From mboxrd@z Thu Jan 1 00:00:00 1970 From: Guenter Roeck Subject: Re: [PATCH] power: reset: Add MAX77620 support Date: Thu, 19 Jan 2017 15:29:34 -0800 Message-ID: <20170119232934.GA18102@roeck-us.net> References: <20170112161507.23774-1-thierry.reding@gmail.com> <20170113034425.7ttvc73aewtbitrk@earth> <20170119122357.GF30182@ulmo.ba.sec> <20170119230036.sjfqvqxgxutis6xs@earth> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from bh-25.webhostbox.net ([208.91.199.152]:48782 "EHLO bh-25.webhostbox.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752628AbdASX3k (ORCPT ); Thu, 19 Jan 2017 18:29:40 -0500 Content-Disposition: inline In-Reply-To: <20170119230036.sjfqvqxgxutis6xs@earth> Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: Sebastian Reichel Cc: Thierry Reding , Laxman Dewangan , Martin Michlmayr , linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, Chaitanya Bandi On Fri, Jan 20, 2017 at 12:00:36AM +0100, Sebastian Reichel wrote: > Hi Thierry, > > > > > [...] > > > > > > Please use register_restart_handler() instead. It has support for > > > priorities, is not arm specific and properly supports unregistering > > > (some handler with lower priority will take over). You can check > > > gpio-restart as an example for the API. > > > > > > If you have some other arm_pm_restart handler (those are tried first) > > > I suggest to convert that to the restart handler framework. Actually > > > it may be a good idea to convert all of them and drop arm_pm_restart, > > > since there are only 4 left: > > > > > > $ git grep "arm_pm_restart =" > > > drivers/firmware/psci.c: arm_pm_restart = psci_sys_reset; > > > arch/arm/mach-prima2/rstc.c: arm_pm_restart = sirfsoc_restart; > > > arch/arm/xen/enlighten.c: arm_pm_restart = xen_restart; > > > arch/arm/kernel/setup.c: arm_pm_restart = mdesc->restart; > > > > > > The first 3 should be easy to update and the last one could > > > be solved by registering a wrapper function as restart handler, > > > which calls mdesc->restart(). > > > > I remember this not being the first time that this confuses me. And from > > looking around a little it seems like I'm not the only one. > > > > Do you know if there's ever been any attempts to formalize all of this > > by adding some sort of framework for this? That way some of the > > confusion may be removed and architecture-specific bits could be > > eliminated more easily. > > We have a framework for restart handlers, which has been written > by Guenter Roeck [0] in 2014. You just have to call register_restart_handler() > during probe and unregister_restart_handler() during removal of > your reboot driver. All reboot drivers in drivers/power/reset use > that framework. > > The restart handlers are invoked by calling do_kernel_restart() > based on their configured priority. That function is called by > the architecture's machine_restart() function. It's currently > used by mips, ppc, arm & arm64 as far as I can see. ARM's > implementation looks like this: > > if (arm_pm_restart) > arm_pm_restart() > else > do_kernel_restart() /* reboot handler framework */ > I actually have a set of patches somewhere which transforms the remaining direct users of arm_pm_restart to use the framework (unless I removed it from my trees - I don't really recall). I just never got around to submit it, and then [2] happened and I lost interest. > No such thing exists for poweroff. Guenter also wrote something for > that [1], but Linus intervened [2]. Anyways, pm_power_off is at > least architecture independent. > That was by far the most frustrating kernel development experience I ever head :-(. Guenter > [0] https://lwn.net/Articles/605298/ > [1] https://lwn.net/Articles/617345/ > [2] http://lists.infradead.org/pipermail/linux-arm-kernel/2015-June/351369.html > > -- Sebastian