* [PATCH v3 18/25] drm: rcar-du: fix common struct sg_table related issues
[not found] ` <CGME20200505084634eucas1p1e0ea160dd77afbf6d2f7e6154ded40d0@eucas1p1.samsung.com>
@ 2020-05-05 8:46 ` Marek Szyprowski
2020-05-05 9:24 ` Geert Uytterhoeven
0 siblings, 1 reply; 2+ messages in thread
From: Marek Szyprowski @ 2020-05-05 8:46 UTC (permalink / raw)
To: dri-devel, iommu, linaro-mm-sig, linux-kernel
Cc: Marek Szyprowski, Christoph Hellwig, Robin Murphy,
Bartlomiej Zolnierkiewicz, linux-arm-kernel, David Airlie,
Daniel Vetter, Mauro Carvalho Chehab, Laurent Pinchart,
Kieran Bingham, linux-media, linux-renesas-soc
The Documentation/DMA-API-HOWTO.txt states that dma_map_sg returns the
numer of the created entries in the DMA address space. However the
subsequent calls to dma_sync_sg_for_{device,cpu} and dma_unmap_sg must be
called with the original number of the entries passed to dma_map_sg. The
sg_table->nents in turn holds the result of the dma_map_sg call as stated
in include/linux/scatterlist.h. A common mistake was to ignore a result
of the dma_map_sg function and don't use the sg_table->orig_nents at all.
To avoid such issues, lets use common dma-mapping wrappers operating
directly on the struct sg_table objects and adjust references to the
nents and orig_nents respectively.
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
---
For more information, see '[PATCH v3 00/25] DRM: fix struct sg_table nents
vs. orig_nents misuse' thread: https://lkml.org/lkml/2020/5/5/187
---
drivers/media/platform/vsp1/vsp1_drm.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/drivers/media/platform/vsp1/vsp1_drm.c b/drivers/media/platform/vsp1/vsp1_drm.c
index a4a45d6..8a2624b 100644
--- a/drivers/media/platform/vsp1/vsp1_drm.c
+++ b/drivers/media/platform/vsp1/vsp1_drm.c
@@ -912,8 +912,9 @@ 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_attrs(vsp1->bus_master, sgt, DMA_TO_DEVICE,
+ DMA_ATTR_SKIP_CPU_SYNC);
+ return sgt->nents;
}
EXPORT_SYMBOL_GPL(vsp1_du_map_sg);
@@ -921,8 +922,8 @@ 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_attrs(vsp1->bus_master, sgt, DMA_TO_DEVICE,
+ DMA_ATTR_SKIP_CPU_SYNC);
}
EXPORT_SYMBOL_GPL(vsp1_du_unmap_sg);
--
1.9.1
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH v3 18/25] drm: rcar-du: fix common struct sg_table related issues
2020-05-05 8:46 ` [PATCH v3 18/25] drm: rcar-du: fix common struct sg_table related issues Marek Szyprowski
@ 2020-05-05 9:24 ` Geert Uytterhoeven
0 siblings, 0 replies; 2+ messages in thread
From: Geert Uytterhoeven @ 2020-05-05 9:24 UTC (permalink / raw)
To: Marek Szyprowski
Cc: DRI Development, Linux IOMMU, linaro-mm-sig,
Linux Kernel Mailing List, Christoph Hellwig, Robin Murphy,
Bartlomiej Zolnierkiewicz, Linux ARM, David Airlie,
Daniel Vetter, Mauro Carvalho Chehab, Laurent Pinchart,
Kieran Bingham, Linux Media Mailing List, Linux-Renesas
Hi Marek,
On Tue, May 5, 2020 at 10:48 AM Marek Szyprowski
<m.szyprowski@samsung.com> wrote:
> The Documentation/DMA-API-HOWTO.txt states that dma_map_sg returns the
> numer of the created entries in the DMA address space. However the
> subsequent calls to dma_sync_sg_for_{device,cpu} and dma_unmap_sg must be
> called with the original number of the entries passed to dma_map_sg. The
> sg_table->nents in turn holds the result of the dma_map_sg call as stated
> in include/linux/scatterlist.h. A common mistake was to ignore a result
> of the dma_map_sg function and don't use the sg_table->orig_nents at all.
>
> To avoid such issues, lets use common dma-mapping wrappers operating
> directly on the struct sg_table objects and adjust references to the
> nents and orig_nents respectively.
>
> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
> ---
> For more information, see '[PATCH v3 00/25] DRM: fix struct sg_table nents
> vs. orig_nents misuse' thread: https://lkml.org/lkml/2020/5/5/187
For the modern lore-users:
https://lore.kernel.org/r/20200505083926.28503-1-m.szyprowski@samsung.com/
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
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2020-05-05 8:46 ` [PATCH v3 18/25] drm: rcar-du: fix common struct sg_table related issues Marek Szyprowski
2020-05-05 9:24 ` Geert Uytterhoeven
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