From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx2.suse.de (cantor2.suse.de [195.135.220.15]) (using TLSv1 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id EE8F71A0423 for ; Thu, 2 Oct 2014 00:47:31 +1000 (EST) Message-ID: <542C13FB.80608@suse.de> Date: Wed, 01 Oct 2014 16:47:23 +0200 From: Alexander Graf MIME-Version: 1.0 To: Geert Uytterhoeven Subject: Re: [PATCH 00/20] powerpc: Convert power off logic to pm_power_off References: <1412170086-57971-1-git-send-email-agraf@suse.de> In-Reply-To: Content-Type: text/plain; charset=utf-8 Cc: Arnd Bergmann , Geoff Levand , Alistair Popple , Scott Wood , Anatolij Gustschin , "linuxppc-dev@lists.ozlabs.org" , Guenter Roeck List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On 01.10.14 16:33, Geert Uytterhoeven wrote: > Hi Alex, > > On Wed, Oct 1, 2014 at 3:27 PM, 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. > > This is touching the same area as last night's > "[RFC PATCH 00/16] kernel: Add support for poweroff handler call chain" > https://lkml.org/lkml/2014/9/30/575 I agree, and I think your patch set is walking into a reasonable direction. However, I really think it should convert all users of pm_power_off - at which point you'll probably get to the same conclusion that ppc_md.power_off is a bad idea :). So in a way, this patch set is semantically a prerequisite to the full conversion you'd probably like to do :). Also, in your cover letter you describe that some methods power off the CPU power while others power off the system power. How do you distinguish between them with a call chain? You probably won't get around to trigger the system power off callback after the CPU power off callback ran ;). Alex