linux-kernel - [RFC PATCH 0/3] PM / Domains: Add support for devices that require multiple domains

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Date:   Tue, 20 Sep 2016 11:28:04 +0100
From:   Jon Hunter <jonathanh@...dia.com>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Kevin Hilman <khilman@...nel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>
CC:     <linux-pm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-tegra@...r.kernel.org>, Jon Hunter <jonathanh@...dia.com>
Subject: [RFC PATCH 0/3] PM / Domains: Add support for devices that require multiple domains

The Tegra124/210 XUSB subsystem (that consists of both host and device
controllers) is partitioned across 3 PM domains which are:
- XUSBA: Superspeed logic (for USB 3.0)
- XUSBB: Device controller
- XUSBC: Host controller

These power domains are not nested and can be powered-up and down
independently of one another. In practice different scenarios require
different combinations of the power domains, for example:
- Superspeed host: XUSBA and XUSBC
- Superspeed device: XUSBA and XUSBB

Although it could be possible to logically nest both the XUSBB and XUSBC
domains under the XUSBA, superspeed may not always be used/required and
so this would keep it on unnecessarily.

Given that Tegra uses device-tree for describing the hardware, it would
be ideal that the device-tree 'power-domains' property for generic PM
domains could be extended to allow more than one PM domain to be
specified. For example, define the following the Tegra210 xHCI device ...

	usb@...90000 {
		compatible = "nvidia,tegra210-xusb";
		...
		power-domains = <&pd_xusbhost>, <&pd_xusbss>;
	};

This RFC extends the generic PM domain framework to allow a device to
define more than one PM domain in the device-tree 'power-domains'
property.

Jon Hunter (3):
  PM / Domains: Add helper functions for finding and attaching PM
    domains
  PM / Domains: Add support for devices with multiple domains
  dt-bindings: Add support for devices with multiple PM domains

 .../devicetree/bindings/power/power_domain.txt     |   5 +-
 drivers/base/power/domain.c                        | 205 +++++++++++++++------
 2 files changed, 155 insertions(+), 55 deletions(-)

-- 
2.1.4