linux-kernel - Re: [PATCH v3 3/4] OPP: Add support of "opp-microwatt" for advanced EM registration

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Message-ID: <20220224091346.xmnpj27vllpa4cuy@vireshk-i7>
Date:   Thu, 24 Feb 2022 14:43:46 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Lukasz Luba <lukasz.luba@....com>
Cc:     linux-kernel@...r.kernel.org, dietmar.eggemann@....com,
        rafael@...nel.org, daniel.lezcano@...aro.org, nm@...com,
        sboyd@...nel.org, mka@...omium.org, dianders@...omium.org,
        robh+dt@...nel.org, devicetree@...r.kernel.org,
        linux-pm@...r.kernel.org
Subject: Re: [PATCH v3 3/4] OPP: Add support of "opp-microwatt" for advanced
 EM registration

On 24-02-22, 08:11, Lukasz Luba wrote:
> diff --git a/drivers/opp/of.c b/drivers/opp/of.c
>  
> +/*
> + * Callback function provided to the Energy Model framework upon registration.
> + * It provides the power used by @dev at @kHz if it is the frequency of an
> + * existing OPP, or at the frequency of the first OPP above @kHz otherwise
> + * (see dev_pm_opp_find_freq_ceil()). This function updates @kHz to the ceiled
> + * frequency and @mW to the associated power.
> + *
> + * Returns 0 on success or a proper -EINVAL value in case of error.
> + */
> +static int __maybe_unused
> +_get_opp_power(unsigned long *mW, unsigned long *kHz, struct device *dev)

Lets call it _get_dt_opp_power() or _get_dt_power() ?

> +{
> +	struct dev_pm_opp *opp;
> +	unsigned long opp_freq, opp_power;
> +
> +	/* Find the right frequency and related OPP */
> +	opp_freq = *kHz * 1000;
> +	opp = dev_pm_opp_find_freq_ceil(dev, &opp_freq);
> +	if (IS_ERR(opp))
> +		return -EINVAL;
> +
> +	opp_power = dev_pm_opp_get_power(opp);

As I said in 2/4, this should really give the total instead.

> +	dev_pm_opp_put(opp);
> +	if (!opp_power)
> +		return -EINVAL;
> +
> +	*kHz = opp_freq / 1000;
> +	*mW = opp_power / 1000;
> +
> +	return 0;
> +}
> +
>  /*
>   * Callback function provided to the Energy Model framework upon registration.
>   * This computes the power estimated by @dev at @kHz if it is the frequency
> @@ -1488,6 +1520,24 @@ static int __maybe_unused _get_power(unsigned long *mW, unsigned long *kHz,
>  	return 0;
>  }
>  
> +static bool _of_has_opp_microwatt_property(struct device *dev)
> +{
> +	unsigned long power, freq = 0;
> +	struct dev_pm_opp *opp;
> +
> +	/* Check if at least one OPP has needed property */
> +	opp = dev_pm_opp_find_freq_ceil(dev, &freq);
> +	if (IS_ERR(opp))
> +		return false;
> +
> +	power = dev_pm_opp_get_power(opp);
> +	dev_pm_opp_put(opp);
> +	if (!power)

What if this particular frequency has 0 power mentioned for some
reason :)

Instead of this heavy stuff, just pick the first OPP from the opp
table and see its power-value.

> +		return false;
> +
> +	return true;
> +}
> +
>  /**
>   * dev_pm_opp_of_register_em() - Attempt to register an Energy Model
>   * @dev		: Device for which an Energy Model has to be registered
> @@ -1517,6 +1567,14 @@ int dev_pm_opp_of_register_em(struct device *dev, struct cpumask *cpus)
>  		goto failed;
>  	}
>  
> +	/* First, try to find more precised Energy Model in DT */
> +	if (_of_has_opp_microwatt_property(dev)) {
> +		struct em_data_callback em_dt_cb = EM_DATA_CB(_get_opp_power);
> +
> +		return em_dev_register_perf_domain(dev, nr_opp, &em_dt_cb,
> +						   cpus, true);
> +	}
> +

We have another em_dev_register_perf_domain() down the line, lets keep
only one such call and get it a callback that should be set in an
if/else loop.

>  	np = of_node_get(dev->of_node);
>  	if (!np) {
>  		ret = -EINVAL;
> -- 
> 2.17.1

-- 
viresh