linux-kernel - Re: [PATCH v6 1/2] PM / Domains: Add support for 'required-opps' to set default perf state

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Message-ID: <5515e731-dc07-5f28-1f80-e616718597a4@gmail.com>
Date:   Tue, 10 Aug 2021 03:37:57 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Rajendra Nayak <rnayak@...eaurora.org>, ulf.hansson@...aro.org,
        bjorn.andersson@...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,
        swboyd@...omium.org, rojay@...eaurora.org, stephan@...hold.net
Subject: Re: [PATCH v6 1/2] PM / Domains: Add support for 'required-opps' to
 set default perf state

10.08.2021 02:46, Dmitry Osipenko пишет:
> 10.08.2021 01:44, Dmitry Osipenko пишет:
>> 10.08.2021 01:26, Dmitry Osipenko пишет:
>>> 04.08.2021 13:58, Rajendra Nayak пишет:
>>>> @@ -2637,6 +2643,8 @@ static int __genpd_dev_pm_attach(struct device *dev, struct device *base_dev,
>>>>  {
>>>>  	struct of_phandle_args pd_args;
>>>>  	struct generic_pm_domain *pd;
>>>> +	struct device_node *np;
>>>> +	int pstate;
>>>>  	int ret;
>>>>  
>>>>  	ret = of_parse_phandle_with_args(dev->of_node, "power-domains",
>>>> @@ -2675,10 +2683,26 @@ 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 = dev->of_node;
>>>> +	if (of_parse_phandle(np, "required-opps", index)) {
> 
> The OF node returned by of_parse_phandle() must be put.
> 
>>>> +		pstate = of_get_required_opp_performance_state(np, index);
> 
> If you have more than one power domain, then this will override the
> pstate which was set for a previous domain. This code doesn't feel solid
> to me, at least a clarifying comment is needed about how it's supposed
> to work.
> 
>>>> +		if (pstate < 0) {
>>>> +			ret = pstate;
>>>> +			dev_err(dev, "failed to set required performance state for power-domain %s: %d\n",
>>>> +				pd->name, ret);
>>>> +		} else {
>>>> +			dev_pm_genpd_set_performance_state(dev, pstate);
>>
>> Where is error handling?
>>
>>>> +			dev_gpd_data(dev)->default_pstate = pstate;
>>>> +		}
>>>> +	}
>>>
>>> Why performance state is set after genpd_power_on()?
> 
> Should set_performance_state() be invoked when power_on=false?
> 
> I assume it should be:
> 
> if (power_on) {
> 	dev_pm_genpd_set_performance_state(dev, pstate);
> 	dev_gpd_data(dev)->default_pstate = pstate;
> } else {
> 	dev_gpd_data(dev)->rpm_pstate = pstate;
> }
> 

Although, thinking a bit more about this, it should be better to skip
setting perf state in a case of power_on=false and let drivers to handle
it, IMO. Too much trouble with it for the core.