redonkable/alistair23-linux
redonkable/alistair23-linux
1
0
Fork 0
Code Releases Activity
alistair23-linux/include/linux/pm_domain.h
Ulf Hansson ba2bbfbf63 PM / Domains: Remove intermediate states from the power off sequence 
Genpd's ->runtime_suspend() (assigned to pm_genpd_runtime_suspend())
doesn't immediately walk the hierarchy of ->runtime_suspend() callbacks.
Instead, pm_genpd_runtime_suspend() calls pm_genpd_poweroff() which
postpones that until *all* the devices in the genpd are runtime suspended.

When pm_genpd_poweroff() discovers that the last device in the genpd is
about to be runtime suspended, it calls __pm_genpd_save_device() for *all*
the devices in the genpd sequentially. Furthermore,
__pm_genpd_save_device() invokes the ->start() callback, walks the
hierarchy of the ->runtime_suspend() callbacks and invokes the ->stop()
callback. This causes a "thundering herd" problem.

Let's address this issue by having pm_genpd_runtime_suspend() immediately
walk the hierarchy of the ->runtime_suspend() callbacks, instead of
postponing that to the power off sequence via pm_genpd_poweroff(). If the
selected ->runtime_suspend() callback doesn't return an error code, call
pm_genpd_poweroff() to see if it's feasible to also power off the PM
domain.

Adopting this change enables us to simplify parts of the code in genpd,
for example the locking mechanism. Additionally, it gives some positive
side effects, as described below.

i)
One device's ->runtime_resume() latency is no longer affected by other
devices' latencies in a genpd.

The complexity genpd has to support the option to abort the power off
sequence suffers from latency issues. More precisely, a device that is
requested to be runtime resumed, may end up waiting for
__pm_genpd_save_device() to complete its operations for *another* device.
That's because pm_genpd_poweroff() can't confirm an abort request while it
waits for __pm_genpd_save_device() to return.

As this patch removes the intermediate states in pm_genpd_poweroff() while
powering off the PM domain, we no longer need the ability to abort that
sequence.

ii)
Make pm_runtime[_status]_suspended() reliable when used with genpd.

Until the last device in a genpd becomes idle, pm_genpd_runtime_suspend()
will return 0 without actually walking the hierarchy of the
->runtime_suspend() callbacks. However, by returning 0 the runtime PM core
considers the device as runtime_suspended, so
pm_runtime[_status]_suspended() will return true, even though the device
isn't (yet) runtime suspended.

After this patch, since pm_genpd_runtime_suspend() immediately walks the
hierarchy of the ->runtime_suspend() callbacks,
pm_runtime[_status]_suspended() will accurately reflect the status of the
device.

iii)
Enable fine-grained PM through runtime PM callbacks in drivers/subsystems.

There are currently cases were drivers/subsystems implements runtime PM
callbacks to deploy fine-grained PM (e.g. gate clocks, move pinctrl to
power-save state, etc.). While using the genpd, pm_genpd_runtime_suspend()
postpones invoking these callbacks until *all* the devices in the genpd
are runtime suspended. In essence, one runtime resumed device prevents
fine-grained PM for other devices within the same genpd.

After this patch, since pm_genpd_runtime_suspend() immediately walks the
hierarchy of the ->runtime_suspend() callbacks, fine-grained PM is enabled
throughout all the levels of runtime PM callbacks.

iiii)
Enable fine-grained PM for IRQ safe devices

Per the definition for an IRQ safe device, its runtime PM callbacks must
be able to execute in atomic context. In the path while genpd walks the
hierarchy of the ->runtime_suspend() callbacks for the device, it uses a
mutex. Therefore, genpd prevents that path to be executed for IRQ safe
devices.

As this patch changes pm_genpd_runtime_suspend() to immediately walk the
hierarchy of the ->runtime_suspend() callbacks and without needing to use
a mutex, fine-grained PM is enabled throughout all the levels of runtime
PM callbacks for IRQ safe devices.

