Messages in this thread | | | From | Peng Fan <> | Subject | RE: [RFC] platform: detach from PM domains on shutdown | Date | Tue, 29 May 2018 07:52:00 +0000 |
| |
> -----Original Message----- > From: Rafael J. Wysocki [mailto:rjw@rjwysocki.net] > Sent: 2018年5月28日 16:32 > To: Peng Fan <peng.fan@nxp.com> > Cc: Rafael J. Wysocki <rafael@kernel.org>; Ulf Hansson > <ulf.hansson@linaro.org>; Rafael J. Wysocki <rafael.j.wysocki@intel.com>; > Fabio Estevam <fabio.estevam@nxp.com>; Greg Kroah-Hartman > <gregkh@linuxfoundation.org>; Linux Kernel Mailing List > <linux-kernel@vger.kernel.org>; Linux PM <linux-pm@vger.kernel.org>; > dl-linux-imx <linux-imx@nxp.com> > Subject: Re: [RFC] platform: detach from PM domains on shutdown > > On Monday, May 28, 2018 10:01:09 AM CEST Peng Fan wrote: > > Hi, Rafael & Uffe > > > > > -----Original Message----- > > > From: Peng Fan > > > Sent: 2018年5月18日 16:53 > > > To: Rafael J. Wysocki <rjw@rjwysocki.net> > > > Cc: Rafael J. Wysocki <rafael@kernel.org>; Ulf Hansson > > > <ulf.hansson@linaro.org>; Rafael J. Wysocki > > > <rafael.j.wysocki@intel.com>; Fabio Estevam <fabio.estevam@nxp.com>; > > > Greg Kroah-Hartman <gregkh@linuxfoundation.org>; Linux Kernel > > > Mailing List <linux-kernel@vger.kernel.org>; Linux PM > > > <linux-pm@vger.kernel.org>; dl-linux-imx <linux-imx@nxp.com> > > > Subject: RE: [RFC] platform: detach from PM domains on shutdown > > > > > > > > > > > > > -----Original Message----- > > > > From: Rafael J. Wysocki [mailto:rjw@rjwysocki.net] > > > > Sent: 2018年5月18日 15:55 > > > > To: Peng Fan <peng.fan@nxp.com> > > > > Cc: Rafael J. Wysocki <rafael@kernel.org>; Ulf Hansson > > > > <ulf.hansson@linaro.org>; Rafael J. Wysocki > > > > <rafael.j.wysocki@intel.com>; Fabio Estevam > > > > <fabio.estevam@nxp.com>; Greg Kroah-Hartman > > > > <gregkh@linuxfoundation.org>; Linux Kernel Mailing List > > > > <linux-kernel@vger.kernel.org>; Linux PM > > > > <linux-pm@vger.kernel.org>; dl-linux-imx <linux-imx@nxp.com> > > > > Subject: Re: [RFC] platform: detach from PM domains on shutdown > > > > > > > > On Thursday, May 17, 2018 2:37:31 PM CEST Peng Fan wrote: > > > > > > > > > > > -----Original Message----- > > > > > > From: rjwysocki@gmail.com [mailto:rjwysocki@gmail.com] On > > > > > > Behalf Of Rafael J. Wysocki > > > > > > Sent: 2018年5月17日 16:01 > > > > > > To: Peng Fan <peng.fan@nxp.com> > > > > > > Cc: Rafael J. Wysocki <rafael@kernel.org>; Ulf Hansson > > > > > > <ulf.hansson@linaro.org>; Rafael J. Wysocki > > > > > > <rafael.j.wysocki@intel.com>; Fabio Estevam > > > > > > <fabio.estevam@nxp.com>; Greg Kroah-Hartman > > > > > > <gregkh@linuxfoundation.org>; Linux Kernel Mailing List > > > > > > <linux-kernel@vger.kernel.org>; Linux PM > > > > > > <linux-pm@vger.kernel.org>; dl-linux-imx <linux-imx@nxp.com> > > > > > > Subject: Re: [RFC] platform: detach from PM domains on > > > > > > shutdown > > > > > > > > > > > > On Thu, May 17, 2018 at 4:33 AM, Peng Fan <peng.fan@nxp.com> > wrote: > > > > > > > > > > > > > > > > > > > > >> -----Original Message----- > > > > > > >> From: rjwysocki@gmail.com [mailto:rjwysocki@gmail.com] On > > > > > > >> Behalf Of Rafael J. Wysocki > > > > > > >> Sent: 2018年5月17日 5:35 > > > > > > >> To: Ulf Hansson <ulf.hansson@linaro.org> > > > > > > >> Cc: Peng Fan <peng.fan@nxp.com>; Rafael J. Wysocki > > > > > > >> <rafael.j.wysocki@intel.com>; Fabio Estevam > > > > > > >> <fabio.estevam@nxp.com>; Greg