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[217.30.68.212]) by smtp.gmail.com with ESMTPSA id 72sm9989341wrk.22.2019.06.18.10.13.38 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Tue, 18 Jun 2019 10:13:38 -0700 (PDT) From: Martin Jansa X-Google-Original-From: Martin Jansa Date: Tue, 18 Jun 2019 19:13:45 +0200 To: Arno Steffens Message-ID: <20190618171345.GB1501@jama> References: MIME-Version: 1.0 In-Reply-To: User-Agent: Mutt/1.12.0 (2019-05-25) Cc: Yocto Project Subject: Re: cortexa9t2hf instead of cortexa9hf X-BeenThere: yocto@yoctoproject.org X-Mailman-Version: 2.1.13 Precedence: list List-Id: Discussion of all things Yocto Project List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 18 Jun 2019 17:13:43 -0000 X-Groupsio-MsgNum: 45642 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="A6N2fC+uXW/VQSAv" Content-Disposition: inline --A6N2fC+uXW/VQSAv Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Jun 17, 2019 at 07:47:36PM +0200, Arno Steffens wrote: > Thanks for explaining this. > I take some time to read about thumb/thumb2. The feedback is mixed. It se= ems to generate more compact code, but some say it speeds up, others it slo= ws down because of reduced function set - and it can cause strange effects. > And mixing this causes time to switch processor mode. So, as I am not an = expert in this and can't decide what ist best on per function base and spee= d is of highest priority, I think I better should use not thumb(2). >=20 > So, do I get it right that with this cortexa9t2hf I just have the option = to compile it for thumb2? But without using a dedicated compiler option it = generates same "standard" arm code and the difference is just to adapt all = the Makefiles for this suffix. >=20 > According to Martin I can get the previous setting by just set ARM_INSTRU= CTION_SET to "arm" instead of "armv7a". Mh - I just afraid that I lose othe= r kinds of optimisation. (I am just a user not an expert in arm architectur= e). I didn't say anything about changing the DEFAULTTUNE. Just ARM_INSTRUCTION_SET to "arm" which will give you "cortexa9hf" again (not "armv7a"). > On the other hand for those like me it is better go the standard way. Onc= e I am sure compiler results will not become worse (see above) I go for the= pain and renaming my toolchain/makefiles/stuff. The results should be almost the same, maybe slightly better, depends on the actual code as Khem mentioned. But if this causes you a lot of pain "renaming my toolchain/makefiles/stuff" then you should probably spend the time on your tooling instead of replacing one hardcoded value with another. Cheers, >=20 > Thanks for you taking the time. > Arno >=20 > > Hello Arno, > > > > Let me try to explain my point of view. Since here (my best guess) we > > have some asynchronous bitbake code which went South upon introducing > > T2 HW extension. > > > > Point [1]: as far as I understand arm, cortexa9t2hf is is just a > > superset of previous cortexa9hf (HW wise). NEON HW extension (NEON > > media coprocessor) exists in both of them. In other words: > > cortexa9t2hf =3D cortexa9hf HW + T2 HW extension. > > > > Point [2]: > > > bitbake gives me in 2.5: > > > TUNE_FEATURES =3D "arm armv7a vfp thumb neon callconvention-ha= rd cortexa9" > > > TARGET_FPU =3D "hard" > > > > > > and in 2.7: > > > TUNE_FEATURES =3D "arm vfp cortexa9 neon thumb callconvention-= hard" > > > TARGET_FPU =3D "hard" > > > > These two lines are the same: you are able to use 32b arm mode, 16bit > > thumb mode, using armv7 HW with neon HW extension, and using HW FP > > extension as well. The Cortex in both cases is A9. > > > > I expect that somebody somewhere in bitbake version 1.42 - 100% sure > > (since 2.5/Sumo uses bitbake 1.38) dropped "armv7a" as TUNE FEATURE, > > and I have no idea if this is done intentionally or not. > > > > Because of that I copied Alex and Ross to CC: into email, so they > > should unveil this mystery (I would prefer "armv7" to stay in bitbake > > 1.42, since A8 and A9 belongs to armv7, A15 belongs to armv8 (IIRC). > > > > Bottom line: nothing to be done by you, Arno, seems that bitbake 1.42 > > should return "armv7" as TUNE FEATURE. > > > > Best Regards, > > Zoran > > _______ > > > > > > On Mon, Jun 17, 2019 at 3:00 PM Arno Steffens wrote: > > > > > > Hello Zoran, > > > thanks. As far as I understand is thumb2 another mode of coding, that= might create more compact code. > > > But I want to keep all compatible to my previous tool-chain and setti= ngs. > > > The only file where I can found this "cortexa9t2hf" is > > > ./meta/conf/machine/include/tune-cortexa9.inc > > > but I can't see how I can control Yocto to generate "cortexa9hf-neon"= as before. > > > Or have I been wrong the time before? > > > > > > bitbake gives me in 2.5: > > > > > > TUNE_FEATURES =3D "arm armv7a vfp thumb neon callconvention-ha= rd cortexa9" > > > TARGET_FPU =3D "hard" > > > > > > and in 2.7: > > > TUNE_FEATURES =3D "arm vfp cortexa9 neon thumb callconvention-= hard" > > > TARGET_FPU =3D "hard" > > > > > > so armv7a seem to be missing. In terms of thumb both is same. But is = that the reason? Where to set it? > > > Arno > > > > > > > > > > > Hello Arno, > > > > > > > > Your question, per say, has little to do with YOCTO forum. But I'll > > > > try (as my best) to answer your question. > > > > > > > > Cortexa9hf should be armv7 A9 Hard Floating (it contains HW FP unit= ). > > > > > > > > Cortexa9t2hf is by analogy armv7 A9 T2 Hard Floating. Now, the > > > > question is what is T2? T2 is addition to the previous architecture > > > > Cortexa9hf, and addition is Thumb-2 mode. > > > > > > > > Hope this helps, > > > > > > > > Zoran > > > > _______ > > > > > > > > On Mon, Jun 17, 2019 at 2:03 PM Arno Steffens wrote: > > > > > > > > > > I switched from Yocto 2.5 to 2.7 and recognised a new architetcur= e name. > > > > > Instead of cortexa9hf it is now build for cortexa9t2hf? Did I do = something wrong or what exactly does this t2 mean? > > > > > Target system is a Zynq7020 system. > > > > > -- > > > > > _______________________________________________ > > > > > yocto mailing list > > > > > yocto@yoctoproject.org > > > > > https://lists.yoctoproject.org/listinfo/yocto > > > > > > > --=20 > _______________________________________________ > yocto mailing list > yocto@yoctoproject.org > https://lists.yoctoproject.org/listinfo/yocto --=20 Martin 'JaMa' Jansa jabber: Martin.Jansa@gmail.com --A6N2fC+uXW/VQSAv Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- iF0EARECAB0WIQRU+ejDffEzV2Je2oc3VSO3ZXaAHAUCXQkbyAAKCRA3VSO3ZXaA HHVKAKCZ4ImJD5o0M25zQw3xiPvg87aYSgCfTmOwbrWZQQXZDyDBhgTcAejNVFU= =6yNt -----END PGP SIGNATURE----- --A6N2fC+uXW/VQSAv--