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[89.176.104.3]) by mx.google.com with ESMTPSA id ck5sm48300352wjb.24.2014.08.22.14.46.21 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 22 Aug 2014 14:46:21 -0700 (PDT) From: Martin Jansa X-Google-Original-From: Martin Jansa Date: Fri, 22 Aug 2014 23:46:26 +0200 To: Peter Seebach Message-ID: <20140822214626.GF20524@jama> References: <53F77370.2060603@balister.org> <20140822133349.76751634@e6410-2> <20140822193910.GD20524@jama> <20140822154954.04d4fc02@e6410-2> MIME-Version: 1.0 In-Reply-To: <20140822154954.04d4fc02@e6410-2> User-Agent: Mutt/1.5.23 (2014-03-12) Cc: openembedded-core@lists.openembedded.org Subject: Re: [PATCH 0/1] Change default for cortexa* to armv7at-neon. X-BeenThere: openembedded-core@lists.openembedded.org X-Mailman-Version: 2.1.12 Precedence: list List-Id: Patches and discussions about the oe-core layer List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 22 Aug 2014 21:46:31 -0000 X-Groupsio-MsgNum: 56863 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="hcut4fGOf7Kh6EdG" Content-Disposition: inline --hcut4fGOf7Kh6EdG Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri, Aug 22, 2014 at 03:49:54PM -0500, Peter Seebach wrote: > On Fri, 22 Aug 2014 21:39:10 +0200 > Martin Jansa wrote: >=20 > > Even enabling thumb seems wrong, because ARM_INSTRUCTION_SET is arm by > > default, so this change is only renaming the feed, but still building > > the same binaries (unless distro sets ARM_INSTRUCTION_SET). >=20 > I think that's okay, because the point is to correctly indicate that > the CPU can run thumb binaries if someone had a reason to make them. >=20 > I mean, strictly speaking, I don't even *know of* an actual chip for which > armv7a-neon is a correct descriptor. Because "armv7a-neon" is a chip which > *cannot* run thumb binaries. Does anyone actually make a neon armv7a which > can't run thumb binaries? >=20 > And yeah, the RFC and ensuing discussion gets to some sort of underlying > questions about what the purpose of DEFAULTTUNE is. I am inclined to think > that the DEFAULTTUNE for a given tune-foo should be either the baseline of > that chipset or a somewhat optimized tune for it. For me it's sane default for shared binary feed and DISTRO config is the right place to decide common denominator for your MACHINEs (if all MACHINEs you support are cortexa9 then yes, it would be better DEFAULTTUNE, if you enable "thumb" in default ARM_INSTRUCTION_SET, then yes it makes sense to enable it in DEFAULTTUNE as well, but changing default DEFAULTTUNE (and TUNE_PKGARCH with that) to have thumb while still building with -marm doesn't make much sense to me and is only confusing. Every distro can use something more "optimized" DEFAULTTUNEs for each MACHINE they use, I do it for SHR: https://github.com/shr-distribution/meta-smartphone/blob/shr/meta-shr-distr= o/conf/distro/include/defaulttunes.inc and for webOS-ports we used it for a while and then reverted back to default, because the difference between cortexa8-neon, cortexa9-neon and armv8a-neon wasn't worth building and maintaining separate binary feed (see links in .inc file) https://github.com/webOS-ports/meta-webos-ports/blob/master/conf/distro/inc= lude/defaulttunes.inc > I note that tune-core2 and tune-corei7 both set tunes (core2-32, corei7-6= 4) > which include target-specific optimizations; this would be comparable to > using cortexa9t-neon as the default tune for tune-cortexa9.inc. >=20 > I don't think the current state of tunings reflects a completely consiste= nt > view of what DEFAULTTUNE means in a tuning file. >=20 > -s > --=20 > Listen, get this. Nobody with a good compiler needs to be justified. --=20 Martin 'JaMa' Jansa jabber: Martin.Jansa@gmail.com --hcut4fGOf7Kh6EdG Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iEYEARECAAYFAlP3ujIACgkQN1Ujt2V2gBy5OwCeIO7aow42DkELuqVyM5vW1ucU ObIAn1nj+NFTtx8khP3j1ilNe47yLJGp =PNmM -----END PGP SIGNATURE----- --hcut4fGOf7Kh6EdG--