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Message-ID: <CADGdYn4=si46x7b5Qa0EJ1vUDKrP3maXBqWwQ6s7gkep-8MxFg@mail.gmail.com>
Date: Sun, 18 Aug 2013 16:11:59 +0530
From: amit daniel kachhap <amit.daniel@...sung.com>
To: Viresh Kumar <viresh.kumar@...aro.org>
Cc: "Rafael J. Wysocki" <rjw@...k.pl>, linaro-kernel@...ts.linaro.org,
"patches@...aro.org" <patches@...aro.org>, cpufreq@...r.kernel.org,
"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
LAK <linux-arm-kernel@...ts.infradead.org>,
Andrew Lunn <andrew@...n.ch>,
"David S. Miller" <davem@...emloft.net>,
Dmitry Eremin-Solenikov <dbaryshkov@...il.com>,
Eric Miao <eric.y.miao@...il.com>,
Hans-Christian Egtvedt <egtvedt@...fundet.no>,
Jesper Nilsson <jesper.nilsson@...s.com>,
John Crispin <blogic@...nwrt.org>,
Kukjin Kim <kgene.kim@...sung.com>,
Linus Walleij <linus.walleij@...aro.org>,
linux-cris-kernel@...s.com, Mikael Starvik <starvik@...s.com>,
Santosh Shilimkar <santosh.shilimkar@...com>,
Sekhar Nori <nsekhar@...com>, Shawn Guo <shawn.guo@...aro.org>,
sparclinux@...r.kernel.org, Stephen Warren <swarren@...dia.com>,
Steven Miao <realmz6@...il.com>,
Tony Luck <tony.luck@...el.com>
Subject: Re: [PATCH V2 01/35] cpufreq: Implement light weight ->target_index() routine
Hi Viresh,
On Tue, Aug 13, 2013 at 7:02 PM, Viresh Kumar <viresh.kumar@...aro.org> wrote:
> Currently prototype of cpufreq_drivers target routines is:
>
> int target(struct cpufreq_policy *policy, unsigned int target_freq,
> unsigned int relation);
>
> And most of the drivers call cpufreq_frequency_table_target() to get a valid
> index of their frequency table which is closest to the target_freq. And they
> don't use target_freq and relation after it.
>
> So, it makes sense to just do this work in cpufreq core before calling
> cpufreq_frequency_table_target() and simply pass index instead. But this can be
> done only with drivers which expose their frequency table with cpufreq core. For
> others we need to stick with the old prototype of target() until those drivers
> are converted to expose frequency tables.
>
> This patch implements the new light weight prototype for target_index() routine.
> It looks like this:
>
> int target_index(struct cpufreq_policy *policy, unsigned int index);
This new API is fine but I have another idea.
Say During the registration of the frequency table cpufreq_policy can
be registered as SCALE_DIRECT or SCALE_STEPS. With SCALE_DIRECT flag,
valid frequency will be requested. With this flags the governor itself
can can figure out if frequency scaling is required or not and very
few calls to __cpufreq_driver_target will happen.
But i agree that in this approach cpufreq_frequency_table_target is
still required but again it can be optimized by binary search as
currently the search is linear.
Thanks,
Amit
>
> CPUFreq core will call cpufreq_frequency_table_target() before calling this
> routine and pass index to it. Because CPUFreq core now requires to call routines
> present in freq_table.c CONFIG_CPU_FREQ_TABLE must be enabled all the time.
>
> This also marks target() interface as deprecated. So, that new drivers avoid
> using it. And
>
> Documentation is updated accordingly.
