Subject: Re: [linux-pm] [PATCH 1/3] cpuidle/powernv: cpuidle backend driver for powernv

From: Daniel Lezcano <[email-masked]>
Date: Sat, 27 Jul 2013 07:27:06 +0200

On 07/23/2013 11:01 AM, Deepthi Dharwar wrote:
> This patch implements a back-end cpuidle driver for
> powernv calling power7_nap and snooze idle states.
> This can be extended by adding more idle states
> in the future to the existing framework.
> 
> Signed-off-by: Deepthi Dharwar <[email-masked]>
> ---
>  arch/powerpc/platforms/powernv/Kconfig          |    9 +
>  arch/powerpc/platforms/powernv/Makefile         |    1 
>  arch/powerpc/platforms/powernv/processor_idle.c |  239 +++++++++++++++++++++++
>  3 files changed, 249 insertions(+)
>  create mode 100644 arch/powerpc/platforms/powernv/processor_idle.c
> 
> diff --git a/arch/powerpc/platforms/powernv/Kconfig b/arch/powerpc/platforms/powernv/Kconfig
> index c24684c..ace2d22 100644
> --- a/arch/powerpc/platforms/powernv/Kconfig
> +++ b/arch/powerpc/platforms/powernv/Kconfig
> @@ -20,3 +20,12 @@ config PPC_POWERNV_RTAS
>  	default y
>  	select PPC_ICS_RTAS
>  	select PPC_RTAS
> +
> +config POWERNV_IDLE
> +	bool "CPUIdle driver for powernv platform"
> +	depends on CPU_IDLE
> +	depends on PPC_POWERNV
> +	default y
> +	help
> +	Select this option to enable processor idle state management
> +	through cpuidle subsystem.
> diff --git a/arch/powerpc/platforms/powernv/Makefile b/arch/powerpc/platforms/powernv/Makefile
> index 7fe5951..c0e44eb 100644
> --- a/arch/powerpc/platforms/powernv/Makefile
> +++ b/arch/powerpc/platforms/powernv/Makefile
> @@ -4,3 +4,4 @@ obj-y			+= opal-rtc.o opal-nvram.o
>  obj-$(CONFIG_SMP)	+= smp.o
>  obj-$(CONFIG_PCI)	+= pci.o pci-p5ioc2.o pci-ioda.o
>  obj-$(CONFIG_EEH)	+= eeh-ioda.o eeh-powernv.o
> +obj-$(CONFIG_POWERNV_IDLE)     += processor_idle.o
> diff --git a/arch/powerpc/platforms/powernv/processor_idle.c b/arch/powerpc/platforms/powernv/processor_idle.c
> new file mode 100644
> index 0000000..f43ad91a
> --- /dev/null
> +++ b/arch/powerpc/platforms/powernv/processor_idle.c
> @@ -0,0 +1,239 @@
> +/*
> + *  processor_idle - idle state cpuidle driver.
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/init.h>
> +#include <linux/moduleparam.h>
> +#include <linux/cpuidle.h>
> +#include <linux/cpu.h>
> +#include <linux/notifier.h>
> +
> +#include <asm/machdep.h>
> +#include <asm/runlatch.h>
> +
> +struct cpuidle_driver powernv_idle_driver = {
> +	.name =		"powernv_idle",
> +	.owner =	THIS_MODULE,
> +};
> +
> +#define MAX_IDLE_STATE_COUNT	2
> +
> +static int max_idle_state = MAX_IDLE_STATE_COUNT - 1;
> +static struct cpuidle_device __percpu *powernv_cpuidle_devices;
> +static struct cpuidle_state *cpuidle_state_table;
> +
> +static int snooze_loop(struct cpuidle_device *dev,
> +			struct cpuidle_driver *drv,
> +			int index)
> +{
> +	int cpu = dev->cpu;
> +
> +	local_irq_enable();
> +	set_thread_flag(TIF_POLLING_NRFLAG);
> +
> +	while ((!need_resched()) && cpu_online(cpu)) {
> +		ppc64_runlatch_off();
> +		HMT_very_low();
> +	}

Why are you using the cpu_online test here ?

> +
> +	HMT_medium();
> +	clear_thread_flag(TIF_POLLING_NRFLAG);
> +	smp_mb();
> +	return index;
> +}
> +
> +
> +static int nap_loop(struct cpuidle_device *dev,
> +				struct cpuidle_driver *drv,
> +				int index)
> +{
> +	ppc64_runlatch_off();
> +	power7_idle();
> +	return index;
> +}
> +
> +/*
> + * States for dedicated partition case.
> + */
> +static struct cpuidle_state powernv_states[MAX_IDLE_STATE_COUNT] = {
> +	{ /* Snooze */
> +		.name = "snooze",
> +		.desc = "snooze",
> +		.flags = CPUIDLE_FLAG_TIME_VALID,
> +		.exit_latency = 0,
> +		.target_residency = 0,
> +		.enter = &snooze_loop },
> +	 { /* Nap */
> +		.name = "Nap",
> +		.desc = "Nap",
> +		.flags = CPUIDLE_FLAG_TIME_VALID,
> +		.exit_latency = 10,
> +		.target_residency = 100,
> +		.enter = &nap_loop },
> +};
> +
> +static int powernv_cpuidle_add_cpu_notifier(struct notifier_block *n,
> +			unsigned long action, void *hcpu)
> +{
> +	int hotcpu = (unsigned long)hcpu;
> +	struct cpuidle_device *dev =
> +			per_cpu_ptr(powernv_cpuidle_devices, hotcpu);
> +
> +	if (dev && cpuidle_get_driver()) {
> +		switch (action) {
> +		case CPU_ONLINE:
> +		case CPU_ONLINE_FROZEN:
> +			cpuidle_pause_and_lock();
> +			cpuidle_enable_device(dev);
> +			cpuidle_resume_and_unlock();
> +			break;
> +
> +		case CPU_DEAD:
> +		case CPU_DEAD_FROZEN:
> +			cpuidle_pause_and_lock();
> +			cpuidle_disable_device(dev);
> +			cpuidle_resume_and_unlock();
> +			break;
> +
> +		default:
> +			return NOTIFY_DONE;
> +		}
> +	}
> +	return NOTIFY_OK;
> +}
> +
> +static struct notifier_block setup_hotplug_notifier = {
> +	.notifier_call = powernv_cpuidle_add_cpu_notifier,
> +};

This is duplicated code with the pseries cpuidle driver and IMHO it
should be moved to the cpuidle framework.

> +/*
> + * powernv_cpuidle_driver_init()
> + */
> +static int powernv_cpuidle_driver_init(void)
> +{
> +	int idle_state;
> +	struct cpuidle_driver *drv = &powernv_idle_driver;
> +
> +	drv->state_count = 0;
> +
> +	for (idle_state = 0; idle_state < MAX_IDLE_STATE_COUNT; ++idle_state) {
> +
> +		if (idle_state > max_idle_state)
> +			break;
> +
> +		/* is the state not enabled? */
> +		if (cpuidle_state_table[idle_state].enter == NULL)
> +			continue;
> +
> +		drv->states[drv->state_count] =	/* structure copy */
> +			cpuidle_state_table[idle_state];
> +
> +		drv->state_count += 1;
> +	}
> +
> +	return 0;
> +}

Instead of doing struct copy, why don't you use the state's 'disable'
field of the driver and then enable the state in the routine ?

> +/* powernv_idle_devices_uninit(void)
> + * unregister cpuidle devices and de-allocate memory
> + */
> +static void powernv_idle_devices_uninit(void)
> +{
> +	int i;
> +	struct cpuidle_device *dev;
> +
> +	for_each_possible_cpu(i) {
> +		dev = per_cpu_ptr(powernv_cpuidle_devices, i);
> +		cpuidle_unregister_device(dev);
> +	}
> +
> +	free_percpu(powernv_cpuidle_devices);
> +	return;
> +}
> +
> +/* powernv_idle_devices_init()
> + * allocate, initialize and register cpuidle device
> + */
> +static int powernv_idle_devices_init(void)
> +{
> +	int i;
> +	struct cpuidle_driver *drv = &powernv_idle_driver;
> +	struct cpuidle_device *dev;
> +
> +	powernv_cpuidle_devices = alloc_percpu(struct cpuidle_device);
> +	if (powernv_cpuidle_devices == NULL)
> +		return -ENOMEM;
> +
> +	for_each_possible_cpu(i) {
> +		dev = per_cpu_ptr(powernv_cpuidle_devices, i);
> +		dev->state_count = drv->state_count;
> +		dev->cpu = i;
> +		if (cpuidle_register_device(dev)) {
> +			printk(KERN_DEBUG \
> +				"cpuidle_register_device %d failed!\n", i);
> +			return -EIO;
> +		}
> +	}
> +	return 0;

There is now the cpuidle_register(struct cpuidle_driver *, cpumask *);

You can get rid of the cpuidle_device struct and this init routine.

> +}
> +
> +/*
> + * powernv_idle_probe()
> + * Choose state table for shared versus dedicated partition
> + */
> +static int powernv_idle_probe(void)
> +{
> +
> +	if (cpuidle_disable != IDLE_NO_OVERRIDE)
> +		return -ENODEV;
> +
> +	cpuidle_state_table = powernv_states;
> +	return 0;
> +}
> +
> +static int __init powernv_processor_idle_init(void)
> +{
> +	int retval;
> +
> +	retval = powernv_idle_probe();
> +	if (retval)
> +		return retval;
> +
> +	powernv_cpuidle_driver_init();
> +	retval = cpuidle_register_driver(&powernv_idle_driver);
> +	if (retval) {
> +		printk(KERN_DEBUG "Registration of powernv driver failed.\n");
> +		return retval;
> +	}
> +
> +	retval = powernv_idle_devices_init();
> +	if (retval) {
> +		powernv_idle_devices_uninit();
> +		cpuidle_unregister_driver(&powernv_idle_driver);
> +		return retval;
> +	}
> +
> +	register_cpu_notifier(&setup_hotplug_notifier);
> +	printk(KERN_DEBUG "powernv_idle_driver registered\n");
> +
> +	return 0;
> +}
> +
> +static void __exit powernv_processor_idle_exit(void)
> +{
> +
> +	unregister_cpu_notifier(&setup_hotplug_notifier);
> +	powernv_idle_devices_uninit();
> +	cpuidle_unregister_driver(&powernv_idle_driver);
> +
> +	return;
> +}
> +
> +module_init(powernv_processor_idle_init);
> +module_exit(powernv_processor_idle_exit);
> +
> +MODULE_AUTHOR("Deepthi Dharwar <[email-masked]>");
> +MODULE_DESCRIPTION("Cpuidle driver for POWERNV");
> +MODULE_LICENSE("GPL");
> 

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