linux-kernel - Re: [PATCH v2] PM / EM: Expose the Energy Model in debugfs

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Date:   Tue, 22 Jan 2019 19:41:36 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Quentin Perret <quentin.perret@....com>
Cc:     rafael@...nel.org, peterz@...radead.org, mingo@...hat.com,
        linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        dietmar.eggemann@....com
Subject: Re: [PATCH v2] PM / EM: Expose the Energy Model in debugfs

On Tue, Jan 22, 2019 at 04:42:47PM +0000, Quentin Perret wrote:
> The recently introduced Energy Model (EM) framework manages power cost
> tables of CPUs. These tables are currently only visible from kernel
> space. However, in order to debug the behaviour of subsystems that use
> the EM (EAS for example), it is often required to know what the power
> costs are from userspace.
> 
> For this reason, introduce under /sys/kernel/debug/energy_model a set of
> directories representing the performance domains of the system. Each
> performance domain contains a set of sub-directories representing the
> different capacity states (cs) and their attributes, as well as a file
> exposing the related CPUs.
> 
> The resulting hierarchy is as follows on Arm juno r0 for example:
> 
>     /sys/kernel/debug/energy_model
>     ├── pd0
>     │   ├── cpus
>     │   ├── cs:450000
>     │   │   ├── cost
>     │   │   ├── frequency
>     │   │   └── power
>     │   ├── cs:575000
>     │   │   ├── cost
>     │   │   ├── frequency
>     │   │   └── power
>     │   ├── cs:700000
>     │   │   ├── cost
>     │   │   ├── frequency
>     │   │   └── power
>     │   ├── cs:775000
>     │   │   ├── cost
>     │   │   ├── frequency
>     │   │   └── power
>     │   └── cs:850000
>     │       ├── cost
>     │       ├── frequency
>     │       └── power
>     └── pd1
>         ├── cpus
>         ├── cs:1100000
>         │   ├── cost
>         │   ├── frequency
>         │   └── power
>         ├── cs:450000
>         │   ├── cost
>         │   ├── frequency
>         │   └── power
>         ├── cs:625000
>         │   ├── cost
>         │   ├── frequency
>         │   └── power
>         ├── cs:800000
>         │   ├── cost
>         │   ├── frequency
>         │   └── power
>         └── cs:950000
>             ├── cost
>             ├── frequency
>             └── power
> 
> Signed-off-by: Quentin Perret <quentin.perret@....com>
> 
> ---
> 
> V2: removed check on return value of debugfs_create_* (Greg KH)
> ---
>  kernel/power/energy_model.c | 57 +++++++++++++++++++++++++++++++++++++
>  1 file changed, 57 insertions(+)

Reviewed-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>