From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-181.mta0.migadu.com (out-181.mta0.migadu.com [91.218.175.181]) (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 87DD12EC0AC for ; Sat, 13 Sep 2025 10:53:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.181 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757760803; cv=none; b=CWQDUl6er4L9I6CF1Rrk4ffvFKrDXwZWRCa37hLmV8nitR2Z5IF8ycVdhLZhlZYJSBW9nH4TmiXIcjRm4+FMJfzvASDx4zDlmHfoGnA2K+yX459Kj+fUK0TCxcoWhDn9Yk3QQ9qLNHhcaq7ZgtZ8Psw1N6ktHFLmz9vH8mf8c9E= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757760803; c=relaxed/simple; bh=qXx1wONTbcgawN/zX0ziVSkmOFKWffOPfCIo4Thq7VI=; h=Message-ID:Date:MIME-Version:From:Subject:To:Cc:Content-Type; b=Lr6ls5qxZTJKnGMY3iV6hv9tQXApIUMZYtspC4pFBR9gUDale9UprZn8fC2dL9FSIxrYWWbj+sIuG7F2VZBKXWxF4Gw/lSjMHA2abbygqwR0P4cszvgD/Mt7Fpol6r14PU1XrzsnRlyecBoHaY0KNrZQr99w0Wxs/SSwGQJ5NHY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=heyquark.com; spf=pass smtp.mailfrom=heyquark.com; dkim=pass (2048-bit key) header.d=heyquark.com header.i=@heyquark.com header.b=ZPwflY85; arc=none smtp.client-ip=91.218.175.181 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=heyquark.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=heyquark.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=heyquark.com header.i=@heyquark.com header.b="ZPwflY85" Message-ID: <3e8cb683-a084-4847-8f69-e1f4d9125c45@heyquark.com> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=heyquark.com; s=key1; t=1757760798; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=1iZiELOPGgRZDBi2au223SZgjALhV2isPuOLR/SKVds=; b=ZPwflY854lfR6+0k+h4yDgxJWLkTlhGcfYHnB/PhTWkU+vIwyWhZXL2UE3uTJ/Xix0zK+U 66IwEf6xsXakDFWxyhzg5a83nJTtKwd9NJnINz/rCmXaV9Cc68bKyH7w0BLmHPvxDQnBrH /+l9KErxJkMkbsE2KDFnkgWqLYMw5nWZqZS9Px0jM1D+spx4jdK6KajIco0RNkdxxcHtaV 3Eoi6Mp6KFCk2A78L+jA21XKKsmGZPFZGrvggAWwSeXCADlOjNHhaRyrU4FTMwimAHNr1o t7axN5rc/TW5uDrrhmLVPsGCp+EF2UhBiCCo9Je2k3qGp0KZ+JF6VdQTsEaskQ== Date: Sat, 13 Sep 2025 20:53:08 +1000 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Ash Logan Subject: 32-bit HIGHMEM and game console downstreams Content-Language: en-US To: arnd@arndb.de, christophe.leroy@csgroup.eu Cc: "linuxppc-dev@lists.ozlabs.org" , "linux-kernel@vger.kernel.org" , officialTechflashYT@gmail.com, AWilcox@Wilcox-Tech.com, Michael Ellerman Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT Hello! LWN recently did a piece on 32-bit support in the kernel, and thought as a user of 32-bit I would share my 2c. [1] I maintain a downstream fork of 6.6 to support the Nintendo Wii U hardware [2]. I'm also in regular contact with another doing the same for the older Wii [3]. Linux on this era of game consoles is doing pretty well :) The Wii and Wii U are both 32-bit PowerPC machines with holes in their memory map, which I think makes them interesting for this discussion. Let me summarize the hardware and kernels involved: Wii (2006) - 1x PowerPC 750CL "Broadway" @ 729MHz - 24MB "MEM1" + 64MB "MEM2" (non-contiguous - MEM2 starts 256MiB in) - Kernel 4.19 (+ CIP patchset), dev has been working on forward-porting all the drivers one major version at a time (he's currently up to 5.15 last I checked) + limited upstream support (hardware bringup, UART, not many peripherals) Wii U (2012) - 3x PowerPC 750CL "Espresso" @ 1.2GHz - 32MB "MEM1" + 2GB "MEM2" (also starts 256MiB in) + various small SRAMs - Kernel 6.6 (+ LTS patchset), I also had a run at upstreaming some of it in 2022 [4] and would eventually like to go again Special mention to the GameCube, basically a slower Wii with only 24MB direct RAM and 16MB of non-mapped "ARAM". Wii Linux has experimental support for this where they use the ARAM as swap. All of these are flatmem devices, as that's all the 32-bit PowerPC arch supports, with the Wii U additionally enabling highmem for its 2GB of RAM. Both devices have a small memory area (MEM1) with the "bulk" of RAM starting at 256MiB. The Wii U in particular sounds like a candidate system for densemem - I would like to read up more about this if I can, I was only able to find seemingly unrelated information about CXL when searching online. There is a somewhat active userbase for both devices. I only have stats for the Wii U side, but some rough nginx grepping for the last few days - Sep 7th-Sep 12th - shows 39 downloads of distribution tarballs and bootloader binaries in that period, not including torrents. In the past 2 weeks - Aug 29th-Sep 12th - 9 people joined the community Discord, 442 total. Anecdotally, the Wii Linux userbase appears at least twice as big (based on their Discord activity). Distribution-wise, we're supported by ArchPOWER [5], Adélie Linux [6], and other distros. The Wii U's Espresso has CPU errata requiring a patched compiler, and both distributions ship separate package repos for this CPU. ArchPOWER requested I rebase onto 6.6 so they could have firmware compression - previously the Wii U was on 4.19 - so there is some demand for newer kernel features as well. I know I'm talking about hobbyist use - and mostly downstream use at that - and I do suspect that in the event of a wider 32-bit deprecation we'd be fine on the final LTS, whatever that ends up being. Still, I think the Wii and Wii U represent a decent number of 32-bit users, so I wanted to add to the conversation here. Thanks, Ash [1] https://lwn.net/Articles/1035727/ [2] https://linux-wiiu.org/ [3] https://wii-linux.org/ [4] https://lore.kernel.org/lkml/20221119113041.284419-1-ash@heyquark.com/ [5] https://archlinuxpower.org/ [6] https://www.adelielinux.org/