From: Waldemar Rymarkiewicz <waldemarx.rymarkiew...@intel.com> The governor updates dbs_info->requested_freq only after increasing or decreasing frequency. There is, however, an use case when this is not sufficient.
Imagine, external module constraining cpufreq policy in a way that policy->max = policy->min = max_available_freq (eg. 1Ghz). CPUfreq will set freq to max_freq and conservative gov will not try downscale/upscale due to the limits. It will just exit instead if (requested_freq > policy->max || requested_freq < policy->min) //max=min=1Ghz -> requested_freq=cur=1Ghz requested_freq = policy->cur; [...] if (requested_freq == policy->max) goto out; In a result, dbs_info->requested_freq is not updated with newly calculated requested_freq=1Ghz. Next, execution of update routine will use again previously stored requested_freq (in my case it was min_available_freq) [...] unsigned int requested_freq = dbs_info->requested_freq; [....] Now, when external module returns to previous policy limits that is policy->min = min_available_freq and policy->max = max_available_freq, conservative governor is not able to decrease frequency because stored requested_freq is still or rather already set to min_available_freq so the check (for decreasing) [...] if (load < cs_tuners->down_threshold) { [....] if (requested_freq == policy->min) goto out; [...] returns from routine before it does any freq change. To fix that just update dbs_info->requested_freq every time we go out from the update routine. Signed-off-by: Waldemar Rymarkiewicz <waldemarx.rymarkiew...@intel.com> --- drivers/cpufreq/cpufreq_conservative.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/drivers/cpufreq/cpufreq_conservative.c b/drivers/cpufreq/cpufreq_conservative.c index f20f20a..7f90f6e 100644 --- a/drivers/cpufreq/cpufreq_conservative.c +++ b/drivers/cpufreq/cpufreq_conservative.c @@ -113,7 +113,6 @@ static unsigned int cs_dbs_update(struct cpufreq_policy *policy) requested_freq = policy->max; __cpufreq_driver_target(policy, requested_freq, CPUFREQ_RELATION_H); - dbs_info->requested_freq = requested_freq; goto out; } @@ -136,10 +135,10 @@ static unsigned int cs_dbs_update(struct cpufreq_policy *policy) requested_freq = policy->min; __cpufreq_driver_target(policy, requested_freq, CPUFREQ_RELATION_L); - dbs_info->requested_freq = requested_freq; } out: + dbs_info->requested_freq = requested_freq; return dbs_data->sampling_rate; } -- 2.10.1