Kroah-Hartman > > > > > > >> <gregkh@linuxfoundation.org>; Linux Kernel Mailing List > > > > > > >> <linux-kernel@vger.kernel.org>; Linux PM > > > > > > >> <linux-pm@vger.kernel.org>; dl-linux-imx > > > > > > >> <linux-imx@nxp.com> > > > > > > >> Subject: Re: [RFC] platform: detach from PM domains on > > > > > > >> shutdown > > > > > > >> > > > > > > >> On Wed, May 16, 2018 at 11:52 AM, Ulf Hansson > > > > > > >> <ulf.hansson@linaro.org> > > > > > > >> wrote: > > > > > > >> > On 15 May 2018 at 11:01, Peng Fan <peng.fan@nxp.com> wrote: > > > > > > >> >> When reboot Linux, the PM domains attached to a device > > > > > > >> >> are not shutdown. To SoCs which relys on reset the whole > > > > > > >> >> SoC, there is no need to shutdown PM domains, but to > > > > > > >> >> Linux running in a virtual machine with devices > > > > > > >> >> pass-through, we could not reset the > > > > whole SoC. > > > > > > >> >> Currently we need Linux to shutdown its PM domains when > reboot. > > > > > > >> > > > > > > > >> > I am not sure I understand exactly why the PM domain > > > > > > >> > needs to be shutdown for these cases, could you please elaborate > a bit on that. > > > > > > >> > > > > > > > >> > BTW, what platform are you running on and also what PM > > > > > > >> > domains are being > > > > > > >> used? > > > > > > >> > > > > > > > >> > Anyway, it seems like there may be need for certain > > > > > > >> > cases, but certainly not all - especially since it may > > > > > > >> > slow down the shutdown process, when not needed. > > > > > > >> > > > > > > > >> > Can we make this runtime configurable, via sysfs or > > > > > > >> > whatever that makes > > > > > > >> sense!? > > > > > > >> > > > > > > > >> >> > > > > > > >> >> commit 2d30bb0b3889 ("platform: Do not detach from PM > > > > > > >> >> domains on shutdown"), removes what this patch tries to > > > > > > >> >> add, because of a > > > > warning. > > > > > > >> >> commit e79aee49bcf9 ("PM: Avoid false-positive warnings > > > > > > >> >> in > > > > > > >> >> dev_pm_domain_set()") already fixes the false alarm warning. > > > > > > >> >> So let's detach the power domain to shutdown PM domains > > > > > > >> >> after driver > > > > > > shutdown. > > > > > > >> >> > > > > > > >> >> Signed-off-by: Peng Fan <peng.fan@nxp.com> > > > > > > >> >> --- > > > > > > >> >> > > > > > > >> >> I do not find a better place to shutdown power domain > > > > > > >> >> when reboot Linux, so add back the line that commit > > > > > > >> >> 2d30bb0b3889 removes, because it is a false alarm > > > > > > >> >> warning as commit > > > > > > >> >> e79aee49bcf9 > > > > describes. > > > > > > >> >> > > > > > > >> >> drivers/base/platform.c | 1 + > > > > > > >> >> 1 file changed, 1 insertion(+) > > > > > > >> >> > > > > > > >> >> diff --git a/drivers/base/platform.c > > > > > > >> >> b/drivers/base/platform.c index > > > > > > >> >> 8075ddc70a17..a5929f24dc3c > > > > > > >> >> 100644 > > > > > > >> >> --- a/drivers/base/platform.c > > > > > > >> >> +++ b/drivers/base/platform.c > > > > > > >> >> @@ -616,6 +616,7 @@ static void > > > > > > >> >> platform_drv_shutdown(struct device > > > > > > >> >> *_dev) > > > > > > >> >> > > > > > > >> >> if (drv->shutdown) > > > > > > >> >> drv->shutdown(dev); > > > > > > >> >> + dev_pm_domain_detach(_dev, true); > > > > > > >> > > > > > > > >> > This would somewhat work, but only for platform devices. > > > > > > >> > To make this fully work, we need to call > > > > > > >> > dev_pm_domain_detach() from amba, spi, etc as well. > > > > > > >> > > > > > > > >> > Perhaps another option to manage this more generally, an > > > > > > >> > without having detach devices, could be to extend the > > > > > > >> > struct dev_pm_domain with a new callback, "->shutdown()" > > > > > > >> > and then make the driver core call it from device_shutdown(). > > > > > > >> > > > > > > >> I'm sensing a possible ordering slippery slope with this > > > > > > >> (it will only work if all of the drivers/bus types etc do > > > > > > >> the right thing in their > > > > > > >> ->shutdown callbacks so nothing depends on the domain going > > > forward). > > > > > > >> > > > > > > >> > Typically, for genpd, I would probably count the number > > > > > > >> > of calls being made to ->shutdown() per PM domain, then > > > > > > >> > when it reaches the number of attached devices to it, allow to > power off it. > > > > > > >> > > > > > > > >> > Let's see what Rafael thinks about it. > > > > > > >> > > > > > > >> I'm not sure about the use case. The hypervisor should be > > > > > > >> able to take care of turning power domains off on the > > > > > > >> client OS reboot in theory. If the client OS leaving the > > > > > > >> hypervisor needs to worry about what state it leaves > > > > > > >> behind, the design of the hypervisor is sort of > > > > > > questionable IMO. > > > > > > > > > > > > > > This is valid concern. But moving the power domain logic > > > > > > > into hypervisor mostly micro-kernel design will introduce > > > > > > > more complexity and > > > > > > make certification harder. > > > > > > > Currently, Let Linux shutdown it's power domain is the > > > > > > > easiest way to me and make things work well after reboot. > > > > > > > > > > > > Well, to put it bluntly, if your hypervisor depends on the > > > > > > guest to do the right thing on exit, it doesn't do its job. I > > > > > > wouldn't have certified it for you if that was my decision. > > > > > > > > > > It is guest os not work well after guest os reboot. The > > > > > hypervisor is not > > > > affected. > > > > > > > > > > Thinking another case without hypervisor, M4 core run RTOS, A35 > > > > > Core run Linux, when Linux rebooting, RTOS should not be > > > > > affected. After Linux reboot itself, because its power domain is > > > > > not paired with > > > > open/shutdown, some devices not function well. > > > > > > > > The question boils down to whether or not devices should be > > > > detached from PM domains on shutdown IMO. > > > > > > > > They are detached from PM domains on driver removal, so I guess > > > > one answer is "yes, in analogy with that". However, the point > > > > about performace brought up by Ulf seems to be valid too. > > > > > > > > In any case, the change should be made for all of the bus types > > > > using PM domains, not just one. > > > > > > Understand, it will increase shutdown time. How about shutdown the > > > power domain in platform_driver->shutdown, let the driver handle > > > it's power domain sthudown by itself? > > > Then no need common framework change. > > > > Do you have more suggestions on how to handle this the power domain > shutdown? > > I think you could add a platform syscore_shutdown hook to turn all power > domains off.
Thanks, Rafael. This is simple enough to me.
Thanks, Peng.
| |