ret = __cpuidle_register_all_cpu_driver(drv);
> -	spin_unlock(&cpuidle_driver_lock);
> +	if (drv->bctimer)
> +		on_each_cpu_mask(drv->cpumask, cpuidle_setup_broadcast_timer,
> +				 (void *)CLOCK_EVT_NOTIFY_BROADCAST_ON, 1);
>  
> -	return ret;
> +	return 0;
>  }
> -EXPORT_SYMBOL_GPL(cpuidle_register_driver);
>  
>  /**
>   * cpuidle_unregister_driver - unregisters a driver
>   * @drv: the driver
>   */
> -void cpuidle_unregister_driver(struct cpuidle_driver *drv)
> +static void __cpuidle_unregister_driver(struct cpuidle_driver *drv)
>  {
> -	spin_lock(&cpuidle_driver_lock);
> -	__cpuidle_unregister_all_cpu_driver(drv);
> -	spin_unlock(&cpuidle_driver_lock);
> -}
> -EXPORT_SYMBOL_GPL(cpuidle_unregister_driver);
> -
> -#else
> -
> -static struct cpuidle_driver *cpuidle_curr_driver;
> +	if (WARN_ON(drv->refcnt > 0))
> +		return;
>  
> -static inline void __cpuidle_set_cpu_driver(struct cpuidle_driver *drv, int cpu)
> -{
> -	cpuidle_curr_driver = drv;
> -}
> +	if (drv->bctimer) {
> +		drv->bctimer = 0;
> +		on_each_cpu_mask(drv->cpumask, cpuidle_setup_broadcast_timer,
> +				 (void *)CLOCK_EVT_NOTIFY_BROADCAST_OFF, 1);
> +	}
>  
> -static inline struct cpuidle_driver *__cpuidle_get_cpu_driver(int cpu)
> -{
> -	return cpuidle_curr_driver;
> +	__cpuidle_unset_driver(drv);
>  }
>  
>  /**
> @@ -187,13 +158,11 @@ static inline struct cpuidle_driver *__cpuidle_get_cpu_driver(int cpu)
>   */
>  int cpuidle_register_driver(struct cpuidle_driver *drv)
>  {
> -	int ret, cpu;
> +	int ret;
>  
> -	cpu = get_cpu();
>  	spin_lock(&cpuidle_driver_lock);
> -	ret = __cpuidle_register_driver(drv, cpu);
> +	ret = __cpuidle_register_driver(drv);
>  	spin_unlock(&cpuidle_driver_lock);
> -	put_cpu();
>  
>  	return ret;
>  }
> @@ -205,16 +174,11 @@ EXPORT_SYMBOL_GPL(cpuidle_register_driver);
>   */
>  void cpuidle_unregister_driver(struct cpuidle_driver *drv)
>  {
> -	int cpu;
> -
> -	cpu = get_cpu();
>  	spin_lock(&cpuidle_driver_lock);
> -	__cpuidle_unregister_driver(drv, cpu);
> +	__cpuidle_unregister_driver(drv);
>  	spin_unlock(&cpuidle_driver_lock);
> -	put_cpu();
>  }
>  EXPORT_SYMBOL_GPL(cpuidle_unregister_driver);
> -#endif
>  
>  /**
>   * cpuidle_get_driver - return the current driver
> diff --git a/include/linux/cpuidle.h b/include/linux/cpuidle.h
> index 8f04062..63d78b1 100644
> --- a/include/linux/cpuidle.h
> +++ b/include/linux/cpuidle.h
> @@ -101,16 +101,20 @@ static inline int cpuidle_get_last_residency(struct cpuidle_device *dev)
>   ****************************/
>  
>  struct cpuidle_driver {
> -	const char		*name;
> -	struct module 		*owner;
> -	int                     refcnt;
> +	const char	     *name;
> +	struct module 	     *owner;
> +	int                  refcnt;

Can you please refrain from fixing white space while doing functional changes?

I know that it's tempting, but it really is better to whitespace cleanup in
a separate patch after your functional changes have been integrated.

>  
>          /* used by the cpuidle framework to setup the broadcast timer */
> -	unsigned int            bctimer:1;
> +	unsigned int         bctimer:1;
> +
>  	/* states array must be ordered in decreasing power consumption */
> -	struct cpuidle_state	states[CPUIDLE_STATE_MAX];
> -	int			state_count;
> -	int			safe_state_index;
> +	struct cpuidle_state states[CPUIDLE_STATE_MAX];
> +	int		     state_count;
> +	int		     safe_state_index;
> +
> +	/* the driver handles the cpus in cpumask */
> +	struct cpumask       *cpumask;
>  };
>  
>  #ifdef CONFIG_CPU_IDLE
> @@ -135,9 +139,6 @@ extern void cpuidle_disable_device(struct cpuidle_device *dev);
>  extern int cpuidle_play_dead(void);
>  
>  extern struct cpuidle_driver *cpuidle_get_cpu_driver(struct cpuidle_device *dev);
> -extern int cpuidle_register_cpu_driver(struct cpuidle_driver *drv, int cpu);
> -extern void cpuidle_unregister_cpu_driver(struct cpuidle_driver *drv, int cpu);
> -
>  #else
>  static inline void disable_cpuidle(void) { }
>  static inline int cpuidle_idle_call(void) { return -ENODEV; }

Thanks,
Rafael