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MORIN" To: Giulio Benetti Message-ID: <20220815145332.GC2854108@scaer> References: <733d97a0-7ee5-d788-6cba-ccac757befdb@benettiengineering.com> <91f0cd4b-a3dd-14db-d490-968b4b31339a@benettiengineering.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <91f0cd4b-a3dd-14db-d490-968b4b31339a@benettiengineering.com> User-Agent: Mutt/1.5.22 (2013-10-16) X-Mailman-Original-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=free.fr; s=smtp-20201208; t=1660575217; bh=V4OGsB/IaGh9b5hvRnDsFMnGtcvxaJl9sHfijvSLt/A=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=OIfqwQKSL3cX1yZ9d4t7da71hQzv0AMXHLmEo0Zad+nvrq97RAHnMvcNXJoIXHKGJ i4di4dwjN3JRhqcoc6ycPEJKuJGQcpsvL3TACWglTu01XKBptu8wIBN7kmuglaUteW plf4CoC9VPI1SX52wuJ5M5eCnOfa7V7uec9cPgTsAxtJQfgbGjEYD6pc9ycSr7pZLq quX88yOdenez1i3F3tGmrVv1kEozukgDzmnpwfDLAyfzmJ57c6sWMk4KfSHPjPpmVX tQOjoXSw/docbeAOuqasxgImZ4nUQDiREdaUFJLWp/7rP0cGAftO0oPDygdBksSVn3 hZiduel7LCVEg== X-Mailman-Original-Authentication-Results: smtp3.osuosl.org; dkim=pass (2048-bit key) header.d=free.fr header.i=@free.fr header.a=rsa-sha256 header.s=smtp-20201208 header.b=OIfqwQKS Subject: Re: [Buildroot] [PATCH 1/1] board/pine64/pinecube: new board X-BeenThere: buildroot@buildroot.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Discussion and development of buildroot List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Jagan Teki , Jan Havran , buildroot@buildroot.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: buildroot-bounces@buildroot.org Sender: "buildroot" Giulio, Jan, All, On 2022-08-14 13:56 +0200, Giulio Benetti spake thusly: > On 14/08/22 11:22, Jan Havran wrote: > >>>+++ b/configs/pinecube_defconfig > >>>+BR2_ARM_FPU_NEON_VFPV4=y > >>This ^^^ should be removed since NEON doesn't support complete FPU > >>standard API, so it's better to keep the default for BR2_cortex_a7 > >I will fix everything and post V2, but one thing I do not understand much is > >this one. > Here there is a very good explanation on why not adding by default > BR2_ARM_FPU_NEON_VFPV4: > https://lists.buildroot.org/pipermail/buildroot/2022-January/634728.html I even tink that, ultimately, we should just remove FPU options that also enable NEON, like BR2_ARM_FPU_NEON_VFPV4, because they do not make sense. Using NEON for floating-point arithmetics should probably left to a per-pacakge setting, where and when t makes sense for that package (e.g. math-intensive packages that can cope with incorrect results (like real-time audio stuff that favour an occasional glitch rather than a packet loss). [--SNIP--] > But yes, if VFPV4 is supported then yes, it makes sense to enable it > instead of keeping the default. So since this board is S3 based and > it supports VFPV4 then you can enable: > BR2_ARM_FPU_VFPV4 > > and same can go with H3 based boards I think. > > @Yann, what do you think about enabling VFPV4 on boards with SoCs > that support VFPV4? (not NEON/VFPV4 of course) Usually, defconfigs are very limited, and what we guarantee is very basic: a booting kernel with basic drivers, and busybox' login and shell. That does not use much floating-point instructions, so that would not benefit much from using a "better" FPU. I previously rejected the big series that bulk-converted all defconfigs in one go, because that was not tested on real hardware. But for a defconfig that was actually tested against real hardware, I think it is OK that it uses a "better" FPU. So, if the pinecube has a VFPv4, BR2_ARM_FPU_VFPV4 or BR2_ARM_FPU_VFPV4_D16 is OK. Also nte that BR2_ARM_FPU_VFPV4 will make use of all the 32 flaoting point registers, i.e. the full range, while BR2_ARM_FPU_VFPV4_D16 will only make use of 16 registers. Not all VFPv4 implementation have 32 registers, so carefully enable the appropriate one (_D16 is safe to use in either case, though). Regards, Yann E. MORIN. -- .-----------------.--------------------.------------------.--------------------. | Yann E. 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