From: Robin Murphy <robin.murphy@arm.com>
To: Marek Szyprowski <m.szyprowski@samsung.com>,
dri-devel@lists.freedesktop.org,
iommu@lists.linux-foundation.org, linaro-mm-sig@lists.linaro.org,
linux-kernel@vger.kernel.org
Cc: Christoph Hellwig <hch@lst.de>,
Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
linux-arm-kernel@lists.infradead.org,
David Airlie <airlied@linux.ie>, Daniel Vetter <daniel@ffwll.ch>,
Russell King <linux@armlinux.org.uk>
Subject: Re: [PATCH v9 04/32] drm: armada: fix common struct sg_table related issues
Date: Tue, 1 Sep 2020 19:26:32 +0100 [thread overview]
Message-ID: <f3a3e178-4d52-7015-1913-bf44993f07f3@arm.com> (raw)
In-Reply-To: <20200826063316.23486-5-m.szyprowski@samsung.com>
On 2020-08-26 07:32, 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.
>
> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
> ---
> drivers/gpu/drm/armada/armada_gem.c | 12 ++++++------
> 1 file changed, 6 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/gpu/drm/armada/armada_gem.c b/drivers/gpu/drm/armada/armada_gem.c
> index 8005614d2e6b..bedd8937d8a1 100644
> --- a/drivers/gpu/drm/armada/armada_gem.c
> +++ b/drivers/gpu/drm/armada/armada_gem.c
> @@ -395,7 +395,7 @@ armada_gem_prime_map_dma_buf(struct dma_buf_attachment *attach,
>
> mapping = dobj->obj.filp->f_mapping;
>
> - for_each_sg(sgt->sgl, sg, count, i) {
> + for_each_sgtable_sg(sgt, sg, i) {
> struct page *page;
>
> page = shmem_read_mapping_page(mapping, i);
> @@ -407,8 +407,8 @@ armada_gem_prime_map_dma_buf(struct dma_buf_attachment *attach,
> sg_set_page(sg, page, PAGE_SIZE, 0);
> }
>
> - if (dma_map_sg(attach->dev, sgt->sgl, sgt->nents, dir) == 0) {
> - num = sgt->nents;
> + if (dma_map_sgtable(attach->dev, sgt, dir, 0)) {
> + num = count;
I think it might be even nicer to get rid of "num" entirely and convert
the cleanup path to for_each_sgtable_sg() for completeness - AFAICS it
should only need an extra "if (sg_page(sg))..." check in that loop. Then
"count" could possibly be squashed into its one remaining use as well,
but maybe it's worth keeping for readability.
Robin.
> goto release;
> }
> } else if (dobj->page) {
> @@ -418,7 +418,7 @@ armada_gem_prime_map_dma_buf(struct dma_buf_attachment *attach,
>
> sg_set_page(sgt->sgl, dobj->page, dobj->obj.size, 0);
>
> - if (dma_map_sg(attach->dev, sgt->sgl, sgt->nents, dir) == 0)
> + if (dma_map_sgtable(attach->dev, sgt, dir, 0))
> goto free_table;
> } else if (dobj->linear) {
> /* Single contiguous physical region - no struct page */
> @@ -449,11 +449,11 @@ static void armada_gem_prime_unmap_dma_buf(struct dma_buf_attachment *attach,
> int i;
>
> if (!dobj->linear)
> - dma_unmap_sg(attach->dev, sgt->sgl, sgt->nents, dir);
> + dma_unmap_sgtable(attach->dev, sgt, dir, 0);
>
> if (dobj->obj.filp) {
> struct scatterlist *sg;
> - for_each_sg(sgt->sgl, sg, sgt->nents, i)
> + for_each_sgtable_sg(sgt, sg, i)
> put_page(sg_page(sg));
> }
>
>
next prev parent reply other threads:[~2020-09-01 18:26 UTC|newest]
Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CGME20200826063527eucas1p21ab50cf46bad1d9ea5d7f202dd6ec722@eucas1p2.samsung.com>
2020-08-26 6:32 ` [PATCH v9 00/32] DRM: fix struct sg_table nents vs. orig_nents misuse Marek Szyprowski
[not found] ` <CGME20200826063527eucas1p1d68954adf1c25e1d760b92ca0845ab48@eucas1p1.samsung.com>
