linux/drivers/cpuidle/governors/ladder.c
Daniel Lezcano 137b944e10 cpuidle: Make it clear that governors cannot be modules
cpufreq governors are defined as modules in the code, but the Kconfig
options do not allow them to be built as modules.  This is not really
a problem, but the cpuidle init ordering is: the cpuidle init
functions (framework and driver) and then the governors.  That leads
to some weirdness in the cpuidle framework.

Namely,  cpuidle_register_device() calls cpuidle_enable_device() which
fails at the first attempt, because governors have not been registered
yet.  When a governor is registered, the framework calls
cpuidle_enable_device() again which runs __cpuidle_register_device()
only then.  Of course, for that to work, the cpuidle_enable_device()
return value has to be ignored by cpuidle_register_device().

Instead of having this cyclic call graph and relying on a positive
side effects of the hackish back and forth cpuidle_enable_device()
calls it is better to fix the cpuidle init ordering.

To that end, replace the module init code with postcore_initcall()
so we have:

 * cpuidle framework : core_initcall
 * cpuidle governors : postcore_initcall
 * cpuidle drivers   : device_initcall

and remove the corresponding module exit code as it is dead anyway
(governors can't be built as modules).

[rjw: Changelog]
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2013-07-15 02:09:47 +02:00

196 lines
5.1 KiB
C

/*
* ladder.c - the residency ladder algorithm
*
* Copyright (C) 2001, 2002 Andy Grover <andrew.grover@intel.com>
* Copyright (C) 2001, 2002 Paul Diefenbaugh <paul.s.diefenbaugh@intel.com>
* Copyright (C) 2004, 2005 Dominik Brodowski <linux@brodo.de>
*
* (C) 2006-2007 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
* Shaohua Li <shaohua.li@intel.com>
* Adam Belay <abelay@novell.com>
*
* This code is licenced under the GPL.
*/
#include <linux/kernel.h>
#include <linux/cpuidle.h>
#include <linux/pm_qos.h>
#include <linux/module.h>
#include <linux/jiffies.h>
#include <asm/io.h>
#include <asm/uaccess.h>
#define PROMOTION_COUNT 4
#define DEMOTION_COUNT 1
struct ladder_device_state {
struct {
u32 promotion_count;
u32 demotion_count;
u32 promotion_time;
u32 demotion_time;
} threshold;
struct {
int promotion_count;
int demotion_count;
} stats;
};
struct ladder_device {
struct ladder_device_state states[CPUIDLE_STATE_MAX];
int last_state_idx;
};
static DEFINE_PER_CPU(struct ladder_device, ladder_devices);
/**
* ladder_do_selection - prepares private data for a state change
* @ldev: the ladder device
* @old_idx: the current state index
* @new_idx: the new target state index
*/
static inline void ladder_do_selection(struct ladder_device *ldev,
int old_idx, int new_idx)
{
ldev->states[old_idx].stats.promotion_count = 0;
ldev->states[old_idx].stats.demotion_count = 0;
ldev->last_state_idx = new_idx;
}
/**
* ladder_select_state - selects the next state to enter
* @drv: cpuidle driver
* @dev: the CPU
*/
static int ladder_select_state(struct cpuidle_driver *drv,
struct cpuidle_device *dev)
{
struct ladder_device *ldev = &__get_cpu_var(ladder_devices);
struct ladder_device_state *last_state;
int last_residency, last_idx = ldev->last_state_idx;
int latency_req = pm_qos_request(PM_QOS_CPU_DMA_LATENCY);
/* Special case when user has set very strict latency requirement */
if (unlikely(latency_req == 0)) {
ladder_do_selection(ldev, last_idx, 0);
return 0;
}
last_state = &ldev->states[last_idx];
if (drv->states[last_idx].flags & CPUIDLE_FLAG_TIME_VALID) {
last_residency = cpuidle_get_last_residency(dev) - \
drv->states[last_idx].exit_latency;
}
else
last_residency = last_state->threshold.promotion_time + 1;
/* consider promotion */
if (last_idx < drv->state_count - 1 &&
!drv->states[last_idx + 1].disabled &&
!dev->states_usage[last_idx + 1].disable &&
last_residency > last_state->threshold.promotion_time &&
drv->states[last_idx + 1].exit_latency <= latency_req) {
last_state->stats.promotion_count++;
last_state->stats.demotion_count = 0;
if (last_state->stats.promotion_count >= last_state->threshold.promotion_count) {
ladder_do_selection(ldev, last_idx, last_idx + 1);
return last_idx + 1;
}
}
/* consider demotion */
if (last_idx > CPUIDLE_DRIVER_STATE_START &&
(drv->states[last_idx].disabled ||
dev->states_usage[last_idx].disable ||
drv->states[last_idx].exit_latency > latency_req)) {
int i;
for (i = last_idx - 1; i > CPUIDLE_DRIVER_STATE_START; i--) {
if (drv->states[i].exit_latency <= latency_req)
break;
}
ladder_do_selection(ldev, last_idx, i);
return i;
}
if (last_idx > CPUIDLE_DRIVER_STATE_START &&
last_residency < last_state->threshold.demotion_time) {
last_state->stats.demotion_count++;
last_state->stats.promotion_count = 0;
if (last_state->stats.demotion_count >= last_state->threshold.demotion_count) {
ladder_do_selection(ldev, last_idx, last_idx - 1);
return last_idx - 1;
}
}
/* otherwise remain at the current state */
return last_idx;
}
/**
* ladder_enable_device - setup for the governor
* @drv: cpuidle driver
* @dev: the CPU
*/
static int ladder_enable_device(struct cpuidle_driver *drv,
struct cpuidle_device *dev)
{
int i;
struct ladder_device *ldev = &per_cpu(ladder_devices, dev->cpu);
struct ladder_device_state *lstate;
struct cpuidle_state *state;
ldev->last_state_idx = CPUIDLE_DRIVER_STATE_START;
for (i = 0; i < drv->state_count; i++) {
state = &drv->states[i];
lstate = &ldev->states[i];
lstate->stats.promotion_count = 0;
lstate->stats.demotion_count = 0;
lstate->threshold.promotion_count = PROMOTION_COUNT;
lstate->threshold.demotion_count = DEMOTION_COUNT;
if (i < drv->state_count - 1)
lstate->threshold.promotion_time = state->exit_latency;
if (i > 0)
lstate->threshold.demotion_time = state->exit_latency;
}
return 0;
}
/**
* ladder_reflect - update the correct last_state_idx
* @dev: the CPU
* @index: the index of actual state entered
*/
static void ladder_reflect(struct cpuidle_device *dev, int index)
{
struct ladder_device *ldev = &__get_cpu_var(ladder_devices);
if (index > 0)
ldev->last_state_idx = index;
}
static struct cpuidle_governor ladder_governor = {
.name = "ladder",
.rating = 10,
.enable = ladder_enable_device,
.select = ladder_select_state,
.reflect = ladder_reflect,
.owner = THIS_MODULE,
};
/**
* init_ladder - initializes the governor
*/
static int __init init_ladder(void)
{
return cpuidle_register_governor(&ladder_governor);
}
postcore_initcall(init_ladder);