From: Viresh Kumar viresh.kumar@linaro.org
[ Upstream commit f55ae08c89873e140c7cac2a7fa161d31a0d60cf ]
For some platforms, the frequency returned by hardware may be slightly different from what is provided in the frequency table. For example, hardware may return 499 MHz instead of 500 MHz. In such cases it is better to avoid getting into unnecessary frequency updates, as we may end up switching policy->cur between the two and sending unnecessary pre/post update notifications, etc.
This patch has chosen allows the hardware frequency and table frequency to deviate by 1 MHz for now, we may want to increase it a bit later on if someone still complains.
Reported-by: Rex-BC Chen rex-bc.chen@mediatek.com Signed-off-by: Viresh Kumar viresh.kumar@linaro.org Tested-by: Jia-wei Chang jia-wei.chang@mediatek.com Reviewed-by: Matthias Brugger matthias.bgg@gmail.com Signed-off-by: Rafael J. Wysocki rafael.j.wysocki@intel.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/cpufreq/cpufreq.c | 11 +++++++++++ 1 file changed, 11 insertions(+)
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c index eeac6d809229..cddf7e13c232 100644 --- a/drivers/cpufreq/cpufreq.c +++ b/drivers/cpufreq/cpufreq.c @@ -28,6 +28,7 @@ #include <linux/suspend.h> #include <linux/syscore_ops.h> #include <linux/tick.h> +#include <linux/units.h> #include <trace/events/power.h>
static LIST_HEAD(cpufreq_policy_list); @@ -1701,6 +1702,16 @@ static unsigned int cpufreq_verify_current_freq(struct cpufreq_policy *policy, b return new_freq;
if (policy->cur != new_freq) { + /* + * For some platforms, the frequency returned by hardware may be + * slightly different from what is provided in the frequency + * table, for example hardware may return 499 MHz instead of 500 + * MHz. In such cases it is better to avoid getting into + * unnecessary frequency updates. + */ + if (abs(policy->cur - new_freq) < HZ_PER_MHZ) + return policy->cur; + cpufreq_out_of_sync(policy, new_freq); if (update) schedule_work(&policy->update);