Re: [RFC PATCH] cpufreq: Introduce macros for cpufreq_frequency_table iteration

[Stratos Karafotis <stratosk@semaphore.gr>]

On 11/04/2014 07:24 πμ, Viresh Kumar wrote:
> On 11 April 2014 03:31, Stratos Karafotis <stratosk@semaphore.gr> wrote:
>> This patch intoduces 2 macros which can be used for iteration
>> over cpufreq_frequency_table:
>>
>> - cpufreq_for_each_entry: iterate over each entry of the table
>> - cpufreq_for_each_valid_entry: iterate over each entry of the
>> table that contains a valid frequency.
>>
>> It should have no functional changes.
>>
>> Signed-off-by: Stratos Karafotis <stratosk@semaphore.gr>
>> ---
>>
>> I found about 20 occurrences in various drivers that these macros
>> can be used. I will proceed with the necessary changes if you
>> approve something like this.
>>
>> Thanks in advance for your time,
> 
> Thanks for your time and I find it useful enough. So its a yes from
> me :)
> 
> But, have you tested this yet?
> 
>> Stratos Karafotis.
>> ---
>>
>>  drivers/cpufreq/freq_table.c | 54 ++++++++++++++++++++------------------------
>>  include/linux/cpufreq.h      | 29 ++++++++++++++++++++++++
>>  2 files changed, 53 insertions(+), 30 deletions(-)
>>
>> diff --git a/drivers/cpufreq/freq_table.c b/drivers/cpufreq/freq_table.c
>> index 08e7bbc..19bf0c4 100644
>> --- a/drivers/cpufreq/freq_table.c
>> +++ b/drivers/cpufreq/freq_table.c
>> @@ -21,22 +21,18 @@
>>  int cpufreq_frequency_table_cpuinfo(struct cpufreq_policy *policy,
>>                                     struct cpufreq_frequency_table *table)
>>  {
>> +       struct cpufreq_frequency_table *pos;
>>         unsigned int min_freq = ~0;
>>         unsigned int max_freq = 0;
>> -       unsigned int i;
>>
>> -       for (i = 0; (table[i].frequency != CPUFREQ_TABLE_END); i++) {
>> -               unsigned int freq = table[i].frequency;
>> -               if (freq == CPUFREQ_ENTRY_INVALID) {
>> -                       pr_debug("table entry %u is invalid, skipping\n", i);
>> +       cpufreq_for_each_valid_entry(pos, table) {
>> +               unsigned int freq = pos->frequency;
> 
> move the definition part to the top of this routine, we don't need
> to create freq for every iteration here. It was bad earlier as well :)
> 
>>
>> -                       continue;
>> -               }
>>                 if (!cpufreq_boost_enabled()
>> -                   && (table[i].flags & CPUFREQ_BOOST_FREQ))
>> +                   && (pos->flags & CPUFREQ_BOOST_FREQ))
>>                         continue;
>>
>> -               pr_debug("table entry %u: %u kHz\n", i, freq);
>> +               pr_debug("table entry %lu: %u kHz\n", pos - table, freq);
>>                 if (freq < min_freq)
>>                         min_freq = freq;
>>                 if (freq > max_freq)
>> @@ -57,7 +53,8 @@ EXPORT_SYMBOL_GPL(cpufreq_frequency_table_cpuinfo);
>>  int cpufreq_frequency_table_verify(struct cpufreq_policy *policy,
>>                                    struct cpufreq_frequency_table *table)
>>  {
>> -       unsigned int next_larger = ~0, freq, i = 0;
>> +       struct cpufreq_frequency_table *pos;
>> +       unsigned int next_larger = ~0, freq;
>>         bool found = false;
>>
>>         pr_debug("request for verification of policy (%u - %u kHz) for cpu %u\n",
>> @@ -65,9 +62,9 @@ int cpufreq_frequency_table_verify(struct cpufreq_policy *policy,
>>
>>         cpufreq_verify_within_cpu_limits(policy);
>>
>> -       for (; freq = table[i].frequency, freq != CPUFREQ_TABLE_END; i++) {
>> -               if (freq == CPUFREQ_ENTRY_INVALID)
>> -                       continue;
>> +       cpufreq_for_each_valid_entry(pos, table) {
>> +               freq = pos->frequency;
>> +
>>                 if ((freq >= policy->min) && (freq <= policy->max)) {
>>                         found = true;
>>                         break;
>> @@ -118,7 +115,8 @@ int cpufreq_frequency_table_target(struct cpufreq_policy *policy,
>>                 .driver_data = ~0,
>>                 .frequency = 0,
>>         };
>> -       unsigned int i;
>> +       struct cpufreq_frequency_table *pos;
>> +       unsigned int i = 0;
>>
>>         pr_debug("request for target %u kHz (relation: %u) for cpu %u\n",
>>                                         target_freq, relation, policy->cpu);
>> @@ -132,10 +130,10 @@ int cpufreq_frequency_table_target(struct cpufreq_policy *policy,
>>                 break;
>>         }
>>
>> -       for (i = 0; (table[i].frequency != CPUFREQ_TABLE_END); i++) {
>> -               unsigned int freq = table[i].frequency;
>> -               if (freq == CPUFREQ_ENTRY_INVALID)
>> -                       continue;
>> +       cpufreq_for_each_valid_entry(pos, table) {
>> +               unsigned int freq = pos->frequency;
> 
> same here.
> 
>> +
>> +               i = pos - table;
>>                 if ((freq < policy->min) || (freq > policy->max))
>>                         continue;
>>                 switch (relation) {
>> @@ -184,8 +182,7 @@ EXPORT_SYMBOL_GPL(cpufreq_frequency_table_target);
>>  int cpufreq_frequency_table_get_index(struct cpufreq_policy *policy,
>>                 unsigned int freq)
>>  {
>> -       struct cpufreq_frequency_table *table;
>> -       int i;
>> +       struct cpufreq_frequency_table *pos, *table;
>>
>>         table = cpufreq_frequency_get_table(policy->cpu);
>>         if (unlikely(!table)) {
>> @@ -193,9 +190,9 @@ int cpufreq_frequency_table_get_index(struct cpufreq_policy *policy,
>>                 return -ENOENT;
>>         }
>>
>> -       for (i = 0; table[i].frequency != CPUFREQ_TABLE_END; i++) {
>> -               if (table[i].frequency == freq)
>> -                       return i;
>> +       cpufreq_for_each_entry(pos, table) {
> 
> use cpufreq_for_each_valid_entry() here as well.
> 
>> +               if (pos->frequency == freq)
>> +                       return pos - table;
>>         }
>>
>>         return -EINVAL;
>> @@ -208,16 +205,13 @@ EXPORT_SYMBOL_GPL(cpufreq_frequency_table_get_index);
>>  static ssize_t show_available_freqs(struct cpufreq_policy *policy, char *buf,
>>                                     bool show_boost)
>>  {
>> -       unsigned int i = 0;
>>         ssize_t count = 0;
>> -       struct cpufreq_frequency_table *table = policy->freq_table;
>> +       struct cpufreq_frequency_table *pos, *table = policy->freq_table;
>>
>>         if (!table)
>>                 return -ENODEV;
>>
>> -       for (i = 0; (table[i].frequency != CPUFREQ_TABLE_END); i++) {
>> -               if (table[i].frequency == CPUFREQ_ENTRY_INVALID)
>> -                       continue;
>> +       cpufreq_for_each_valid_entry(pos, table) {
>>                 /*
>>                  * show_boost = true and driver_data = BOOST freq
>>                  * display BOOST freqs
>> @@ -229,10 +223,10 @@ static ssize_t show_available_freqs(struct cpufreq_policy *policy, char *buf,
>>                  * show_boost = false and driver_data != BOOST freq
>>                  * display NON BOOST freqs
>>                  */
>> -               if (show_boost ^ (table[i].flags & CPUFREQ_BOOST_FREQ))
>> +               if (show_boost ^ (pos->flags & CPUFREQ_BOOST_FREQ))
>>                         continue;
>>
>> -               count += sprintf(&buf[count], "%d ", table[i].frequency);
>> +               count += sprintf(&buf[count], "%d ", pos->frequency);
>>         }
>>         count += sprintf(&buf[count], "\n");
>>
>> diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
>> index 5ae5100..1c221c8 100644
>> --- a/include/linux/cpufreq.h
>> +++ b/include/linux/cpufreq.h
>> @@ -468,6 +468,35 @@ struct cpufreq_frequency_table {
>>                                     * order */
>>  };
>>
>> +static inline bool validate_entry(struct cpufreq_frequency_table *pos)
>> +{
>> +       while (pos->frequency != CPUFREQ_TABLE_END)
>> +               if (pos->frequency == CPUFREQ_ENTRY_INVALID)
>> +                       pos++;
> 
> This is why I asked you if you have tested it or not.
> pos is a local variable here and so pos++ wouldn't reflect in the parent
> function. But your code will still work as we will check again for the next
> INVALID frequency.

