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Subject[PATCH v2] PM / Domains: Skip timings during syscore suspend/resume
Date
From: Geert Uytterhoeven <geert+renesas@glider.be>

The PM Domain code uses ktime_get() to perform various latency
measurements. However, if ktime_get() is called while timekeeping is
suspended, the following warning is printed:

WARNING: CPU: 0 PID: 1340 at kernel/time/timekeeping.c:576 ktime_get+0x3

This happens when resuming the PM Domain that contains the clock events
source, which calls pm_genpd_syscore_poweron(). Chain of operations is:

timekeeping_resume()
{
clockevents_resume()
sh_cmt_clock_event_resume()
pm_genpd_syscore_poweron()
pm_genpd_sync_poweron()
genpd_syscore_switch()
genpd_power_on()
ktime_get(), but timekeeping_suspended == 1
...
timekeeping_suspended = 0;
}

Fix this by adding a "timed" parameter to genpd_power_{on,off}() and
pm_genpd_sync_power{off,on}(), to indicate whether latency measurements
are allowed. This parameter is passed as false in
genpd_syscore_switch() (i.e. during syscore suspend/resume), and true in
all other cases.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
---
Seen on r8a7791/koelsch with CPG Clock Domain, _and_
genpd->power_{off,on}() populated for debugging purposes.

This is v2 of "PM / Domains: Skip latency measurements if timekeeping is
suspended".

Changes:
v2:
- Add a "timed" parameter instead of checking the
timekeeping_suspended flag, which is supposed to be private to the
time subsystem.
---
drivers/base/power/domain.c | 42 ++++++++++++++++++++++++++----------------
1 file changed, 26 insertions(+), 16 deletions(-)

diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
index 2327613d453929db..cdd547bd67df8218 100644
--- a/drivers/base/power/domain.c
+++ b/drivers/base/power/domain.c
@@ -181,7 +181,7 @@ static void genpd_recalc_cpu_exit_latency(struct generic_pm_domain *genpd)
genpd->cpuidle_data->idle_state->exit_latency = usecs64;
}

-static int genpd_power_on(struct generic_pm_domain *genpd)
+static int genpd_power_on(struct generic_pm_domain *genpd, bool timed)
{
ktime_t time_start;
s64 elapsed_ns;
@@ -190,6 +190,9 @@ static int genpd_power_on(struct generic_pm_domain *genpd)
if (!genpd->power_on)
return 0;

+ if (!timed)
+ return genpd->power_on(genpd);
+
time_start = ktime_get();
ret = genpd->power_on(genpd);
if (ret)
@@ -208,7 +211,7 @@ static int genpd_power_on(struct generic_pm_domain *genpd)
return ret;
}

-static int genpd_power_off(struct generic_pm_domain *genpd)
+static int genpd_power_off(struct generic_pm_domain *genpd, bool timed)
{
ktime_t time_start;
s64 elapsed_ns;
@@ -217,6 +220,9 @@ static int genpd_power_off(struct generic_pm_domain *genpd)
if (!genpd->power_off)
return 0;

+ if (!timed)
+ return genpd->power_off(genpd);
+
time_start = ktime_get();
ret = genpd->power_off(genpd);
if (ret == -EBUSY)
@@ -305,7 +311,7 @@ static int __pm_genpd_poweron(struct generic_pm_domain *genpd)
}
}

- ret = genpd_power_on(genpd);
+ ret = genpd_power_on(genpd, true);
if (ret)
goto err;

@@ -615,7 +621,7 @@ static int pm_genpd_poweroff(struct generic_pm_domain *genpd)
* the pm_genpd_poweron() restore power for us (this shouldn't
* happen very often).
*/
- ret = genpd_power_off(genpd);
+ ret = genpd_power_off(genpd, true);
if (ret == -EBUSY) {
genpd_set_active(genpd);
goto out;
@@ -827,6 +833,7 @@ static bool genpd_dev_active_wakeup(struct generic_pm_domain *genpd,
/**
* pm_genpd_sync_poweroff - Synchronously power off a PM domain and its masters.
* @genpd: PM domain to power off, if possible.
+ * @timed: True if latency measurements are allowed.
*
* Check if the given PM domain can be powered off (during system suspend or
* hibernation) and do that if so. Also, in that case propagate to its masters.
@@ -836,7 +843,8 @@ static bool genpd_dev_active_wakeup(struct generic_pm_domain *genpd,
* executed sequentially, so it is guaranteed that it will never run twice in
* parallel).
*/
-static void pm_genpd_sync_poweroff(struct generic_pm_domain *genpd)
+static void pm_genpd_sync_poweroff(struct generic_pm_domain *genpd,
+ bool timed)
{
struct gpd_link *link;

@@ -847,26 +855,28 @@ static void pm_genpd_sync_poweroff(struct generic_pm_domain *genpd)
|| atomic_read(&genpd->sd_count) > 0)
return;

- genpd_power_off(genpd);
+ genpd_power_off(genpd, timed);

genpd->status = GPD_STATE_POWER_OFF;

list_for_each_entry(link, &genpd->slave_links, slave_node) {
genpd_sd_counter_dec(link->master);
- pm_genpd_sync_poweroff(link->master);
+ pm_genpd_sync_poweroff(link->master, timed);
}
}

/**
* pm_genpd_sync_poweron - Synchronously power on a PM domain and its masters.
* @genpd: PM domain to power on.
+ * @timed: True if latency measurements are allowed.
*
* This function is only called in "noirq" and "syscore" stages 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)
+static void pm_genpd_sync_poweron(struct generic_pm_domain *genpd,
+ bool timed)
{
struct gpd_link *link;

@@ -874,11 +884,11 @@ static void pm_genpd_sync_poweron(struct generic_pm_domain *genpd)
return;

list_for_each_entry(link, &genpd->slave_links, slave_node) {
- pm_genpd_sync_poweron(link->master);
+ pm_genpd_sync_poweron(link->master, timed);
genpd_sd_counter_inc(link->master);
}

- genpd_power_on(genpd);
+ genpd_power_on(genpd, timed);

genpd->status = GPD_STATE_ACTIVE;
}
@@ -1056,7 +1066,7 @@ static int pm_genpd_suspend_noirq(struct device *dev)
* the same PM domain, so it is not necessary to use locking here.
*/
genpd->suspended_count++;
- pm_genpd_sync_poweroff(genpd);
+ pm_genpd_sync_poweroff(genpd, true);

return 0;
}
@@ -1086,7 +1096,7 @@ static int pm_genpd_resume_noirq(struct device *dev)
* 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_sync_poweron(genpd);
+ pm_genpd_sync_poweron(genpd, true);
genpd->suspended_count--;

return genpd_start_dev(genpd, dev);
@@ -1300,7 +1310,7 @@ static int pm_genpd_restore_noirq(struct device *dev)
* If the domain was off before the hibernation, make
* sure it will be off going forward.
*/
- genpd_power_off(genpd);
+ genpd_power_off(genpd, true);

return 0;
}
@@ -1309,7 +1319,7 @@ static int pm_genpd_restore_noirq(struct device *dev)
if (genpd->suspend_power_off)
return 0;

- pm_genpd_sync_poweron(genpd);
+ pm_genpd_sync_poweron(genpd, true);

return genpd_start_dev(genpd, dev);
}
@@ -1367,9 +1377,9 @@ static void genpd_syscore_switch(struct device *dev, bool suspend)

if (suspend) {
genpd->suspended_count++;
- pm_genpd_sync_poweroff(genpd);
+ pm_genpd_sync_poweroff(genpd, false);
} else {
- pm_genpd_sync_poweron(genpd);
+ pm_genpd_sync_poweron(genpd, false);
genpd->suspended_count--;
}
}
--
1.9.1


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