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Commit fc5cbf0c authored by Axel Haslam's avatar Axel Haslam Committed by Rafael J. Wysocki
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PM / Domains: Support for multiple states 



Some hardware (eg. OMAP), has the ability to enter different low power
modes for a given power domain. This allows for more fine grained control
over the power state of the platform. As a typical example, some registers
of the hardware may be implemented with retention flip-flops and be able
to retain their state at lower voltages allowing for faster on/off
latencies and an increased window of opportunity to enter an intermediate
low power state other than "off"

When trying to set a power domain to off, the genpd governor will choose
the deepest state that will respect the qos constraints of all the devices
and sub-domains on the power domain. The state chosen by the governor is
saved in the "state_idx" field of the generic_pm_domain structure and
shall be used by the power_off and power_on callbacks to perform the
necessary actions to set the power domain into (and out of) the state
indicated by state_idx.

States must be declared in ascending order from shallowest to deepest,
deepest meaning the state which takes longer to enter and exit.

For platforms that don't declare any states, a single a single "off"
state is used. Once all platforms are converted to use the state array,
the legacy on/off latencies will be removed.

[ Lina: Modified genpd state initialization and remove use of
        save_state_latency_ns in genpd timing data ]
Suggested-by: default avatarKevin Hilman <khilman@linaro.org>
Signed-off-by: default avatarLina Iyer <lina.iyer@linaro.org>
Signed-off-by: default avatarAxel Haslam <ahaslam+renesas@baylibre.com>
Acked-by: default avatarUlf Hansson <ulf.hansson@linaro.org>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent 18558cae

drivers/base/power/domain.c

+34 −5
Original line number Diff line number Diff line
@@ -104,6 +104,7 @@ static void genpd_sd_counter_inc(struct generic_pm_domain *genpd) 


static int genpd_power_on(struct generic_pm_domain *genpd, bool timed)

{

	unsigned int state_idx = genpd->state_idx;

	ktime_t time_start;

	s64 elapsed_ns;

	int ret;
@@ -120,10 +121,10 @@ static int genpd_power_on(struct generic_pm_domain *genpd, bool timed) 
		return ret;



	elapsed_ns = ktime_to_ns(ktime_sub(ktime_get(), time_start));

	if (elapsed_ns <= genpd->power_on_latency_ns)

	if (elapsed_ns <= genpd->states[state_idx].power_on_latency_ns)

		return ret;



	genpd->power_on_latency_ns = elapsed_ns;

	genpd->states[state_idx].power_on_latency_ns = elapsed_ns;

	genpd->max_off_time_changed = true;

	pr_debug("%s: Power-%s latency exceeded, new value %lld ns\n",

		 genpd->name, "on", elapsed_ns);
@@ -133,6 +134,7 @@ static int genpd_power_on(struct generic_pm_domain *genpd, bool timed) 


static int genpd_power_off(struct generic_pm_domain *genpd, bool timed)

{

	unsigned int state_idx = genpd->state_idx;

	ktime_t time_start;

	s64 elapsed_ns;

	int ret;
@@ -149,10 +151,10 @@ static int genpd_power_off(struct generic_pm_domain *genpd, bool timed) 
		return ret;



	elapsed_ns = ktime_to_ns(ktime_sub(ktime_get(), time_start));

	if (elapsed_ns <= genpd->power_off_latency_ns)

	if (elapsed_ns <= genpd->states[state_idx].power_off_latency_ns)

		return ret;



	genpd->power_off_latency_ns = elapsed_ns;

	genpd->states[state_idx].power_off_latency_ns = elapsed_ns;

	genpd->max_off_time_changed = true;

	pr_debug("%s: Power-%s latency exceeded, new value %lld ns\n",

		 genpd->name, "off", elapsed_ns);
@@ -585,6 +587,8 @@ static void pm_genpd_sync_poweroff(struct generic_pm_domain *genpd, 
	    || atomic_read(&genpd->sd_count) > 0)

		return;



	/* Choose the deepest state when suspending */

	genpd->state_idx = genpd->state_count - 1;

	genpd_power_off(genpd, timed);



	genpd->status = GPD_STATE_POWER_OFF;
@@ -1508,6 +1512,26 @@ void pm_genpd_init(struct generic_pm_domain *genpd, 
		genpd->dev_ops.start = pm_clk_resume;

	}



	if (genpd->state_idx >= GENPD_MAX_NUM_STATES) {

		pr_warn("Initial state index out of bounds.\n");

		genpd->state_idx = GENPD_MAX_NUM_STATES - 1;

	}



	if (genpd->state_count > GENPD_MAX_NUM_STATES) {

		pr_warn("Limiting states to  %d\n", GENPD_MAX_NUM_STATES);

		genpd->state_count = GENPD_MAX_NUM_STATES;

	}



	/* Use only one "off" state if there were no states declared */

	if (genpd->state_count == 0) {

		genpd->states[0].power_on_latency_ns =

					genpd->power_on_latency_ns;

		genpd->states[0].power_off_latency_ns =

					genpd->power_off_latency_ns;



		genpd->state_count = 1;

