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[CPUFREQ] allow ondemand and conservative cpufreq governors to be use…
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…d as default

Depending on the transition latency of the HW for cpufreq switches, the
ondemand or conservative governor cannot be used with certain cpufreq
drivers.  Still the ondemand should be the default governor on a wide range
of systems.  This patch allows this and lets the governor fallback to the
performance governor at cpufreq driver load time, if the driver does not
support fast enough frequency switching.

Main benefit is that on e.g.  installation or other systems without
userspace support a working dynamic cpufreq support can be achieved on most
systems by simply loading the cpufreq driver.  This is especially essential
for recent x86(_64) laptop hardware which may rely on working dynamic
cpufreq OS support.

Signed-off-by: Thomas Renninger <trenn@suse.de>
Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Bryan Wu <bryan.wu@analog.com>
Cc: Andi Kleen <ak@suse.de>
Cc: "Luck, Tony" <tony.luck@intel.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Dave Jones <davej@redhat.com>
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@watologo1
watologo1 authored and Dave Jones committed Oct 4, 2007
1 parent 8122c6c commit 1c25624
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Showing 5 changed files with 70 additions and 30 deletions.
27 changes: 23 additions & 4 deletions drivers/cpufreq/Kconfig
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Original file line number Diff line number Diff line change
Expand Up @@ -56,10 +56,6 @@ config CPU_FREQ_STAT_DETAILS

If in doubt, say N.

# Note that it is not currently possible to set the other governors (such as ondemand)
# as the default, since if they fail to initialise, cpufreq will be
# left in an undefined state.

choice
prompt "Default CPUFreq governor"
default CPU_FREQ_DEFAULT_GOV_USERSPACE if CPU_FREQ_SA1100 || CPU_FREQ_SA1110
Expand All @@ -85,6 +81,29 @@ config CPU_FREQ_DEFAULT_GOV_USERSPACE
program shall be able to set the CPU dynamically without having
to enable the userspace governor manually.

config CPU_FREQ_DEFAULT_GOV_ONDEMAND
bool "ondemand"
select CPU_FREQ_GOV_ONDEMAND
select CPU_FREQ_GOV_PERFORMANCE
help
Use the CPUFreq governor 'ondemand' as default. This allows
you to get a full dynamic frequency capable system by simply
loading your cpufreq low-level hardware driver.
Be aware that not all cpufreq drivers support the ondemand
governor. If unsure have a look at the help section of the
driver. Fallback governor will be the performance governor.

config CPU_FREQ_DEFAULT_GOV_CONSERVATIVE
bool "conservative"
select CPU_FREQ_GOV_CONSERVATIVE
select CPU_FREQ_GOV_PERFORMANCE
help
Use the CPUFreq governor 'conservative' as default. This allows
you to get a full dynamic frequency capable system by simply
loading your cpufreq low-level hardware driver.
Be aware that not all cpufreq drivers support the conservative
governor. If unsure have a look at the help section of the
driver. Fallback governor will be the performance governor.
endchoice

config CPU_FREQ_GOV_PERFORMANCE
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12 changes: 12 additions & 0 deletions drivers/cpufreq/cpufreq.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1484,6 +1484,18 @@ static int __cpufreq_governor(struct cpufreq_policy *policy,
unsigned int event)
{
int ret;
struct cpufreq_governor *gov = CPUFREQ_PERFORMANCE_GOVERNOR;

if (policy->governor->max_transition_latency &&
policy->cpuinfo.transition_latency >
policy->governor->max_transition_latency) {
printk(KERN_WARNING "%s governor failed, too long"
" transition latency of HW, fallback"
" to %s governor\n",
policy->governor->name,
gov->name);
policy->governor = gov;
}

if (!try_module_get(policy->governor->owner))
return -EINVAL;
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19 changes: 9 additions & 10 deletions drivers/cpufreq/cpufreq_conservative.c
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Original file line number Diff line number Diff line change
Expand Up @@ -58,7 +58,7 @@ static unsigned int def_sampling_rate;
#define DEF_SAMPLING_RATE_LATENCY_MULTIPLIER (1000)
#define DEF_SAMPLING_DOWN_FACTOR (1)
#define MAX_SAMPLING_DOWN_FACTOR (10)
#define TRANSITION_LATENCY_LIMIT (10 * 1000)
#define TRANSITION_LATENCY_LIMIT (10 * 1000 * 1000)

static void do_dbs_timer(struct work_struct *work);

Expand Down Expand Up @@ -466,9 +466,6 @@ static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
(!policy->cur))
return -EINVAL;

if (policy->cpuinfo.transition_latency >
(TRANSITION_LATENCY_LIMIT * 1000))
return -EINVAL;
if (this_dbs_info->enable) /* Already enabled */
break;

