linux-kernel - [PATCH] tick/idle/powerpc: Do not register idle states with CPUIDLE_FLAG_TIMER

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Message-ID: <20150624064801.30680.3246.stgit@perfhull-ltc.austin.ibm.com>
Date:	Wed, 24 Jun 2015 01:48:01 -0500
From:	Preeti U Murthy <preeti@...ux.vnet.ibm.com>
To:	benh@...nel.crashing.org, daniel.lezcano@...aro.org,
	rjw@...ysocki.net
Cc:	mark.rutland@....com, lorenzo.pieralisi@....com,
	linux-pm@...r.kernel.org, mpe@...erman.id.au, will.deacon@....com,
	linux-kernel@...r.kernel.org, shreyas@...ux.vnet.ibm.com,
	svaidy@...ux.vnet.ibm.com, linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH] tick/idle/powerpc: Do not register idle states with
 CPUIDLE_FLAG_TIMER_STOP set in periodic mode

On some archs, the local clockevent device stops in deep cpuidle states.
The broadcast framework is used to wakeup cpus in these idle states, in
which either an external clockevent device is used to send wakeup ipis
or the hrtimer broadcast framework kicks in in the absence of such a
device. One cpu is nominated as the broadcast cpu and this cpu sends
wakeup ipis to sleeping cpus at the appropriate time. This is the
implementation in the oneshot mode of broadcast.

In periodic mode of broadcast however, the presence of such cpuidle
states results in the cpuidle driver calling tick_broadcast_enable()
which shuts down the local clockevent devices of all the cpus and
appoints the tick broadcast device as the clockevent device for each of
them. This works on those archs where the tick broadcast device is a
real clockevent device.  But on archs which depend on the hrtimer mode
of broadcast, the tick broadcast device hapens to be a pseudo device.
The consequence is that the local clockevent devices of all cpus are
shutdown and the kernel hangs at boot time in periodic mode.

Let us thus not register the cpuidle states which have
CPUIDLE_FLAG_TIMER_STOP flag set, on archs which depend on the hrtimer
mode of broadcast in periodic mode. This patch takes care of doing this
on powerpc. The cpus would not have entered into such deep cpuidle
states in periodic mode on powerpc anyway. So there is no loss here.

Signed-off-by: Preeti U Murthy <preeti@...ux.vnet.ibm.com>
---
 drivers/cpuidle/cpuidle-powernv.c |   15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/drivers/cpuidle/cpuidle-powernv.c b/drivers/cpuidle/cpuidle-powernv.c
index 5937207..3442764 100644
--- a/drivers/cpuidle/cpuidle-powernv.c
+++ b/drivers/cpuidle/cpuidle-powernv.c
@@ -60,6 +60,8 @@ static int nap_loop(struct cpuidle_device *dev,
 	return index;
 }

+/* Register for fastsleep only in oneshot mode of broadcast */
+#ifdef CONFIG_TICK_ONESHOT
 static int fastsleep_loop(struct cpuidle_device *dev,
 				struct cpuidle_driver *drv,
 				int index)
@@ -83,7 +85,7 @@ static int fastsleep_loop(struct cpuidle_device *dev,

 	return index;
 }
-
+#endif
 /*
  * States for dedicated partition case.
  */
@@ -209,7 +211,14 @@ static int powernv_add_idle_states(void)
 			powernv_states[nr_idle_states].flags = 0;
 			powernv_states[nr_idle_states].target_residency = 100;
 			powernv_states[nr_idle_states].enter = &nap_loop;
-		} else if (flags[i] & OPAL_PM_SLEEP_ENABLED ||
+		}
+
+		/*
+		 * All cpuidle states with CPUIDLE_FLAG_TIMER_STOP set must come
+		 * within this config dependency check.
+		 */
+#ifdef CONFIG_TICK_ONESHOT
+		if (flags[i] & OPAL_PM_SLEEP_ENABLED ||
 			flags[i] & OPAL_PM_SLEEP_ENABLED_ER1) {
 			/* Add FASTSLEEP state */
 			strcpy(powernv_states[nr_idle_states].name, "FastSleep");
@@ -218,7 +227,7 @@ static int powernv_add_idle_states(void)
 			powernv_states[nr_idle_states].target_residency = 300000;
 			powernv_states[nr_idle_states].enter = &fastsleep_loop;
 		}
-
+#endif
 		powernv_states[nr_idle_states].exit_latency =
 				((unsigned int)latency_ns[i]) / 1000;

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