2020-08-26 6:32 ` [PATCH v9 01/32] drm: prime: add common helper to check scatterlist contiguity Marek Szyprowski
2020-09-01 17:23 ` Robin Murphy
[not found] ` <CGME20200826063528eucas1p1502c849c0fd337245541e1b31352d87f@eucas1p1.samsung.com>
2020-08-26 6:32 ` [PATCH v9 02/32] drm: prime: use sgtable iterators in drm_prime_sg_to_page_addr_arrays() Marek Szyprowski
2020-09-01 17:24 ` Robin Murphy
[not found] ` <CGME20200826063529eucas1p19d797cf74bf653bf68b0a0e860806dbf@eucas1p1.samsung.com>
2020-08-26 6:32 ` [PATCH v9 03/32] drm: core: fix common struct sg_table related issues Marek Szyprowski
2020-09-01 17:46 ` Robin Murphy
[not found] ` <CGME20200826063529eucas1p24a398fd2bacf53a33a14d7977a097f61@eucas1p2.samsung.com>
2020-08-26 6:32 ` [PATCH v9 04/32] drm: armada: " Marek Szyprowski
2020-09-01 18:26 ` Robin Murphy [this message]
[not found] ` <CGME20200826063530eucas1p16acb847d7da0ea734bef507688a76c5a@eucas1p1.samsung.com>
2020-08-26 6:32 ` [PATCH v9 05/32] drm: etnaviv: " Marek Szyprowski
2020-09-01 18:39 ` Robin Murphy
[not found] ` <CGME20200826063531eucas1p21c9277fe2a91e632e40822fb04a2c095@eucas1p2.samsung.com>
2020-08-26 6:32 ` [PATCH v9 06/32] drm: exynos: use common helper for a scatterlist contiguity check Marek Szyprowski
[not found] ` <CGME20200826063531eucas1p18dbb3c42b2ecc490360e7a75cf579af6@eucas1p1.samsung.com>
2020-08-26 6:32 ` [PATCH v9 07/32] drm: exynos: fix common struct sg_table related issues Marek Szyprowski
[not found] ` <CGME20200826063532eucas1p2a9e0215f483104d45af0560d5dbfa8e0@eucas1p2.samsung.com>
2020-08-26 6:32 ` [PATCH v9 08/32] drm: i915: " Marek Szyprowski
2020-09-01 18:42 ` Robin Murphy
2020-09-01 19:38 ` [Intel-gfx] " Ruhl, Michael J
2020-09-01 19:54 ` Robin Murphy
2020-09-01 20:32 ` Ruhl, Michael J
[not found] ` <CGME20200826063533eucas1p1e346ac4a683f929be8adc344b3fe9ea0@eucas1p1.samsung.com>
2020-08-26 6:32 ` [PATCH v9 09/32] drm: lima: " Marek Szyprowski
[not found] ` <CGME20200826063533eucas1p1fad2f2afb117b026081468d2d840ab0f@eucas1p1.samsung.com>
2020-08-26 6:32 ` [PATCH v9 10/32] drm: mediatek: use common helper for a scatterlist contiguity check Marek Szyprowski
2020-09-01 18:44 ` Robin Murphy
2020-09-01 22:59 ` Chun-Kuang Hu
[not found] ` <CGME20200826063534eucas1p2647f5e9679f79f568e184b092f743f8b@eucas1p2.samsung.com>
2020-08-26 6:32 ` [PATCH v9 11/32] drm: mediatek: use common helper for extracting pages array Marek Szyprowski
2020-09-01 18:54 ` Robin Murphy
2020-09-01 23:16 ` Chun-Kuang Hu
[not found] ` <CGME20200826063535eucas1p10cef37d8364216cf57c97e96d3959dd2@eucas1p1.samsung.com>
2020-08-26 6:32 ` [PATCH v9 12/32] drm: msm: fix common struct sg_table related issues Marek Szyprowski
2020-09-01 19:14 ` Robin Murphy
2020-09-01 23:48 ` Rob Clark
[not found] ` <CGME20200826063535eucas1p1a98e3295a64f14d475371ac0b003782f@eucas1p1.samsung.com>
2020-08-26 6:32 ` [PATCH v9 13/32] drm: omapdrm: use common helper for extracting pages array Marek Szyprowski
2020-09-01 19:17 ` Robin Murphy
[not found] ` <CGME20200826063536eucas1p2e29d2b061b8b74c06c9ea61ad6737ba2@eucas1p2.samsung.com>
2020-08-26 6:32 ` [PATCH v9 14/32] drm: omapdrm: fix common struct sg_table related issues Marek Szyprowski
2020-09-01 19:33 ` Robin Murphy
2020-09-02 8:00 ` Tomi Valkeinen
2020-09-04 12:06 ` Marek Szyprowski
2020-09-04 12:27 ` Marek Szyprowski
[not found] ` <CGME20200826063536eucas1p2d9ea013228bcfbd5778959274aa01b78@eucas1p2.samsung.com>
