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=-13.6 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable 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 BFD1EC433E2 for ; Tue, 1 Sep 2020 20:01:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 989EC207EA for ; Tue, 1 Sep 2020 20:01:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732648AbgIAUBJ (ORCPT ); Tue, 1 Sep 2020 16:01:09 -0400 Received: from foss.arm.com ([217.140.110.172]:49270 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726936AbgIAUBD (ORCPT ); Tue, 1 Sep 2020 16:01:03 -0400 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 C75DA1FB; Tue, 1 Sep 2020 13:01:02 -0700 (PDT) Received: from [10.57.40.122] (unknown [10.57.40.122]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 8CE313F66F; Tue, 1 Sep 2020 13:01:00 -0700 (PDT) Subject: Re: [PATCH v9 17/32] drm: rockchip: fix common struct sg_table related issues To: Marek Szyprowski , dri-devel@lists.freedesktop.org, iommu@lists.linux-foundation.org, linaro-mm-sig@lists.linaro.org, linux-kernel@vger.kernel.org Cc: Christoph Hellwig , Bartlomiej Zolnierkiewicz , linux-arm-kernel@lists.infradead.org, David Airlie , Daniel Vetter , Sandy Huang , =?UTF-8?Q?Heiko_St=c3=bcbner?= , linux-rockchip@lists.infradead.org References: <20200826063316.23486-1-m.szyprowski@samsung.com> <20200826063316.23486-18-m.szyprowski@samsung.com> From: Robin Murphy Message-ID: Date: Tue, 1 Sep 2020 21:00:59 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; rv:68.0) Gecko/20100101 Thunderbird/68.12.0 MIME-Version: 1.0 In-Reply-To: <20200826063316.23486-18-m.szyprowski@samsung.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020-08-26 07:33, Marek Szyprowski wrote: > The Documentation/DMA-API-HOWTO.txt states that the dma_map_sg() function > returns the number of the created entries in the DMA address space. > However the subsequent calls to the dma_sync_sg_for_{device,cpu}() and > dma_unmap_sg must be called with the original number of the entries > passed to the dma_map_sg(). > > struct sg_table is a common structure used for describing a non-contiguous > memory buffer, used commonly in the DRM and graphics subsystems. It > consists of a scatterlist with memory pages and DMA addresses (sgl entry), > as well as the number of scatterlist entries: CPU pages (orig_nents entry) > and DMA mapped pages (nents entry). > > It turned out that it was a common mistake to misuse nents and orig_nents > entries, calling DMA-mapping functions with a wrong number of entries or > ignoring the number of mapped entries returned by the dma_map_sg() > function. > > To avoid such issues, lets use a common dma-mapping wrappers operating > directly on the struct sg_table objects and use scatterlist page > iterators where possible. This, almost always, hides references to the > nents and orig_nents entries, making the code robust, easier to follow > and copy/paste safe. Reviewed-by: Robin Murphy (Until now I hadn't noticed the crimes against the API that rockchip_gem_get_pages() is committing, but it's not this patch's fault... I'll have to take a closer look at that) > Signed-off-by: Marek Szyprowski > --- > drivers/gpu/drm/rockchip/rockchip_drm_gem.c | 23 +++++++++------------ > 1 file changed, 10 insertions(+), 13 deletions(-) > > diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_gem.c b/drivers/gpu/drm/rockchip/rockchip_drm_gem.c > index 2970e534e2bb..cb50f2ba2e46 100644 > --- a/drivers/gpu/drm/rockchip/rockchip_drm_gem.c > +++ b/drivers/gpu/drm/rockchip/rockchip_drm_gem.c > @@ -36,8 +36,8 @@ static int rockchip_gem_iommu_map(struct rockchip_gem_object *rk_obj) > > rk_obj->dma_addr = rk_obj->mm.start; > > - ret = iommu_map_sg(private->domain, rk_obj->dma_addr, rk_obj->sgt->sgl, > - rk_obj->sgt->nents, prot); > + ret = iommu_map_sgtable(private->domain, rk_obj->dma_addr, rk_obj->sgt, > + prot); > if (ret < rk_obj->base.size) { > DRM_ERROR("failed to map buffer: size=%zd request_size=%zd\n", > ret, rk_obj->base.size); > @@ -98,11 +98,10 @@ static int rockchip_gem_get_pages(struct rockchip_gem_object *rk_obj) > * TODO: Replace this by drm_clflush_sg() once it can be implemented > * without relying on symbols that are not exported. > */ > - for_each_sg(rk_obj->sgt->sgl, s, rk_obj->sgt->nents, i) > + for_each_sgtable_sg(rk_obj->sgt, s, i) > sg_dma_address(s) = sg_phys(s); > > - dma_sync_sg_for_device(drm->dev, rk_obj->sgt->sgl, rk_obj->sgt->nents, > - DMA_TO_DEVICE); > + dma_sync_sgtable_for_device(drm->dev, rk_obj->sgt, DMA_TO_DEVICE); > > return 0; > > @@ -350,8 +349,8 @@ void rockchip_gem_free_object(struct drm_gem_object *obj) > if (private->domain) { > rockchip_gem_iommu_unmap(rk_obj); > } else { > - dma_unmap_sg(drm->dev, rk_obj->sgt->sgl, > - rk_obj->sgt->nents, DMA_BIDIRECTIONAL); > + dma_unmap_sgtable(drm->dev, rk_obj->sgt, > + DMA_BIDIRECTIONAL, 0); > } > drm_prime_gem_destroy(obj, rk_obj->sgt); > } else { > @@ -476,15 +475,13 @@ rockchip_gem_dma_map_sg(struct drm_device *drm, > struct sg_table *sg, > struct rockchip_gem_object *rk_obj) > { > - int count = dma_map_sg(drm->dev, sg->sgl, sg->nents, > - DMA_BIDIRECTIONAL); > - if (!count) > - return -EINVAL; > + int err = dma_map_sgtable(drm->dev, sg, DMA_BIDIRECTIONAL, 0); > + if (err) > + return err; > > if (drm_prime_get_contiguous_size(sg) < attach->dmabuf->size) { > DRM_ERROR("failed to map sg_table to contiguous linear address.\n"); > - dma_unmap_sg(drm->dev, sg->sgl, sg->nents, > - DMA_BIDIRECTIONAL); > + dma_unmap_sgtable(drm->dev, sg, DMA_BIDIRECTIONAL, 0); > return -EINVAL; > } > >