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=-6.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS 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 76A95C04EBE for ; Thu, 8 Oct 2020 10:05:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1B30B21527 for ; Thu, 8 Oct 2020 10:05:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729351AbgJHKF3 (ORCPT ); Thu, 8 Oct 2020 06:05:29 -0400 Received: from mx2.suse.de ([195.135.220.15]:53932 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725849AbgJHKF3 (ORCPT ); Thu, 8 Oct 2020 06:05:29 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 983DBAD20; Thu, 8 Oct 2020 10:05:26 +0000 (UTC) Message-ID: <12f33d487eabd626db4c07ded5a1447795eed355.camel@suse.de> Subject: Re: [PATCH 1/4] of/fdt: Update zone_dma_bits when running in bcm2711 From: Nicolas Saenz Julienne To: Catalin Marinas 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 Date: Thu, 08 Oct 2020 12:05:25 +0200 In-Reply-To: <20201002115541.GC7034@gaia> References: <20201001161740.29064-1-nsaenzjulienne@suse.de> <20201001161740.29064-2-nsaenzjulienne@suse.de> <20201001171500.GN21544@gaia> <20201001172320.GQ21544@gaia> <20201002115541.GC7034@gaia> Content-Type: multipart/signed; micalg="pgp-sha256"; protocol="application/pgp-signature"; boundary="=-UgRFrRCNh36xLg4FQaLM" User-Agent: Evolution 3.36.5 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --=-UgRFrRCNh36xLg4FQaLM Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Hi Catalin, sorry for the late reply. 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 wr= ote: > > > > > 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 */ > > > > > =20 > > > > > #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); > > > > > } > > > > > =20 > > > > > +void __init early_init_dt_update_zone_dma_bits(void) > > > > > +{ > > > > > + unsigned long dt_root =3D of_get_flat_dt_root(); > > > > > + > > > > > + if (of_flat_dt_is_compatible(dt_root, "brcm,bcm2711")) > > > > > + zone_dma_bits =3D 30; > > > > > +} > > > >=20 > > > > I think we could keep this entirely in the arm64 setup_machine_fdt(= ) and > > > > not pollute the core code with RPi4-specific code. > > >=20 > > > Actually, even better, could we not move the check to > > > arm64_memblock_init() when we initialise zone_dma_bits? > >=20 > > I did it this way as I vaguely remembered Rob saying he wanted to centr= alise > > all early boot fdt code in one place. But I'll be happy to move it ther= e. >=20 > 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 =3D=3D 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)? >=20 > 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 tha= t 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. Regards, Nicolas --=-UgRFrRCNh36xLg4FQaLM Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part Content-Transfer-Encoding: 7bit -----BEGIN PGP SIGNATURE----- iQEzBAABCAAdFiEErOkkGDHCg2EbPcGjlfZmHno8x/4FAl9+5GUACgkQlfZmHno8 x/6e8wf9EJ0i1Wi9BCOQEMRii/Avn31umkWy/c6brw125hfV8Jcwwn6RlD9oTrD6 57UaLxdLJjFjZcCHmPhOG7zcMwfsP/Ft5hmeS6ECAgOl3bL6jDRpnrQ80+gEO3U2 rJ0sgrVHJp+ZC0Yf1HedSnj0EpgjbQFc3iPJHEW19XVLbZ61cu8keEKDZevaHONm BssWhdVqPaNW8Z9LuT04V4y+JXxLCjflB88QQD+UA5BbdLLRPn2DGZKErUwyyF8O U68UbaCmHEPIddLXLdHde657lQS0pT99yCJzyGA8S9k3XbNLcPK304WYZj1Qib8Z DI2imsq4V1HT3TAyebIj++LJgx/Uyg== =Sv3m -----END PGP SIGNATURE----- --=-UgRFrRCNh36xLg4FQaLM--