idle, x86: Allow off-lined CPU to enter deeper C states

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>

4 files changed, 67 insertions, 1 deletions

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 66d250c00d11..93a2a0932b51 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 0e8e2de2ed3e..6b1d32a161ae 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 f7cab5e9c4d6..3e146b2ada4a 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 f3ebbba368b3..d557bcd0ada7 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