Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752301Ab3C0RGZ (ORCPT ); Wed, 27 Mar 2013 13:06:25 -0400 Received: from cam-admin0.cambridge.arm.com ([217.140.96.50]:52069 "EHLO cam-admin0.cambridge.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751402Ab3C0RGY (ORCPT ); Wed, 27 Mar 2013 13:06:24 -0400 Date: Wed, 27 Mar 2013 17:05:56 +0000 From: Will Deacon To: Rob Herring Cc: Stefano Stabellini , "xen-devel@lists.xensource.com" , "linux@arm.linux.org.uk" , "arnd@arndb.de" , "nico@linaro.org" , Marc Zyngier , "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" Subject: Re: [PATCH v3] [RFC] arm: use PSCI if available Message-ID: <20130327170555.GA20990@mudshark.cambridge.arm.com> References: <1364388639-11210-1-git-send-email-stefano.stabellini@eu.citrix.com> <20130327133811.GE18429@mudshark.cambridge.arm.com> <51531F76.2090200@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <51531F76.2090200@gmail.com> 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: 2003 Lines: 41 On Wed, Mar 27, 2013 at 04:33:58PM +0000, Rob Herring wrote: > On 03/27/2013 08:38 AM, Will Deacon wrote: > > On Wed, Mar 27, 2013 at 12:50:39PM +0000, Stefano Stabellini wrote: > >> +struct smp_operations __initdata psci_smp_ops = { > >> + .smp_init_cpus = psci_smp_init_cpus, > >> + .smp_prepare_cpus = psci_smp_prepare_cpus, > >> + .smp_secondary_init = psci_secondary_init, > >> + .smp_boot_secondary = psci_boot_secondary, > >> +}; > >> +#endif > > > > As I said before, I don't agree with bolting these two interfaces together > > like this and, as it stands, I'm afraid I have to NAK this patch. > > > > A potential alternative is to have a set of virt_smp_ops, which have > > wrappers around the psci functions, but that requires agreement from Xen and > > KVM to implement the same PSCI interface, which feels unfair to me. > > I need the same smp ops for highbank. By using mach-virt Xen is using > the same interface as KVM. This patch does not change that, but rather > allows other platforms to use the same smp ops as well. > > Isn't the whole point of PSCI to have a common interface? No one is > making Xen use PSCI at all. It is a choice and since they are making > that choice, why would the PSCI interface be different? The channel is common, sure, but I wouldn't expect the semantics of each call to be identical between firmware implementations (going back to my previous examples of CPU IDs and implementation-defined state parameters). If a platform happens to have an id-mapping from smp_operations to psci, then I still think there should be an indirection in there so that we have the flexibility to change the smp_operations if we wish and not give platforms the false impression that these two things are equivalent. 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/