Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932068Ab3DZPwI (ORCPT ); Fri, 26 Apr 2013 11:52:08 -0400 Received: from smtp02.citrix.com ([66.165.176.63]:16952 "EHLO SMTP02.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756120Ab3DZPwF (ORCPT ); Fri, 26 Apr 2013 11:52:05 -0400 X-IronPort-AV: E=Sophos;i="4.87,559,1363132800"; d="scan'208";a="20799633" Date: Fri, 26 Apr 2013 16:36:26 +0100 From: Stefano Stabellini X-X-Sender: sstabellini@kaball.uk.xensource.com To: Nicolas Pitre CC: Will Deacon , Stefano Stabellini , "xen-devel@lists.xensource.com" , "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "arnd@arndb.de" , "rob.herring@calxeda.com" , "linux@arm.linux.org.uk" , "olof@lixom.net" Subject: Re: [PATCH v8 1/2] arm: introduce psci_smp_ops In-Reply-To: Message-ID: References: <1366828819-10745-1-git-send-email-stefano.stabellini@eu.citrix.com> <20130425084711.GA12848@mudshark.cambridge.arm.com> <20130425104508.GG12848@mudshark.cambridge.arm.com> User-Agent: Alpine 2.02 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3209 Lines: 65 On Thu, 25 Apr 2013, Nicolas Pitre wrote: > On Thu, 25 Apr 2013, Will Deacon wrote: > > > On Thu, Apr 25, 2013 at 11:12:54AM +0100, Stefano Stabellini wrote: > > > On Thu, 25 Apr 2013, Will Deacon wrote: > > > > > +/* > > > > > + * cpu_suspend Suspend the execution on a CPU > > > > > + * @state we don't currently describe affinity levels, so just pass 0. > > > > > + * @entry_point the first instruction to be executed on return > > > > > + * returns 0 success, < 0 on failure > > > > > + * > > > > > + * cpu_off Power down a CPU > > > > > + * @state we don't currently describe affinity levels, so just pass 0. > > > > > + * no return on successful call > > > > > + * > > > > > + * cpu_on Power up a CPU > > > > > + * @cpuid cpuid of target CPU, as from MPIDR > > > > > + * @entry_point the first instruction to be executed on return > > > > > + * returns 0 success, < 0 on failure > > > > > + * > > > > > + * migrate Migrate the context to a different CPU > > > > > + * @cpuid cpuid of target CPU, as from MPIDR > > > > > + * returns 0 success, < 0 on failure > > > > > + * > > > > > + */ > > > > > > > > Can you move these comments into psci-smp.c please? They're really specific > > > > to the implementation there, and if we put them in a header we're lying to > > > > ourselves about the parameters actually described by the PSCI specification. > > > > > > You have a good point about the PSCI spec. > > > > > > However from the Linux POV these comments should regard the functions > > > exported by psci_operations, not the firmware interface, this is why I > > > think it makes sense to keep them in psci.h. > > > What we are saying is for example that psci_operations.cpu_on returns 0 > > > on success and < 0 on failure, and it takes a cpuid and an entry point > > > as parameters. We are not saying anything about the firmware interface. > > > > I disagree. You're explicitly stating that we pass the `cpuid of target CPU, > > as from MPIDR'. That's simply not true -- the firmware could choose any > > numbering scheme to identify the CPUs. For KVM and Xen, it *is* the mpidr, > > which is why psci-smp.c works at all, but that's where the comment belongs, > > not in this header file. > > At some point, the _kernel_ API for interfacing with the firmware's PSCI > will have to ensure uniformity somehow. The PSCI interface code could > translate the passed MPIDR into whatever the firmware decided to use for > identifying CPUs if needed, keeping this issue localized. That is what I had in mind when I said to keep the comment in psci.h before. We have to draw the line somewhere to expose a uniform internal kernel API. However it is a bit difficult to do now given that we have only one user of the API. I don't feel to strongly about this, please let me know what is the final decision and I'll update the code accordingly. I remind you that the merge window is approaching :-) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/