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=-3.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 2A2F4C2BB84 for ; Wed, 16 Sep 2020 09:38:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DA76322224 for ; Wed, 16 Sep 2020 09:38:05 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=ffwll.ch header.i=@ffwll.ch header.b="T6LbbPjB" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726822AbgIPJiF (ORCPT ); Wed, 16 Sep 2020 05:38:05 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43294 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726696AbgIPJiE (ORCPT ); Wed, 16 Sep 2020 05:38:04 -0400 Received: from mail-wr1-x444.google.com (mail-wr1-x444.google.com [IPv6:2a00:1450:4864:20::444]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 71CECC061788 for ; Wed, 16 Sep 2020 02:38:01 -0700 (PDT) Received: by mail-wr1-x444.google.com with SMTP id e16so6189310wrm.2 for ; Wed, 16 Sep 2020 02:38:01 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ffwll.ch; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=BAzRRIK8v7JChf1JsBCe57FCd6YM507dSSUg9G+yDXQ=; b=T6LbbPjB6GDxDA+6v39RkYYRs/xN0kVLglJ+50Ffd73lPfUO0KgjveykyAoXazlHY8 BTKyiMtBFl3BCfhTe0N0v4CVqxWhCfLBw7JWtX75c/f6GEHT+gRZlvl3YCGCl3Zr6bpx CsWogiwEWIw2ApnI09fpCtv4JUFPP/7YyAXZc= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=BAzRRIK8v7JChf1JsBCe57FCd6YM507dSSUg9G+yDXQ=; b=UvLBJcW9o2ZX1w9yXOWkCkPSDTzfItgrJmdkdrrMoMuW7DEi2CKQ6RZB4j1qxn0stV wgIZOD4Wz9bo3hxYwQsPTrOyZMDA79xgal6VTpFx2QLMzst26QTkpiWdh/767ba9K523 0YhBoaZen2HBtSonKDEbe3Eebb0vFEEq/qUX6bfg7VsBPHjRPLiRvCLSV+/7pBkmjNWO 16eRWIzylPIPaa0Huug65+WqxnpDRQYhkpDrs3qygRYiFurtXZtOCEAlj6Wh6B0bC1Fh CjGS39b8yC399CdF2/JXhcJfuefH95dBudmpFJNZ31Ar6VuXrZVxfOLTsq65Il7ATiSj Wu5A== X-Gm-Message-State: AOAM532j4ulCqWQqEAeKBe/hNa4gpeMSCAYbU3Jyx9VfyoEyL3A7WK/H PR9B88XhdobvElIOXj9ss38lPw== X-Google-Smtp-Source: ABdhPJw3Y7czwYvM941LlyOYnNW/rTDHKpG+JUXszB6P9qd/Lqa6QqYntED9lIWpEw+GbimKaOiZIw== X-Received: by 2002:a5d:61c7:: with SMTP id q7mr26159918wrv.343.1600249079953; Wed, 16 Sep 2020 02:37:59 -0700 (PDT) Received: from phenom.ffwll.local ([2a02:168:57f4:0:efd0:b9e5:5ae6:c2fa]) by smtp.gmail.com with ESMTPSA id k84sm4227735wmf.6.2020.09.16.02.37.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 16 Sep 2020 02:37:59 -0700 (PDT) Date: Wed, 16 Sep 2020 11:37:56 +0200 From: Daniel Vetter To: Thomas Zimmermann Cc: sumit.semwal@linaro.org, christian.koenig@amd.com, daniel@ffwll.ch, airlied@linux.ie, sam@ravnborg.org, mark.cave-ayland@ilande.co.uk, kraxel@redhat.com, davem@davemloft.net, maarten.lankhorst@linux.intel.com, mripard@kernel.org, l.stach@pengutronix.de, linux+etnaviv@armlinux.org.uk, christian.gmeiner@gmail.com, jani.nikula@linux.intel.com, joonas.lahtinen@linux.intel.com, rodrigo.vivi@intel.com, thierry.reding@gmail.com, jonathanh@nvidia.com, pawel@osciak.com, m.szyprowski@samsung.com, kyungmin.park@samsung.com, tfiga@chromium.org, mchehab@kernel.org, chris@chris-wilson.co.uk, matthew.auld@intel.com, thomas.hellstrom@intel.com, linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org, etnaviv@lists.freedesktop.org, intel-gfx@lists.freedesktop.org, linux-tegra@vger.kernel.org, sparclinux@vger.kernel.org Subject: Re: [PATCH 0/3] dma-buf: Flag vmap'ed memory as system or I/O memory Message-ID: <20200916093756.GC438822@phenom.ffwll.local> References: <20200914112521.1327-1-tzimmermann@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200914112521.1327-1-tzimmermann@suse.de> X-Operating-System: Linux phenom 5.7.0-1-amd64 Sender: linux-tegra-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-tegra@vger.kernel.org On Mon, Sep 14, 2020 at 01:25:18PM +0200, Thomas Zimmermann wrote: > Dma-buf provides vmap() and vunmap() for retrieving and releasing mappings > of dma-buf memory in kernel address space. The functions operate with plain > addresses and the assumption is that the memory can be accessed with load > and store operations. This is not the case on some architectures (e.g., > sparc64) where I/O memory can only be accessed with dedicated instructions. > > This patchset introduces struct dma_buf_map, which contains the address of > a buffer and a flag that tells whether system- or I/O-memory instructions > are required. > > Some background: updating the DRM framebuffer console on sparc64 makes the > kernel panic. This is because the framebuffer memory cannot be accessed with > system-memory instructions. We currently employ a workaround in DRM to > address this specific problem. [1] > > To resolve the problem, we'd like to address it at the most common point, > which is the dma-buf framework. The dma-buf mapping ideally knows if I/O > instructions are required and exports this information to it's users. The > new structure struct dma_buf_map stores the buffer address and a flag that > signals I/O memory. Affected users of the buffer (e.g., drivers, frameworks) > can then access the memory accordingly. > > This patchset only introduces struct dma_buf_map, and updates struct dma_buf > and it's interfaces. Further patches can update dma-buf users. For example, > there's a prototype patchset for DRM that fixes the framebuffer problem. [2] > > Further work: TTM, one of DRM's memory managers, already exports an > is_iomem flag of its own. It could later be switched over to exporting struct > dma_buf_map, thus simplifying some code. Several DRM drivers expect their > fbdev console to operate on I/O memory. These could possibly be switched over > to the generic fbdev emulation, as soon as the generic code uses struct > dma_buf_map. > > [1] https://lore.kernel.org/dri-devel/20200725191012.GA434957@ravnborg.org/ > [2] https://lore.kernel.org/dri-devel/20200806085239.4606-1-tzimmermann@suse.de/ lgtm, imo ready to convert the follow-up patches over to this. But I think would be good to get at least some ack from the ttm side for the overall plan. Also, I think we should put all the various helpers (writel/readl, memset, memcpy, whatever else) into the dma-buf-map.h helper, so that most code using this can just treat it as an abstract pointer type and never look underneath it. -Daniel > > Thomas Zimmermann (3): > dma-buf: Add struct dma-buf-map for storing struct dma_buf.vaddr_ptr > dma-buf: Use struct dma_buf_map in dma_buf_vmap() interfaces > dma-buf: Use struct dma_buf_map in dma_buf_vunmap() interfaces > > Documentation/driver-api/dma-buf.rst | 3 + > drivers/dma-buf/dma-buf.c | 40 +++--- > drivers/gpu/drm/drm_gem_cma_helper.c | 16 ++- > drivers/gpu/drm/drm_gem_shmem_helper.c | 17 ++- > drivers/gpu/drm/drm_prime.c | 14 +- > drivers/gpu/drm/etnaviv/etnaviv_gem_prime.c | 13 +- > drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c | 13 +- > .../drm/i915/gem/selftests/i915_gem_dmabuf.c | 18 ++- > drivers/gpu/drm/tegra/gem.c | 23 ++-- > .../common/videobuf2/videobuf2-dma-contig.c | 17 ++- > .../media/common/videobuf2/videobuf2-dma-sg.c | 19 ++- > .../common/videobuf2/videobuf2-vmalloc.c | 21 ++- > include/drm/drm_prime.h | 5 +- > include/linux/dma-buf-map.h | 126 ++++++++++++++++++ > include/linux/dma-buf.h | 11 +- > 15 files changed, 274 insertions(+), 82 deletions(-) > create mode 100644 include/linux/dma-buf-map.h > > -- > 2.28.0 > -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch