Re: [PATCH v3 1/3] cpufreq: Add boost frequency support in core

Lukasz Majewski
2013-06-17T07:15:49Z

On Mon, 17 Jun 2013 11:13:18 +0530, Viresh Kumar wrote:
> On 14 June 2013 13:08, Lukasz Majewski <l.majewski@samsung.com> wrote:
> > Changes for v2:
> > - Removal of cpufreq_boost structure and move its fields to
> > cpufreq_driver structure
> > - Flag to indicate if global boost attribute is already defined
> > - Extent the pr_{err|debbug} functions to show current function
> > names
> >
> > Changes for v3:
> > - Method for reading boost status
> > - Removal of cpufreq_frequency_table_max()
> > - Extent cpufreq_frequency_table_cpuinfo() to support boost
> > parameter
> > - boost_supported flag added to cpufreq_driver struct
> > - "boost" sysfs attribute control flag removed
> > - One global flag describing state of the boost defined at cpufreq
> > core
> > - Rename cpufreq_driver's low_level_boost field to set_boost_freq()
> > - Usage of cpufreq_sysfs_{remove|add}_file() routines
>
> Latest change log first please.

Ok.

>
> > diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> > index 2ce86ed..02e57db 100644
> > --- a/drivers/cpufreq/cpufreq.c
> > +++ b/drivers/cpufreq/cpufreq.c
> > @@ -40,6 +40,7 @@
> > * also protects the cpufreq_cpu_data array.
> > */
> > static struct cpufreq_driver *cpufreq_driver;
> > +static bool cpufreq_boost_enabled;
> > static DEFINE_PER_CPU(struct cpufreq_policy *, cpufreq_cpu_data);
> > #ifdef CONFIG_HOTPLUG_CPU
> > /* This one keeps track of the previously set governor of a
> > removed CPU */ @@ -315,6 +316,30 @@
> > EXPORT_SYMBOL_GPL(cpufreq_notify_transition); /*********************************************************************
> > * SYSFS
> > INTERFACE *
> > *********************************************************************/
> > +ssize_t show_boost(struct kobject *kobj,
> > + struct attribute *attr, char *buf)
> > +{
> > + return sprintf(buf, "%d\n", cpufreq_boost_enabled);
> > +}
> > +
> > +static ssize_t store_boost(struct kobject *kobj, struct attribute
> > *attr,
> > + const char *buf, size_t count)
> > +{
> > + int ret, enable;
> > +
> > + ret = sscanf(buf, "%d", &enable);
> > + if (ret != 1 || enable < 0 || enable > 1)
> > + return -EINVAL;
> > +
> > + if (cpufreq_boost_trigger_state(enable)) {
> > + pr_err("%s: Cannot %sable boost!\n", __func__,
> > + enable ? "en" : "dis");
>
> Please don't use %sable as discussed earlier.

My bad. I've overlooked this one.

>
> > + return -EINVAL;
> > + }
> > +
> > + return count;
> > +}
> > +define_one_global_rw(boost);
> >
> > static struct cpufreq_governor *__find_governor(const char
> > *str_governor) {
> > @@ -1896,6 +1921,55 @@ static struct notifier_block __refdata
> > cpufreq_cpu_notifier = { };
> >
> > /*********************************************************************
> > + *
> > BOOST *
> > +
> > *********************************************************************/
> > +int cpufreq_boost_trigger_state(int state) +{
> > + struct cpufreq_frequency_table *freq_table;
> > + struct cpufreq_policy *policy;
> > + unsigned long flags;
> > + int ret = 0, cpu;
> > +
> > + if (!cpufreq_driver->boost_supported)
> > + return -ENODEV;
>
> This can't happen. sysfs directory is present only when we
> have boost supported.

I know, that we shall not look into the future. But this method will be
used when somebody would like to enable boost from kernel. Let's say
new governor or such :-).

I can remove this and add it later, but I think, that it is safer to
add it straightaway.

>
> > + if (cpufreq_boost_enabled != state) {
> > + if (cpufreq_driver->set_boost_freq) {
> > + ret = cpufreq_driver->set_boost_freq(state);
>
> I thought this routine was for setting boost frequency and not
> for enabling boost feature. If boost has to be enabled separately
> then this routine must take care of it while setting freq.
>
> So, in other words, this must not be called here.

This function explicitly follows current logic of acpi-cpufreq.c.

I would like to avoid modifying legacy/working code as much as
possible (especially when I hadn't yet received any feedback about
acpi-cpufreq.c file changes).

>
> > + if (ret) {
> > + pr_err("%s: BOOST cannot enable
> > (%d)\n",
> > + __func__, ret);
> > + return ret;
> > + }
> > + }
> > +
> > + for_each_possible_cpu(cpu) {
> > + policy = cpufreq_cpu_get(cpu);
>
> In case this code is required, it would make more sense to keep list
> of all available policies, which we can iterate through.

Maybe I don't get the big picture, but why we cannot iterate
through possible CPUs? At least one shall have valid policy and
freq_table combination.

I've already proposed list of all policies (at v1), but we decided to
abandon this idea.

In which way list is better than iteration through all possible per-cpu
variables, which store policies?

>
> > + freq_table =
> > cpufreq_frequency_get_table(cpu);
> > + if (policy && freq_table) {
> > +
> > write_lock_irqsave(&cpufreq_driver_lock, flags);
> > +
> > cpufreq_frequency_table_cpuinfo(policy,
> > +
> > freq_table,
> > +
> > state);
>
> We obviously don't need the last param to this routine and so bunch
> of changes you did in this patch.
>
> cpufreq_frequency_table_cpuinfo() can itself check if boost is enabled
> or not.

Yes, you are right. We can check if boost is supported and enabled
inside this function.

>
> > + cpufreq_boost_enabled = state;
> > +
> > write_unlock_irqrestore(&cpufreq_driver_lock,
> > + flags);
> > + }
> > + }
>
> I am not sure if this is required at all. Or what complications can be
> there when we update max/min on the fly here.

Correct me if I'm wrong, but I'm using scripts for tests which run
simultaneously and enables/disables boost feature. I don't recall if
there is a lock at sysfs, which would prevent from simultaneous write
to the "boost" sysfs attribute.

I will doubble check that.

>
> > + }
> > +
> > + pr_debug("%s: cpufreq BOOST %s\n", __func__,
> > + state ? "enabled" : "disabled");
> > +
> > + return 0;
> > +}
> > +
> > +int cpufreq_boost_state(void)
>
> s/cpufreq_boost_state/cpufreq_boost_enabled

OK.

>
> > +{
> > + return cpufreq_boost_enabled;
>
> s/cpufreq_boost_enabled/boost_enabled
>
> > +}
> > +
> > +/*********************************************************************
> > * REGISTER / UNREGISTER CPUFREQ
> > DRIVER *
> > *********************************************************************/
> >
> > @@ -1934,6 +2008,15 @@ int cpufreq_register_driver(struct
> > cpufreq_driver *driver_data) cpufreq_driver = driver_data;
> > write_unlock_irqrestore(&cpufreq_driver_lock, flags);
> >
> > + if (cpufreq_driver->boost_supported) {
> > + ret = cpufreq_sysfs_create_file(&(boost.attr));
> > + if (ret) {
> > + pr_err("%s: cannot register global boost
> > sysfs file\n",
> > + __func__);
> > + goto err_null_driver;
> > + }
> > + }
> > +
> > ret = subsys_interface_register(&cpufreq_interface);
> > if (ret)
> > goto err_null_driver;
> > @@ -1990,6 +2073,10 @@ int cpufreq_unregister_driver(struct
> > cpufreq_driver *driver) pr_debug("unregistering driver %s\n",
> > driver->name);
> >
> > subsys_interface_unregister(&cpufreq_interface);
> > +
> > + if (cpufreq_driver->boost_supported)
> > + cpufreq_sysfs_remove_file(&(boost.attr));
> > +
> > unregister_hotcpu_notifier(&cpufreq_cpu_notifier);
> >
> > write_lock_irqsave(&cpufreq_driver_lock, flags);
>
> This part looked good :)
>
> > diff --git a/drivers/cpufreq/freq_table.c
> > b/drivers/cpufreq/freq_table.c index d7a7966..f1a4d785 100644
> > --- a/drivers/cpufreq/freq_table.c
> > +++ b/drivers/cpufreq/freq_table.c
> > @@ -21,7 +21,8 @@
> > *********************************************************************/
> >
> > int cpufreq_frequency_table_cpuinfo(struct cpufreq_policy *policy,
> > - struct cpufreq_frequency_table
> > *table)
> > + struct cpufreq_frequency_table
> > *table,
> > + int boost)
> > {
> > unsigned int min_freq = ~0;
> > unsigned int max_freq = 0;
> > @@ -31,9 +32,11 @@ int cpufreq_frequency_table_cpuinfo(struct
> > cpufreq_policy *policy, unsigned int freq = table[i].frequency;
> > if (freq == CPUFREQ_ENTRY_INVALID) {
> > pr_debug("table entry %u is invalid,
> > skipping\n", i); -
> > continue;
> > }
> > + if (!boost && table[i].index == CPUFREQ_BOOST_FREQ)
> > + continue;
> > +
> > pr_debug("table entry %u: %u kHz, %u index\n",
> > i, freq, table[i].index);
> > if (freq < min_freq)
> > @@ -171,7 +174,8 @@ static DEFINE_PER_CPU(struct
> > cpufreq_frequency_table *, cpufreq_show_table); /**
> > * show_available_freqs - show available frequencies for the
> > specified CPU */
> > -static ssize_t show_available_freqs(struct cpufreq_policy *policy,
> > char *buf) +static ssize_t show_available_freqs(struct
> > cpufreq_policy *policy, char *buf,
> > + int show_boost)
> > {
> > unsigned int i = 0;
> > unsigned int cpu = policy->cpu;
> > @@ -186,22 +190,42 @@ static ssize_t show_available_freqs(struct
> > cpufreq_policy *policy, char *buf) for (i = 0;
> > (table[i].frequency != CPUFREQ_TABLE_END); i++) { if
> > (table[i].frequency == CPUFREQ_ENTRY_INVALID) continue;
> > + if (show_boost && table[i].index !=
> > CPUFREQ_BOOST_FREQ)
> > + continue;
> > + if (!show_boost && table[i].index ==
> > CPUFREQ_BOOST_FREQ)
> > + continue;
>
> Maybe, this instead of above two if statements:
>
> if (show_boost ^ (table[i].index == CPUFREQ_BOOST_FREQ))
> continue

Yes. Good point.

>
> > count += sprintf(&buf[count], "%d ",
> > table[i].frequency); }
> > count += sprintf(&buf[count], "\n");
> >
> > return count;
> > -
> > }
> >
> > -struct freq_attr cpufreq_freq_attr_scaling_available_freqs = {
> > - .attr = { .name = "scaling_available_frequencies",
> > - .mode = 0444,
> > - },
> > - .show = show_available_freqs,
> > -};
> > +/**
> > + * show_scaling_available_frequencies - show normal boost
> > frequencies for
>
> s/boost /

Ok.

>
> > + * the specified CPU
> > + */
> > +static ssize_t scaling_available_frequencies_show(struct
> > cpufreq_policy *policy,
> > + char *buf)
> > +{
> > + return show_available_freqs(policy, buf, 0);
> > +}
> > +cpufreq_attr_available_freq(scaling_available);
> > EXPORT_SYMBOL_GPL(cpufreq_freq_attr_scaling_available_freqs);
> >
> > +/**
> > + * show_available_boost_freqs - show available boost frequencies
> > for
> > + * the specified CPU
> > + */
> > +static ssize_t scaling_boost_frequencies_show(struct
> > cpufreq_policy *policy,
> > + char *buf)
> > +{
> > + return show_available_freqs(policy, buf, 1);
> > +}
> > +cpufreq_attr_available_freq(scaling_boost);
> > +EXPORT_SYMBOL_GPL(cpufreq_freq_attr_scaling_boost_freqs);
> > +
> > /*
> > * if you use these, you must assure that the frequency table is
> > valid
> > * all the time between get_attr and put_attr!
>
> > diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
> > index ab1932c..027442d 100644
> > --- a/include/linux/cpufreq.h
> > +++ b/include/linux/cpufreq.h
> > @@ -266,6 +266,10 @@ struct cpufreq_driver {
> > int (*suspend) (struct cpufreq_policy *policy);
> > int (*resume) (struct cpufreq_policy *policy);
> > struct freq_attr **attr;
> > +
> > + /* platform specific boost support code */
> > + bool boost_supported;
> > + int (*set_boost_freq) (int state);
> > };
> >
> > /* flags */
> > @@ -318,6 +322,10 @@ __ATTR(_name, _perm, show_##_name, NULL)
> > static struct freq_attr _name = \
> > __ATTR(_name, 0644, show_##_name, store_##_name)
> >
> > +#define cpufreq_attr_available_freq(_name) \
> > +struct freq_attr cpufreq_freq_attr_##_name##_freqs = \
> > +__ATTR_RO(_name##_frequencies)
>
> What is this doing in cpufreq.h? It will only be used by freq_table.c
> file.

I wanted to add those #defines to the place where other similar ones
are placed.

I can put it to freq_table.c.

>
>
> Again, I couldn't see how boost freqs are getting used? You have
> probably made them part of normal freq range here and so they
> might be used during normal operations. But we wanted it to be
> used only when we have few cpus on... etc.. Where is that logic?

The logic is as follow:
- cpufreq_driver exports .attr field. When driver supports boost then
two attributes are exported (even when boost is not enabled, but
supported):
- scaling_available_frequencies (only normal frequencies - this
attribute is unchanged)
- scaling_boost_frequencies - list possible boost frequencies.

When boost is not supported - then only scaling_available_frequencies
is exported (as it is done now).

Please refer to patch 3/3.

--
Best regards,

Lukasz Majewski

Samsung R&D Institute Poland (SRPOL) | Linux Platform Group