From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752614AbbCPKM3 (ORCPT ); Mon, 16 Mar 2015 06:12:29 -0400 Received: from mail-qc0-f171.google.com ([209.85.216.171]:33171 "EHLO mail-qc0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751047AbbCPKM0 convert rfc822-to-8bit (ORCPT ); Mon, 16 Mar 2015 06:12:26 -0400 MIME-Version: 1.0 In-Reply-To: <7hr3sspyj3.fsf@deeprootsystems.com> References: <1426087648-3862-1-git-send-email-eric@anholt.net> <6516096.HanqZ05BXy@vostro.rjw.lan> <7hr3sspyj3.fsf@deeprootsystems.com> Date: Mon, 16 Mar 2015 11:12:25 +0100 Message-ID: Subject: Re: [PATCH] PM / Domains: If an OF node is found but no device probed yet, defer. From: Ulf Hansson To: Kevin Hilman , Eric Anholt Cc: Geert Uytterhoeven , "Rafael J. Wysocki" , "linux-kernel@vger.kernel.org" , Tomasz Figa , Greg Kroah-Hartman , Linux PM list 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 March 2015 at 19:01, Kevin Hilman wrote: > Geert Uytterhoeven writes: > >> On Wed, Mar 11, 2015 at 11:08 PM, Rafael J. Wysocki wrote: >>> More CCes. >>> >>> On Wednesday, March 11, 2015 08:27:28 AM Eric Anholt wrote: >>>> If we've declared a power domain in the OF, and the OF node is found >>>> but the requested domain hasn't been registered on it yet, then we >>>> probably have just tried to probe before the power domain driver has. >>>> Defer our device's probe until it shows up. >>>> >>>> Signed-off-by: Eric Anholt >>> >>> Kevin, Ulf, any chance to have a look at this, please? >>> >>>> --- >>>> >>>> I ran into this when turning my ad-hoc code for BCM2835 (Raspberry Pi) >>>> USB poweron support in the DWC2 controller to an OF-based power domain >>>> declaration. >> >> I guess you are initializing the PM domains from module_init()? >> >> I use core_initcall() in arch/arm/mach-shmobile/pm-rmobile.c to make sure it's >> initialized earlier, as e.g. the interrupt controller uses postcore_initcall(). > > Yeah, I think most existing users are initizling PM domains early, but IMO > we should be working towards supporting PM domains that are created > later as well (as this patch does.) I do agree, that we _should_ allow PM domains to be created later/any time. Unfortunate, that's not going to be a simple one-liner patch. :-) To have genpd_dev_pm_attach() return -EPROBE_DEFER, due to that the PM domain hasn’t been _initialized_ yet, we need to know whether a PM domain exists at all for the device. In principle we need to split the work done by genpd_dev_pm_attach() into the two parts described below. 1. At struct device creation time, done from the "OF core", we also need to parse for a PM domain node. If such is found, we somehow needs to assigned it to the device. Normally we would have assigned the struct dev_pm_domain in the struct device to deal with this, but that has some implications. Currently the struct dev_pm_domain is created from SoC specific code and it's also done at different init levels. 2. At ->probe(), genpd shall return -EPROBE_DEFER, if the device's assigned PM domain hasn’t been initialized yet. Implementing 2) should be trivial, but 1) could be a bit harder. Anyway, if anyone want to have a stab on it, I will gladly review such patches. Kind regards Uffe > >>>> drivers/base/power/domain.c | 2 +- >>>> 1 file changed, 1 insertion(+), 1 deletion(-) >>>> >>>> diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c >>>> index ba4abbe..2b93c98 100644 >>>> --- a/drivers/base/power/domain.c >>>> +++ b/drivers/base/power/domain.c >>>> @@ -2064,7 +2064,7 @@ EXPORT_SYMBOL_GPL(of_genpd_del_provider); >>>> struct generic_pm_domain *of_genpd_get_from_provider( >>>> struct of_phandle_args *genpdspec) >>>> { >>>> - struct generic_pm_domain *genpd = ERR_PTR(-ENOENT); >>>> + struct generic_pm_domain *genpd = ERR_PTR(-EPROBE_DEFER); >> >> Currently platform_drv_probe() just continues if dev_pm_domain_attach() returns >> a different error than -EPROBE_DEFER, which is what you are seeing. >> >> Your change does have the side effect that a new DT with PM domains won't >> work on an older kernel that doesn't have the PM domain driver yet. > > Is that a real problem though? Using newer DTs on older kernels can > cause many types of problems. > > Kevin