Re: [linux-pm] [PATCH 08/18] cpuidle: create bootparam "cpuidle.off=1"

[Deepthi Dharwar <deepthi@linux.vnet.ibm.com>]

On Saturday 02 April 2011 11:52 AM, Len Brown wrote:
> From: Len Brown <len.brown@intel.com>
> 
> useful for disabling cpuidle to fall back
> to architecture-default idle loop
> 
> cpuidle drivers and governors will fail to register.
> on x86 they'll say so:
> 
> intel_idle: intel_idle yielding to (null)
> ACPI: acpi_idle yielding to (null)
> 
> Signed-off-by: Len Brown <len.brown@intel.com>
> ---
>  Documentation/kernel-parameters.txt |    3 +++
>  drivers/cpuidle/cpuidle.c           |   10 ++++++++++
>  drivers/cpuidle/cpuidle.h           |    1 +
>  drivers/cpuidle/driver.c            |    3 +++
>  drivers/cpuidle/governor.c          |    3 +++
>  5 files changed, 20 insertions(+), 0 deletions(-)
> 
> diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
> index f4a04c0..08e8a22 100644
> --- a/Documentation/kernel-parameters.txt
> +++ b/Documentation/kernel-parameters.txt
> @@ -546,6 +546,9 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
>  			/proc/<pid>/coredump_filter.
>  			See also Documentation/filesystems/proc.txt.
> 
> +	cpuidle.off=1	[CPU_IDLE]
> +			disable the cpuidle sub-system
> +
>  	cpcihp_generic=	[HW,PCI] Generic port I/O CompactPCI driver
>  			Format:
>  			<first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
> diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
> index bf50924..faae2c3 100644
> --- a/drivers/cpuidle/cpuidle.c
> +++ b/drivers/cpuidle/cpuidle.c
> @@ -28,6 +28,12 @@ LIST_HEAD(cpuidle_detected_devices);
>  static void (*pm_idle_old)(void);
> 
>  static int enabled_devices;
> +static int off __read_mostly;
> +
> +int cpuidle_disabled(void)
> +{
> +	return off;
> +}
> 
>  #if defined(CONFIG_ARCH_HAS_CPU_IDLE_WAIT)
>  static void cpuidle_kick_cpus(void)
> @@ -427,6 +433,9 @@ static int __init cpuidle_init(void)
>  {
>  	int ret;
> 
> +	if (cpuidle_disabled())
> +		return -ENODEV;
> +
>  	pm_idle_old = pm_idle;
> 
>  	ret = cpuidle_add_class_sysfs(&cpu_sysdev_class);
> @@ -438,4 +447,5 @@ static int __init cpuidle_init(void)
>  	return 0;
>  }
> 
> +module_param(off, int, 0444);
>  core_initcall(cpuidle_init);
> diff --git a/drivers/cpuidle/cpuidle.h b/drivers/cpuidle/cpuidle.h
> index 33e50d5..38c3fd8 100644
> --- a/drivers/cpuidle/cpuidle.h
> +++ b/drivers/cpuidle/cpuidle.h
> @@ -13,6 +13,7 @@ extern struct list_head cpuidle_governors;
>  extern struct list_head cpuidle_detected_devices;
>  extern struct mutex cpuidle_lock;
>  extern spinlock_t cpuidle_driver_lock;
> +extern int cpuidle_disabled(void);
> 
>  /* idle loop */
>  extern void cpuidle_install_idle_handler(void);
> diff --git a/drivers/cpuidle/driver.c b/drivers/cpuidle/driver.c
> index fd1601e..3f7e3ce 100644
> --- a/drivers/cpuidle/driver.c
> +++ b/drivers/cpuidle/driver.c
> @@ -26,6 +26,9 @@ int cpuidle_register_driver(struct cpuidle_driver *drv)
>  	if (!drv)
>  		return -EINVAL;
> 
> +	if (cpuidle_disabled())
> +		return -ENODEV;
> +
>  	spin_lock(&cpuidle_driver_lock);
>  	if (cpuidle_curr_driver) {
>  		spin_unlock(&cpuidle_driver_lock);
> diff --git a/drivers/cpuidle/governor.c b/drivers/cpuidle/governor.c
> index 724c164..ea2f8e7 100644
> --- a/drivers/cpuidle/governor.c
> +++ b/drivers/cpuidle/governor.c
> @@ -81,6 +81,9 @@ int cpuidle_register_governor(struct cpuidle_governor *gov)
>  	if (!gov || !gov->select)
>  		return -EINVAL;
> 
> +	if (cpuidle_disabled())
> +		return -ENODEV;
> +
>  	mutex_lock(&cpuidle_lock);
>  	if (__cpuidle_find_governor(gov->name) == NULL) {
>  		ret = 0;

Hi Len,
We would like to know as to when the patch that completely removes
pm_idle for x86 "cpuidle: stop using pm_idle" and that which introduces
bootparam cpuidle.off "cpuidle: create bootparam cpuidle.off=1"
be pushed ? Are there any dependencies that needs to be addressed
before queuing it up for the next merge window ? If yes, can you please
let us know what the dependencies are. We need these patches for running 
cpuidle driver for pseries.  
https://lkml.org/lkml/2011/6/7/375

Thanks
- Deepthi