Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757000Ab3DYLLt (ORCPT ); Thu, 25 Apr 2013 07:11:49 -0400 Received: from cam-admin0.cambridge.arm.com ([217.140.96.50]:63456 "EHLO cam-admin0.cambridge.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755155Ab3DYLLs (ORCPT ); Thu, 25 Apr 2013 07:11:48 -0400 Date: Thu, 25 Apr 2013 12:11:25 +0100 From: Will Deacon To: Stefano Stabellini Cc: "xen-devel@lists.xensource.com" , "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "arnd@arndb.de" , "nicolas.pitre@linaro.org" , "rob.herring@calxeda.com" , "linux@arm.linux.org.uk" , "olof@lixom.net" Subject: Re: [PATCH v8 1/2] arm: introduce psci_smp_ops Message-ID: <20130425111125.GI12848@mudshark.cambridge.arm.com> References: <1366828819-10745-1-git-send-email-stefano.stabellini@eu.citrix.com> <20130425084711.GA12848@mudshark.cambridge.arm.com> <20130425104508.GG12848@mudshark.cambridge.arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2402 Lines: 55 On Thu, Apr 25, 2013 at 12:08:02PM +0100, Stefano Stabellini wrote: > On Thu, 25 Apr 2013, Will Deacon wrote: > > On Thu, Apr 25, 2013 at 11:12:54AM +0100, Stefano Stabellini wrote: > > > 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. > > I see, you want to keep psci_operations true to the firmware interface > while explaining that psci_smp makes some assumptions about it. Precisely! :) > So the comment should be something like: > > /* > * psci_smp assumes that the following is true about PSCI: > * > * 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 > * > */ That's certainly better, but I'd still rather see the comment with the implementation as there's a greater potential for confusion having it here. Will -- 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/