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Subject[PATCH 1/15] PM / Domains: Introduce simplified power on routine for system resume
Date

Introduce function pm_genpd_sync_poweron() for restoring domain power
during resume from system suspend and hibernation. It can be much
simpler than pm_genpd_poweron(), because it doesn't have to care
about locking and it can skip many checks done by the latter.

Modify pm_genpd_resume_noirq() and pm_genpd_restore_noirq() to use
the new function.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
---
drivers/base/power/domain.c | 34 ++++++++++++++++++++++++++++++----
1 file changed, 30 insertions(+), 4 deletions(-)

Index: linux/drivers/base/power/domain.c
===================================================================
--- linux.orig/drivers/base/power/domain.c
+++ linux/drivers/base/power/domain.c
@@ -777,6 +777,32 @@ static void pm_genpd_sync_poweroff(struc
}

/**
+ * pm_genpd_sync_poweron - Synchronously power on a PM domain and its masters.
+ * @genpd: PM domain to power on.
+ *
+ * This function is only called in "noirq" stage of system power transitions, so
+ * it need not acquire locks (all of the "noirq" callbacks are executed
+ * sequentially, so it is guaranteed that it will never run twice in parallel).
+ */
+static void pm_genpd_sync_poweron(struct generic_pm_domain *genpd)
+{
+ struct gpd_link *link;
+
+ if (genpd->status != GPD_STATE_POWER_OFF)
+ return;
+
+ list_for_each_entry(link, &genpd->slave_links, slave_node) {
+ pm_genpd_sync_poweron(link->master);
+ genpd_sd_counter_inc(link->master);
+ }
+
+ if (genpd->power_on)
+ genpd->power_on(genpd);
+
+ genpd->status = GPD_STATE_ACTIVE;
+}
+
+/**
* resume_needed - Check whether to resume a device before system suspend.
* @dev: Device to check.
* @genpd: PM domain the device belongs to.
@@ -979,7 +1005,7 @@ static int pm_genpd_resume_noirq(struct
* guaranteed that this function will never run twice in parallel for
* the same PM domain, so it is not necessary to use locking here.
*/
- pm_genpd_poweron(genpd);
+ pm_genpd_sync_poweron(genpd);
genpd->suspended_count--;

return genpd_start_dev(genpd, dev);
@@ -1186,8 +1212,8 @@ static int pm_genpd_restore_noirq(struct
if (genpd->suspended_count++ == 0) {
/*
* The boot kernel might put the domain into arbitrary state,
- * so make it appear as powered off to pm_genpd_poweron(), so
- * that it tries to power it on in case it was really off.
+ * so make it appear as powered off to pm_genpd_sync_poweron(),
+ * so that it tries to power it on in case it was really off.
*/
genpd->status = GPD_STATE_POWER_OFF;
if (genpd->suspend_power_off) {
@@ -1205,7 +1231,7 @@ static int pm_genpd_restore_noirq(struct
if (genpd->suspend_power_off)
return 0;

- pm_genpd_poweron(genpd);
+ pm_genpd_sync_poweron(genpd);

return dev_gpd_data(dev)->always_on ? 0 : genpd_start_dev(genpd, dev);
}


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