[CPUFREQ] allow ondemand and conservative cpufreq governors to be used 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>

1 files changed, 9 insertions, 10 deletions

diff --git a/drivers/cpufreq/cpufreq_conservative.c b/drivers/cpufreq/cpufreq_conservative.c
index 26f440ccc3fb..4bd33ce8a6f3 100644
--- a/drivers/cpufreq/cpufreq_conservative.c
+++ b/drivers/cpufreq/cpufreq_conservative.c
@@ -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);
 
@@ -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;
                  
@@ -551,15 +548,17 @@ 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)
@@ -567,7 +566,7 @@ 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);
 }