From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754483AbbAGUGY (ORCPT ); Wed, 7 Jan 2015 15:06:24 -0500 Received: from mezzanine.sirena.org.uk ([106.187.55.193]:42037 "EHLO mezzanine.sirena.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753229AbbAGUGW (ORCPT ); Wed, 7 Jan 2015 15:06:22 -0500 Date: Wed, 7 Jan 2015 20:05:30 +0000 From: Mark Brown To: Arnd Bergmann Cc: Jon Masters , linux-arm-kernel@lists.infradead.org, Catalin Marinas , Rob Herring , Randy Dunlap , Robert Richter , Jason Cooper , "linaro-acpi@lists.linaro.org" , Marc Zyngier , Daniel Lezcano , Liviu Dudau , Robert Moore , Will Deacon , "linux-kernel@vger.kernel.org" , "linux-acpi@vger.kernel.org" , "Rafael J. Wysocki" , Lv Zheng , Bjorn Helgaas , Olof Johansson Message-ID: <20150107200530.GK2634@sirena.org.uk> References: <1413553034-20956-1-git-send-email-hanjun.guo@linaro.org> <20150107172741.GY2634@sirena.org.uk> <54AD7098.5010700@redhat.com> <1610983.9vqJdsL27R@wuerfel> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="lAj5KC0HpR6BT8lj" Content-Disposition: inline In-Reply-To: <1610983.9vqJdsL27R@wuerfel> X-Cookie: What's so funny? User-Agent: Mutt/1.5.23 (2014-03-12) X-SA-Exim-Connect-IP: 94.175.94.161 X-SA-Exim-Mail-From: broonie@sirena.org.uk Subject: Re: [Linaro-acpi] [PATCH v5 18/18] Documentation: ACPI for ARM64 X-SA-Exim-Version: 4.2.1 (built Mon, 26 Dec 2011 16:24:06 +0000) X-SA-Exim-Scanned: Yes (on mezzanine.sirena.org.uk) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --lAj5KC0HpR6BT8lj Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Wed, Jan 07, 2015 at 08:48:48PM +0100, Arnd Bergmann wrote: > On Wednesday 07 January 2015 12:44:56 Jon Masters wrote: > > On 01/07/2015 12:27 PM, Mark Brown wrote: > > > That level of hardware compatibility does partly come from the need to > > > run existing software. I'd expect that similar effects will start to > > > come into play with ARMv8 ACPI systems if they become successful; people > > > will do things like ensure compatibility with common IPs that have > > > existing Linux drivers that distros tend to include as standard. > > Agreed. > There are two problems I see in trying to do the same thing on ARM: > * we don't have a single vendor that makes de-facto standards that > everyone else has to copy in the way that the few remaining x86 > vendors copy everything that Intel does. In fact, we prefer to > have a large number of independent vendors. Right, I'd guess that (modulo any standards being defined and becoming successful) it'll more be a case of vendors keeping compatibility with their own stuff. We *are* seeing greater reliance on off the shelf IPs for more boring things like DMA and basic bus controllers but there's plenty of other areas that still affect servers. > * There is a general mindset about deprecating unwanted features > early. ARMv8 aarch32 bit mode removes support for older instructions > or makes them optional. Even the virtualization mode doesn't allow > to trap on architecture version specific differences, so you can't > completely emulate an older architecture level. > This is nice for implementers but not so much for users that rely > on old (mis-)features. It's also not just the CPU core, other > components also get easily replaced, like a GICv3 that is not > a strict superset of GICv2. This is indeed worrying, though hopefully the fact that we're already seeing negative impacts in the app ecosystem for Android will have focused some minds - once you're talking about full system images it gets even more fun. --lAj5KC0HpR6BT8lj Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iQEcBAEBAgAGBQJUrZGJAAoJECTWi3JdVIfQwDsIAIKQvB2wIDZg0V3EuvWCvzEc GUYiujqZtG6hjCbkNpx4Afq9bRCu/0BfTjnCF8SCgJf51RQUqzZj2BFXFd6nJQEu HbgjNqNY4kkswMVGc85LQUT87CHeAzI2IcetVHHm82KMtTE2WXU/rcNWU4BCF+Vz fUJ079xrvZ7yV2zlIj/YkpUtlOrOD16nlQhoWN1+Ox/AVqCG5Ymj1kWeDSj9i00+ rAxNpyRDVFJ3tL5mcf7kmrEtQ5q9NCLtWPXKj57lzUDRfSYL0h5eFC0iZt6SiWJh tyPh82nFAi4aQ8wlaDtZYf258Km+OB5NNnhYAlEbgQNq46cVw9bfeRNsWHjGGls= =nN2H -----END PGP SIGNATURE----- --lAj5KC0HpR6BT8lj--