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=-6.5 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 79C03C2D0FD for ; Wed, 13 May 2020 14:23:12 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 4298B204EA for ; Wed, 13 May 2020 14:23:12 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b="pH1mj81L" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4298B204EA Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=ideasonboard.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=dri-devel-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id C6C766E18E; Wed, 13 May 2020 14:23:11 +0000 (UTC) Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [213.167.242.64]) by gabe.freedesktop.org (Postfix) with ESMTPS id 206B46E18E for ; Wed, 13 May 2020 14:23:10 +0000 (UTC) Received: from pendragon.ideasonboard.com (81-175-216-236.bb.dnainternet.fi [81.175.216.236]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id 6D87851F; Wed, 13 May 2020 16:23:08 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1589379788; bh=5O0na2DMiyEwLbl3btgk9akjCBMQkQ7SFKipuPV1wEA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=pH1mj81La2wuE/YKdMXdaFC6dPVPCdpdSi0cuzqw8PjTHID3iK73wYjzUCAE4HvrR zN4hlCqtr1aD6xyomzlUiZrk1MQX1W3Bf9lN5A5B5od6IilQufrh8/enV5IVqdJkjO bB3T1akcTlxGSYFdE9fzoJ30Xmff9mcari/gTrDc= Date: Wed, 13 May 2020 17:23:02 +0300 From: Laurent Pinchart To: Marek Szyprowski Subject: Re: [PATCH v5 29/38] drm: rcar-du: fix common struct sg_table related issues Message-ID: <20200513142302.GK5945@pendragon.ideasonboard.com> References: <20200513132114.6046-1-m.szyprowski@samsung.com> <20200513133245.6408-1-m.szyprowski@samsung.com> <20200513133245.6408-29-m.szyprowski@samsung.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200513133245.6408-29-m.szyprowski@samsung.com> X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-renesas-soc@vger.kernel.org, Bartlomiej Zolnierkiewicz , David Airlie , linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org, iommu@lists.linux-foundation.org, Kieran Bingham , Mauro Carvalho Chehab , Robin Murphy , Christoph Hellwig , linux-arm-kernel@lists.infradead.org, linux-media@vger.kernel.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" Hi Marek, Thank you for the patch. On Wed, May 13, 2020 at 03:32:36PM +0200, 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. > > dma_map_sgtable() function returns zero or an error code, so adjust the > return value check for the vsp1_du_map_sg() function. > > Signed-off-by: Marek Szyprowski This is a very nice simplification, I've always foudn the dma_map_sg API cumbersome to use. Reviewed-by: Laurent Pinchart I assume you will get the whole series merged in one go. If I need to pick the patch up at any point, please let me know. Otherwise I'll wait until I see it upstream, no reply needed :-) > --- > For more information, see '[PATCH v5 00/38] DRM: fix struct sg_table nents > vs. orig_nents misuse' thread: > https://lore.kernel.org/linux-iommu/20200513132114.6046-1-m.szyprowski@samsung.com/T/ > --- > drivers/gpu/drm/rcar-du/rcar_du_vsp.c | 3 +-- > drivers/media/platform/vsp1/vsp1_drm.c | 8 ++++---- > 2 files changed, 5 insertions(+), 6 deletions(-) > > diff --git a/drivers/gpu/drm/rcar-du/rcar_du_vsp.c b/drivers/gpu/drm/rcar-du/rcar_du_vsp.c > index 5e4faf2..2fc1816 100644 > --- a/drivers/gpu/drm/rcar-du/rcar_du_vsp.c > +++ b/drivers/gpu/drm/rcar-du/rcar_du_vsp.c > @@ -197,9 +197,8 @@ int rcar_du_vsp_map_fb(struct rcar_du_vsp *vsp, struct drm_framebuffer *fb, > goto fail; > > ret = vsp1_du_map_sg(vsp->vsp, sgt); > - if (!ret) { > + if (ret) { > sg_free_table(sgt); > - ret = -ENOMEM; > goto fail; > } > } > diff --git a/drivers/media/platform/vsp1/vsp1_drm.c b/drivers/media/platform/vsp1/vsp1_drm.c > index a4a45d6..86d5e3f 100644 > --- a/drivers/media/platform/vsp1/vsp1_drm.c > +++ b/drivers/media/platform/vsp1/vsp1_drm.c > @@ -912,8 +912,8 @@ int vsp1_du_map_sg(struct device *dev, struct sg_table *sgt) > * skip cache sync. This will need to be revisited when support for > * non-coherent buffers will be added to the DU driver. > */ > - return dma_map_sg_attrs(vsp1->bus_master, sgt->sgl, sgt->nents, > - DMA_TO_DEVICE, DMA_ATTR_SKIP_CPU_SYNC); > + return dma_map_sgtable(vsp1->bus_master, sgt, DMA_TO_DEVICE, > + DMA_ATTR_SKIP_CPU_SYNC); > } > EXPORT_SYMBOL_GPL(vsp1_du_map_sg); > > @@ -921,8 +921,8 @@ void vsp1_du_unmap_sg(struct device *dev, struct sg_table *sgt) > { > struct vsp1_device *vsp1 = dev_get_drvdata(dev); > > - dma_unmap_sg_attrs(vsp1->bus_master, sgt->sgl, sgt->nents, > - DMA_TO_DEVICE, DMA_ATTR_SKIP_CPU_SYNC); > + dma_unmap_sgtable(vsp1->bus_master, sgt, DMA_TO_DEVICE, > + DMA_ATTR_SKIP_CPU_SYNC); > } > EXPORT_SYMBOL_GPL(vsp1_du_unmap_sg); > -- Regards, Laurent Pinchart _______________________________________________ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel