Re: [PATCH v10 02/27] PM / Domains: Add support for CPU devices to genpd

[Daniel Lezcano]

On 29/11/2018 18:46, Ulf Hansson wrote:
> To enable a device belonging to a CPU to be attached to a PM domain managed
> by genpd, let's do a few changes to it, as to make it convenient to manage
> the specifics around CPUs.
> 
> To be able to quickly find out what CPUs that are attached to a genpd,
> which typically becomes useful from a genpd governor as following changes
> is about to show, let's add a cpumask to the struct generic_pm_domain. At
> the point when a CPU device gets attached to a genpd, let's update its
> cpumask. Moreover, let's also propagate changes to the cpumask upwards in
> the topology to the master PM domains. In this way, the cpumask for a genpd
> hierarchically reflects all CPUs attached to the topology below it.
> 
> Finally, let's make this an opt-in feature, to avoid having to manage CPUs
> and the cpumask for a genpd that doesn't need it. For that reason, let's
> add a new genpd configuration bit, GENPD_FLAG_CPU_DOMAIN.
> 
> Cc: Lina Iyer <ilina@xxxxxxxxxxxxxx>
> Co-developed-by: Lina Iyer <lina.iyer@xxxxxxxxxx>
> Signed-off-by: Ulf Hansson <ulf.hansson@xxxxxxxxxx>
> ---
> 
> Changes in v10:
> 	- Don't allocate the cpumask when not used.
> 	- Simplify the code that updates the cpumask.
> 	- Document the GENPD_FLAG_CPU_DOMAIN.
> 
> ---
>  drivers/base/power/domain.c | 66 ++++++++++++++++++++++++++++++++++++-
>  include/linux/pm_domain.h   | 13 ++++++++
>  2 files changed, 78 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
> index e27b91d36a2a..c3ff8e395308 100644
> --- a/drivers/base/power/domain.c
> +++ b/drivers/base/power/domain.c
> @@ -20,6 +20,7 @@
>  #include <linux/sched.h>
>  #include <linux/suspend.h>
>  #include <linux/export.h>
> +#include <linux/cpu.h>
>  
>  #include "power.h"
>  
> @@ -126,6 +127,7 @@ static const struct genpd_lock_ops genpd_spin_ops = {
>  #define genpd_is_irq_safe(genpd)	(genpd->flags & GENPD_FLAG_IRQ_SAFE)
>  #define genpd_is_always_on(genpd)	(genpd->flags & GENPD_FLAG_ALWAYS_ON)
>  #define genpd_is_active_wakeup(genpd)	(genpd->flags & GENPD_FLAG_ACTIVE_WAKEUP)
> +#define genpd_is_cpu_domain(genpd)	(genpd->flags & GENPD_FLAG_CPU_DOMAIN)
>  
>  static inline bool irq_safe_dev_in_no_sleep_domain(struct device *dev,
>  		const struct generic_pm_domain *genpd)
> @@ -1377,6 +1379,56 @@ static void genpd_free_dev_data(struct device *dev,
>  	dev_pm_put_subsys_data(dev);
>  }
>  
> +static void __genpd_update_cpumask(struct generic_pm_domain *genpd,
> +				   int cpu, bool set, unsigned int depth)
> +{
> +	struct gpd_link *link;
> +
> +	if (!genpd_is_cpu_domain(genpd))
> +		return;

With this test, we won't continue updating the cpumask for the other
masters. Is it done on purpose ?