Unfortunately this patch also comes with a drawback, as described in the
summary below.

Driver's/subsystem's runtime PM callbacks may be invoked even when the
genpd hasn't actually powered off the PM domain, potentially introducing
unnecessary latency.

However, in most cases, saving/restoring register contexts for devices are
typically fast operations or can be optimized in device specific ways
(e.g. shadow copies of register contents in memory, device-specific checks
to see if context has been lost before restoring context, etc.).

Still, in some cases the driver/subsystem may suffer from latency if
runtime PM is used in a very fine-grained manner (e.g. for each IO request
or xfer). To prevent that extra overhead, the driver/subsystem may deploy
the runtime PM autosuspend feature.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Reviewed-by: Kevin Hilman <khilman@linaro.org>
Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
Tested-by: Lina Iyer <lina.iyer@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2015-07-31 23:31:52 +02:00

320 lines
9.4 KiB
C
Raw Blame History

/*
* pm_domain.h - Definitions and headers related to device power domains.
*
* Copyright (C) 2011 Rafael J. Wysocki <rjw@sisk.pl>, Renesas Electronics Corp.
*
* This file is released under the GPLv2.
*/
#ifndef _LINUX_PM_DOMAIN_H
#define _LINUX_PM_DOMAIN_H
#include <linux/device.h>
#include <linux/mutex.h>
#include <linux/pm.h>
#include <linux/err.h>
#include <linux/of.h>
#include <linux/notifier.h>
#include <linux/cpuidle.h>
/* Defines used for the flags field in the struct generic_pm_domain */
#define GENPD_FLAG_PM_CLK (1U << 0) /* PM domain uses PM clk */
enum gpd_status {
GPD_STATE_ACTIVE = 0, /* PM domain is active */
GPD_STATE_POWER_OFF, /* PM domain is off */
};
struct dev_power_governor {
bool (*power_down_ok)(struct dev_pm_domain *domain);
bool (*stop_ok)(struct device *dev);
};
struct gpd_dev_ops {
int (*start)(struct device *dev);
int (*stop)(struct device *dev);
int (*save_state)(struct device *dev);
int (*restore_state)(struct device *dev);
bool (*active_wakeup)(struct device *dev);
};
struct gpd_cpuidle_data {
unsigned int saved_exit_latency;
struct cpuidle_state *idle_state;
};
struct generic_pm_domain {
struct dev_pm_domain domain; /* PM domain operations */
struct list_head gpd_list_node; /* Node in the global PM domains list */
struct list_head master_links; /* Links with PM domain as a master */
struct list_head slave_links; /* Links with PM domain as a slave */
struct list_head dev_list; /* List of devices */
struct mutex lock;
struct dev_power_governor *gov;
struct work_struct power_off_work;
const char *name;
unsigned int in_progress; /* Number of devices being suspended now */
atomic_t sd_count; /* Number of subdomains with power "on" */
enum gpd_status status; /* Current state of the domain */
unsigned int device_count; /* Number of devices */
unsigned int suspended_count; /* System suspend device counter */
unsigned int prepared_count; /* Suspend counter of prepared devices */
bool suspend_power_off; /* Power status before system suspend */
int (*power_off)(struct generic_pm_domain *domain);
s64 power_off_latency_ns;
int (*power_on)(struct generic_pm_domain *domain);
s64 power_on_latency_ns;
struct gpd_dev_ops dev_ops;
s64 max_off_time_ns; /* Maximum allowed "suspended" time. */
bool max_off_time_changed;
bool cached_power_down_ok;
struct gpd_cpuidle_data *cpuidle_data;
int (*attach_dev)(struct generic_pm_domain *domain,
