linux-kernel - Re: [PATCH v4 1/2] PM / Domains: Add support for 'required-opps' to set default perf state

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Message-ID: <43c77084-cfea-ef7f-8454-6f0dbc3b6577@codeaurora.org>
Date:   Mon, 19 Jul 2021 17:20:49 +0530
From:   Rajendra Nayak <rnayak@...eaurora.org>
To:     Stephen Boyd <swboyd@...omium.org>, bjorn.andersson@...aro.org,
        ulf.hansson@...aro.org, viresh.kumar@...aro.org
Cc:     linux-pm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        rojay@...eaurora.org, stephan@...hold.net
Subject: Re: [PATCH v4 1/2] PM / Domains: Add support for 'required-opps' to
 set default perf state


On 7/17/2021 1:49 AM, Stephen Boyd wrote:
> Quoting Rajendra Nayak (2021-07-16 03:00:57)
>> Some devics within power domains with performance states do not
> 
> devices
> 
>> support DVFS, but still need to vote on a default/static state
>> while they are active. They can express this using the 'required-opps'
>> property in device tree, which points to the phandle of the OPP
>> supported by the corresponding power-domains.
>>
>> Add support to parse this information from DT and then set the
>> specified performance state during attach and drop it on detach.
>> Also drop/set as part of runtime suspend/resume callbacks.
>>
>> Signed-off-by: Rajendra Nayak <rnayak@...eaurora.org>
>> ---
>>   drivers/base/power/domain.c | 37 ++++++++++++++++++++++++++++++++++---
>>   include/linux/pm_domain.h   |  1 +
>>   2 files changed, 35 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
>> index a934c67..dcc0b71 100644
>> --- a/drivers/base/power/domain.c
>> +++ b/drivers/base/power/domain.c
>> @@ -1000,6 +1008,8 @@ static int genpd_runtime_resume(struct device *dev)
>>          genpd_stop_dev(genpd, dev);
>>   err_poweroff:
>>          if (!pm_runtime_is_irq_safe(dev) || genpd_is_irq_safe(genpd)) {
>> +               if (default_pstate)
>> +                       dev_pm_genpd_set_performance_state(dev, 0);
>>                  genpd_lock(genpd);
>>                  gpd_data->rpm_pstate = genpd_drop_performance_state(dev);
> 
> Maybe this should be
> 
> 		  prev_state = genpd_drop_performance_state(dev);
> 		  if (!default_pstate)
> 		  	gdp_data->rpm_pstate = prev_state;
> 
> so we don't call dev_pm_genpd_set_performance_state() effectively twice?
> Also it would make sure we call dev_pm_genpd_set_performance_state()
> underneath the genpd_lock() if that is important. Similarly do that on
> suspend path.

looking through this more, I think I can completely drop any special
handling for default_pstate in runtime suspend and resume. The existing
drop/restore login Ulf has added should take care of it.
I'll test and respin soon.

> 
>>                  genpd_power_off(genpd, true, 0);
>> @@ -2598,6 +2608,12 @@ static void genpd_dev_pm_detach(struct device *dev, bool power_off)
>>
>>          dev_dbg(dev, "removing from PM domain %s\n", pd->name);
>>
>> +       /* Drop the default performance state */
>> +       if (dev_gpd_data(dev)->default_pstate) {
>> +               dev_pm_genpd_set_performance_state(dev, 0);
>> +               dev_gpd_data(dev)->default_pstate = 0;
>> +       }
>> +
>>          for (i = 1; i < GENPD_RETRY_MAX_MS; i <<= 1) {
>>                  ret = genpd_remove_device(pd, dev);
>>                  if (ret != -EAGAIN)
>> @@ -2675,10 +2692,24 @@ static int __genpd_dev_pm_attach(struct device *dev, struct device *base_dev,
>>                  genpd_unlock(pd);
>>          }
>>
>> -       if (ret)
>> +       if (ret) {
>>                  genpd_remove_device(pd, dev);
>> +               return -EPROBE_DEFER;
>> +       }
>> +
>> +       /* Set the default performance state */
>> +       np = base_dev->of_node;
>> +       if (of_parse_phandle(np, "required-opps", index)) {
>> +               pstate = of_get_required_opp_performance_state(np, index);
>> +               if (pstate < 0) {
>> +                       dev_err(dev, "failed to set pstate:%d", pstate);
> 
> Missing newline on printk. Also can we spell out pstate as "failed to
> set required performance state %d for power-domain %d"?

thanks, will fix when I respin.
Thanks for the review.

> 
>> +                       ret = pstate;
>> +               }
>> +               dev_pm_genpd_set_performance_state(dev, pstate);
>> +               dev_gpd_data(dev)->default_pstate = pstate;
>> +       }
>>
>> -       return ret ? -EPROBE_DEFER : 1;
>> +       return ret ? ret : 1;
>>   }
>>
>>   /**

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