Message-ID: <35950d34-5cab-1b09-9864-49217a83f68d@codeaurora.org>
Date:   Tue, 3 Aug 2021 10:08:26 +0530
From:   Rajendra Nayak <rnayak@...eaurora.org>
To:     Ulf Hansson <ulf.hansson@...aro.org>
Cc:     Bjorn Andersson <bjorn.andersson@...aro.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        DTML <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Roja Rani Yarubandi <rojay@...eaurora.org>,
        Stephan Gerhold <stephan@...hold.net>
Subject: Re: [PATCH v5 1/2] PM / Domains: Add support for 'required-opps' to
 set default perf state


On 8/2/2021 6:29 PM, Ulf Hansson wrote:
> On Tue, 20 Jul 2021 at 09:12, Rajendra Nayak <rnayak@...eaurora.org> wrote:
>>
>> Some devices within power domains with performance states do not
>> 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.
>> runtime suspend/resume callbacks already have logic to drop/set
>> the vote as needed and should take care of dropping the default
>> perf state vote on runtime suspend and restore it back on runtime
>> resume.
>>
>> Signed-off-by: Rajendra Nayak <rnayak@...eaurora.org>
>> ---
>>   drivers/base/power/domain.c | 28 +++++++++++++++++++++++++---
>>   include/linux/pm_domain.h   |  1 +
>>   2 files changed, 26 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
>> index a934c67..f454031 100644
>> --- a/drivers/base/power/domain.c
>> +++ b/drivers/base/power/domain.c
>> @@ -2598,6 +2598,12 @@ 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)
>> @@ -2635,9 +2641,10 @@ static void genpd_dev_pm_sync(struct device *dev)
>>   static int __genpd_dev_pm_attach(struct device *dev, struct device *base_dev,
>>                                   unsigned int index, bool power_on)
>>   {
>> +       struct device_node *np;
>>          struct of_phandle_args pd_args;
>>          struct generic_pm_domain *pd;
>> -       int ret;
>> +       int ret, pstate;
>>
>>          ret = of_parse_phandle_with_args(dev->of_node, "power-domains",
>>                                  "#power-domain-cells", index, &pd_args);
>> @@ -2675,10 +2682,25 @@ 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;
> 
> Please use dev->of_node instead (it is set to the same of_node as
> base_dev by the callers of __genpd_dev_pm_attach) as it's more
> consistent with existing code.
> 
>> +       if (of_parse_phandle(np, "required-opps", index)) {
>> +               pstate = of_get_required_opp_performance_state(np, index);
>> +               if (pstate < 0) {
>> +                       ret = pstate;
>> +                       dev_err(dev, "failed to set required performance state for power-domain %s: %d\n",
>> +                               pd->name, ret);
>> +               }
>> +               dev_pm_genpd_set_performance_state(dev, pstate);
>> +               dev_gpd_data(dev)->default_pstate = pstate;
> 
> This doesn't look entirely correct to me. If we fail to translate a
> required opp to a performance state, we shouldn't try to set it.

yeah, that does not seem right at all :(

> Perhaps it's also easier to call
> of_get_required_opp_performance_state() unconditionally of whether a
> "required-opps" specifier exists. If it fails with the translation,
> then we just skip setting a default state and continue with returning
> 1.
> 
> Would that work?

I think it should, I'll redo the error handling, hopefully right this time,
and re-post. Thanks for the review.

> 
>> +       }
>>
>> -       return ret ? -EPROBE_DEFER : 1;
>> +       return ret ? ret : 1;
>>   }
>>
>>   /**
>> diff --git a/include/linux/pm_domain.h b/include/linux/pm_domain.h
>> index 21a0577..67017c9 100644
>> --- a/include/linux/pm_domain.h
>> +++ b/include/linux/pm_domain.h
>> @@ -198,6 +198,7 @@ struct generic_pm_domain_data {
>>          struct notifier_block *power_nb;
>>          int cpu;
>>          unsigned int performance_state;
>> +       unsigned int default_pstate;
>>          unsigned int rpm_pstate;
>>          ktime_t next_wakeup;
>>          void *data;
>> --
>> QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member
>> of Code Aurora Forum, hosted by The Linux Foundation
>>
> 
> Kind regards
> Uffe
> 

-- 
QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member
of Code Aurora Forum, hosted by The Linux Foundation

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