linux-kernel - Re: [PATCH v6 04/10] PM / EM: add support for other devices than CPUs in Energy Model

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Message-ID: <20200423151250.GB65632@linaro.org>
Date:   Thu, 23 Apr 2020 17:12:50 +0200
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     Lukasz Luba <lukasz.luba@....com>
Cc:     linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
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Subject: Re: [PATCH v6 04/10] PM / EM: add support for other devices than
 CPUs in Energy Model

On Fri, Apr 10, 2020 at 09:42:04AM +0100, Lukasz Luba wrote:
> Add support for other devices that CPUs. The registration function
> does not require a valid cpumask pointer and is ready to handle new
> devices. Some of the internal structures has been reorganized in order to
> keep consistent view (like removing per_cpu pd pointers). To track usage
> of the Energy Model structures, they are protected with kref.

Why not add the energy model structure in the struct device directly?

For instance for the em_cpu_get() function, the cpu id allows to retrieve the
cpu device and then from there, the energy model instead of browsing another
list. The em_device life cycle will be tied to the struct device.

Then when the struct device and the em_device are connected, add the debugfs
with a struct device list for those which are energy aware, so you end up with
a structure:

struct em_device {
	struct device *dev;
	struct list_head em_dev_list;
};

(a global single dentry for debugfs to do a recursive delete is enough).

Locks when inspecting and add/removal called from the struct device release
function. So no need of an extra refcounting.

Does it make sense?