From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754040AbbLIKsI (ORCPT ); Wed, 9 Dec 2015 05:48:08 -0500 Received: from mail-wm0-f44.google.com ([74.125.82.44]:33904 "EHLO mail-wm0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753630AbbLIKsD (ORCPT ); Wed, 9 Dec 2015 05:48:03 -0500 Date: Wed, 9 Dec 2015 11:47:58 +0100 From: Alexander Aring To: Kevin Hilman Cc: Jon Hunter , Eric Anholt , "Rafael J. Wysocki" , Mark Rutland , devicetree@vger.kernel.org, Ulf Hansson , Florian Fainelli , Pawel Moll , Stephen Warren , Greg Kroah-Hartman , linux-pm@vger.kernel.org, Lee Jones , linux-kernel@vger.kernel.org, Rob Herring , linux-rpi-kernel@lists.infradead.org, Pavel Machek , Len Brown , Ian Campbell , linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH v2 1/5] power: domain: add pm_genpd_exit Message-ID: <20151209104752.GB1036@omega> References: <1449251148-19344-1-git-send-email-eric@anholt.net> <1449251148-19344-2-git-send-email-eric@anholt.net> <5665599A.4060509@nvidia.com> <7h8u54lqbv.fsf@deeprootsystems.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <7h8u54lqbv.fsf@deeprootsystems.com> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On Tue, Dec 08, 2015 at 10:59:00AM -0800, Kevin Hilman wrote: > Jon Hunter writes: > > > On 04/12/15 17:45, Eric Anholt wrote: > >> From: Alexander Aring > >> > >> This patch adds function pm_genpd_exit for undo a pm_genpd_init. This > >> is useful for multiple power domains while probing. If the probing fails > >> after one pm_genpd_init was called we need to undo all previous > >> registrations of generic pm domains inside the gpd_list list. > >> > >> There is a check on IS_ERR_OR_NULL(genpd) which is useful to check again > >> registered power domains and not registered domains, the driver can use > >> this mechanism to have an array with registered and non-registered power > >> domains, where non-registered power domains are NULL. > >> > >> Cc: Rafael J. Wysocki > >> Cc: Kevin Hilman > >> Cc: Ulf Hansson > >> Cc: Pavel Machek > >> Cc: Len Brown > >> Cc: Greg Kroah-Hartman > >> Signed-off-by: Alexander Aring > >> Signed-off-by: Eric Anholt > >> Acked-by: Ulf Hansson > >> --- > >> drivers/base/power/domain.c | 22 ++++++++++++++++++++++ > >> include/linux/pm_domain.h | 4 ++++ > >> 2 files changed, 26 insertions(+) > >> > >> diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c > >> index 167418e..e7aca27 100644 > >> --- a/drivers/base/power/domain.c > >> +++ b/drivers/base/power/domain.c > >> @@ -1509,6 +1509,28 @@ void pm_genpd_init(struct generic_pm_domain *genpd, > >> } > >> EXPORT_SYMBOL_GPL(pm_genpd_init); > >> > >> +/** > >> + * pm_genpd_exit - Uninitialize a generic I/O PM domain object. > >> + * @genpd: PM domain object to uninitialize. > >> + */ > >> +void pm_genpd_exit(struct generic_pm_domain *genpd) > >> +{ > >> + if (IS_ERR_OR_NULL(genpd)) > >> + return; > >> + > >> + /* check if domain is still in registered inside the pm subsystem */ > >> + WARN_ON_ONCE(!list_empty(&genpd->master_links) || > >> + !list_empty(&genpd->slave_links) || > >> + !list_empty(&genpd->dev_list)); > >> + > > > > Why not return an error here? Seems bad to remove it, if it could still > > be referenced by other domains. > > I had pointed this out as well in an earlier review. > I talked with Ulf Hansson about such handling and there exists currently no handling to remove the pm_genpd on error handling (what our use case is for RPi domains). The real solution would be a "pm_genpd_exit_recursive" functionality to remove subdomains, etc -> simple everything. Anway I am not a expert into power domain functionality and this simple approach was enough to him to add "something" which we have actually a lack of support. Now "returning an errno" here: I don't know how it should be handled in an "error handling" case. The WARN_ON_ONCE should say "somebody use this API wrong" which is a very unlikely case. These lists should be empty when calling pm_genpd_exit before in any case. Example: the error case is while probing, how we react on a -EBUSY there "in an error case" -> simple ignore it? But then nobody see that the use of this function is wrong. Should it be something like that? err_probe: WARN_ON_ONCE(pm_genpd_exit(foo) < 0); This function should be "void" here, I never saw some unregistration functionality which returns some "int" for error handling. Which brings us back to the "real" solution, a "pm_genpd_exit_recursive" functionality which unregister everything which belongs to a "generic_pm_domain". To have a "pm_genpd_exit" is only the first step. That we can improve error handling for pm_genpd_init. (Which RPi power domains use and doesn't register any subdomains, etc. for probing). > > Also not sure if you need to lock around the above test and removing the > > domain. > > > >> + mutex_lock(&gpd_list_lock); > >> + list_del(&genpd->gpd_list_node); > >> + mutex_unlock(&gpd_list_lock); > >> + > >> + mutex_destroy(&genpd->lock); > >> +} > >> +EXPORT_SYMBOL_GPL(pm_genpd_exit); > >> + > > > > BTW, I