> +	list_for_each_entry(link, &genpd->slave_links, slave_node) {
> +		struct generic_pm_domain *master = link->master;
> +
> +		genpd_lock_nested(master, depth + 1);
> +		__genpd_update_cpumask(master, cpu, set, depth + 1);
> +		genpd_unlock(master);
> +	}
> +
> +	if (set)
> +		cpumask_set_cpu(cpu, genpd->cpus);
> +	else
> +		cpumask_clear_cpu(cpu, genpd->cpus);
> +}
> +
> +static void genpd_update_cpumask(struct generic_pm_domain *genpd,
> +				 struct device *dev, bool set)
> +{
> +	int cpu;
> +
> +	if (!genpd_is_cpu_domain(genpd))
> +		return;
> +
> +	for_each_possible_cpu(cpu) {
> +		if (get_cpu_device(cpu) == dev) {
> +			__genpd_update_cpumask(genpd, cpu, set, 0);
> +			return;
> +		}
> +	}
> +}
> +
> +static void genpd_set_cpumask(struct generic_pm_domain *genpd,
> +			      struct device *dev)
> +{
> +	genpd_update_cpumask(genpd, dev, true);
> +}
> +
> +static void genpd_clear_cpumask(struct generic_pm_domain *genpd,
> +				struct device *dev)
> +{
> +	genpd_update_cpumask(genpd, dev, false);
> +}
> +
>  static int genpd_add_device(struct generic_pm_domain *genpd, struct device *dev,
>  			    struct gpd_timing_data *td)
>  {
> @@ -1398,6 +1450,8 @@ static int genpd_add_device(struct generic_pm_domain *genpd, struct device *dev,
>  	if (ret)
>  		goto out;
>  
> +	genpd_set_cpumask(genpd, dev);
> +
>  	dev_pm_domain_set(dev, &genpd->domain);
>  
>  	genpd->device_count++;
> @@ -1459,6 +1513,7 @@ static int genpd_remove_device(struct generic_pm_domain *genpd,
>  	if (genpd->detach_dev)
>  		genpd->detach_dev(genpd, dev);
>  
> +	genpd_clear_cpumask(genpd, dev);
>  	dev_pm_domain_set(dev, NULL);
>  
>  	list_del_init(&pdd->list_node);
> @@ -1686,11 +1741,18 @@ int pm_genpd_init(struct generic_pm_domain *genpd,
>  	if (genpd_is_always_on(genpd) && !genpd_status_on(genpd))
>  		return -EINVAL;
>  
> +	if (genpd_is_cpu_domain(genpd) &&
> +	    !zalloc_cpumask_var(&genpd->cpus, GFP_KERNEL))
> +		return -ENOMEM;
> +
>  	/* Use only one "off" state if there were no states declared */
>  	if (genpd->state_count == 0) {
>  		ret = genpd_set_default_power_state(genpd);
> -		if (ret)
> +		if (ret) {
> +			if (genpd_is_cpu_domain(genpd))
> +				free_cpumask_var(genpd->cpus);
>  			return ret;
> +		}
>  	} else if (!gov) {
>  		pr_warn("%s : no governor for states\n", genpd->name);
>  	}
> @@ -1736,6 +1798,8 @@ static int genpd_remove(struct generic_pm_domain *genpd)
>  	list_del(&genpd->gpd_list_node);
>  	genpd_unlock(genpd);
>  	cancel_work_sync(&genpd->power_off_work);
> +	if (genpd_is_cpu_domain(genpd))
> +		free_cpumask_var(genpd->cpus);
>  	if (genpd->free_state) {
>  		kfree(genpd->states);
>  		genpd->states = NULL;
> diff --git a/include/linux/pm_domain.h b/include/linux/pm_domain.h
> index f9e09bd4152c..5a4673605d22 100644
> --- a/include/linux/pm_domain.h
> +++ b/include/linux/pm_domain.h
> @@ -16,6 +16,7 @@
>  #include <linux/of.h>
>  #include <linux/notifier.h>
>  #include <linux/spinlock.h>
> +#include <linux/cpumask.h>
>  
>  /*
>   * Flags to control the behaviour of a genpd.
> @@ -42,11 +43,22 @@
>   * GENPD_FLAG_ACTIVE_WAKEUP:	Instructs genpd to keep the PM domain powered
>   *				on, in case any of its attached devices is used
>   *				in the wakeup path to serve system wakeups.
> + *
> + * GENPD_FLAG_CPU_DOMAIN:	Instructs genpd that it should expect to get
> + *				devices attached, which may belong to CPUs or
> + *				possibly have subdomains with CPUs attached.
> + *				This flag enables the genpd backend driver to
> + *				deploy idle power management support for CPUs
> + *				and groups of CPUs. Note that, the backend
> + *				driver must then comply with the so called,
> + *				last-man-standing algorithm, for the CPUs in the
> + *				PM domain.
>   */
>  #define GENPD_FLAG_PM_CLK	 (1U << 0)
>  #define GENPD_FLAG_IRQ_SAFE	 (1U << 1)
>  #define GENPD_FLAG_ALWAYS_ON	 (1U << 2)
>  #define GENPD_FLAG_ACTIVE_WAKEUP (1U << 3)
> +#define GENPD_FLAG_CPU_DOMAIN	 (1U << 4)
>  
>  enum gpd_status {
>  	GPD_STATE_ACTIVE = 0,	/* PM domain is active */
> @@ -93,6 +105,7 @@ struct generic_pm_domain {
>  	unsigned int suspended_count;	/* System suspend device counter */
>  	unsigned int prepared_count;	/* Suspend counter of prepared devices */
>  	unsigned int performance_state;	/* Aggregated max performance state */
> +	cpumask_var_t cpus;		/* A cpumask of the attached CPUs */
>  	int (*power_off)(struct generic_pm_domain *domain);
>  	int (*power_on)(struct generic_pm_domain *domain);
>  	unsigned int (*opp_to_performance_state)(struct generic_pm_domain *genpd,
> 


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