Subject: [PATCH RFC 06/27] PM / Domains: add debugfs 'states' and 'timings' seq files

From: [email-masked] (Marc Titinger)
Date: Wed, 16 Dec 2015 12:07:13 +0100

On 11/12/2015 12:46, Ulf Hansson wrote:
> On 17 November 2015 at 23:37, Lina Iyer <[email-masked]> wrote:

Hi Ulf,

thanks for the review, comments and questions below.

Best Regards,
Marc.

>> From: Marc Titinger <[email-masked]>
>>
>> This purpose of these debug seq-files is to help investigate
>> generic power domain state transitions, based on device constraints.
>> requires the "multiple states" patches from Axel Haslam.
>
> This last sentence doesn't belong in the change-log, please remove it.
>
>>
>> also rename 'summary' from 'pm_genpd_summary'
>>
>> sample output for 'states'
>> ==========================
>>
>>    Domain             State name        Eval = 2200nter + Exit = Min_off_on (ns)
>> -----------------------------------------------------------------------
>> a53_pd               cluster-sleep-0      1500000+800000=2300000
>> a57_pd               d1-retention         1000000+800000=1800000
>> a57_pd               cluster-sleep-0      1500000+800000=2300000
>>
>> sample output for 'timings'
>> ===========================
>>
>>      Domain Devices, Timings in ns
>>                         Stop/Start Save/Restore, Effective
>> ----------------------------------------------------  ---
>> a53_pd
>>      /cpus/cpu at 100        1060  /660    1580  /1940  ,0 (cached stop)
>>      /cpus/cpu at 101        1060  /740    1520  /1600  ,0 (cached stop)
>>      /cpus/cpu at 102        880   /620    1380  /1780  ,0 (cached stop)
>>      /cpus/cpu at 103        1080  /640    1340  /1600  ,0 (cached stop)
>> a57_pd
>>      /cpus/cpu at 0          1160  /740    3280  /1800  ,0 (cached stop)
>>      /cpus/cpu at 1          780   /1400   1440  /2080  ,0 (cached stop)
>>      /D1                  600   /540    7140  /6420  ,2199460 (cached stop)
>>
>> Signed-off-by: Marc Titinger <[email-masked]>
>
> A general comment. Static functions in genpd shall start with one of
> the following prefix.
>
> genpd_*
> _genpd_*
> __genpd_*
>
> Please change accordingly.

Many static routines were already prefixed like the exported functions 
with "pm_", shall I make a separate patch for this renaming ?

>
>> ---
>>   drivers/base/power/domain.c | 115 +++++++++++++++++++++++++++++++++++++++++---
>>   1 file changed, 107 insertions(+), 8 deletions(-)
>>
>> diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
>> index c300293..9a0df09 100644
>> --- a/drivers/base/power/domain.c
>> +++ b/drivers/base/power/domain.c
>> @@ -2169,21 +2169,120 @@ static const struct file_operations pm_genpd_summary_fops = {
>>          .release = single_release,
>>   };
>>
>> +static int pm_genpd_states_show(struct seq_file *s, void *data)
>> +{
>> +       struct generic_pm_domain *genpd;
>> +
>> +       seq_puts(s,
>> +                "\n  Domain             State name        Enter + Exit = Min_off_on (ns)\n");
>> +       seq_puts(s,
>> +                "-----------------------------------------------------------------------\n");
>> +
>
> You must hold the gpd_list_lock while traversing the gpd list.
>
>> +       list_for_each_entry(genpd, &gpd_list, gpd_list_node) {
>> +
>> +               int i;
>> +
>> +               for (i = 0; i < genpd->state_count; i++) {
>
> To be sure you have valid data, you should hold the genpd lock here.
>

At some point while testing with calling suspend from the power_off 
handler, the cpu would go to sleep with the lock held, hence using this 
seq-file would not work.

while I agree, I think it is not super likely that a 
domain/child/devices/states are added or removed at this point (the DT 
is parsed already), would using list_for_each_entry_safe be safe enough ?