>
> Cc: Andrew Lunn <andrew@...n.ch>
> Cc: David S. Miller <davem@...emloft.net>
> Cc: Dmitry Eremin-Solenikov <dbaryshkov@...il.com>
> Cc: Eric Miao <eric.y.miao@...il.com>
> Cc: Hans-Christian Egtvedt <egtvedt@...fundet.no>
> Cc: Jesper Nilsson <jesper.nilsson@...s.com>
> Cc: John Crispin <blogic@...nwrt.org>
> Cc: Kukjin Kim <kgene.kim@...sung.com>
> Cc: Linus Walleij <linus.walleij@...aro.org>
> Cc: linux-cris-kernel@...s.com
> Cc: Mikael Starvik <starvik@...s.com>
> Cc: Santosh Shilimkar <santosh.shilimkar@...com>
> Cc: Sekhar Nori <nsekhar@...com>
> Cc: Shawn Guo <shawn.guo@...aro.org>
> Cc: sparclinux@...r.kernel.org
> Cc: Stephen Warren <swarren@...dia.com>
> Cc: Steven Miao <realmz6@...il.com>
> Cc: Tony Luck <tony.luck@...el.com>
> Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
> ---
> Documentation/cpu-freq/cpu-drivers.txt | 27 +++++++++++------
> Documentation/cpu-freq/governors.txt | 4 +--
> drivers/cpufreq/Kconfig | 1 +
> drivers/cpufreq/cpufreq.c | 55 +++++++++++++++++++++++++++-------
> include/linux/cpufreq.h | 4 ++-
> 5 files changed, 68 insertions(+), 23 deletions(-)
>
> diff --git a/Documentation/cpu-freq/cpu-drivers.txt b/Documentation/cpu-freq/cpu-drivers.txt
> index 40282e6..8b1a445 100644
> --- a/Documentation/cpu-freq/cpu-drivers.txt
> +++ b/Documentation/cpu-freq/cpu-drivers.txt
> @@ -23,8 +23,8 @@ Contents:
> 1.1 Initialization
> 1.2 Per-CPU Initialization
> 1.3 verify
> -1.4 target or setpolicy?
> -1.5 target
> +1.4 target/target_index or setpolicy?
> +1.5 target/target_index
> 1.6 setpolicy
> 2. Frequency Table Helpers
>
> @@ -56,7 +56,8 @@ cpufreq_driver.init - A pointer to the per-CPU initialization
> cpufreq_driver.verify - A pointer to a "verification" function.
>
> cpufreq_driver.setpolicy _or_
> -cpufreq_driver.target - See below on the differences.
> +cpufreq_driver.target/
> +target_index - See below on the differences.
>
> And optionally
>
> @@ -66,7 +67,7 @@ cpufreq_driver.resume - A pointer to a per-CPU resume function
> which is called with interrupts disabled
> and _before_ the pre-suspend frequency
> and/or policy is restored by a call to
> - ->target or ->setpolicy.
> + ->target/target_index or ->setpolicy.
>
> cpufreq_driver.attr - A pointer to a NULL-terminated list of
> "struct freq_attr" which allow to
> @@ -103,8 +104,8 @@ policy->governor must contain the "default policy" for
> this CPU. A few moments later,
> cpufreq_driver.verify and either
> cpufreq_driver.setpolicy or
> - cpufreq_driver.target is called with
> - these values.
> + cpufreq_driver.target/target_index is called
> + with these values.
>
> For setting some of these values (cpuinfo.min[max]_freq, policy->min[max]), the
> frequency table helpers might be helpful. See the section 2 for more information
> @@ -133,20 +134,28 @@ range) is within policy->min and policy->max. If necessary, increase
> policy->max first, and only if this is no solution, decrease policy->min.
>
>
> -1.4 target or setpolicy?
> +1.4 target/target_index or setpolicy?
> ----------------------------
>
> Most cpufreq drivers or even most cpu frequency scaling algorithms
> only allow the CPU to be set to one frequency. For these, you use the
> -->target call.
> +->target/target_index call.
>
> Some cpufreq-capable processors switch the frequency between certain
> limits on their own. These shall use the ->setpolicy call
>
>
> -1.4. target
> +1.4. target/target_index
> -------------
>
> +The target_index call has two arguments: struct cpufreq_policy *policy,
> +and unsigned int index (into the exposed frequency table).
> +
> +The CPUfreq driver must set the new frequency when called here. The
> +actual frequency must be determined by freq_table[index].frequency.
> +
> +Deprecated:
> +----------
> The target call has three arguments: struct cpufreq_policy *policy,
> unsigned int target_frequency, unsigned int relation.
