Messages in this thread | | | Date | Tue, 27 Oct 2020 08:36:15 +0530 | From | Viresh Kumar <> | Subject | Re: [PATCH v2 1/4] cpufreq: Introduce CPUFREQ_NEED_UPDATE_LIMITS driver flag |
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On 23-10-20, 17:35, Rafael J. Wysocki wrote: > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > > Generally, a cpufreq driver may need to update some internal upper > and lower frequency boundaries on policy max and min changes, > respectively, but currently this does not work if the target > frequency does not change along with the policy limit. > > Namely, if the target frequency does not change along with the > policy min or max, the "target_freq == policy->cur" check in > __cpufreq_driver_target() prevents driver callbacks from being > invoked and they do not even have a chance to update the > corresponding internal boundary. > > This particularly affects the "powersave" and "performance" > governors that always set the target frequency to one of the > policy limits and it never changes when the other limit is updated. > > To allow cpufreq the drivers needing to update internal frequency > boundaries on policy limits changes to avoid this issue, introduce > a new driver flag, CPUFREQ_NEED_UPDATE_LIMITS, that (when set) will > neutralize the check mentioned above. > > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > --- > > New patch in v2. > > --- > drivers/cpufreq/cpufreq.c | 3 ++- > include/linux/cpufreq.h | 10 +++++++++- > 2 files changed, 11 insertions(+), 2 deletions(-) > > Index: linux-pm/include/linux/cpufreq.h > =================================================================== > --- linux-pm.orig/include/linux/cpufreq.h > +++ linux-pm/include/linux/cpufreq.h > @@ -297,7 +297,7 @@ __ATTR(_name, 0644, show_##_name, store_ > > struct cpufreq_driver { > char name[CPUFREQ_NAME_LEN]; > - u8 flags; > + u16 flags; > void *driver_data; > > /* needed by all drivers */ > @@ -417,6 +417,14 @@ struct cpufreq_driver { > */ > #define CPUFREQ_IS_COOLING_DEV BIT(7) > > +/* > + * Set by drivers that need to update internale upper and lower boundaries along > + * with the target frequency and so the core and governors should also invoke > + * the diver if the target frequency does not change, but the policy min or max > + * may have changed. > + */ > +#define CPUFREQ_NEED_UPDATE_LIMITS BIT(8) > + > int cpufreq_register_driver(struct cpufreq_driver *driver_data); > int cpufreq_unregister_driver(struct cpufreq_driver *driver_data); > > Index: linux-pm/drivers/cpufreq/cpufreq.c > =================================================================== > --- linux-pm.orig/drivers/cpufreq/cpufreq.c > +++ linux-pm/drivers/cpufreq/cpufreq.c > @@ -2191,7 +2191,8 @@ int __cpufreq_driver_target(struct cpufr > * exactly same freq is called again and so we can save on few function > * calls. > */ > - if (target_freq == policy->cur) > + if (target_freq == policy->cur && > + !(cpufreq_driver->flags & CPUFREQ_NEED_UPDATE_LIMITS))
I was wondering if the same change should be made in the target_index part as we do this kind of check again ? But then I thought that since we know there are no users of that right now, why bother :)
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
-- viresh
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