Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 1a022e3f authored by Boris Ostrovsky's avatar Boris Ostrovsky Committed by Len Brown
Browse files

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: default avatarBoris Ostrovsky <boris.ostrovsky@amd.com>
Signed-off-by: default avatarLen Brown <len.brown@intel.com>
parent e0751058

arch/x86/kernel/smpboot.c

+3 −1
Original line number Diff line number Diff line
@@ -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>
@@ -1422,6 +1423,7 @@ void native_play_dead(void) 
	tboot_shutdown(TB_SHUTDOWN_WFS);



	mwait_play_dead();	/* Only returns on failure */

	if (cpuidle_play_dead())

		hlt_play_dead();

}

drivers/acpi/processor_idle.c

+31 −0
Original line number Diff line number Diff line
@@ -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;

drivers/cpuidle/cpuidle.c

+28 −0
Original line number Diff line number Diff line
@@ -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

 *

include/linux/cpuidle.h

+5 −0
Original line number Diff line number Diff line
@@ -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