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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>
hifive-unleashed-5.1
Boris Ostrovsky 2012-03-13 19:55:09 +01:00 committed by Len Brown
parent e07510585a
commit 1a022e3f1b
4 changed files with 67 additions and 1 deletions
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4
arch/x86/kernel/smpboot.c
View File

@ -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 */

31
drivers/acpi/processor_idle.c
View File

@ -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;

28
drivers/cpuidle/cpuidle.c
View File

@ -71,6 +71,34 @@ 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
*

5
include/linux/cpuidle.h
View File

@ -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