Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756153AbbDNVSP (ORCPT ); Tue, 14 Apr 2015 17:18:15 -0400 Received: from foss.arm.com ([217.140.101.70]:34812 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755685AbbDNVRh (ORCPT ); Tue, 14 Apr 2015 17:17:37 -0400 Date: Tue, 14 Apr 2015 22:17:26 +0100 From: Catalin Marinas To: Kumar Gala Cc: Mark Rutland , "devicetree@vger.kernel.org" , "linux-arm-msm@vger.kernel.org" , Will Deacon , "linux-kernel@vger.kernel.org" , "arm@kernel.org" , "abhimany@codeaurora.org" , "linux-arm-kernel@lists.infradead.org" Subject: Re: [RFC PATCH 0/5] Add smp booting support for Qualcomm ARMv8 SoCs Message-ID: <20150414211720.GA56647@MBP> References: <1428601031-5366-1-git-send-email-galak@codeaurora.org> <20150410100529.GA6854@e104818-lin.cambridge.arm.com> <20150414163613.GM28709@leverpostej> <07185B2C-3F37-4E70-9096-1EF5EA8D68CE@codeaurora.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <07185B2C-3F37-4E70-9096-1EF5EA8D68CE@codeaurora.org> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3101 Lines: 64 On Tue, Apr 14, 2015 at 02:49:04PM -0500, Kumar Gala wrote: > On Apr 14, 2015, at 11:36 AM, Mark Rutland wrote: > > On Fri, Apr 10, 2015 at 11:05:29AM +0100, Catalin Marinas wrote: > >> On Thu, Apr 09, 2015 at 12:37:06PM -0500, Kumar Gala wrote: > >>> This patch set adds support for SMP boot on the MSM8x16 family of Qualcomm SoCs. > >>> > >>> To support SMP on the MSM8x16 SoCs we need to add ARMv8/64-bit SCM interfaces to > >>> setup the boot/release addresses for the secondary CPUs. In addition we need > >>> a uniquie set of cpu ops. I'm aware the desired methods for booting secondary > >>> CPUs is either via spintable or PSCI. However, these SoCs are shipping with a > >>> firmware that does not support those methods. > >> > >> And the reason is? Some guesses: > >> > >> a) QC doesn't think boot interface (and cpuidle) standardisation is > >> worth the effort (to put it nicely) > >> b) The hardware was available before we even mentioned PSCI > >> c) PSCI is not suitable for the QC's SCM interface > >> d) Any combination of the above > >> > >> I strongly suspect it's point (a). Should we expect future QC hardware > >> to do the same? > >> > >> You could argue the reason was (b), though we've been discussing PSCI > >> for at least two years and, according to QC press releases, MSM8916 > >> started sampling in 2014. > >> > >> The only valid reason is (c) and if that's the case, I would expect a > >> proposal for a new firmware interface protocol (it could be PSCI-based), > >> well documented, that can be shared with others that may encounter the > >> same shortcomings. > > > > There's no need to even fork PSCI. The PSCI specification will evolve > > over time as vendors request changes and we try to accomodate them. > > > > If there's something that PSCI doesn't do that you need it to, contact > > ARM. Other vendors already have. Mostly yes but there may be valid reasons for not being able to use PSCI. The spin-table method is still a firmware interface, though not necessarily secure (a.k.a. SMC-based). The ACPI parking protocol is another and, who knows, maybe we define a way to park CPUs back to firmware without SMC calls (when EL3 is not available). > But what is someone to do between the period of getting PSCI spec > updated and needing to ship a product with firmware? > > The take still sounds like if you don’t implement an exact version of > PSCI you are screwed from being supported in the upstream ARM64 > kernel. These are silly arguments. There is a big difference between "we couldn't get the firmware implementing the standard for the early silicon but we are working on fixing it for future revisions" vs. "we don't give a s**t about these standards, the kernel must be inclusive". So please make up your mind on which direction you want to pursue. -- Catalin -- 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/