had just submitted a similar patch here [0]. So I would also like > > to see such an API added. > :-) > Between the two of you, maybe come up with an agreed upon patch and > re-submit. > > Kevin > > > Cheers > > Jon > > > > [0] http://marc.info/?l=devicetree&m=144924138932726&w=2 From mboxrd@z Thu Jan 1 00:00:00 1970 From: alex.aring@gmail.com (Alexander Aring) Date: Wed, 9 Dec 2015 11:47:58 +0100 Subject: [PATCH v2 1/5] power: domain: add pm_genpd_exit In-Reply-To: <7h8u54lqbv.fsf@deeprootsystems.com> References: <1449251148-19344-1-git-send-email-eric@anholt.net> <1449251148-19344-2-git-send-email-eric@anholt.net> <5665599A.4060509@nvidia.com> <7h8u54lqbv.fsf@deeprootsystems.com> Message-ID: <20151209104752.GB1036@omega> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hi, On Tue, Dec 08, 2015 at 10:59:00AM -0800, Kevin Hilman wrote: > Jon Hunter writes: > > > On 04/12/15 17:45, Eric Anholt wrote: > >> From: Alexander Aring > >> > >> This patch adds function pm_genpd_exit for undo a pm_genpd_init. This > >> is useful for multiple power domains while probing. If the probing fails > >> after one pm_genpd_init was called we need to undo all previous > >> registrations of generic pm domains inside the gpd_list list. > >> > >> There is a check on IS_ERR_OR_NULL(genpd) which is useful to check again > >> registered power domains and not registered domains, the driver can use > >> this mechanism to have an array with registered and non-registered power > >> domains, where non-registered power domains are NULL. > >> > >> Cc: Rafael J. Wysocki > >> Cc: Kevin Hilman > >> Cc: Ulf Hansson > >> Cc: Pavel Machek > >> Cc: Len Brown > >> Cc: Greg Kroah-Hartman > >> Signed-off-by: Alexander Aring > >> Signed-off-by: Eric Anholt > >> Acked-by: Ulf Hansson > >> --- > >> drivers/base/power/domain.c | 22 ++++++++++++++++++++++ > >> include/linux/pm_domain.h | 4 ++++ > >> 2 files changed, 26 insertions(+) > >> > >> diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c > >> index 167418e..e7aca27 100644 > >> --- a/drivers/base/power/domain.c > >> +++ b/drivers/base/power/domain.c > >> @@ -1509,6 +1509,28 @@ void pm_genpd_init(struct generic_pm_domain *genpd, > >> } > >> EXPORT_SYMBOL_GPL(pm_genpd_init); > >> > >> +/** > >> + * pm_genpd_exit - Uninitialize a generic I/O PM domain object. > >> + * @genpd: PM domain object to uninitialize. > >> + */ > >> +void pm_genpd_exit(struct generic_pm_domain *genpd) > >> +{ > >> + if (IS_ERR_OR_NULL(genpd)) > >> + return; > >> + > >> + /* check if domain is still in registered inside the pm subsystem */ > >> + WARN_ON_ONCE(!list_empty(&genpd->master_links) || > >> + !list_empty(&genpd->slave_links) || > >> + !list_empty(&genpd->dev_list)); > >> + > > > > Why not return an error here? Seems bad to remove it, if it could still > > be referenced by other domains. > > I had pointed this out as well in an earlier review. > I talked with Ulf Hansson about such handling and there exists currently no handling to remove the pm_genpd on error handling (what our use case is for RPi domains). The real solution would be a "pm_genpd_exit_recursive" functionality to remove subdomains, etc -> simple everything. Anway I am not a expert into power domain functionality and this simple approach was enough to him to add "something" which we have actually a lack of support. Now "returning an errno" here: I don't know how it should be handled in an "error handling" case. The WARN_ON_ONCE should say "somebody use this API wrong" which is a very unlikely case. These lists should be empty when calling pm_genpd_exit before in any case. Example: the error case is while probing, how we react on a -EBUSY there "in an error case" -> simple ignore it? But then nobody see that the use of this function is wrong. Should it be something like that? err_probe: WARN_ON_ONCE(pm_genpd_exit(foo) < 0); This function should be "void" here, I never saw some unregistration functionality which returns some "int" for error handling. Which brings us back to the "real" solution, a "pm_genpd_exit_recursive" functionality which unregister everything which belongs to a "generic_pm_domain". To have a "pm_genpd_exit" is only the first step. That we can improve error handling for pm_genpd_init. (Which RPi power domains use and doesn't register any subdomains, etc. for probing). > > Also not sure if you need to lock around the above test and removing the > > domain. > > > >> + mutex_lock(&gpd_list_lock); > >> + list_del(&genpd->gpd_list_node); > >> + mutex_unlock(&gpd_list_lock); > >> + > >> + mutex_destroy(&genpd->lock); > >> +} > >> +EXPORT_SYMBOL_GPL(pm_genpd_exit); > >> + > > > > BTW, I had just submitted a similar patch here [0]. So I would also like > > to see such an API added. > :-) > Between the two of you, maybe come up with an agreed upon patch and > re-submit. > > Kevin > > > Cheers > > Jon > > > > [0] http://marc.info/?l=devicetree&m=144924138932726&w=2