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authorViresh Kumar <viresh.kumar@linaro.org>2022-05-04 11:21:35 +0300
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2022-05-06 21:56:21 +0300
commitf55ae08c89873e140c7cac2a7fa161d31a0d60cf (patch)
treea605e4d6436833eb0dc7c621e6eb0e47f171019a /drivers/cpufreq/cpufreq.c
parent02678c08822f45246e5efa371c91c9e154e34e11 (diff)
downloadlinux-f55ae08c89873e140c7cac2a7fa161d31a0d60cf.tar.xz
cpufreq: Avoid unnecessary frequency updates due to mismatch
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>
Diffstat (limited to 'drivers/cpufreq/cpufreq.c')
-rw-r--r--drivers/cpufreq/cpufreq.c11
1 files changed, 11 insertions, 0 deletions
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 0d58b0f8f3af..233e8af48848 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);
@@ -1708,6 +1709,16 @@ 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);