Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752345AbcJFIZ6 (ORCPT ); Thu, 6 Oct 2016 04:25:58 -0400 Received: from hqemgate15.nvidia.com ([216.228.121.64]:17707 "EHLO hqemgate15.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751027AbcJFIZ4 (ORCPT ); Thu, 6 Oct 2016 04:25:56 -0400 X-PGP-Universal: processed; by hqpgpgate101.nvidia.com on Thu, 06 Oct 2016 01:25:54 -0700 Subject: Re: [RFC PATCH 0/3] PM / Domains: Add support for devices that require multiple domains To: Rajendra Nayak , "Rafael J. Wysocki" , Kevin Hilman , Ulf Hansson References: <1474367287-10402-1-git-send-email-jonathanh@nvidia.com> <57F5E986.40704@codeaurora.org> CC: , , From: Jon Hunter Message-ID: <8ba7aa10-0c2f-98ca-c7bd-00e1724e5972@nvidia.com> Date: Thu, 6 Oct 2016 09:25:44 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.3.0 MIME-Version: 1.0 In-Reply-To: <57F5E986.40704@codeaurora.org> X-Originating-IP: [10.21.132.115] X-ClientProxiedBy: DRUKMAIL102.nvidia.com (10.25.59.20) To UKMAIL101.nvidia.com (10.26.138.13) Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1767 Lines: 45 Hi Rajendra, On 06/10/16 07:04, Rajendra Nayak wrote: > > On 09/20/2016 03:58 PM, 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. > > Hey Jon, so does this RFC provide a way to just specify multiple Powerdomains > for a device (which then will *all* be powered on/off together) or does > it also provide for more granular control of these powerdomains? Only to specify multiple power-domains for a device and not the later. > The above statement seems to suggest you would need more granular control > of these powerdomains (like keeping XUSBA off in case superspeed it not > needed) but I can't seem to figure out how you achieve it with this series. It is an interesting point but today we have always kept the superspeed partition on if the device is configured for superspeed regardless of what is actually connected. I will check to see if the h/w would allow us to turn it off if a non-superspeed device is in use but I did not think so. Do you have any interesting use-cases that would make use of this or require other such enhancements? Cheers Jon -- nvpublic