Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753387AbdCMOmj (ORCPT ); Mon, 13 Mar 2017 10:42:39 -0400 Received: from mail-ua0-f182.google.com ([209.85.217.182]:36290 "EHLO mail-ua0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752541AbdCMOmW (ORCPT ); Mon, 13 Mar 2017 10:42:22 -0400 MIME-Version: 1.0 In-Reply-To: <3e88692d-613b-9c25-2554-7d399c45637a@nvidia.com> References: <1474367287-10402-1-git-send-email-jonathanh@nvidia.com> <52493231-71f4-1b62-b325-8532e63e4229@nvidia.com> <3e88692d-613b-9c25-2554-7d399c45637a@nvidia.com> From: Ulf Hansson Date: Mon, 13 Mar 2017 15:42:19 +0100 Message-ID: Subject: Re: [RFC PATCH 0/3] PM / Domains: Add support for devices that require multiple domains To: Jon Hunter Cc: Geert Uytterhoeven , "Rafael J. Wysocki" , Kevin Hilman , Rajendra Nayak , Stanimir Varbanov , Stephen Boyd , Marek Szyprowski , Linux PM list , "linux-kernel@vger.kernel.org" , "linux-tegra@vger.kernel.org" , Bjorn Andersson 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-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by mail.home.local id v2DEgpk0024941 Content-Length: 3866 Lines: 92 On 13 March 2017 at 15:09, Jon Hunter wrote: > Hi Ulf, > > On 13/03/17 11:45, Ulf Hansson wrote: >> +Björn >> >> On 13 March 2017 at 10:37, Jon Hunter wrote: >>> Hi Rafael, Kevin, Ulf, >>> >>> 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>; > }; This could work. However, let's involve DT maintainers to make sure we get their input to this. Perhaps they prefer a different approach. > > 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 > > Are there any potential pitfalls of the above? So if I understand correctly, you would like to extend genpd with some new APIs. It's worth a try, however my main worries are these: 1) These new API must not be allowed to be abused. I have seen that before as when people try to handle some corner cases, I don't want to that to happen again. To avoid that, perhaps we should continue the re-structuring and thus move structures/datas that are currently public, to be internal to genpd. To get a clean interface. 2) I wouldn't be surprised if we run into some tricky corner cases, as we get a mixture of devices handled by runtime PM and in some other cases via new APIs. Perhaps that can be sorted out!? Kind regards Uffe