cpufreq: Fix GOV_LIMITS handling for the userspace governor

Currently, the userspace governor only updates frequency on GOV_LIMITS if policy->cur falls outside policy->{min/max}. However, it is also necessary to update current frequency on GOV_LIMITS to match the user requested value if it can be achieved within the new policy->{max/min}.

This was previously the behaviour in the governor until commit d1922f0 ("cpufreq: Simplify userspace governor") which incorrectly assumed that policy->cur == user requested frequency via scaling_setspeed. This won't be true if the user requested frequency falls outside policy->{min/max}.
Ex: a temporary thermal cap throttled the user requested frequency.

Fix this by doing a partial revert of commit d1922f0 to bring back the per-cpu cpu_set_freq variable that stores the user requested frequency. The governor will then try to achieve this request on every GOV_LIMITS.

---
 drivers/cpufreq/cpufreq_userspace.c | 20 ++++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

b/drivers/cpufreq/cpufreq_userspace.c
index 4d16f45..ae03ba7 100644

@@ -18,6 +18,8 @@
 #include <linux/module.h>
 #include <linux/mutex.h>
 
+static DEFINE_PER_CPU(unsigned int, cpu_set_freq); /* CPU freq desired by
+							userspace */
 static DEFINE_PER_CPU(unsigned int, cpu_is_managed);
 static DEFINE_MUTEX(userspace_mutex);
 

@@ -38,6 +40,8 @@ static int cpufreq_set(struct cpufreq_policy *policy,

unsigned int freq)
if (!per_cpu(cpu_is_managed, policy->cpu))
goto err;

+ per_cpu(cpu_set_freq, policy->cpu) = freq;
+
ret = __cpufreq_driver_target(policy, freq, CPUFREQ_RELATION_L);
err:
mutex_unlock(&userspace_mutex);
@@ -62,6 +66,7 @@ static int cpufreq_governor_userspace(struct cpufreq_policy *policy,

mutex_lock(&userspace_mutex); per_cpu(cpu_is_managed, cpu) = 1;
+ per_cpu(cpu_set_freq, cpu) = policy->cur;
mutex_unlock(&userspace_mutex);
break;
case CPUFREQ_GOV_STOP:
@@ -69,20 +74,27 @@ static int cpufreq_governor_userspace(struct cpufreq_policy *policy,

mutex_lock(&userspace_mutex); per_cpu(cpu_is_managed, cpu) = 0;
+ per_cpu(cpu_set_freq, cpu) = 0;
mutex_unlock(&userspace_mutex); break;
case CPUFREQ_GOV_LIMITS:
mutex_lock(&userspace_mutex);
- pr_debug("limit event for cpu %u: %u - %u kHz, currently %u kHz\n",
+ pr_debug("limit event for cpu %u: %u - %u kHz, "
+ "currently %u kHz, last set to %u kHz\n",
cpu, policy->min, policy->max,
- policy->cur);
+ policy->cur, per_cpu(cpu_set_freq, cpu));

- if (policy->max < policy->cur)
+ if (policy->max < per_cpu(cpu_set_freq, cpu)) {
__cpufreq_driver_target(policy, policy->max,
CPUFREQ_RELATION_H);
- else if (policy->min > policy->cur)
+ } else if (policy->min > per_cpu(cpu_set_freq, cpu)) {
__cpufreq_driver_target(policy, policy->min,
CPUFREQ_RELATION_L);
+ } else {
+ __cpufreq_driver_target(policy,
+ per_cpu(cpu_set_freq, cpu),
+ CPUFREQ_RELATION_L);
+ }
mutex_unlock(&userspace_mutex);
break;
}

2.1.4

-----------------------------------------------------------------------------------
This email message is for the sole use of the intended recipient(s) and may contain
confidential information.  Any unauthorized review, use, disclosure or distribution
is prohibited.  If you are not the intended recipient, please contact the sender by
reply email and destroy all copies of the original message.
-----------------------------------------------------------------------------------

Urg...

Add this here (just before your sob)

Good catch :)

viresh