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=-5.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 DD48EC433DF for ; Fri, 9 Oct 2020 15:25:48 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 7B0DE22261 for ; Fri, 9 Oct 2020 15:25:48 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="CLebdPL9" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7B0DE22261 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References:Message-ID: Subject:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=vyGOs2dKCQ99eS1Nj+YRf7jhmdn7yg0BWpAvYbO3POY=; b=CLebdPL9HA7gt4cjA0irQKv03 Mn3jqhvzNU+JiYr5wQ5hvnA4tGylZky/gRtVoXxvhWcAf144j1ImwIHLHMBpOqw/+d9fquO6V7abQ 1gi8zNzvrqyLcuBR6uSc5KkJt71zT4T/wrpWCrENOrrtZPdbyYHK2e4oI557oOOl8oOYRyi+fWhle SbhV2iXiAsn+wdfJ1FDYtIEKrhv1NkuPc7SjgrXk3bp+XLZ/Z5lsW+MODAAxPyQBS9BHvV/ScT1O/ 6qNziUR/oN9Qjj0CUhziZZhE5lPNimW18AJ5fkEeFWXaOu0mFKX94hUQS1Fjlw+MH3brlr4iGmOM3 T+SZ/ajQg==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kQuGC-0004Yd-FN; Fri, 09 Oct 2020 15:24:44 +0000 Received: from foss.arm.com ([217.140.110.172]) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kQuG8-0004Xg-Vk; Fri, 09 Oct 2020 15:24:42 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 1542D1063; Fri, 9 Oct 2020 08:24:40 -0700 (PDT) Received: from e121166-lin.cambridge.arm.com (e121166-lin.cambridge.arm.com [10.1.196.255]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 4D02D3F70D; Fri, 9 Oct 2020 08:24:38 -0700 (PDT) Date: Fri, 9 Oct 2020 16:24:33 +0100 From: Lorenzo Pieralisi To: Ard Biesheuvel Subject: Re: [PATCH 1/4] of/fdt: Update zone_dma_bits when running in bcm2711 Message-ID: <20201009152433.GA19953@e121166-lin.cambridge.arm.com> References: <20201001161740.29064-2-nsaenzjulienne@suse.de> <20201001171500.GN21544@gaia> <20201001172320.GQ21544@gaia> <20201002115541.GC7034@gaia> <12f33d487eabd626db4c07ded5a1447795eed355.camel@suse.de> <20201009071013.GA12208@lst.de> <513833810c15b5efeab7c3cbae1963a78c71a79f.camel@suse.de> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201009_112441_121631_27F14A89 X-CRM114-Status: GOOD ( 38.77 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Linux ARM , "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" , Frank Rowand , Catalin Marinas , Linux Kernel Mailing List , Linux Memory Management List , iommu@lists.linux-foundation.org, Rob Herring , linux-rpi-kernel@lists.infradead.org, Will Deacon , Christoph Hellwig , Nicolas Saenz Julienne , Robin Murphy 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 Fri, Oct 09, 2020 at 11:13:59AM +0200, Ard Biesheuvel wrote: > On Fri, 9 Oct 2020 at 10:36, Nicolas Saenz Julienne > wrote: > > > > On Fri, 2020-10-09 at 09:37 +0200, Ard Biesheuvel wrote: > > > On Fri, 9 Oct 2020 at 09:11, Christoph Hellwig wrote: > > > > On Thu, Oct 08, 2020 at 12:05:25PM +0200, Nicolas Saenz Julienne wrote: > > > > > Sadly I just realised that the series is incomplete, we have RPi4 users that > > > > > want to boot unsing ACPI, and this series would break things for them. I'll > > > > > have a word with them to see what we can do for their use-case. > > > > > > > > Stupid question: why do these users insist on a totally unsuitable > > > > interface? And why would we as Linux developers care to support such > > > > a aims? > > > > > > The point is really whether we want to revert changes in Linux that > > > made both DT and ACPI boot work without quirks on RPi4. > > > > Well, and broke a big amount of devices that were otherwise fine. > > > > Yeah that was unfortunate. > > > > Having to check the RPi4 compatible string or OEM id in core init code is > > > awful, regardless of whether you boot via ACPI or via DT. > > > > > > The problem with this hardware is that it uses a DMA mask which is > > > narrower than 32, and the arm64 kernel is simply not set up to deal > > > with that at all. On DT, we have DMA ranges properties and the likes > > > to describe such limitations, on ACPI we have _DMA methods as well as > > > DMA range attributes in the IORT, both of which are now handled > > > correctly. So all the information is there, we just have to figure out > > > how to consume it early on. > > > > Is it worth the effort just for a single board? I don't know about ACPI but > > parsing dma-ranges that early at boot time is not trivial. My intuition tells > > me that it'd be even harder for ACPI, being a more complex data structure. > > > > Yes, it will be harder, especially for the _DMA methods. > > > > Interestingly, this limitation always existed in the SoC, but it > > > wasn't until they started shipping it with more than 1 GB of DRAM that > > > it became a problem. This means issues like this could resurface in > > > the future with existing SoCs when they get shipped with more memory, > > > and so I would prefer fixing this in a generic way. > > > > Actually what I proposed here is pretty generic. Specially from arm64's > > perspective. We call early_init_dt_scan(), which sets up zone_dma_bits based on > > whatever it finds in DT. Both those operations are architecture independent. > > arm64 arch code doesn't care about the logic involved in ascertaining > > zone_dma_bits. I get that the last step isn't generic. But it's all setup so as > > to make it as such whenever it's worth the effort. > > > > The problem is that, while we are providing a full description of the > SoC's capabilities, we short circuit this by inserting knowledge into > the code (that is shared between all DT architectures) that > "brcm,bcm2711" is special, and needs a DMA zone override. > > I think for ACPI boot, we might be able to work around this by cold > plugging the memory above 1 GB, but I have to double check whether it > won't get pulled into ZONE_DMA32 anyway (unless anyone can answer that > for me here from the top of their head) Is this information that we can infer from IORT nodes and make it generic (ie make a DMA limit out of all IORT nodes allowed ranges) ? We can move this check to IORT code and call it from arm64 if it can be made to work. Thanks, Lorenzo _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel