linux-kernel - How to power gate a specific single device from outside?

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Message-ID: <CAHKzcEP6dQ1PxB35yCW_R1W8yZCCsJN_HqiZ6uq2d+sZp_9EYw@mail.gmail.com>
Date:   Tue, 24 Oct 2017 10:34:49 +0200
From:   Waldemar Rymarkiewicz <waldemar.rymarkiewicz@...il.com>
To:     linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org
Subject: How to power gate a specific single device from outside?

Hi

I am looking for a convenient way to power gate specific single device
when the platform is running in backup mode - the platform lost main
power supply and it's on backup buttery now. The intention is to save
max power in backup mode and switch off all unnecessary blocks.

I could not find anything standard that let me power gate single
device from userland. Perhaps it's considered as a too risky operation
to expose to the user. I don't want to touch drivers too much as well
not to make them dependant on extra system feature. Better to have a
separate module that handles this system mode and forces some drivers
to unload/power gate their HW.

Are there already some proven solutions/ideas around the kernel that
can be used straight away?

Suggestions appreciated.

/Waldek