Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752636AbdCOJDz convert rfc822-to-8bit (ORCPT ); Wed, 15 Mar 2017 05:03:55 -0400 Received: from hqemgate15.nvidia.com ([216.228.121.64]:6953 "EHLO hqemgate15.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751310AbdCOJDt (ORCPT ); Wed, 15 Mar 2017 05:03:49 -0400 X-PGP-Universal: processed; by hqnvupgp08.nvidia.com on Wed, 15 Mar 2017 02:01:14 -0700 Subject: Re: [RFC PATCH 0/3] PM / Domains: Add support for devices that require multiple domains To: "Nayak, Rajendra" , Ulf Hansson References: <1474367287-10402-1-git-send-email-jonathanh@nvidia.com> <52493231-71f4-1b62-b325-8532e63e4229@nvidia.com> <3e88692d-613b-9c25-2554-7d399c45637a@nvidia.com> CC: Geert Uytterhoeven , "Rafael J. Wysocki" , Kevin Hilman , Stanimir Varbanov , Stephen Boyd , "Marek Szyprowski" , Linux PM list , "linux-kernel@vger.kernel.org" , "linux-tegra@vger.kernel.org" , Bjorn Andersson From: Jon Hunter Message-ID: <3827826f-72b6-d5f8-eca0-5a3a8cfe32d0@nvidia.com> Date: Wed, 15 Mar 2017 09:03:26 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.7.0 MIME-Version: 1.0 In-Reply-To: X-Originating-IP: [10.21.132.151] X-ClientProxiedBy: DRUKMAIL101.nvidia.com (10.25.59.19) To UKMAIL101.nvidia.com (10.26.138.13) Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3545 Lines: 91 Hi Rajendra, On 15/03/17 03:47, Nayak, Rajendra wrote: > Hey Jon, > >>>> Looks like there is still some interest/needs in/for this. Any thoughts >>>> on how we can move this forward? >>> >>> At the Linaro Connect last week, I was talking to Björn, Rajendra and >>> Stephen more about these related issues. >>> >>> It definitely seems like we need to progress with this somehow, >>> meaning we need a solution for being able to associate a device with >>> more than one PM domain. In that context, I don't think genpd based on >>> its current design, is a good fit to solve the problem. >>> >>> Instead I think we need something entirely new (perhaps some code can >>> be borrowed from genpd), which is more similar to the clock/regulator >>> framework. In other words, what you also were suggesting in a earlier >>> reply. >>> In this way, the driver/subsystem gains full flexibility of managing >>> its device's PM domains, which seems like the best future-proof >>> solution. >> >> I agree, I think that that would give us the most flexibility to handle >> whatever scenario. However, I was thinking that we could still use the >> genpd core to register pm-domains with and control. My thought was to >> allow devices to have a bindings with multiple pm-domains ... >> >> dev-xyz { >> ... >> power-domains = <&domain-a>, <&domain-b>; >> }; >> >> Then in the genpd core we do having something like ... >> >> diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c >> index e697dec9d25b..d1ae6ddf4903 100644 >> --- a/drivers/base/power/domain.c >> +++ b/drivers/base/power/domain.c >> @@ -2026,6 +2026,15 @@ int genpd_dev_pm_attach(struct device *dev) >> >> "samsung,power-domain", 0); >> if (!pd_args.np) >> return -ENOENT; >> + } else if (ret > 1) { >> + /* >> + * If there are more than one PM domain defined for a >> device, >> + * then these need to be manually controlled by the >> device >> + * driver because the genpd core cannot bind a device >> with >> + * more than one PM domain. >> + */ >> + dev_dbg(dev, "cannot add PM domains, %d detected!\n", >> ret); >> + return 0; >> } >> >> Then add some new public APIs for getting and controlling the >> pm-domains ... >> >> struct generic_pm_domain *pm_genpd_get(struct device *dev, char *name); >> - Use 'dev->of_node' to look-up pm-domain if populated, else uses name. >> >> struct generic_pm_domain *of_pm_genpd_get(struct device *dev, int index); >> void pm_genpd_put(struct generic_pm_domain *pd); >> int pm_genpd_power_on(struct generic_pm_domain *pd); >> int pm_genpd_power_off(struct generic_pm_domain *pd); >> - Power on/off APIs would be synchronous types > > These would also need some kind of usecounting I guess, since genpd > otherwise relies on runtime PM to do the usecounting. Yes exactly. > This overall seems like a reasonable approach to solve the problem we > have. While we discussed this approach at connect, we thought it would > be a good idea to bring out some RFC on these lines to get the > discussion going. Do you think you would be able to work on some quick > RFC around these lines, else if you think you would be busy in the near > term I can help with hacking up the changes as well. Yes I plan too. I will let you know if I get side tracked on something else. Cheers! Jon -- nvpublic