Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Subject: Re: [PATCH RFC] powercap/drivers/energy_model: protocode: Add
 powercap energy model based
To:     Amit Kucheria <amitk@kernel.org>
Cc:     "Rafael J. Wysocki" <rafael@kernel.org>,
        Lukasz Luba <lukasz.luba@arm.com>,
        Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
        Ram Chandrasekar <rkumbako@codeaurora.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Linux PM list <linux-pm@vger.kernel.org>
References: <20200707171457.31540-1-daniel.lezcano@linaro.org>
 <CAHLCerPq_f3t=cgS0MXvWuRvPaBrAs2dZEyeNSOyZ3OXHgHNeg@mail.gmail.com>
From:   Daniel Lezcano <daniel.lezcano@linaro.org>
Message-ID: <d8338e31-3d9b-a0b4-bf0f-6e74a7ae4fbf@linaro.org>
Date:   Fri, 11 Sep 2020 09:58:04 +0200
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101
 Thunderbird/68.10.0
MIME-Version: 1.0
In-Reply-To: <CAHLCerPq_f3t=cgS0MXvWuRvPaBrAs2dZEyeNSOyZ3OXHgHNeg@mail.gmail.com>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 8bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk


Hi Amit,

thanks for taking the time to review the series and read this long
description.

On 10/09/2020 11:48, Amit Kucheria wrote:

[ ... ]

>> +
>> +config POWERCAP_EM
>> +        bool "Energy model based power capping"
>> +       depends on ENERGY_MODEL
>> +       default y
> 
> Don't make it default ;-)

Thanks for pointing this out :D

[ ... ]

>> +       pc_package = powercap_em_register(pct, "package", pc_soc,
>> +                                         &zone_ops, 1, &constraint_ops);
> 
> Will the soc and package hierarchy eventually be dynamically read from
> devicetree or similar and these hardcoded registration removed?

Yes, that's correct.

> For the rest of the devices, IMO, it makes sense to use the genpd
> hierarchy to reflect the powercap hierarchy. I whipped up the
> following patch to show how it might be achieved. What needs to be
> done is to now reflect the parent-child/sibling relationships of genpd
> into powercap. Initially I thought we'd need to additional DT
> properties in the genpd bindings but I think we might be able to read
> the device-specific energy model data directly to populate the
> powercap constraints.

We need a way to describe the power constraints relationship of the
domains to populate the hierarchy of the powercap directories.

In the DT it may look like that (very roughly):

power-constraints {
	power-constraint: package {
		compatible = "power-constraint,virtual";
	};

	power-constraint: perfdomain0 {
		compatible = "power-constraint,cpu";
		device = <&cpu_l0>;
		parent = <&package>;
	};

	power-constraint: perfdomain1 {
		compatible = "power-constraint,cpu";
		device = <&cpu_b0>;
		parent = <&package>;
	};

	power-constraint: gpu {
		compatible = "power-constraint,gpu";
		parent = <&package>
	};
};


-- 
<http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs

Follow Linaro:  <http://www.facebook.com/pages/Linaro> Facebook |
<http://twitter.com/#!/linaroorg> Twitter |
<http://www.linaro.org/linaro-blog/> Blog