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s=20161025; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to:cc; bh=cMN4yc6Yg7k+g95Y7UmZLiL/P6GU424U+ZDesgvhHgU=; b=L886LuLL23pYFu8DHbXrYfu8RKoME6NzooH2k5XmsjdO9EdOHLaVYOLkIpvqqpamJX o/NGHsd2V3rEx9aUZeU6vUw7X1oQzYUa3prbqdF1UQTh3VSh/E82io3mhwyGFHxS1X+z EdfrJl6wj8jyp8TJvLaoz9KQYxRUCgJvAzC8h7PK1qSCjzqAc/fTj0YAzFpKN3nFyQL3 g9lS4zjru8xp5baIpxyeuGy1OdYqM8O193zXlVv+Yw/6w+V0/STps5gQSMsc0J7/k9PR Ha0RclLTwNGg4NnVF6OrBHnn8s9L7sxdcAaqMWTyadaieVo3y0mYHtlJ+Zjl1OyEVNef mh/Q== X-Gm-Message-State: AOAM533GVjf5vMzkCrAvMsMjIgfewstfqkbPASV7OY9jw8j7I+MIY7p4 vSS+QJNfvFk+SBFJQGQLhh+FJlS1oM2Rxcfuhjk= X-Google-Smtp-Source: ABdhPJxT71L+T05yz/hq+Tsn15GIbWhZTIbquxkVkxucO5ulY894g/8MmOt6pCNq9/8xQxw7L9Urp1FEelq55p0lqoU= X-Received: by 2002:a05:6402:274f:: with SMTP id z15mr20502581edd.21.1627919118096; Mon, 02 Aug 2021 08:45:18 -0700 (PDT) MIME-Version: 1.0 Received: by 2002:a17:906:3018:0:0:0:0 with HTTP; Mon, 2 Aug 2021 08:45:17 -0700 (PDT) In-Reply-To: <20210802141245.1146772-1-arnd@kernel.org> References: <20210802141245.1146772-1-arnd@kernel.org> From: Martin Guy Date: Mon, 2 Aug 2021 17:45:17 +0200 Message-ID: Subject: Re: [PATCH] ARM: ep93xx: remove MaverickCrunch support To: Arnd Bergmann List-Id: Cc: Russell King , Hartley Sweeten , Alexander Sverdlin , soc@kernel.org, Nikita Shubin , Arnd Bergmann , Oleg Nesterov , Hubert Feurstein , Lukasz Majewski , Catalin Marinas , Will Deacon , Nathan Chancellor , Nick Desaulniers , Linus Walleij , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210802_084521_393211_6FB2D359 X-CRM114-Status: GOOD ( 23.58 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 02/08/2021, Arnd Bergmann wrote: > The MaverickCrunch support for ep93xx never made it into glibc This is true, but is not needed except for preserving FP registers in catch/throw exeptions or longjmps. > was removed from gcc in its 4.8 release in 2012. I was sad about that, as I had managed to get it working correctly in 4.2 4.3 and 4.4. Unfortunately the GCC ARM maintainer at the time was paid by ARM, and they had no interest in it, as I gather the ARM-Cirrus partnership ended up disappointingly. > It is now one of > the last parts of arch/arm/ that fails to build with the clang > integrated assembler Even if crunch support is not configured? > According to Hartley Sweeten: > > "Martin Guy did a lot of work trying to get the maverick crunch working > but I was never able to successfully use it for anything. > It "kind" of works but depending on the EP93xx silicon revision It works fine on all production revisions except D0 (the first one) which is so rare as to be unfindable. All the others from D1 on have the exact same HW bugs. > there are still a number of hardware bugs that either give imprecise or garbage results. Not my experience, See http://martinwguy.net/crunch/#CorrectnessTests If "imprecise" means "doesn't handle unnormalized FP values correctly" then yes, that's a feature if you need the 2.5 to 4gimes speedup it provides. But I would be interested (Hartley) if you have a concrete example. > This touches mostly the ep93xx platform, The ep93xx is the only chip series it was ever included in. > If there are remaining users of MaverickCrunch, they can use LTS > kernels for at least another five years before kernel support ends. The only user ! am aware of is the HEAT deep space telescope in the Antarctic http://martinwguy.blogspot.com/2015/10/maverickcrunch-code-runs-on-heat-deep.html Personally I have no problem with removing kernel support if that makes people's lives easier in some way. M M _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel