Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755944AbcJFMWW (ORCPT ); Thu, 6 Oct 2016 08:22:22 -0400 Received: from mail-wm0-f42.google.com ([74.125.82.42]:36278 "EHLO mail-wm0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753292AbcJFMWP (ORCPT ); Thu, 6 Oct 2016 08:22:15 -0400 MIME-Version: 1.0 In-Reply-To: <1474367287-10402-1-git-send-email-jonathanh@nvidia.com> References: <1474367287-10402-1-git-send-email-jonathanh@nvidia.com> From: Ulf Hansson Date: Thu, 6 Oct 2016 14:22:12 +0200 Message-ID: Subject: Re: [RFC PATCH 0/3] PM / Domains: Add support for devices that require multiple domains To: Jon Hunter Cc: "Rafael J. Wysocki" , Kevin Hilman , "linux-pm@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-tegra@vger.kernel.org" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2003 Lines: 48 On 20 September 2016 at 12:28, Jon Hunter wrote: > 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@70090000 { > 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. First, I don't really like extending the internal logic of genpd to deal with multiple PM domains per device. *If* this really is needed, I think we should try to extend the struct device to cover this, then make genpd to use it somehow. Second, another way of seeing this is: Depending on the current runtime selected configuration you need to re-configure the PM domain topology - but the device would still remain in the same PM domain. In other words, you would need to remove/add subdomain(s) depending on the selected configuration. Would that better reflect the HW? [...] Kind regards Uffe