[3.13.y.z extended stable] Patch "ARM: OMAP4: Fix the boot regression with CPU_IDLE enabled" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    ARM: OMAP4: Fix the boot regression with CPU_IDLE enabled

to the linux-3.13.y-queue branch of the 3.13.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.13.y-queue

This patch is scheduled to be released in version 3.13.11.4.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.13.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 986ab7172c76362f7247acd59ac2e8b5ea21dd77 Mon Sep 17 00:00:00 2001
From: Santosh Shilimkar <santosh.shilimkar at ti.com>
Date: Mon, 12 May 2014 17:37:59 -0400
Subject: ARM: OMAP4: Fix the boot regression with CPU_IDLE enabled

commit 4b353a706a86598ba47307c47301c3c428b79e09 upstream.

On OMAP4 panda board, there have been several bug reports about boot
hang and lock-ups with CPU_IDLE enabled. The root cause of the issue
is missing interrupts while in idle state. Commit cb7094e8 {cpuidle / omap4 :
use CPUIDLE_FLAG_TIMER_STOP flag} moved the broadcast notifiers to common
code for right reasons but on OMAP4 which suffers from a nasty ROM code
bug with GIC, commit ff999b8a {ARM: OMAP4460: Workaround for ROM bug ..},
we loose interrupts which leads to issues like lock-up, hangs etc.

Patch reverts commit cb7094 {cpuidle / omap4 : use CPUIDLE_FLAG_TIMER_STOP
flag} and 54769d6 {cpuidle: OMAP4: remove timer broadcast initialization} to
avoid the issue. With this change, OMAP4 panda boards, the mentioned
issues are getting fixed. We no longer loose interrupts which was the cause
of the regression.

Fixes: cb7094e8 (cpuidle / omap4 : use CPUIDLE_FLAG_TIMER_STOP flag)
Fixes: ff999b8a (cpuidle: OMAP4: remove timer broadcast initialization)
Cc: Roger Quadros <rogerq at ti.com>
Cc: Kevin Hilman <khilman at linaro.org>
Cc: Tony Lindgren <tony at atomide.com>
Cc: Daniel Lezcano <daniel.lezcano at linaro.org>
Reported-tested-by: Roger Quadros <rogerq at ti.com>
Reported-tested-by: Kevin Hilman <khilman at linaro.org>
Tested-by: Tony Lindgren <tony at atomide.com>
Signed-off-by: Santosh Shilimkar <santosh.shilimkar at ti.com>
Signed-off-by: Tony Lindgren <tony at atomide.com>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 arch/arm/mach-omap2/cpuidle44xx.c | 25 +++++++++++++++++++++----
 1 file changed, 21 insertions(+), 4 deletions(-)

diff --git a/arch/arm/mach-omap2/cpuidle44xx.c b/arch/arm/mach-omap2/cpuidle44xx.c
index 4c8982a..d159ec3 100644
--- a/arch/arm/mach-omap2/cpuidle44xx.c
+++ b/arch/arm/mach-omap2/cpuidle44xx.c
@@ -14,6 +14,7 @@
 #include <linux/cpuidle.h>
 #include <linux/cpu_pm.h>
 #include <linux/export.h>
+#include <linux/clockchips.h>

 #include <asm/cpuidle.h>
 #include <asm/proc-fns.h>
@@ -80,6 +81,7 @@ static int omap_enter_idle_coupled(struct cpuidle_device *dev,
 			int index)
 {
 	struct idle_statedata *cx = state_ptr + index;
+	int cpu_id = smp_processor_id();

 	/*
 	 * CPU0 has to wait and stay ON until CPU1 is OFF state.
@@ -104,6 +106,8 @@ static int omap_enter_idle_coupled(struct cpuidle_device *dev,
 		}
 	}

+	clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER, &cpu_id);
+
 	/*
 	 * Call idle CPU PM enter notifier chain so that
 	 * VFP and per CPU interrupt context is saved.
@@ -147,6 +151,8 @@ static int omap_enter_idle_coupled(struct cpuidle_device *dev,
 		(cx->mpu_logic_state == PWRDM_POWER_OFF))
 		cpu_cluster_pm_exit();

+	clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_EXIT, &cpu_id);
+
 fail:
 	cpuidle_coupled_parallel_barrier(dev, &abort_barrier);
 	cpu_done[dev->cpu] = false;
@@ -154,6 +160,16 @@ fail:
 	return index;
 }

+/*
+ * For each cpu, setup the broadcast timer because local timers
+ * stops for the states above C1.
+ */
+static void omap_setup_broadcast_timer(void *arg)
+{
+	int cpu = smp_processor_id();
+	clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ON, &cpu);
+}
+
 static struct cpuidle_driver omap4_idle_driver = {
 	.name				= "omap4_idle",
 	.owner				= THIS_MODULE,
@@ -171,8 +187,7 @@ static struct cpuidle_driver omap4_idle_driver = {
 			/* C2 - CPU0 OFF + CPU1 OFF + MPU CSWR */
 			.exit_latency = 328 + 440,
 			.target_residency = 960,
-			.flags = CPUIDLE_FLAG_TIME_VALID | CPUIDLE_FLAG_COUPLED |
-			         CPUIDLE_FLAG_TIMER_STOP,
+			.flags = CPUIDLE_FLAG_TIME_VALID | CPUIDLE_FLAG_COUPLED,
 			.enter = omap_enter_idle_coupled,
 			.name = "C2",
 			.desc = "CPUx OFF, MPUSS CSWR",
@@ -181,8 +196,7 @@ static struct cpuidle_driver omap4_idle_driver = {
 			/* C3 - CPU0 OFF + CPU1 OFF + MPU OSWR */
 			.exit_latency = 460 + 518,
 			.target_residency = 1100,
-			.flags = CPUIDLE_FLAG_TIME_VALID | CPUIDLE_FLAG_COUPLED |
-			         CPUIDLE_FLAG_TIMER_STOP,
+			.flags = CPUIDLE_FLAG_TIME_VALID | CPUIDLE_FLAG_COUPLED,
 			.enter = omap_enter_idle_coupled,
 			.name = "C3",
 			.desc = "CPUx OFF, MPUSS OSWR",
@@ -213,5 +227,8 @@ int __init omap4_idle_init(void)
 	if (!cpu_clkdm[0] || !cpu_clkdm[1])
 		return -ENODEV;

+	/* Configure the broadcast timer on each cpu */
+	on_each_cpu(omap_setup_broadcast_timer, NULL, 1);
+
 	return cpuidle_register(&omap4_idle_driver, cpu_online_mask);
 }
--
1.9.1