From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-1.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, FROM_LOCAL_NOVOWEL,HEADER_FROM_DIFFERENT_DOMAINS,HK_RANDOM_FROM, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 346ECC433DB for ; Thu, 14 Jan 2021 23:10:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EBB1623A5C for ; Thu, 14 Jan 2021 23:10:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730844AbhANXKS (ORCPT ); Thu, 14 Jan 2021 18:10:18 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36248 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730809AbhANXKS (ORCPT ); Thu, 14 Jan 2021 18:10:18 -0500 Received: from mail-ej1-x634.google.com (mail-ej1-x634.google.com [IPv6:2a00:1450:4864:20::634]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 70CE5C061575 for ; Thu, 14 Jan 2021 15:09:37 -0800 (PST) Received: by mail-ej1-x634.google.com with SMTP id t16so10630438ejf.13 for ; Thu, 14 Jan 2021 15:09:37 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=VLCIXId9Ur9EEU+g0ZhcxPqlBXoFwGkEQByEAfvt7pM=; b=vcqi2AFNMuHivlPqf62balXOKuMVUeY1LDDZ4fmw8Hnj3tSgqsyBXm7JbDJF9WlPPY 8bJIm6Ttru3yi691agA+flqNijZxjZb73DiVbR3W1rDlicn5SY0T/u1wnGLhVdhlhusq iUDZ9zEiHaVMoNHxfKYLw2zfMNEvElIMBgtsFc0UubmiNgcefy6G100CRGjkC/Onmh7E CjaXGFSpX5neYOuFEg9uZCFcuk5tlNK3ZFh7zBff8qbLnavJLnhaCot0fn+g7eT1+kDi OBkCWhRl94dCP59/v7lWm1x+W8Jhv/AloiQ2A0eS0Kn6dxP02VJmvd7nNTv1Jp6G4AgO AkuQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=VLCIXId9Ur9EEU+g0ZhcxPqlBXoFwGkEQByEAfvt7pM=; b=et2IXG1IGh0DGU+Wzz5Mlw1i8yVznwfMxMQ4GfMDGW6JY2dPPlmSgvVcPnlahjGn4H KuzaPNwawhC6RI5DG7eR6+15gRnQAKAsdLq2Nv33BAoG5ctVIwU4uxMH4/k+O4rDVR7/ xFEn9Ciihjya3lRLfHEqv9QZpBcX3m0dcYpCBVye9c6ZWdLKh7A+QwOhE1iBvguoGFgE Leo042G7j5qK9MsQeolTxsBS6qYNnWzLPLt4G/9f8YRvbcfAx9/NrPVGFKmyjDNBW55v hsigIU2psi7joquYjOQwTqLimt0LO0bl1vzbyqNXqOwBPUK7fyaAPGmQNtId7Y9RaG9Q biig== X-Gm-Message-State: AOAM531/N0FwjzmV3ZPI/9K4h8SurtPSR7LR+jyaI0sC9omFvFR/Ncvf GYpUTYsM1rteqhJy05yptZcb/U6h0ejNrs5JpWQ= X-Google-Smtp-Source: ABdhPJylRuPBI5F/xw1RjkvPX3agtRPjZbW8XqRSubVW2OyOOiBrBkicF/VAeeSVmuQoI3+o0JJeE48HWUCWmjOj0hM= X-Received: by 2002:a17:906:22c7:: with SMTP id q7mr6812484eja.486.1610665776265; Thu, 14 Jan 2021 15:09:36 -0800 (PST) MIME-Version: 1.0 References: <1be37673-db0e-f09d-68c8-f929be4019ab@physik.fu-berlin.de> In-Reply-To: From: Max Filippov Date: Thu, 14 Jan 2021 15:09:24 -0800 Message-ID: Subject: Re: Old platforms: bring out your dead To: Arnd Bergmann Cc: John Paul Adrian Glaubitz , Linus Walleij , Gerhard Pircher , Arnd Bergmann , Linux Kernel Mailing List , linux-m68k , Sparc kernel list , Linux-sh list Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-m68k@vger.kernel.org Hi Arnd, On Thu, Jan 14, 2021 at 1:25 PM Arnd Bergmann wrote: > | arch/mips/Kconfig:config HIGHMEM > | arch/xtensa/Kconfig:config HIGHMEM > > AFAICT On MIPS (prior to MIPS32r3) and xtensa, you have at > most 512MB in the linear map, so the VMSPLIT_2G or VMSPLIT_4G_4G > tricks won't work. Regarding xtensa this was done to minimize difference between MMUv2 and MMUv3 virtual memory layouts. MMUv2 has been obsoleted more than 10 years ago, and MMUv3 is much more flexible and can do e.g. 4GB linear map. The only piece of xtensa MMUv2 hardware that I have has 96MB of DRAM which fits into its linear mapping. So maybe it's time to do a cleanup and rearrange virtual memory layout to eliminate the need of highmem. > I have no idea who uses xtensa systems with lots of memory on > modern kernels. We definitely use it for development internally at Cadence/Tensilica, mainly on simulators, but also on FPGA boards (e.g. on KC705 we can use all of the 1GB onboard DRAM). In the last few years we've had a few support requests for linux on xtensa cores with MMU, but AFAICT none of them had to deal with more than 512MB of onboard memory. -- Thanks. -- Max