	}



	mutex_lock(&gpd_list_lock);

	list_add(&genpd->gpd_list_node, &gpd_list);

	mutex_unlock(&gpd_list_lock);
@@ -1872,7 +1896,12 @@ static int pm_genpd_summary_one(struct seq_file *s, 


	if (WARN_ON(genpd->status >= ARRAY_SIZE(status_lookup)))

		goto exit;

	seq_printf(s, "%-30s  %-15s ", genpd->name, status_lookup[genpd->status]);

	seq_printf(s, "%-30s  %s", genpd->name, status_lookup[genpd->status]);



	if (genpd->status == GPD_STATE_POWER_OFF)

		seq_printf(s, " %-13d ", genpd->state_idx);

	else

		seq_printf(s, " %-15s ", "");



	/*

	 * Modifications on the list require holding locks on both

drivers/base/power/domain_governor.c

+40 −24
Original line number Diff line number Diff line
@@ -98,7 +98,8 @@ static bool default_stop_ok(struct device *dev) 
 *

 * This routine must be executed under the PM domain's lock.

 */

static bool default_power_down_ok(struct dev_pm_domain *pd)

static bool __default_power_down_ok(struct dev_pm_domain *pd,

				     unsigned int state)

{

	struct generic_pm_domain *genpd = pd_to_genpd(pd);

	struct gpd_link *link;
@@ -106,27 +107,9 @@ static bool default_power_down_ok(struct dev_pm_domain *pd) 
	s64 min_off_time_ns;

	s64 off_on_time_ns;



	if (genpd->max_off_time_changed) {

		struct gpd_link *link;

	off_on_time_ns = genpd->states[state].power_off_latency_ns +

		genpd->states[state].power_on_latency_ns;



		/*

		 * We have to invalidate the cached results for the masters, so

		 * use the observation that default_power_down_ok() is not

		 * going to be called for any master until this instance

		 * returns.

		 */

		list_for_each_entry(link, &genpd->slave_links, slave_node)

			link->master->max_off_time_changed = true;



		genpd->max_off_time_changed = false;

		genpd->cached_power_down_ok = false;

		genpd->max_off_time_ns = -1;

	} else {

		return genpd->cached_power_down_ok;

	}



	off_on_time_ns = genpd->power_off_latency_ns +

				genpd->power_on_latency_ns;



	min_off_time_ns = -1;

	/*
@@ -186,8 +169,6 @@ static bool default_power_down_ok(struct dev_pm_domain *pd) 
			min_off_time_ns = constraint_ns;

	}



	genpd->cached_power_down_ok = true;



	/*

	 * If the computed minimum device off time is negative, there are no

	 * latency constraints, so the domain can spend arbitrary time in the
@@ -201,10 +182,45 @@ static bool default_power_down_ok(struct dev_pm_domain *pd) 
	 * time and the time needed to turn the domain on is the maximum

	 * theoretical time this domain can spend in the "off" state.

	 */

	genpd->max_off_time_ns = min_off_time_ns - genpd->power_on_latency_ns;

	genpd->max_off_time_ns = min_off_time_ns -

		genpd->states[state].power_on_latency_ns;

	return true;

}



static bool default_power_down_ok(struct dev_pm_domain *pd)

{

	struct generic_pm_domain *genpd = pd_to_genpd(pd);

	struct gpd_link *link;



	if (!genpd->max_off_time_changed)

		return genpd->cached_power_down_ok;



	/*

	 * We have to invalidate the cached results for the masters, so

	 * use the observation that default_power_down_ok() is not

	 * going to be called for any master until this instance

	 * returns.

	 */

	list_for_each_entry(link, &genpd->slave_links, slave_node)

		link->master->max_off_time_changed = true;



	genpd->max_off_time_ns = -1;

	genpd->max_off_time_changed = false;

	genpd->cached_power_down_ok = true;

	genpd->state_idx = genpd->state_count - 1;



	/* Find a state to power down to, starting from the deepest. */

	while (!__default_power_down_ok(pd, genpd->state_idx)) {

		if (genpd->state_idx == 0) {

			genpd->cached_power_down_ok = false;

			break;

		}

		genpd->state_idx--;

	}



	return genpd->cached_power_down_ok;

}



static bool always_on_power_down_ok(struct dev_pm_domain *domain)

{

	return false;

include/linux/pm_domain.h

+11 −0
Original line number Diff line number Diff line
@@ -19,6 +19,8 @@ 
/* Defines used for the flags field in the struct generic_pm_domain */

#define GENPD_FLAG_PM_CLK	(1U << 0) /* PM domain uses PM clk */



#define GENPD_MAX_NUM_STATES	8 /* Number of possible low power states */



enum gpd_status {

	GPD_STATE_ACTIVE = 0,	/* PM domain is active */

	GPD_STATE_POWER_OFF,	/* PM domain is off */
@@ -37,6 +39,11 @@ struct gpd_dev_ops { 
	bool (*active_wakeup)(struct device *dev);

};



struct genpd_power_state {

	s64 power_off_latency_ns;

	s64 power_on_latency_ns;

};



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 */
@@ -66,6 +73,10 @@ struct generic_pm_domain { 
	void (*detach_dev)(struct generic_pm_domain *domain,

			   struct device *dev);

	unsigned int flags;		/* Bit field of configs for genpd */

	struct genpd_power_state states[GENPD_MAX_NUM_STATES];

	unsigned int state_count; /* number of states */

	unsigned int state_idx; /* state that genpd will go to when off */



};



static inline struct generic_pm_domain *pd_to_genpd(struct dev_pm_domain *pd)