linux-kernel - [PATCH 11/15] PM / Domains: Do not measure start time for "irq safe" devices

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Message-Id: <201208060147.29559.rjw@sisk.pl>
Date:	Mon, 6 Aug 2012 01:47:29 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Linux PM list <linux-pm@...r.kernel.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	"Linux-sh list" <linux-sh@...r.kernel.org>,
	Magnus Damm <magnus.damm@...il.com>,
	Paul Mundt <lethal@...ux-sh.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH 11/15] PM / Domains: Do not measure start time for "irq safe" devices

The genpd_start_dev() routine used by pm_genpd_runtime_resume()
to put "irq safe" devices into the full power state measures the
time necessary to "start" the device and updates its PM QoS timing
data if necessary.  This may lead to a deadlock if the given device
is a clock source and genpd_start_dev() is invoked from within the
clock source's .enable() routine, which will happen if that routine
uses pm_runtime_get_sync(), for example, to ensure that the device
is operational.

For this reason, introduce a special routine analogous to
genpd_start_dev(), called genpd_start_dev_no_timing(), that doesn't
carry out the time measurement, and make pm_genpd_runtime_resume()
use it instead of genpd_start_dev() to power up "irq safe" devices.

Signed-off-by: Rafael J. Wysocki <rjw@...k.pl>
---
 drivers/base/power/domain.c |    8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

Index: linux/drivers/base/power/domain.c
===================================================================
--- linux.orig/drivers/base/power/domain.c
+++ linux/drivers/base/power/domain.c
@@ -75,6 +75,12 @@ static int genpd_start_dev(struct generi
 					start_latency_ns, "start");
 }

+static int genpd_start_dev_no_timing(struct generic_pm_domain *genpd,
+				     struct device *dev)
+{
+	return GENPD_DEV_CALLBACK(genpd, int, start, dev);
+}
+
 static bool genpd_sd_counter_dec(struct generic_pm_domain *genpd)
 {
 	bool ret = false;
@@ -626,7 +632,7 @@ static int pm_genpd_runtime_resume(struc

 	/* If power.irq_safe, the PM domain is never powered off. */
 	if (dev->power.irq_safe)
-		return genpd_start_dev(genpd, dev);
+		return genpd_start_dev_no_timing(genpd, dev);

 	mutex_lock(&genpd->lock);
 	ret = __pm_genpd_poweron(genpd);

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