Expand Down Expand Up @@ -551,23 +548,25 @@ static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
return 0;
}

static struct cpufreq_governor cpufreq_gov_dbs = {
.name = "conservative",
.governor = cpufreq_governor_dbs,
.owner = THIS_MODULE,
struct cpufreq_governor cpufreq_gov_conservative = {
.name = "conservative",
.governor = cpufreq_governor_dbs,
.max_transition_latency = TRANSITION_LATENCY_LIMIT,
.owner = THIS_MODULE,
};
EXPORT_SYMBOL(cpufreq_gov_conservative);

static int __init cpufreq_gov_dbs_init(void)
{
return cpufreq_register_governor(&cpufreq_gov_dbs);
return cpufreq_register_governor(&cpufreq_gov_conservative);
}

static void __exit cpufreq_gov_dbs_exit(void)
{
/* Make sure that the scheduled work is indeed not running */
flush_scheduled_work();

cpufreq_unregister_governor(&cpufreq_gov_dbs);
cpufreq_unregister_governor(&cpufreq_gov_conservative);
}


Expand Down
22 changes: 9 additions & 13 deletions drivers/cpufreq/cpufreq_ondemand.c
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Original file line number Diff line number Diff line change
Expand Up @@ -47,7 +47,7 @@ static unsigned int def_sampling_rate;
(def_sampling_rate / MIN_SAMPLING_RATE_RATIO)
#define MAX_SAMPLING_RATE (500 * def_sampling_rate)
#define DEF_SAMPLING_RATE_LATENCY_MULTIPLIER (1000)
#define TRANSITION_LATENCY_LIMIT (10 * 1000)
#define TRANSITION_LATENCY_LIMIT (10 * 1000 * 1000)

static void do_dbs_timer(struct work_struct *work);

Expand Down Expand Up @@ -508,12 +508,6 @@ static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
if ((!cpu_online(cpu)) || (!policy->cur))
return -EINVAL;

if (policy->cpuinfo.transition_latency >
(TRANSITION_LATENCY_LIMIT * 1000)) {
printk(KERN_WARNING "ondemand governor failed to load "
"due to too long transition latency\n");
return -EINVAL;
}
if (this_dbs_info->enable) /* Already enabled */
break;

Expand Down Expand Up @@ -585,11 +579,13 @@ static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
return 0;
}

static struct cpufreq_governor cpufreq_gov_dbs = {
.name = "ondemand",
.governor = cpufreq_governor_dbs,
.owner = THIS_MODULE,
struct cpufreq_governor cpufreq_gov_ondemand = {
.name = "ondemand",
.governor = cpufreq_governor_dbs,
.max_transition_latency = TRANSITION_LATENCY_LIMIT,
.owner = THIS_MODULE,
};
EXPORT_SYMBOL(cpufreq_gov_ondemand);

static int __init cpufreq_gov_dbs_init(void)
{
Expand All @@ -598,12 +594,12 @@ static int __init cpufreq_gov_dbs_init(void)
printk(KERN_ERR "Creation of kondemand failed\n");
return -EFAULT;
}
return cpufreq_register_governor(&cpufreq_gov_dbs);
return cpufreq_register_governor(&cpufreq_gov_ondemand);
}

static void __exit cpufreq_gov_dbs_exit(void)
{
cpufreq_unregister_governor(&cpufreq_gov_dbs);
cpufreq_unregister_governor(&cpufreq_gov_ondemand);
destroy_workqueue(kondemand_wq);
}

Expand Down
20 changes: 17 additions & 3 deletions include/linux/cpufreq.h
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Original file line number Diff line number Diff line change
Expand Up @@ -155,6 +155,9 @@ struct cpufreq_governor {
char name[CPUFREQ_NAME_LEN];
int (*governor) (struct cpufreq_policy *policy,
unsigned int event);
unsigned int max_transition_latency; /* HW must be able to switch to
next freq faster than this value in nano secs or we
will fallback to performance governor */
struct list_head governor_list;
struct module *owner;
};
Expand Down Expand Up @@ -279,12 +282,23 @@ static inline unsigned int cpufreq_quick_get(unsigned int cpu)
*********************************************************************/


#ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_PERFORMANCE
/*
Performance governor is fallback governor if any other gov failed to
auto load due latency restrictions
*/
extern struct cpufreq_governor cpufreq_gov_performance;
#define CPUFREQ_DEFAULT_GOVERNOR &cpufreq_gov_performance
#define CPUFREQ_PERFORMANCE_GOVERNOR (&cpufreq_gov_performance)
#ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_PERFORMANCE
#define CPUFREQ_DEFAULT_GOVERNOR (&cpufreq_gov_performance)
#elif defined(CONFIG_CPU_FREQ_DEFAULT_GOV_USERSPACE)
extern struct cpufreq_governor cpufreq_gov_userspace;
#define CPUFREQ_DEFAULT_GOVERNOR &cpufreq_gov_userspace
#define CPUFREQ_DEFAULT_GOVERNOR (&cpufreq_gov_userspace)
#elif defined(CONFIG_CPU_FREQ_DEFAULT_GOV_ONDEMAND)
extern struct cpufreq_governor cpufreq_gov_ondemand;
#define CPUFREQ_DEFAULT_GOVERNOR (&cpufreq_gov_ondemand)
#elif defined(CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE)
extern struct cpufreq_governor cpufreq_gov_conservative;
#define CPUFREQ_DEFAULT_GOVERNOR (&cpufreq_gov_conservative)
#endif


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