Messages in this thread | | | From | "Rafael J. Wysocki" <> | Date | Mon, 27 Jul 2020 15:52:41 +0200 | Subject | Re: [PATCH v2 2/7] cpufreq: set invariance scale factor on transition end |
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On Wed, Jul 22, 2020 at 11:38 AM Ionela Voinescu <ionela.voinescu@arm.com> wrote: > > While the move of the invariance setter calls (arch_set_freq_scale()) > from cpufreq drivers to cpufreq core maintained the previous > functionality for existing drivers that use target_index() and > fast_switch() for frequency switching, it also gives the possibility > of adding support for users of the target() callback, which is exploited > here. > > To be noted that the target() callback has been flagged as deprecated > since: > > commit 9c0ebcf78fde ("cpufreq: Implement light weight ->target_index() routine") > > It also doesn't have that many users: > > cpufreq-nforce2.c:371:2: .target = nforce2_target, > cppc_cpufreq.c:416:2: .target = cppc_cpufreq_set_target, > gx-suspmod.c:439:2: .target = cpufreq_gx_target, > pcc-cpufreq.c:573:2: .target = pcc_cpufreq_target, > > Similarly to the path taken for target_index() calls in the cpufreq core > during a frequency change, all of the drivers above will mark the end of a > frequency change by a call to cpufreq_freq_transition_end(). > > Therefore, cpufreq_freq_transition_end() can be used as the location for > the arch_set_freq_scale() call to potentially inform the scheduler of the > frequency change. > > This change maintains the previous functionality for the drivers that > implement the target_index() callback, while also adding support for the > few drivers that implement the deprecated target() callback. > > Two notes are worthwhile here: > - In __target_index(), cpufreq_freq_transition_end() is called only for > drivers that have synchronous notifications enabled. There is only one > driver that disables them, > > drivers/cpufreq/powernow-k8.c:1142: .flags = CPUFREQ_ASYNC_NOTIFICATION, > > which is deprecated. > > - Despite marking a successful frequency change, many cpufreq drivers > will populate the new policy->cur with the new requested frequency, > although this might not be the one granted by the hardware. > > Therefore, the call to arch_set_freq_scale() is a "best effort" one, > and it is up to the architecture if the new frequency is used in the > new frequency scale factor setting or eventually used by the scheduler. > The architecture is in a better position to decide if it has better > methods to obtain more accurate information regarding the current > frequency (for example the use of counters). > > Signed-off-by: Ionela Voinescu <ionela.voinescu@arm.com> > Cc: Rafael J. Wysocki <rjw@rjwysocki.net> > Cc: Viresh Kumar <viresh.kumar@linaro.org> > --- > drivers/cpufreq/cpufreq.c | 15 ++++++--------- > 1 file changed, 6 insertions(+), 9 deletions(-) > > diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c > index bac4101546db..3497c1cd6818 100644 > --- a/drivers/cpufreq/cpufreq.c > +++ b/drivers/cpufreq/cpufreq.c > @@ -448,6 +448,10 @@ void cpufreq_freq_transition_end(struct cpufreq_policy *policy, > > cpufreq_notify_post_transition(policy, freqs, transition_failed); > > + arch_set_freq_scale(policy->related_cpus, > + policy->cur, > + policy->cpuinfo.max_freq); > + > policy->transition_ongoing = false; > policy->transition_task = NULL; > > @@ -2159,7 +2163,7 @@ int __cpufreq_driver_target(struct cpufreq_policy *policy, > unsigned int relation) > { > unsigned int old_target_freq = target_freq; > - int index, retval; > + int index; > > if (cpufreq_disabled()) > return -ENODEV; > @@ -2190,14 +2194,7 @@ int __cpufreq_driver_target(struct cpufreq_policy *policy, > > index = cpufreq_frequency_table_target(policy, target_freq, relation); > > - retval = __target_index(policy, index); > - > - if (!retval) > - arch_set_freq_scale(policy->related_cpus, > - policy->freq_table[index].frequency, > - policy->cpuinfo.max_freq); > - > - return retval; > + return __target_index(policy, index); > } > EXPORT_SYMBOL_GPL(__cpufreq_driver_target); > > --
I would fold this patch into the previous one.
I don't see much reason for it to be separate and it looks like folding it in would cause the previous patch to be simpler.
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