Re: [PATCH v2] PM / runtime: Rework pm_runtime_force_suspend/resume()

["Rafael J. Wysocki" <rjw@rjwysocki.net>]

On Tuesday, January 9, 2018 5:03:18 PM CET Rafael J. Wysocki wrote:
> On Tue, Jan 9, 2018 at 4:30 PM, Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> > Hi Rafael,
> >
> > CC usb
> >
> > On Tue, Jan 9, 2018 at 4:00 PM, Rafael J. Wysocki <rafael@kernel.org> wrote:
> >> On Tue, Jan 9, 2018 at 2:37 PM, Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> >>> On Wed, Jan 3, 2018 at 12:06 PM, Rafael J. Wysocki <rjw@rjwysocki.net> wrote:
> >>>> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> >>>>
> >>>> One of the limitations of pm_runtime_force_suspend/resume() is that
> >>>> if a parent driver wants to use these functions, all of its child
> >>>> drivers have to do that too because of the parent usage counter
> >>>> manipulations necessary to get the correct state of the parent during
> >>>> system-wide transitions to the working state (system resume).
> >>>> However, that limitation turns out to be artificial, so remove it.
> >>>>
> >>>> Namely, pm_runtime_force_suspend() only needs to update the children
> >>>> counter of its parent (if there's is a parent) when the device can
> >>>> stay in suspend after the subsequent system resume transition, as
> >>>> that counter is correct already otherwise.  Now, if the parent's
> >>>> children counter is not updated, it is not necessary to increment
> >>>> the parent's usage counter in that case any more, as long as the
> >>>> children counters of devices are checked along with their usage
> >>>> counters in order to decide whether or not the devices may be left
> >>>> in suspend after the subsequent system resume transition.
> >>>>
> >>>> Accordingly, modify pm_runtime_force_suspend() to only call
> >>>> pm_runtime_set_suspended() for devices whose usage and children
> >>>> counters are at the "no references" level (the runtime PM status
> >>>> of the device needs to be updated to "suspended" anyway in case
> >>>> this function is called once again for the same device during the
> >>>> transition under way), drop the parent usage counter incrementation
> >>>> from it and update pm_runtime_force_resume() to compensate for these
> >>>> changes.
> >>>>
> >>>> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> >>>
> >>> This patch causes a regression during system resume on Renesas Salvator-XS
> >>> with R-Car H3 ES2.0:
> >>
> >> I have dropped it for now, but we need to address the underlying issue.
> >>
> >>>     SError Interrupt on CPU3, code 0xbf000002 -- SError
> >>>     SError Interrupt on CPU2, code 0xbf000002 -- SError
> >>>     CPU: 3 PID: 1769 Comm: kworker/u16:13 Not tainted
> >>> 4.15.0-rc7-arm64-renesas-05338-gf14cf570a813c9ca-dirty #97
> >>>     CPU: 2 PID: 1774 Comm: kworker/u16:18 Not tainted
> >>> 4.15.0-rc7-arm64-renesas-05338-gf14cf570a813c9ca-dirty #97
> >>>     Hardware name: Renesas Salvator-X 2nd version board based on
> >>> r8a7795 ES2.0+ (DT)
> >>>     Hardware name: Renesas Salvator-X 2nd version board based on
> >>> r8a7795 ES2.0+ (DT)
> >>>     Workqueue: events_unbound async_run_entry_fn
> >>>     Workqueue: events_unbound async_run_entry_fn
> >>>     pstate: 60000005 (nZCv daif -PAN -UAO)
> >>>     pstate: 60000005 (nZCv daif -PAN -UAO)
> >>>     pc : rcar_gen3_phy_usb2_init+0x34/0xf8
> >>>     pc : rcar_gen3_phy_usb2_init+0x34/0xf8
> >>>     lr : phy_init+0x64/0xcc
> >>>     lr : phy_init+0x64/0xcc
> >>>     ...
> >>>     Kernel panic - not syncing: Asynchronous SError Interrupt
> >>>
> >>> Note that before, it printed a warning instead:
> >>>
> >>>     Enabling runtime PM for inactive device (ee0a0200.usb-phy) with
> >>> active children
> >>>     WARNING: CPU: 0 PID: 1741 at drivers/base/power/runtime.c:1300
> >>> pm_runtime_enable+0x94/0xd8
> >>>
> >>> Reverting commit 0408584d580d4a2c ("PM / runtime: Rework
> >>> pm_runtime_force_suspend/resume()") fixes the crash.
> >>>
> >>> Note that applying Ulf's "[PATCH v2 0/3] phy: core: Re-work runtime PM
> >>> deployment and fix an issue"
> >>> (https://www.spinics.net/lists/linux-renesas-soc/msg21719.html) instead
> >>> does not fix the crash.
> >>
> >> OK
> >>
> >>> With more debug code added, it seems the EHCI module clocks (701-703) are
> >>> enabled earlier than before. I guess this triggers the workqueue to perform
> >>> an operation while another related device (HSUSB 704?) is still disabled?
> >>
> >> Probably.
> >>
> >> Likely a device that wasn't resumed before resumes now and that causes
> >> the issue to appear.
> >>
> >> I'm wondering if adding the ignore_children check to the patch helps.
> >> If not, there clearly is a resume ordering issue that is papered over
> >> by the current code.
> >
> > Something fishy is going on. Status of the USB PHYs differ before/after
> > system suspend, according to /sys/kernel/debug/pm_genpd/pm_genpd_summary:
> >
> > -    /devices/platform/soc/ee0a0200.usb-phy              active
> > -    /devices/platform/soc/ee0c0200.usb-phy              active
> > -    /devices/platform/soc/ee080200.usb-phy              active
> > +    /devices/platform/soc/ee0a0200.usb-phy              suspended
> > +    /devices/platform/soc/ee0c0200.usb-phy              suspended
> > +    /devices/platform/soc/ee080200.usb-phy              suspended
> 
> Yeah.
> 
> That's because of the pm_runtime_force_suspend/resume() called by
> genpd.  These functions generally may cause devices active before
> system suspend to be left in suspend after it.  That generally is a
> good idea if the device was not really in use before the system
> suspend, but there is a problem that the driver of it may not be
> prepared for that to happen (and also the way to determine the "not
> really in use" case may not be as expected by the driver).

