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: Kevin Hilman <khilman@linaro.org>
Signed-off-by: Lina Iyer <lina.iyer@linaro.org>
Signed-off-by: Axel Haslam <ahaslam+renesas@baylibre.com>
Acked-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

1 files changed, 34 insertions, 5 deletions

diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
index 301b785f9f56..4c6f46b5c444 100644
--- a/drivers/base/power/domain.c
+++ b/drivers/base/power/domain.c
@@ -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