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Subject[PATCH 58/76] idle, x86: Allow off-lined CPU to enter deeper C states
Date
From: Boris Ostrovsky <boris.ostrovsky@amd.com>

Currently when a CPU is off-lined it enters either MWAIT-based idle or,
if MWAIT is not desired or supported, HLT-based idle (which places the
processor in C1 state). This patch allows processors without MWAIT
support to stay in states deeper than C1.

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@amd.com>
Signed-off-by: Len Brown <len.brown@intel.com>
---
arch/x86/kernel/smpboot.c | 4 +++-
drivers/acpi/processor_idle.c | 31 +++++++++++++++++++++++++++++++
drivers/cpuidle/cpuidle.c | 28 ++++++++++++++++++++++++++++
include/linux/cpuidle.h | 5 +++++
4 files changed, 67 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 66d250c..93a2a09 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -50,6 +50,7 @@
#include <linux/tboot.h>
#include <linux/stackprotector.h>
#include <linux/gfp.h>
+#include <linux/cpuidle.h>

#include <asm/acpi.h>
#include <asm/desc.h>
@@ -1422,7 +1423,8 @@ void native_play_dead(void)
tboot_shutdown(TB_SHUTDOWN_WFS);

mwait_play_dead(); /* Only returns on failure */
- hlt_play_dead();
+ if (cpuidle_play_dead())
+ hlt_play_dead();
}

#else /* ... !CONFIG_HOTPLUG_CPU */
diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
index 0e8e2de..6b1d32a 100644
--- a/drivers/acpi/processor_idle.c
+++ b/drivers/acpi/processor_idle.c
@@ -770,6 +770,35 @@ static int acpi_idle_enter_c1(struct cpuidle_device *dev,
return index;
}

+
+/**
+ * acpi_idle_play_dead - enters an ACPI state for long-term idle (i.e. off-lining)
+ * @dev: the target CPU
+ * @index: the index of suggested state
+ */
+static int acpi_idle_play_dead(struct cpuidle_device *dev, int index)
+{
+ struct cpuidle_state_usage *state_usage = &dev->states_usage[index];
+ struct acpi_processor_cx *cx = cpuidle_get_statedata(state_usage);
+
+ ACPI_FLUSH_CPU_CACHE();
+
+ while (1) {
+
+ if (cx->entry_method == ACPI_CSTATE_HALT)
+ halt();
+ else if (cx->entry_method == ACPI_CSTATE_SYSTEMIO) {
+ inb(cx->address);
+ /* See comment in acpi_idle_do_entry() */
+ inl(acpi_gbl_FADT.xpm_timer_block.address);
+ } else
+ return -ENODEV;
+ }
+
+ /* Never reached */
+ return 0;
+}
+
/**
* acpi_idle_enter_simple - enters an ACPI state without BM handling
* @dev: the target CPU
@@ -1077,12 +1106,14 @@ static int acpi_processor_setup_cpuidle_states(struct acpi_processor *pr)
state->flags |= CPUIDLE_FLAG_TIME_VALID;

state->enter = acpi_idle_enter_c1;
+ state->enter_dead = acpi_idle_play_dead;
drv->safe_state_index = count;
break;

case ACPI_STATE_C2:
state->flags |= CPUIDLE_FLAG_TIME_VALID;
state->enter = acpi_idle_enter_simple;
+ state->enter_dead = acpi_idle_play_dead;
drv->safe_state_index = count;
break;

diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
index f7cab5e..3e146b2 100644
--- a/drivers/cpuidle/cpuidle.c
+++ b/drivers/cpuidle/cpuidle.c
@@ -72,6 +72,34 @@ typedef int (*cpuidle_enter_t)(struct cpuidle_device *dev,
static cpuidle_enter_t cpuidle_enter_ops;

/**
+ * cpuidle_play_dead - cpu off-lining
+ *
+ * Only returns in case of an error
+ */
+int cpuidle_play_dead(void)
+{
+ struct cpuidle_device *dev = __this_cpu_read(cpuidle_devices);
+ struct cpuidle_driver *drv = cpuidle_get_driver();
+ int i, dead_state = -1;
+ int power_usage = -1;
+
+ /* Find lowest-power state that supports long-term idle */
+ for (i = CPUIDLE_DRIVER_STATE_START; i < drv->state_count; i++) {
+ struct cpuidle_state *s = &drv->states[i];
+
+ if (s->power_usage < power_usage && s->enter_dead) {
+ power_usage = s->power_usage;
+ dead_state = i;
+ }
+ }
+
+ if (dead_state != -1)
+ return drv->states[dead_state].enter_dead(dev, dead_state);
+
+ return -ENODEV;
+}
+
+/**
* cpuidle_idle_call - the main idle loop
*
* NOTE: no locks or semaphores should be used here
diff --git a/include/linux/cpuidle.h b/include/linux/cpuidle.h
index f3ebbba..d557bcd 100644
--- a/include/linux/cpuidle.h
+++ b/include/linux/cpuidle.h
@@ -51,6 +51,8 @@ struct cpuidle_state {
int (*enter) (struct cpuidle_device *dev,
struct cpuidle_driver *drv,
int index);
+
+ int (*enter_dead) (struct cpuidle_device *dev, int index);
};

/* Idle State Flags */
@@ -147,6 +149,8 @@ extern int cpuidle_wrap_enter(struct cpuidle_device *dev,
struct cpuidle_driver *drv, int index,
int (*enter)(struct cpuidle_device *dev,
struct cpuidle_driver *drv, int index));
+extern int cpuidle_play_dead(void);
+
#else
static inline void disable_cpuidle(void) { }
static inline int cpuidle_idle_call(void) { return -ENODEV; }
@@ -168,6 +172,7 @@ static inline int cpuidle_wrap_enter(struct cpuidle_device *dev,
int (*enter)(struct cpuidle_device *dev,
struct cpuidle_driver *drv, int index))
{ return -ENODEV; }
+static inline int cpuidle_play_dead(void) {return -ENODEV; }

#endif

--
1.7.10.rc2.19.gfae9d


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