>> +                       seq_printf(s, "%-20s %-20s %lld+%lld=%lld\n",
>> +                                  genpd->name,
>> +                                  genpd->states[i].name,
>> +                                  genpd->states[i].power_on_latency_ns,
>> +                                  genpd->states[i].power_off_latency_ns,
>> +                                  genpd->states[i].power_off_latency_ns
>> +                                  + genpd->states[i].power_on_latency_ns);
>> +               }
>> +
>> +       }
>> +
>> +       seq_puts(s, "\n");
>> +
>> +       return 0;
>> +}
>> +
>> +static int pm_genpd_states_open(struct inode *inode, struct file *file)
>> +{
>> +       return single_open(file, pm_genpd_states_show, NULL);
>> +}
>> +
>> +static const struct file_operations pm_genpd_states_fops = {
>> +       .open = pm_genpd_states_open,
>> +       .read = seq_read,
>> +       .llseek = seq_lseek,
>> +       .release = single_release,
>> +};
>> +
>> +static int pm_genpd_timing_show(struct seq_file *s, void *data)
>> +{
>> +       struct generic_pm_domain *genpd;
>> +
>> +       seq_puts(s, "\n    Domain Devices, Timings in ns\n");
>> +       seq_puts(s,
>> +                "                       Stop/Start Save/Restore, Effective\n");
>> +       seq_puts(s,
>> +                "----------------------------------------------------  ---\n");
>> +
>
> You must hold the gpd_list_lock while traversing the gpd list.
>
>
>> +       list_for_each_entry(genpd, &gpd_list, gpd_list_node) {
>> +               struct pm_domain_data *pm_data;
>> +
>> +               seq_printf(s, "%-30s", genpd->name);
>> +
>
> You must hold the genpd lock while traversing the device list.
>
>> +               list_for_each_entry(pm_data, &genpd->dev_list, list_node) {
>> +                       struct gpd_timing_data *td = &to_gpd_data(pm_data)->td;
>> +
>> +                       if (!pm_data->dev->of_node)
>> +                               continue;
>> +
>> +                       seq_printf(s,
>> +                                  "\n    %-20s %-6lld/%-6lld %-6lld/%-6lld,%lld %s%s",
>> +                                  pm_data->dev->of_node->full_name,
>> +                                  td->stop_latency_ns, td->start_latency_ns,
>> +                                  td->save_state_latency_ns,
>> +                                  td->restore_state_latency_ns,
>
> This needs a re-base as these values have been merged.
>
>> +                                  td->effective_constraint_ns,
>> +                                  td->cached_stop_ok ? "(cached stop) " : "",
>> +                                  td->constraint_changed ? "(changed)" : "");
>> +               }
>> +               seq_puts(s, "\n");
>> +       }
>> +       return 0;
>> +}
>> +
>> +static int pm_genpd_timing_open(struct inode *inode, struct file *file)
>> +{
>> +       return single_open(file, pm_genpd_timing_show, NULL);
>> +}
>> +
>> +static const struct file_operations pm_genpd_timing_fops = {
>> +       .open = pm_genpd_timing_open,
>> +       .read = seq_read,
>> +       .llseek = seq_lseek,
>> +       .release = single_release,
>> +};
>> +
>>   static int __init pm_genpd_debug_init(void)
>>   {
>> -       struct dentry *d;
>> +       struct dentry *d = NULL;
>>
>>          pm_genpd_debugfs_dir = debugfs_create_dir("pm_genpd", NULL);
>>
>> -       if (!pm_genpd_debugfs_dir)
>> -               return -ENOMEM;
>> +       if (pm_genpd_debugfs_dir)
>
> In case when CONFIG_DEBUG_FS is unset, this doesn't work very well, as
> pm_genpd_debugfs_dir will contain an error code.
>
> Since you are anyway make quite big change to the debugfs support for
> genpd, perhaps you can try to fix that up as well!?

Ah yes ok, will do.

>
>> +               d = debugfs_create_file("summary", S_IRUGO,
>> +                               pm_genpd_debugfs_dir, NULL,
>> +                               &pm_genpd_summary_fops);
>> +       if (d)
>> +               d = debugfs_create_file("states", S_IRUGO,
>> +                               pm_genpd_debugfs_dir, NULL,
>> +                               &pm_genpd_states_fops);
>> +       if (d)
>> +               d = debugfs_create_file("timings", S_IRUGO,
>> +                               pm_genpd_debugfs_dir, NULL,
>> +                               &pm_genpd_timing_fops);
>> +       if (d)
>> +               return 0;
>>
>> -       d = debugfs_create_file("pm_genpd_summary", S_IRUGO,
>> -                       pm_genpd_debugfs_dir, NULL, &pm_genpd_summary_fops);
>> -       if (!d)
>> -               return -ENOMEM;
>> +       debugfs_remove_recursive(pm_genpd_debugfs_dir /*can be null*/);
>>
>> -       return 0;
>> +       return -ENOMEM;
>>   }
>>   late_initcall(pm_genpd_debug_init);
>>
>
> Kind regards
> Uffe
>