From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752291AbdCOI6H convert rfc822-to-8bit (ORCPT ); Wed, 15 Mar 2017 04:58:07 -0400 Received: from hqemgate14.nvidia.com ([216.228.121.143]:12406 "EHLO hqemgate14.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751198AbdCOI6E (ORCPT ); Wed, 15 Mar 2017 04:58:04 -0400 X-PGP-Universal: processed; by hqpgpgate101.nvidia.com on Wed, 15 Mar 2017 01:58:03 -0700 From: Jon Hunter Subject: Re: [RFC PATCH 0/3] PM / Domains: Add support for devices that require multiple domains To: 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 , Rajendra Nayak , Stanimir Varbanov , Stephen Boyd , Marek Szyprowski , Linux PM list , "linux-kernel@vger.kernel.org" , "linux-tegra@vger.kernel.org" , Bjorn Andersson Message-ID: <03e7f4d0-0c1b-edbb-3e24-83faf4b3a12b@nvidia.com> Date: Wed, 15 Mar 2017 08:57:56 +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: UKMAIL102.nvidia.com (10.26.138.15) 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 On 13/03/17 14:42, Ulf Hansson wrote: > 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. No problem. I should point out the above is for the #power-domain-cells = <0> case. >> >> 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. OK, fair enough. Any in particular you are concerned about? > 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!? Right that is a concern, however, I think that in the long-term we would be better off with the power-domains being controlled by the same underlying code as opposed to something different. Cheers Jon -- nvpublic