>
> diff --git a/Documentation/cpu-freq/governors.txt b/Documentation/cpu-freq/governors.txt
> index 219970b..77ec215 100644
> --- a/Documentation/cpu-freq/governors.txt
> +++ b/Documentation/cpu-freq/governors.txt
> @@ -40,7 +40,7 @@ Most cpufreq drivers (in fact, all except one, longrun) or even most
> cpu frequency scaling algorithms only offer the CPU to be set to one
> frequency. In order to offer dynamic frequency scaling, the cpufreq
> core must be able to tell these drivers of a "target frequency". So
> -these specific drivers will be transformed to offer a "->target"
> +these specific drivers will be transformed to offer a "->target/target_index"
> call instead of the existing "->setpolicy" call. For "longrun", all
> stays the same, though.
>
> @@ -71,7 +71,7 @@ CPU can be set to switch independently | CPU can only be set
> / the limits of policy->{min,max}
> / \
> / \
> - Using the ->setpolicy call, Using the ->target call,
> + Using the ->setpolicy call, Using the ->target/target_index call,
> the limits and the the frequency closest
> "policy" is set. to target_freq is set.
> It is assured that it
> diff --git a/drivers/cpufreq/Kconfig b/drivers/cpufreq/Kconfig
> index 534fcb8..2d06754 100644
> --- a/drivers/cpufreq/Kconfig
> +++ b/drivers/cpufreq/Kconfig
> @@ -2,6 +2,7 @@ menu "CPU Frequency scaling"
>
> config CPU_FREQ
> bool "CPU Frequency scaling"
> + select CPU_FREQ_TABLE
> help
> CPU Frequency scaling allows you to change the clock speed of
> CPUs on the fly. This is a nice method to save power, because
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index 37a6874..f1b0e0f 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -47,6 +47,11 @@ static LIST_HEAD(cpufreq_policy_list);
> static DEFINE_PER_CPU(char[CPUFREQ_NAME_LEN], cpufreq_cpu_governor);
> #endif
>
> +static inline bool has_target(void)
> +{
> + return cpufreq_driver->target_index || cpufreq_driver->target;
> +}
> +
> /*
> * cpu_policy_rwsem is a per CPU reader-writer semaphore designed to cure
> * all cpufreq/hotplug/workqueue/etc related lock issues.
> @@ -377,7 +382,7 @@ static int cpufreq_parse_governor(char *str_governor, unsigned int *policy,
> *policy = CPUFREQ_POLICY_POWERSAVE;
> err = 0;
> }
> - } else if (cpufreq_driver->target) {
> + } else if (has_target()) {
> struct cpufreq_governor *t;
>
> mutex_lock(&cpufreq_governor_mutex);
> @@ -539,7 +544,7 @@ static ssize_t show_scaling_available_governors(struct cpufreq_policy *policy,
> ssize_t i = 0;
> struct cpufreq_governor *t;
>
> - if (!cpufreq_driver->target) {
> + if (!has_target()) {
> i += sprintf(buf, "performance powersave");
> goto out;
> }
> @@ -822,7 +827,7 @@ static int cpufreq_add_dev_interface(struct cpufreq_policy *policy,
> if (ret)
> goto err_out_kobj_put;
> }
> - if (cpufreq_driver->target) {
> + if (has_target()) {
> ret = sysfs_create_file(&policy->kobj, &scaling_cur_freq.attr);
> if (ret)
> goto err_out_kobj_put;
> @@ -871,10 +876,10 @@ static int cpufreq_add_policy_cpu(struct cpufreq_policy *policy,
> unsigned int cpu, struct device *dev,
> bool frozen)
> {
> - int ret = 0, has_target = !!cpufreq_driver->target;
> + int ret = 0;
> unsigned long flags;
>
> - if (has_target) {
> + if (has_target()) {
> ret = __cpufreq_governor(policy, CPUFREQ_GOV_STOP);
> if (ret) {
> pr_err("%s: Failed to stop governor\n", __func__);
> @@ -893,7 +898,7 @@ static int cpufreq_add_policy_cpu(struct cpufreq_policy *policy,
>
> unlock_policy_rwsem_write(policy->cpu);
>
> - if (has_target) {
> + if (has_target()) {
> if ((ret = __cpufreq_governor(policy, CPUFREQ_GOV_START)) ||
> (ret = __cpufreq_governor(policy, CPUFREQ_GOV_LIMITS))) {