struct device *dev);
void (*detach_dev)(struct generic_pm_domain *domain,
struct device *dev);
unsigned int flags; /* Bit field of configs for genpd */
};
static inline struct generic_pm_domain *pd_to_genpd(struct dev_pm_domain *pd)
{
return container_of(pd, struct generic_pm_domain, domain);
}
struct gpd_link {
struct generic_pm_domain *master;
struct list_head master_node;
struct generic_pm_domain *slave;
struct list_head slave_node;
};
struct gpd_timing_data {
s64 stop_latency_ns;
s64 start_latency_ns;
s64 save_state_latency_ns;
s64 restore_state_latency_ns;
s64 effective_constraint_ns;
bool constraint_changed;
bool cached_stop_ok;
};
struct pm_domain_data {
struct list_head list_node;
struct device *dev;
};
struct generic_pm_domain_data {
struct pm_domain_data base;
struct gpd_timing_data td;
struct notifier_block nb;
};
#ifdef CONFIG_PM_GENERIC_DOMAINS
static inline struct generic_pm_domain_data *to_gpd_data(struct pm_domain_data *pdd)
{
return container_of(pdd, struct generic_pm_domain_data, base);
}
static inline struct generic_pm_domain_data *dev_gpd_data(struct device *dev)
{
return to_gpd_data(dev->power.subsys_data->domain_data);
}
extern struct generic_pm_domain *pm_genpd_lookup_dev(struct device *dev);
extern int __pm_genpd_add_device(struct generic_pm_domain *genpd,
struct device *dev,
struct gpd_timing_data *td);
extern int __pm_genpd_name_add_device(const char *domain_name,
struct device *dev,
struct gpd_timing_data *td);
extern int pm_genpd_remove_device(struct generic_pm_domain *genpd,
struct device *dev);
extern int pm_genpd_add_subdomain(struct generic_pm_domain *genpd,
struct generic_pm_domain *new_subdomain);
extern int pm_genpd_add_subdomain_names(const char *master_name,
const char *subdomain_name);
extern int pm_genpd_remove_subdomain(struct generic_pm_domain *genpd,
struct generic_pm_domain *target);
extern int pm_genpd_attach_cpuidle(struct generic_pm_domain *genpd, int state);
extern int pm_genpd_name_attach_cpuidle(const char *name, int state);
extern int pm_genpd_detach_cpuidle(struct generic_pm_domain *genpd);
extern int pm_genpd_name_detach_cpuidle(const char *name);
extern void pm_genpd_init(struct generic_pm_domain *genpd,
struct dev_power_governor *gov, bool is_off);
extern int pm_genpd_poweron(struct generic_pm_domain *genpd);
extern int pm_genpd_name_poweron(const char *domain_name);
extern void pm_genpd_poweroff_unused(void);
extern struct dev_power_governor simple_qos_governor;
extern struct dev_power_governor pm_domain_always_on_gov;
#else
static inline struct generic_pm_domain_data *dev_gpd_data(struct device *dev)
{
return ERR_PTR(-ENOSYS);
}
static inline struct generic_pm_domain *pm_genpd_lookup_dev(struct device *dev)
{
return NULL;
}
static inline int __pm_genpd_add_device(struct generic_pm_domain *genpd,
struct device *dev,
struct gpd_timing_data *td)
{
return -ENOSYS;
}
static inline int __pm_genpd_name_add_device(const char *domain_name,
struct device *dev,
struct gpd_timing_data *td)
{
return -ENOSYS;
}
static inline int pm_genpd_remove_device(struct generic_pm_domain *genpd,
struct device *dev)
{
return -ENOSYS;
}
static inline int pm_genpd_add_subdomain(struct generic_pm_domain *genpd,
struct generic_pm_domain *new_sd)
{
return -ENOSYS;
}
static inline int pm_genpd_add_subdomain_names(const char *master_name,
const char *subdomain_name)
{
return -ENOSYS;
}
static inline int pm_genpd_remove_subdomain(struct generic_pm_domain *genpd,