So below is something to try (untested).

I know that Ulf will be protesting, but that's what I would do unless there
are really *really* good reasons not to.


---
 drivers/base/power/domain.c |   34 +++++++++++++++++++++-------------
 1 file changed, 21 insertions(+), 13 deletions(-)

Index: linux-pm/drivers/base/power/domain.c
===================================================================
--- linux-pm.orig/drivers/base/power/domain.c
+++ linux-pm/drivers/base/power/domain.c
@@ -1048,8 +1048,9 @@ static int genpd_finish_suspend(struct d
 	if (ret)
 		return ret;
 
-	if (genpd->dev_ops.stop && genpd->dev_ops.start) {
-		ret = pm_runtime_force_suspend(dev);
+	if (genpd->dev_ops.stop && genpd->dev_ops.start &&
+	    !pm_runtime_status_suspended(dev)) {
+		ret = genpd_stop_dev(genpd, dev);
 		if (ret)
 			return ret;
 	}
@@ -1101,8 +1102,12 @@ static int genpd_resume_noirq(struct dev
 	genpd->suspended_count--;
 	genpd_unlock(genpd);
 
-	if (genpd->dev_ops.stop && genpd->dev_ops.start)
-		ret = pm_runtime_force_resume(dev);
+	if (genpd->dev_ops.stop && genpd->dev_ops.start &&
+	    !pm_runtime_status_suspended(dev)) {
+		ret = genpd_start_dev(genpd, dev);
+		if (ret)
+			return ret;
+	}
 
 	ret = pm_generic_resume_noirq(dev);
 	if (ret)
@@ -1123,7 +1128,7 @@ static int genpd_resume_noirq(struct dev
 static int genpd_freeze_noirq(struct device *dev)
 {
 	const struct generic_pm_domain *genpd;
-	int ret = 0;
+	int ret;
 
 	dev_dbg(dev, "%s()\n", __func__);
 
@@ -1135,8 +1140,9 @@ static int genpd_freeze_noirq(struct dev
 	if (ret)
 		return ret;
 
-	if (genpd->dev_ops.stop && genpd->dev_ops.start)
-		ret = pm_runtime_force_suspend(dev);
+	if (genpd->dev_ops.stop && genpd->dev_ops.start &&
+	    !pm_runtime_status_suspended(dev))
+		ret = genpd_stop_dev(genpd, dev);
 
 	return ret;
 }
@@ -1151,7 +1157,7 @@ static int genpd_freeze_noirq(struct dev
 static int genpd_thaw_noirq(struct device *dev)
 {
 	const struct generic_pm_domain *genpd;
-	int ret = 0;
+	int ret;
 
 	dev_dbg(dev, "%s()\n", __func__);
 
@@ -1159,8 +1165,9 @@ static int genpd_thaw_noirq(struct devic
 	if (IS_ERR(genpd))
 		return -EINVAL;
 
-	if (genpd->dev_ops.stop && genpd->dev_ops.start) {
-		ret = pm_runtime_force_resume(dev);
+	if (genpd->dev_ops.stop && genpd->dev_ops.start &&
+	    !pm_runtime_status_suspended(dev)) {
+		ret = genpd_start_dev(genpd, dev);
 		if (ret)
 			return ret;
 	}
@@ -1193,7 +1200,7 @@ static int genpd_poweroff_noirq(struct d
 static int genpd_restore_noirq(struct device *dev)
 {
 	struct generic_pm_domain *genpd;
-	int ret = 0;
+	int ret;
 
 	dev_dbg(dev, "%s()\n", __func__);
 
@@ -1217,8 +1224,9 @@ static int genpd_restore_noirq(struct de
 	genpd_sync_power_on(genpd, true, 0);
 	genpd_unlock(genpd);
 
-	if (genpd->dev_ops.stop && genpd->dev_ops.start) {
-		ret = pm_runtime_force_resume(dev);
+	if (genpd->dev_ops.stop && genpd->dev_ops.start &&
+	    !pm_runtime_status_suspended(dev)) {
+		ret = genpd_start_dev(genpd, dev);
 		if (ret)
 			return ret;
 	}