[PATCH] ACPI, cpuidle: Fix suspend/resume regression caused by cpuidle cleanup.

[Deepthi Dharwar <deepthi@linux.vnet.ibm.com>]

From: Deepthi Dharwar <deepthi@linux.vnet.ibm.com>

Fix suspend/resume regression caused by cpuidle cleanup.

Commit e978aa7d7d57d04eb5f88a7507c4fb98577def77 ( cpuidle: Move
dev->last_residency update to driver enter routine; remove dev->last_state)
was  breaking suspend on laptops, as reported in the below link
	- https://lkml.org/lkml/2011/11/11/164

This was fixed in commit 3439a8da16bcad6b0982ece938c9f8299bb53584
(ACPI / cpuidle: Remove acpi_idle_suspend (to fix suspend regression)
by removing acpi_idle_suspend flag.
	- https://lkml.org/lkml/2011/11/14/74

But this fix did not work on all systems
as Suspend/resume regression was reported on Lenovo S10-3
recently by Dave.
	- https://lkml.org/lkml/2012/5/27/115
It looked like with commit e978aa7d broke suspend and
with commit 3439a8da resume was not working with acpi_idle driver.

This patch fixes the regression that caused this issue
in the first place. acpi_idle_suspend flag is essential on
some x86 systems to prevent the cpus from going to deeper C-states
when suspend is triggered ( commit b04e7bdb984 )
So reverting the commit 3439a8da is essential.

By default, irqs are disabled in cpu_idle arch specific call
and re-enabled in idle state return path . As the acpi_idle_suspend
flag was being set during suspend, which prevented the cpus
going to deeper idle states, it is essential to
enabling the irqs in its return path too.

To address the suspend issue,
we were not re-enabling the interrupts while returning from
acpi_idle_enter_bm() routine if acpi_idle_suspend flag is set.
and this was causing suspend failure.

In addition to the above fix, a sanity check has also been added
in x86 arch specific cpu_idle call to ensure that the idle call
always returns with IRQs enabled.

This patch applies on 3.5-rc2
---

Reported-and-Tested-by: Dav Hansen <dave@linux.vnet.ibm.com>
Tested-by: Preeti Murthy <preeti@linux.vnet.ibm.com>
Signed-off-by: Deepthi Dharwar <deepthi@linux.vnet.ibm.com>
Reviewed-by: Srivatsa S Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---
 arch/x86/kernel/process.c     |    6 ++++++
 drivers/acpi/processor_idle.c |   28 ++++++++++++++++++++++++++++
 2 files changed, 34 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 735279e..8ab76ad 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -460,6 +460,12 @@ void cpu_idle(void)
 				pm_idle();

 			rcu_idle_exit();
+
+			/*
+			 * Sanity check to ensure that idle call returns
+			 * with IRQs enabled
+			 */
+			WARN_ON(irqs_disabled());
 			start_critical_timings();

 			/* In many cases the interrupt that ended idle
diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
index f3decb3..c2ffd84 100644
--- a/drivers/acpi/processor_idle.c
+++ b/drivers/acpi/processor_idle.c
@@ -224,6 +224,7 @@ static void lapic_timer_state_broadcast(struct acpi_processor *pr,
 /*
  * Suspend / resume control
  */
+static int acpi_idle_suspend;
 static u32 saved_bm_rld;

 static void acpi_idle_bm_rld_save(void)
@@ -242,13 +243,21 @@ static void acpi_idle_bm_rld_restore(void)

 int acpi_processor_suspend(struct acpi_device * device, pm_message_t state)
 {
+	if (acpi_idle_suspend == 1)
+		return 0;
+
 	acpi_idle_bm_rld_save();
+	acpi_idle_suspend = 1;
 	return 0;
 }

 int acpi_processor_resume(struct acpi_device * device)
 {
+	if (acpi_idle_suspend == 0)
+		return 0;
+
 	acpi_idle_bm_rld_restore();
+	acpi_idle_suspend = 0;
 	return 0;
 }

@@ -754,6 +763,12 @@ static int acpi_idle_enter_c1(struct cpuidle_device *dev,

 	local_irq_disable();

+	if (acpi_idle_suspend) {
+		local_irq_enable();
+		cpu_relax();
+		return -EINVAL;
+	}
+
 	lapic_timer_state_broadcast(pr, cx, 1);
 	kt1 = ktime_get_real();
 	acpi_idle_do_entry(cx);
@@ -823,6 +838,12 @@ static int acpi_idle_enter_simple(struct cpuidle_device *dev,

 	local_irq_disable();

+	if (acpi_idle_suspend) {
+		local_irq_enable();
+		cpu_relax();
+		return -EINVAL;
+	}
+
 	if (cx->entry_method != ACPI_CSTATE_FFH) {
 		current_thread_info()->status &= ~TS_POLLING;
 		/*
@@ -901,6 +922,13 @@ static int acpi_idle_enter_bm(struct cpuidle_device *dev,
 	if (unlikely(!pr))
 		return -EINVAL;

+	if (acpi_idle_suspend) {
+		if (irqs_disabled())
+			local_irq_enable();
+		cpu_relax();
+		return -EINVAL;
+	}
+
 	if (!cx->bm_sts_skip && acpi_idle_bm_check()) {
 		if (drv->safe_state_index >= 0) {
 			return drv->states[drv->safe_state_index].enter(dev,

Regards,
Deepthi