struct generic_pm_domain *target)
{
return -ENOSYS;
}
static inline int pm_genpd_attach_cpuidle(struct generic_pm_domain *genpd, int st)
{
return -ENOSYS;
}
static inline int pm_genpd_name_attach_cpuidle(const char *name, int state)
{
return -ENOSYS;
}
static inline int pm_genpd_detach_cpuidle(struct generic_pm_domain *genpd)
{
return -ENOSYS;
}
static inline int pm_genpd_name_detach_cpuidle(const char *name)
{
return -ENOSYS;
}
static inline void pm_genpd_init(struct generic_pm_domain *genpd,
struct dev_power_governor *gov, bool is_off)
{
}
static inline int pm_genpd_poweron(struct generic_pm_domain *genpd)
{
return -ENOSYS;
}
static inline int pm_genpd_name_poweron(const char *domain_name)
{
return -ENOSYS;
}
static inline void pm_genpd_poweroff_unused(void) {}
#define simple_qos_governor NULL
#define pm_domain_always_on_gov NULL
#endif
static inline int pm_genpd_add_device(struct generic_pm_domain *genpd,
struct device *dev)
{
return __pm_genpd_add_device(genpd, dev, NULL);
}
static inline int pm_genpd_name_add_device(const char *domain_name,
struct device *dev)
{
return __pm_genpd_name_add_device(domain_name, dev, NULL);
}
#ifdef CONFIG_PM_GENERIC_DOMAINS_SLEEP
extern void pm_genpd_syscore_poweroff(struct device *dev);
extern void pm_genpd_syscore_poweron(struct device *dev);
#else
static inline void pm_genpd_syscore_poweroff(struct device *dev) {}
static inline void pm_genpd_syscore_poweron(struct device *dev) {}
#endif
/* OF PM domain providers */
struct of_device_id;
struct genpd_onecell_data {
struct generic_pm_domain **domains;
unsigned int num_domains;
};
typedef struct generic_pm_domain *(*genpd_xlate_t)(struct of_phandle_args *args,
void *data);
#ifdef CONFIG_PM_GENERIC_DOMAINS_OF
int __of_genpd_add_provider(struct device_node *np, genpd_xlate_t xlate,
void *data);
void of_genpd_del_provider(struct device_node *np);
struct generic_pm_domain *of_genpd_get_from_provider(
struct of_phandle_args *genpdspec);
struct generic_pm_domain *__of_genpd_xlate_simple(
struct of_phandle_args *genpdspec,
void *data);
struct generic_pm_domain *__of_genpd_xlate_onecell(
struct of_phandle_args *genpdspec,
void *data);
int genpd_dev_pm_attach(struct device *dev);
#else /* !CONFIG_PM_GENERIC_DOMAINS_OF */
static inline int __of_genpd_add_provider(struct device_node *np,
genpd_xlate_t xlate, void *data)
{
return 0;
}
static inline void of_genpd_del_provider(struct device_node *np) {}
static inline struct generic_pm_domain *of_genpd_get_from_provider(
struct of_phandle_args *genpdspec)
{
return NULL;
}
#define __of_genpd_xlate_simple NULL
#define __of_genpd_xlate_onecell NULL
static inline int genpd_dev_pm_attach(struct device *dev)
{
return -ENODEV;
}
#endif /* CONFIG_PM_GENERIC_DOMAINS_OF */
static inline int of_genpd_add_provider_simple(struct device_node *np,
struct generic_pm_domain *genpd)
{
return __of_genpd_add_provider(np, __of_genpd_xlate_simple, genpd);
}
static inline int of_genpd_add_provider_onecell(struct device_node *np,
struct genpd_onecell_data *data)
{
return __of_genpd_add_provider(np, __of_genpd_xlate_onecell, data);
}
#ifdef CONFIG_PM
extern int dev_pm_domain_attach(struct device *dev, bool power_on);
extern void dev_pm_domain_detach(struct device *dev, bool power_off);
#else
static inline int dev_pm_domain_attach(struct device *dev, bool power_on)
{
return -ENODEV;
}
static inline void dev_pm_domain_detach(struct device *dev, bool power_off) {}
#endif
#endif /* _LINUX_PM_DOMAIN_H */
View git blame Copy permalink