Of course, you are right!
Yes, I partially tested it. But my frequency table didn't contain an
invalid entry. I will fix it.

> Another important thing: This routine is going to be used from a Macro
> and so making it inline is very *inefficient*. We are going to use it from
> Atleast 20-25 places (as you mentioned) and we definitely aren't looking
> to have so many copies of this one :)
> 
> So, you should move this to cpufreq.c

OK, I will do it. I was thinking about performance but as you mentioned
20 copies are too much. :)

>> +               else
>> +                       return true;
>> +       return false;
>> +}
>> +
>> +/*
>> + * cpufreq_for_each_entry -    iterate over a cpufreq_frequency_table
>> + * @pos:       the cpufreq_frequency_table * to use as a loop cursor.
>> + * @table:     the cpufreq_frequency_table * to iterate over.
>> + */
>> +
>> +#define cpufreq_for_each_entry(pos, table)     \
>> +       for (pos = table; pos->frequency != CPUFREQ_TABLE_END; pos++)
>> +
>> +/*
>> + * cpufreq_for_each_valid_entry -     iterate over a cpufreq_frequency_table
>> + *     exluding CPUFREQ_ENTRY_INVALID frequencies.
>> + * @pos:        the cpufreq_frequency_table * to use as a loop cursor.
>> + * @table:      the cpufreq_frequency_table * to iterate over.
>> + */
>> +
>> +#define cpufreq_for_each_valid_entry(pos, table)       \
>> +       for (pos = table; validate_entry(pos); pos++)
>> +
>>  int cpufreq_frequency_table_cpuinfo(struct cpufreq_policy *policy,
>>                                     struct cpufreq_frequency_table *table);
> 
> Otherwise looks fine. Please update all drivers as well :)
> 

I will prepare the patches with your suggestions.
Thank you very much for your review!


Stratos