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 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 28FE9CA101F for ; Fri, 12 Sep 2025 16:49:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:CC:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=cnmFDlEOsmIEfqMrpAweTNFX9QftyJSBrntOrKfce2w=; b=U3/e73OIhYmItTIpTsAPbyD8F4 rSn6RZ1aT2cQY3LlDXK7HoVufTXkzE9BeZCR3N0nsS4sxVJnMnaSzva9mhu+UxCI5X3h6wTO1eaST 6CFGRrVX/FPTnxptRgNuDoaVTnK9phCEuvuZpebQNdk5Q+lU8+Tdpin25uQ8NheHQZPOy6kz3oZxa TsvaNta01k0m5B+9ExW8YDTaDhi+QiNbkSYJdLpyGSU/nadvnX8tGnDVe7H9rnhMaTJOmMPLd82QY CA8QxWbw7Nto+UfoKbcMEcM2vi8E0ug8nuykrx2km8mAMtivcvhzPWajSyAkUyFjS8AqSwQLveQQ5 qbCIoumA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1ux6y3-0000000AcKx-2O7U; Fri, 12 Sep 2025 16:49:47 +0000 Received: from esa.microchip.iphmx.com ([68.232.153.233]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1ux6y0-0000000AcJA-3Ox8 for linux-arm-kernel@lists.infradead.org; Fri, 12 Sep 2025 16:49:46 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=microchip.com; i=@microchip.com; q=dns/txt; s=mchp; t=1757695785; x=1789231785; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=u1apkPsXybe68Jt3zrIWLyQZ7H3ZjR0gWhhluRQrN3k=; b=z/Bp2ta5KHcG5dl1LZVjVrXnqozabOTOwL9uTjgILmb6BWP8owpWrcRC L1IprKG7JnS3keKo7QfCm988c0w4H88eqG14Vun9B0knsuXiQF99BCunb PC3XuWuf2hQCO24cga2D8jYE2X0NLd4mvp8BSGOY4pBOJjIbe0YmtzqwT aI1oLT/cb8Wi46ZfYTh2AZ5JPfQlrwjz4q85+EGL7X+x8E4UOXe6wiKc6 5CBi7arvShMj1zcqOdJ1qCMoR8zPgoLwli57u6D0Dr1PIPit/oWLCvRWo w71zcBdkVAW3iWmAfYLlMXxsD3K5glAV4FPjJJmu9olMBX1byNMp7FFNX Q==; X-CSE-ConnectionGUID: s3gPgfU6QPiurXqxeBySFg== X-CSE-MsgGUID: 0XiE5fKtQqWtnhAnsP3idA== X-IronPort-AV: E=Sophos;i="6.18,259,1751266800"; d="scan'208";a="46433595" X-Amp-Result: SKIPPED(no attachment in message) Received: from unknown (HELO email.microchip.com) ([170.129.1.10]) by esa3.microchip.iphmx.com with ESMTP/TLS/ECDHE-RSA-AES128-GCM-SHA256; 12 Sep 2025 09:49:42 -0700 Received: from chn-vm-ex02.mchp-main.com (10.10.85.144) by chn-vm-ex04.mchp-main.com (10.10.85.152) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.58; Fri, 12 Sep 2025 09:49:38 -0700 Received: from [10.159.245.205] (10.10.85.11) by chn-vm-ex02.mchp-main.com (10.10.85.144) with Microsoft SMTP Server id 15.1.2507.58 via Frontend Transport; Fri, 12 Sep 2025 09:49:32 -0700 Message-ID: Date: Fri, 12 Sep 2025 18:49:31 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [TECH TOPIC] Reaching consensus on CONFIG_HIGHMEM phaseout To: Arnd Bergmann , CC: , , , , , , Christophe Leroy , Richard Weinberger , "Lucas Stach" , Linus Walleij , Geert Uytterhoeven , Ankur Arora , David Hildenbrand , "Mike Rapoport" , Lorenzo Stoakes , Matthew Wilcox , Andrew Morton , "Liam R. Howlett" , Vlastimil Babka , Suren Baghdasaryan , "Ira Weiny" , Nishanth Menon , =?UTF-8?Q?Heiko_St=C3=BCbner?= , Alexander Sverdlin , "Chester A. Unal" , Sergio Paracuellos , Andreas Larsson , "Mihai Sain" , Alexandre Belloni , Claudiu Beznea References: <4ff89b72-03ff-4447-9d21-dd6a5fe1550f@app.fastmail.com> From: Nicolas Ferre Content-Language: en-US, fr Organization: microchip In-Reply-To: <4ff89b72-03ff-4447-9d21-dd6a5fe1550f@app.fastmail.com> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250912_094945_028413_240435BD X-CRM114-Status: GOOD ( 12.07 ) 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: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Arnd, On 09/09/2025 at 23:23, Arnd Bergmann wrote: > I'm still collecting information about which of the remaining highmem > users plan to keep updating their kernels and for what reason. We have 1GB of memory on our latest Cortex-A7 SAMA7D65 evaluation boards [1] (full production announced beg. 2025). The wide range of DDR types supported make some of these types interesting to use at such density. Both our Cortex-A7 SoCs don't have IOMMU; core and DMAs can address the full range of the 32 bit address space, so we're quite standard/simplistic in this area. We use CMA with large chunks as our camera or display interfaces address "modern-ish" resolutions (~1080p). We use CONFIG_HIGHMEM and activated it for simplicity, conformance to usual user-space workloads and planned to add it to our sama7_defconfig [2]. I understand that we might reconsider this "by default" choice and move to one of the solutions you highlighted in your message, lwn.net article or recent talk at ELC-E. Of course we plan to maintain these boards and keep updating our kernel "offer" once a year for those associated SoCs (with maintaining upstream, as usual). As you said, being ARMv7, we're quite confident for now. As you mentioned, we've recently released one ARMv5te arm926ejs-based soc: the SAM9x75 family. But we don't have the intention to use too big memory sizes on them, even if they do address large screens, with LVDS and MIPI or modern camera interfaces... I don't have too much info about our customer's use cases as they are very, very diverse, but don't hesitate to reach out to me if you have questions about a particular combination of use. Thanks for your regular update on these topics. Best regards, Nicolas [1]: for instance: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm/boot/dts/microchip/at91-sama7d65_curiosity.dts#n29 [2]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm/configs/sama7_defconfig