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=-8.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 302F5C04EBE for ; Thu, 8 Oct 2020 10:14:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CE7C821734 for ; Thu, 8 Oct 2020 10:14:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729381AbgJHKOA (ORCPT ); Thu, 8 Oct 2020 06:14:00 -0400 Received: from mail.kernel.org ([198.145.29.99]:49808 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729341AbgJHKN7 (ORCPT ); Thu, 8 Oct 2020 06:13:59 -0400 Received: from gaia (unknown [95.149.105.49]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id BC20720708; Thu, 8 Oct 2020 10:13:56 +0000 (UTC) Date: Thu, 8 Oct 2020 11:13:54 +0100 From: Catalin Marinas To: Nicolas Saenz Julienne Cc: Rob Herring , devicetree@vger.kernel.org, will@kernel.org, Frank Rowand , linux-kernel@vger.kernel.org, linux-mm@kvack.org, iommu@lists.linux-foundation.org, linux-rpi-kernel@lists.infradead.org, robin.murphy@arm.com, hch@lst.de, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH 1/4] of/fdt: Update zone_dma_bits when running in bcm2711 Message-ID: <20201008101353.GE7661@gaia> References: <20201001161740.29064-1-nsaenzjulienne@suse.de> <20201001161740.29064-2-nsaenzjulienne@suse.de> <20201001171500.GN21544@gaia> <20201001172320.GQ21544@gaia> <20201002115541.GC7034@gaia> <12f33d487eabd626db4c07ded5a1447795eed355.camel@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <12f33d487eabd626db4c07ded5a1447795eed355.camel@suse.de> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org On Thu, Oct 08, 2020 at 12:05:25PM +0200, Nicolas Saenz Julienne wrote: > On Fri, 2020-10-02 at 12:55 +0100, Catalin Marinas wrote: > > On Thu, Oct 01, 2020 at 07:31:19PM +0200, Nicolas Saenz Julienne wrote: > > > On Thu, 2020-10-01 at 18:23 +0100, Catalin Marinas wrote: > > > > On Thu, Oct 01, 2020 at 06:15:01PM +0100, Catalin Marinas wrote: > > > > > On Thu, Oct 01, 2020 at 06:17:37PM +0200, Nicolas Saenz Julienne wrote: > > > > > > diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c > > > > > > index 4602e467ca8b..cd0d115ef329 100644 > > > > > > --- a/drivers/of/fdt.c > > > > > > +++ b/drivers/of/fdt.c > > > > > > @@ -25,6 +25,7 @@ > > > > > > #include > > > > > > #include > > > > > > #include > > > > > > +#include /* for zone_dma_bits */ > > > > > > > > > > > > #include /* for COMMAND_LINE_SIZE */ > > > > > > #include > > > > > > @@ -1198,6 +1199,14 @@ void __init early_init_dt_scan_nodes(void) > > > > > > of_scan_flat_dt(early_init_dt_scan_memory, NULL); > > > > > > } > > > > > > > > > > > > +void __init early_init_dt_update_zone_dma_bits(void) > > > > > > +{ > > > > > > + unsigned long dt_root = of_get_flat_dt_root(); > > > > > > + > > > > > > + if (of_flat_dt_is_compatible(dt_root, "brcm,bcm2711")) > > > > > > + zone_dma_bits = 30; > > > > > > +} > > > > > > > > > > I think we could keep this entirely in the arm64 setup_machine_fdt() and > > > > > not pollute the core code with RPi4-specific code. > > > > > > > > Actually, even better, could we not move the check to > > > > arm64_memblock_init() when we initialise zone_dma_bits? > > > > > > I did it this way as I vaguely remembered Rob saying he wanted to centralise > > > all early boot fdt code in one place. But I'll be happy to move it there. > > > > I can see Rob replied and I'm fine if that's his preference. However, > > what I don't particularly like is that in the arm64 code, if > > zone_dma_bits == 24, we set it to 32 assuming that it wasn't touched by > > the early_init_dt_update_zone_dma_bits(). What if at some point we'll > > get a platform that actually needs 24 here (I truly hope not, but just > > the principle of relying on magic values)? > > > > So rather than guessing, I'd prefer if the arch code can override > > ZONE_DMA_BITS_DEFAULT. Then, in arm64, we'll just set it to 32 and no > > need to explicitly touch the zone_dma_bits variable. > > Yes, sonds like the way to go. TBH I wasn't happy with that solution either, > but couldn't think of a nicer alternative. > > 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. Is there a way to get some SoC information from ACPI? -- Catalin