[PATCH v2] PM / Domains: Skip timings during syscore suspend/resume

[Geert Uytterhoeven <geert@linux-m68k.org>]

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