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Date: Thu, 4 Feb 2016 02:25:17 +0100
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Saravana Kannan <skannan@...eaurora.org>
Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>,
Linux PM list <linux-pm@...r.kernel.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Viresh Kumar <viresh.kumar@...aro.org>,
Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
Juri Lelli <juri.lelli@....com>,
Steve Muckle <steve.muckle@...aro.org>
Subject: Re: [PATCH 3/11] cpufreq: governor: Use common global_dbs_data pointer
On Thu, Feb 4, 2016 at 2:11 AM, Saravana Kannan <skannan@...eaurora.org> wrote:
> On 02/03/2016 03:22 PM, Rafael J. Wysocki wrote:
>>
>> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>>
>> If the ondemand and conservative governors cannot use per-policy
>> tunables (CPUFREQ_HAVE_GOVERNOR_PER_POLICY is not set in the cpufreq
>> driver), all policy objects point to the same single dbs_data object.
>> Additionally, that object is pointed to by a global pointer hidden in
>> the governor's data structures.
>>
>> There is no reason for that pointer to be buried in those
>> data structures, though, so make it explicitly global.
>>
>> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>> ---
>> drivers/cpufreq/cpufreq_governor.c | 20 ++++++++++----------
>> drivers/cpufreq/cpufreq_governor.h | 20 ++++++++++----------
>> 2 files changed, 20 insertions(+), 20 deletions(-)
>>
>> Index: linux-pm/drivers/cpufreq/cpufreq_governor.h
>> ===================================================================
>> --- linux-pm.orig/drivers/cpufreq/cpufreq_governor.h
>> +++ linux-pm/drivers/cpufreq/cpufreq_governor.h
>> @@ -78,7 +78,7 @@ __ATTR(_name, 0644, show_##_name##_gov_p
>> static ssize_t show_##file_name##_gov_sys \
>> (struct kobject *kobj, struct attribute *attr, char *buf) \
>> { \
>> - struct _gov##_dbs_tuners *tuners =
>> _gov##_dbs_cdata.gdbs_data->tuners; \
>> + struct _gov##_dbs_tuners *tuners = global_dbs_data->tuners; \
>> return sprintf(buf, "%u\n", tuners->file_name); \
>> } \
>> \
>> @@ -94,7 +94,7 @@ static ssize_t show_##file_name##_gov_po
>> static ssize_t store_##file_name##_gov_sys \
>> (struct kobject *kobj, struct attribute *attr, const char *buf, size_t
>> count) \
>> { \
>> - struct dbs_data *dbs_data = _gov##_dbs_cdata.gdbs_data; \
>> + struct dbs_data *dbs_data = global_dbs_data; \
>> return store_##file_name(dbs_data, buf, count); \
>> } \
>> \
>> @@ -201,19 +201,14 @@ struct cs_dbs_tuners {
>> /* Common Governor data across policies */
>> struct dbs_data;
>> struct common_dbs_data {
>> - /* Common across governors */
>> + struct cpufreq_governor gov;
>> +
>> #define GOV_ONDEMAND 0
>> #define GOV_CONSERVATIVE 1
>> int governor;
>> struct attribute_group *attr_group_gov_sys; /* one governor -
>> system */
>> struct attribute_group *attr_group_gov_pol; /* one governor -
>> policy */
>>
>> - /*
>> - * Common data for platforms that don't set
>> - * CPUFREQ_HAVE_GOVERNOR_PER_POLICY
>> - */
>> - struct dbs_data *gdbs_data;
>> -
>> struct cpu_dbs_info *(*get_cpu_cdbs)(int cpu);
>> void *(*get_cpu_dbs_info_s)(int cpu);
>> unsigned int (*gov_dbs_timer)(struct cpufreq_policy *policy);
>> @@ -233,6 +228,11 @@ struct dbs_data {
>> void *tuners;
>> };
>>
>> +/*
>> + * Common governor data for platforms without
>> CPUFREQ_HAVE_GOVERNOR_PER_POLICY.
>> + */
>> +extern struct dbs_data *global_dbs_data;
>> +
>> /* Governor specific ops, will be passed to dbs_data->gov_ops */
>> struct od_ops {
>> void (*powersave_bias_init_cpu)(int cpu);
>> @@ -256,7 +256,7 @@ static inline int delay_for_sampling_rat
>> static ssize_t show_sampling_rate_min_gov_sys \
>> (struct kobject *kobj, struct attribute *attr, char *buf) \
>> { \
>> - struct dbs_data *dbs_data = _gov##_dbs_cdata.gdbs_data; \
>> + struct dbs_data *dbs_data = global_dbs_data; \
>> return sprintf(buf, "%u\n", dbs_data->min_sampling_rate); \
>> } \
>> \
>> Index: linux-pm/drivers/cpufreq/cpufreq_governor.c
>> ===================================================================
>> --- linux-pm.orig/drivers/cpufreq/cpufreq_governor.c
>> +++ linux-pm/drivers/cpufreq/cpufreq_governor.c
>> @@ -22,6 +22,9 @@
>>
>> #include "cpufreq_governor.h"
>>
>> +struct dbs_data *global_dbs_data;
>> +EXPORT_SYMBOL_GPL(global_dbs_data);
>> +
>> DEFINE_MUTEX(dbs_data_mutex);
>> EXPORT_SYMBOL_GPL(dbs_data_mutex);
>>
>> @@ -377,22 +380,19 @@ static int cpufreq_governor_init(struct
>> latency * LATENCY_MULTIPLIER));
>>
>> if (!have_governor_per_policy())
>> - cdata->gdbs_data = dbs_data;
>> + global_dbs_data = dbs_data;
>>
>> policy->governor_data = dbs_data;
>>
>> ret = sysfs_create_group(get_governor_parent_kobj(policy),
>> get_sysfs_attr(dbs_data));
>> - if (ret)
>> - goto reset_gdbs_data;
>> -
>> - return 0;
>> + if (!ret)
>> + return 0;
>
>
> I think the previous method of a handling the error is easier to read and
> more in line with the typical kernel coding style. The successful path ends
> in an unconditional return statement and the error paths are handled with a
> goto.
You are talking about something like this now:
if (condition)
goto label;
return 0;
label:
do stuff
I'm sorry, but I fail to see how this is easier to read than
if (!condition)
return 0;
do stuff
The return statement is not unconditional in either case, but in the
first one it is just obfuscated by using the label and goto which are
completely unnecessary.
>
> This also doesn't seem relevant to what the patch is trying to do. So, I'd
> prefer that it be left as is.
>
This is a fair point, though. I can make that change later. :-)
Thanks,
Rafael
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