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=-8.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 D136EC433B4 for ; Fri, 9 Apr 2021 13:35:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AD32F60241 for ; Fri, 9 Apr 2021 13:35:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231819AbhDINff (ORCPT ); Fri, 9 Apr 2021 09:35:35 -0400 Received: from mout.kundenserver.de ([212.227.17.10]:60757 "EHLO mout.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231127AbhDINff (ORCPT ); Fri, 9 Apr 2021 09:35:35 -0400 Received: from mail-ot1-f46.google.com ([209.85.210.46]) by mrelayeu.kundenserver.de (mreue109 [213.165.67.113]) with ESMTPSA (Nemesis) id 1MKKd7-1lHJaB3nAt-00Lmj3; Fri, 09 Apr 2021 15:35:21 +0200 Received: by mail-ot1-f46.google.com with SMTP id k14-20020a9d7dce0000b02901b866632f29so5711168otn.1; Fri, 09 Apr 2021 06:35:20 -0700 (PDT) X-Gm-Message-State: AOAM532xvLKvGNL2LF61vwvwtwLHReYP9333LL2z5p1rlYjdMf69CKzw fSpUfUYdMVyq9818UN5Y7dhxe7yzwRDpnGLAGHc= X-Google-Smtp-Source: ABdhPJynlbx4kLNikSNjAjnCb5vtFq6G/850R+R5+xWMARHqWLy+tfY7F0Z+Hrp7Hz4KWDmPvvGBCrUcX4hM8LkZWnk= X-Received: by 2002:a9d:758b:: with SMTP id s11mr12240759otk.305.1617975319390; Fri, 09 Apr 2021 06:35:19 -0700 (PDT) MIME-Version: 1.0 References: <20210409112035.27221-1-david@redhat.com> In-Reply-To: <20210409112035.27221-1-david@redhat.com> From: Arnd Bergmann Date: Fri, 9 Apr 2021 15:35:03 +0200 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v3] drivers: introduce and use WANT_DMA_CMA for soft dependencies on DMA_CMA To: David Hildenbrand Cc: Linux Kernel Mailing List , Linux-MM , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Daniel Vetter , Joel Stanley , Andrew Jeffery , Lucas Stach , Russell King , Christian Gmeiner , Paul Cercueil , Linus Walleij , Christoph Hellwig , Marek Szyprowski , Robin Murphy , Andrew Morton , Mike Rapoport , Bartlomiej Zolnierkiewicz , Eric Anholt , Michal Simek , Masahiro Yamada , "Alexander A. Klimov" , Peter Collingbourne , Suman Anna , Jason Gunthorpe , dri-devel , linux-aspeed , Linux ARM , The etnaviv authors , "open list:BROADCOM NVRAM DRIVER" , Linux Fbdev development list , "open list:IOMMU DRIVERS" Content-Type: text/plain; charset="UTF-8" X-Provags-ID: V03:K1:/7zXw/c1UfESlEruqAGXS8UzIHuJI2NxiDK7tVwMgfdq4wYKuFS 6pXkdJchhga4+TmhN9Ms++pwBTz9yL9aKgjVvkvHHvhiWjciAWR+WA3f421jDGE5exNDCzr Zk5rhoQb9IDWjo/pGPYYeB2HOtt/KqEOaWYPozig6+QzGPuhVphXpUk/7G2o29IHNdPUcek fajs/Hllr8UunECmkMm7A== X-UI-Out-Filterresults: notjunk:1;V03:K0:Ug59u7F3OJQ=:3IXoa0MamCC3tSceenqEE6 Q79+SXOGJ/h7Ykjqa6HuOBjWxBa8k1io25xcFGxpQDn5WLf5vIQ04Q7VygmOtvaDZU34kLSWx 3WtRiTo6IJMGXSre12X0/Tp6Yzk7E81VxdfylZacU9F8rwfU8fpA5K5e8gx8N/QAE4FZLg6AW 5wU9f6mF6tQuLiyMAonPYwaVG0slmNcPh447tFDuIc9sQPklyKSNEBzRsSoFxmvPmWWASKKEW BblFUNyAg6zFxLiQZeahg/nmKUn//83+AutMsoa5nDPJmO8xSe6MIyetduAmheLONxu5JJYfG p/TpJ6nkCuxUfDqGueDOCICsT7xcRKuQNdCODZhVZCmHt5oVXblvQQTU8RpfzPbN19SXMoLRb EbiTZbIFeHKKv5M++TMmBAT4T2WFokbdEyo5UT1cFpUmNgeCCizy7OXCSouDqXcv6yGaHGiuo g9Ph9lviL6CiZVSiRw51AcD+QMmrz2o= Precedence: bulk List-ID: X-Mailing-List: linux-fbdev@vger.kernel.org On Fri, Apr 9, 2021 at 1:21 PM David Hildenbrand wrote: > > Random drivers should not override a user configuration of core knobs > (e.g., CONFIG_DMA_CMA=n). Applicable drivers would like to use DMA_CMA, > which depends on CMA, if possible; however, these drivers also have to > tolerate if DMA_CMA is not available/functioning, for example, if no CMA > area for DMA_CMA use has been setup via "cma=X". In the worst case, the > driver cannot do it's job properly in some configurations. > > For example, commit 63f5677544b3 ("drm/etnaviv: select CMA and DMA_CMA if > available") documents > While this is no build dependency, etnaviv will only work correctly > on most systems if CMA and DMA_CMA are enabled. Select both options > if available to avoid users ending up with a non-working GPU due to > a lacking kernel config. > So etnaviv really wants to have DMA_CMA, however, can deal with some cases > where it is not available. > > Let's introduce WANT_DMA_CMA and use it in most cases where drivers > select CMA/DMA_CMA, or depend on DMA_CMA (in a wrong way via CMA because > of recursive dependency issues). > > We'll assume that any driver that selects DRM_GEM_CMA_HELPER or > DRM_KMS_CMA_HELPER would like to use DMA_CMA if possible. > > With this change, distributions can disable CONFIG_CMA or > CONFIG_DMA_CMA, without it silently getting enabled again by random > drivers. Also, we'll now automatically try to enabled both, CONFIG_CMA > and CONFIG_DMA_CMA if they are unspecified and any driver is around that > selects WANT_DMA_CMA -- also implicitly via DRM_GEM_CMA_HELPER or > DRM_KMS_CMA_HELPER. > > For example, if any driver selects WANT_DMA_CMA and we do a > "make olddefconfig": > > 1. With "# CONFIG_CMA is not set" and no specification of > "CONFIG_DMA_CMA" > > -> CONFIG_DMA_CMA won't be part of .config > > 2. With no specification of CONFIG_CMA or CONFIG_DMA_CMA > > Contiguous Memory Allocator (CMA) [Y/n/?] (NEW) > DMA Contiguous Memory Allocator (DMA_CMA) [Y/n/?] (NEW) > > 3. With "# CONFIG_CMA is not set" and "# CONFIG_DMA_CMA is not set" > > -> CONFIG_DMA_CMA will be removed from .config > > Note: drivers/remoteproc seems to be special; commit c51e882cd711 > ("remoteproc/davinci: Update Kconfig to depend on DMA_CMA") explains that > there is a real dependency to DMA_CMA for it to work; leave that dependency > in place and don't convert it to a soft dependency. I don't think this dependency is fundamentally different from the others, though davinci machines tend to have less memory than a lot of the other machines, so it's more likely to fail without CMA. Regardless of this, Reviewed-by: Arnd Bergmann