From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from esa.microchip.iphmx.com (esa.microchip.iphmx.com [68.232.153.233]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A8DFD32145E; Fri, 12 Sep 2025 16:49:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=68.232.153.233 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757695791; cv=none; b=Ojhfdx6NGuX1xqZw/E4IQMzd2b/Z7/IuR/u26gPS6IlAvpr2WDjNd5r8vYuPtHudHeemXrdXcsmc3nkt0+Q34Li0eRQzzv2w9hC8Qgo0k0XgSzzhC/l+YWxQFNHdduslLxCwBtfDQibEJQa2FyaV/pacqDABYXivRKZzuH1kInk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757695791; c=relaxed/simple; bh=u1apkPsXybe68Jt3zrIWLyQZ7H3ZjR0gWhhluRQrN3k=; h=Message-ID:Date:MIME-Version:Subject:To:CC:References:From: In-Reply-To:Content-Type; b=qcRp9/TpuhvvGBKitCa0U52rY+GnU4L4nAQFoYzwr0ASD/tKppUS3F8143rvigVahsgaBKPv7PYTSG5M8jensYp6FgWic5i5T3MFRVshnfmgP7XQ6qJkb7WqDFXefVop/MBDTtpLVBJ/jVNNK08fm2bYBJxkbK39E5gE9JrDAbY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=microchip.com; spf=pass smtp.mailfrom=microchip.com; dkim=pass (2048-bit key) header.d=microchip.com header.i=@microchip.com header.b=qr7OyQyB; arc=none smtp.client-ip=68.232.153.233 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=microchip.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=microchip.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=microchip.com header.i=@microchip.com header.b="qr7OyQyB" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=microchip.com; i=@microchip.com; q=dns/txt; s=mchp; t=1757695790; x=1789231790; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=u1apkPsXybe68Jt3zrIWLyQZ7H3ZjR0gWhhluRQrN3k=; b=qr7OyQyBDYKpscyEM28tV1X85Pv/vB1ZALdCQl5nK11rCN06r7vFP9vC eUtb48ZJh6c4S1kUpSweaQ3NECITpA/moz8qlP4iWoiynK8jSEzb3wcJN HxpEacSFyIXxWfRlA0JQGhQx5k4h0hwD+pBjSXQy32R+9iGvjDv4zkQQJ oNYP09vm1DsqpxZh/AGQ4zYVBnCkxFlXA6cGEo2VJ1IIGa2xVHqligvH2 EbKTAQGWjnjM3fUKvCUbAJgZu5pKDydqVhw8dMrTuiYTC66ptHXpb1Nj4 GZ/Eo+oaXovr0Dhq87eTY0hokCn2pS6o2w/5+UGcJpZbWfnQI+54Elkil A==; 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 Precedence: bulk X-Mailing-List: imx@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: 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 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