2020-08-26 6:32 ` [PATCH v9 15/32] drm: panfrost: " Marek Szyprowski
[not found] ` <CGME20200826063537eucas1p1462d4761c8eb6d762fe5ea0fbd3b6e3b@eucas1p1.samsung.com>
2020-08-26 6:33 ` [PATCH v9 16/32] drm: rockchip: use common helper for a scatterlist contiguity check Marek Szyprowski
2020-09-01 19:34 ` Robin Murphy
[not found] ` <CGME20200826063537eucas1p2d9a362f619920ad84c46f36cd13ec362@eucas1p2.samsung.com>
2020-08-26 6:33 ` [PATCH v9 17/32] drm: rockchip: fix common struct sg_table related issues Marek Szyprowski
2020-09-01 20:00 ` Robin Murphy
[not found] ` <CGME20200826063538eucas1p2a9fe42c2ccee634c41ba9f3dd43dc3c4@eucas1p2.samsung.com>
2020-08-26 6:33 ` [PATCH v9 18/32] drm: tegra: " Marek Szyprowski
2020-09-01 20:11 ` Robin Murphy
[not found] ` <CGME20200826063539eucas1p2ed946c6214cdb8574ab288350db22f1a@eucas1p2.samsung.com>
2020-08-26 6:33 ` [PATCH v9 19/32] drm: v3d: " Marek Szyprowski
[not found] ` <CGME20200826063539eucas1p2cb72ff20abae82c3e027833f958fd7a1@eucas1p2.samsung.com>
2020-08-26 6:33 ` [PATCH v9 20/32] drm: virtio: " Marek Szyprowski
[not found] ` <CGME20200826063540eucas1p2e9f9f9133322205269e50fd01bf64bcc@eucas1p2.samsung.com>
2020-08-26 6:33 ` [PATCH v9 21/32] drm: vmwgfx: " Marek Szyprowski
[not found] ` <CGME20200826063540eucas1p2dc6829c66ae13b8e787ca40b9aede3df@eucas1p2.samsung.com>
2020-08-26 6:33 ` [PATCH v9 22/32] drm: xen: " Marek Szyprowski
[not found] ` <CGME20200826063541eucas1p2ec5d8a396f52ce690641659b74819e60@eucas1p2.samsung.com>
2020-08-26 6:33 ` [PATCH v9 23/32] xen: gntdev: " Marek Szyprowski
[not found] ` <CGME20200826063542eucas1p1713d37f4589ddaca27e1968b5fe44027@eucas1p1.samsung.com>
2020-08-26 6:33 ` [PATCH v9 24/32] drm: host1x: " Marek Szyprowski
2020-09-01 20:13 ` Robin Murphy
[not found] ` <CGME20200826063542eucas1p18d9d201e3e26c08d26c3ea2a2b2a079d@eucas1p1.samsung.com>
2020-08-26 6:33 ` [PATCH v9 25/32] drm: rcar-du: " Marek Szyprowski
[not found] ` <CGME20200826063543eucas1p1c2fde4802f125f25caa02f4453b8a284@eucas1p1.samsung.com>
2020-08-26 6:33 ` [PATCH v9 26/32] dmabuf: " Marek Szyprowski
[not found] ` <CGME20200826063544eucas1p230abe33c28618e82608c5b40eb50fa87@eucas1p2.samsung.com>
2020-08-26 6:33 ` [PATCH v9 27/32] staging: tegra-vde: " Marek Szyprowski
[not found] ` <CGME20200826063544eucas1p15980885bbdbc43e35f350f228994bee7@eucas1p1.samsung.com>
2020-08-26 6:33 ` [PATCH v9 28/32] misc: fastrpc: " Marek Szyprowski
2020-09-01 20:14 ` Robin Murphy
[not found] ` <CGME20200826063545eucas1p22eb2c7a643a299f3e1696b4c5bae0694@eucas1p2.samsung.com>
2020-08-26 6:33 ` [PATCH v9 29/32] rapidio: " Marek Szyprowski
2020-09-01 20:15 ` Robin Murphy
[not found] ` <CGME20200826063546eucas1p268558dcd08ac9b43843f9f5e23da227d@eucas1p2.samsung.com>
2020-08-26 6:33 ` [PATCH v9 30/32] samples: vfio-mdev/mbochs: " Marek Szyprowski
2020-09-01 20:16 ` Robin Murphy
[not found] ` <CGME20200826063629eucas1p1a3c9c93e281b4c432a6d9940e734e3c4@eucas1p1.samsung.com>
2020-08-26 6:33 ` [PATCH v9 31/32] media: pci: fix common ALSA DMA-mapping related codes Marek Szyprowski
2020-09-01 20:24 ` Robin Murphy
[not found] ` <CGME20200826063629eucas1p194665c749b5a37c74e6445370fd7f7c4@eucas1p1.samsung.com>
2020-08-26 6:33 ` [PATCH v9 32/32] videobuf2: use sgtable-based scatterlist wrappers Marek Szyprowski
2020-09-01 20:19 ` Robin Murphy
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