> pr_err("%s: Failed to start governor\n", __func__);
> @@ -1204,7 +1209,7 @@ static int __cpufreq_remove_dev(struct device *dev,
> return -EINVAL;
> }
>
> - if (cpufreq_driver->target) {
> + if (has_target()) {
> ret = __cpufreq_governor(policy, CPUFREQ_GOV_STOP);
> if (ret) {
> pr_err("%s: Failed to stop governor\n", __func__);
> @@ -1244,7 +1249,7 @@ static int __cpufreq_remove_dev(struct device *dev,
>
> /* If cpu is last user of policy, free policy */
> if (cpus == 1) {
> - if (cpufreq_driver->target) {
> + if (has_target()) {
> ret = __cpufreq_governor(policy,
> CPUFREQ_GOV_POLICY_EXIT);
> if (ret) {
> @@ -1282,7 +1287,7 @@ static int __cpufreq_remove_dev(struct device *dev,
> if (!frozen)
> cpufreq_policy_free(policy);
> } else {
> - if (cpufreq_driver->target) {
> + if (has_target()) {
> if ((ret = __cpufreq_governor(policy, CPUFREQ_GOV_START)) ||
> (ret = __cpufreq_governor(policy, CPUFREQ_GOV_LIMITS))) {
> pr_err("%s: Failed to start governor\n",
> @@ -1646,11 +1651,39 @@ int __cpufreq_driver_target(struct cpufreq_policy *policy,
> pr_debug("target for CPU %u: %u kHz, relation %u, requested %u kHz\n",
> policy->cpu, target_freq, relation, old_target_freq);
>
> + /*
> + * This might look like a redundant call as we are checking it again
> + * after finding index. But it is left intentionally for cases where
> + * exactly same freq is called again and so we can save on few function
> + * calls.
> + */
> if (target_freq == policy->cur)
> return 0;
>
> if (cpufreq_driver->target)
> retval = cpufreq_driver->target(policy, target_freq, relation);
> + else if (cpufreq_driver->target_index) {
> + struct cpufreq_frequency_table *freq_table;
> + int index;
> +
> + freq_table = cpufreq_frequency_get_table(policy->cpu);
> + if (unlikely(!freq_table)) {
> + pr_err("%s: Unable to find freq_table\n", __func__);
> + return retval;
> + }
> +
> + retval = cpufreq_frequency_table_target(policy, freq_table,
> + target_freq, relation, &index);
> + if (unlikely(retval)) {
> + pr_err("%s: Unable to find matching freq\n", __func__);
> + return retval;
> + }
> +
> + if (freq_table[index].frequency == policy->cur)
> + return 0;
> +
> + retval = cpufreq_driver->target_index(policy, index);
> + }
>
> return retval;
> }
> @@ -1983,7 +2016,7 @@ int cpufreq_update_policy(unsigned int cpu)
> pr_debug("Driver did not initialize current freq");
> policy->cur = new_policy.cur;
> } else {
> - if (policy->cur != new_policy.cur && cpufreq_driver->target)
> + if (policy->cur != new_policy.cur && has_target())
> cpufreq_out_of_sync(cpu, policy->cur,
> new_policy.cur);
> }
> @@ -2058,7 +2091,7 @@ int cpufreq_register_driver(struct cpufreq_driver *driver_data)
> return -ENODEV;
>
> if (!driver_data || !driver_data->verify || !driver_data->init ||
> - ((!driver_data->setpolicy) && (!driver_data->target)))
> + (!driver_data->setpolicy && !has_target()))
> return -EINVAL;
>
> pr_debug("trying to register driver %s\n", driver_data->name);
> diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
> index 4907eb2..ff9c8df 100644
> --- a/include/linux/cpufreq.h
> +++ b/include/linux/cpufreq.h
> @@ -195,9 +195,11 @@ struct cpufreq_driver {
>
> /* define one out of two */
> int (*setpolicy) (struct cpufreq_policy *policy);
> - int (*target) (struct cpufreq_policy *policy,
> + int (*target) (struct cpufreq_policy *policy, /* Deprecated */
> unsigned int target_freq,
> unsigned int relation);
> + int (*target_index) (struct cpufreq_policy *policy,
> + unsigned int index);
>
> /* should be defined, if possible */
> unsigned int (*get) (unsigned int cpu);
> --
> 1.7.12.rc2.18.g61b472e
>
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