From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from bh-25.webhostbox.net (bh-25.webhostbox.net [208.91.199.152]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id C33911A070E for ; Thu, 2 Oct 2014 13:03:00 +1000 (EST) Received: from mailnull by bh-25.webhostbox.net with sa-checked (Exim 4.82) (envelope-from ) id 1XZWfT-003O5y-2H for linuxppc-dev@lists.ozlabs.org; Thu, 02 Oct 2014 03:02:59 +0000 Message-ID: <542CBDB7.9010808@roeck-us.net> Date: Wed, 01 Oct 2014 19:51:35 -0700 From: Guenter Roeck MIME-Version: 1.0 To: Alexander Graf , Scott Wood Subject: Re: [PATCH 00/20] powerpc: Convert power off logic to pm_power_off References: <1412170086-57971-1-git-send-email-agraf@suse.de> <1412203153.13320.352.camel@snotra.buserror.net> <542C8C69.2010509@suse.de> <1412206127.13320.362.camel@snotra.buserror.net> <542C91D5.3030305@suse.de> In-Reply-To: <542C91D5.3030305@suse.de> Content-Type: text/plain; charset=utf-8; format=flowed Cc: Arnd Bergmann , Geoff Levand , Alistair Popple , Anatolij Gustschin , linuxppc-dev@lists.ozlabs.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On 10/01/2014 04:44 PM, Alexander Graf wrote: > > > On 02.10.14 01:28, Scott Wood wrote: >> On Thu, 2014-10-02 at 01:21 +0200, Alexander Graf wrote: >>> >>> On 02.10.14 00:39, Scott Wood wrote: >>>> On Wed, 2014-10-01 at 15:27 +0200, Alexander Graf wrote: >>>>> The generic Linux framework to power off the machine is a function pointer >>>>> called pm_power_off. The trick about this pointer is that device drivers can >>>>> potentially implement it rather than board files. >>>>> >>>>> Today on PowerPC we set pm_power_off to invoke our generic full machine power >>>>> off logic which then calls ppc_md.power_off to invoke machine specific power >>>>> off. >>>>> >>>>> However, when we want to add a power off GPIO via the "gpio-poweroff" driver, >>>>> this card house falls apart. That driver only registers itself if pm_power_off >>>>> is NULL to ensure it doesn't override board specific logic. However, since we >>>>> always set pm_power_off to the generic power off logic (which will just not >>>>> power off the machine if no ppc_md.power_off call is implemented), we can't >>>>> implement power off via the generic GPIO power off driver. >>>>> >>>>> To fix this up, let's get rid of the ppc_md.power_off logic and just always use >>>>> pm_power_off as was intended. Then individual drivers such as the GPIO power off >>>>> driver can implement power off logic via that function pointer. >>>>> >>>>> With this patch set applied and a few patches on top of QEMU that implement a >>>>> power off GPIO on the virt e500 machine, I can successfully turn off my virtual >>>>> machine after halt. >>>> >>>> Are there any plans to handle restart similarly? >>> Guess I am missing some context here. Support for a restart handler call chain will be added in 3.18. Currently its primary goal is to replace arm_pm_restart, but it would be a one-liner to add support for it to powerpc (see below). >>> I don't see an immediate need for it, as we do have access to reset via >>> the guts device. >> >> The guts device is problematic from a hardware description perspective, >> as we advertise a bunch of things to the guest that we don't implement. >> E.g. the only reason we don't currently have a problem with Linux trying >> to use guts to sync the timebase across cores is that by chance we >> happen to expose a guts that corresponds to a single-cpu SoC. > > True, and it is slightly ugly to expose a specific SoC's guts in our > generic pv machine type. > >> >>> I also don't see any generic driver in Linux that would implement reset >>> via a gpio controller device, so apparently it's not incredibly common >>> to implement reset via gpio. >> Again, I may be missing something. How about drivers/power/reset/gpio-restart.c ? It would be really simple make it work with powerpc; all you would have to do is to add a call to do_kernel_restart() to the powerpc machine_restart() function. >> There wasn't a generic gpio-power-off driver either until a couple years >> ago... Regardless of whether it's done via gpio, using ppc_md for it is >> bad for the same reasons as for power-off. > > I agree. Today, only ARM has a comparable mechanism for drivers to hook > a reset handler into the machine specific reset path. > Not anymore ... > I'd say let's wait for Guenter to finish the power off rework and then > tackle a generic reset call chain based approach next. > Please have a look into the restart handler; the code is in linux-next. That should probably solve your restart related problems. A branch on top of v3.17-rc2 is at https://git.kernel.org/cgit/linux/kernel/git/groeck/linux-staging.git/log/?h=restart-handler Thanks, Guenter