| Message ID | 20200619103636.11974-9-m.szyprowski@samsung.com (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
| Series | None | expand |
On 19.06.2020 12:36, 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> Reviewed-by <a.hajda@samsung.com> Regards Andrzej > --- > drivers/gpu/drm/exynos/exynos_drm_g2d.c | 10 +++++----- > 1 file changed, 5 insertions(+), 5 deletions(-) > > diff --git a/drivers/gpu/drm/exynos/exynos_drm_g2d.c b/drivers/gpu/drm/exynos/exynos_drm_g2d.c > index fcee33a43aca..7014a8cd971a 100644 > --- a/drivers/gpu/drm/exynos/exynos_drm_g2d.c > +++ b/drivers/gpu/drm/exynos/exynos_drm_g2d.c > @@ -395,8 +395,8 @@ static void g2d_userptr_put_dma_addr(struct g2d_data *g2d, > return; > > out: > - dma_unmap_sg(to_dma_dev(g2d->drm_dev), g2d_userptr->sgt->sgl, > - g2d_userptr->sgt->nents, DMA_BIDIRECTIONAL); > + dma_unmap_sgtable(to_dma_dev(g2d->drm_dev), g2d_userptr->sgt, > + DMA_BIDIRECTIONAL, 0); > > pages = frame_vector_pages(g2d_userptr->vec); > if (!IS_ERR(pages)) { > @@ -511,10 +511,10 @@ static dma_addr_t *g2d_userptr_get_dma_addr(struct g2d_data *g2d, > > g2d_userptr->sgt = sgt; > > - if (!dma_map_sg(to_dma_dev(g2d->drm_dev), sgt->sgl, sgt->nents, > - DMA_BIDIRECTIONAL)) { > + ret = dma_map_sgtable(to_dma_dev(g2d->drm_dev), sgt, > + DMA_BIDIRECTIONAL, 0); > + if (ret) { > DRM_DEV_ERROR(g2d->dev, "failed to map sgt with dma region.\n"); > - ret = -ENOMEM; > goto err_sg_free_table; > } >
On 07.07.2020 11:40, Andrzej Hajda wrote: > On 19.06.2020 12:36, 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> > Just fixing my signature :) Reviewed-by: Andrzej Hajda <a.hajda@samsung.com> Regards Andrzej
20. 6. 19. 오후 7:36에 Marek Szyprowski 이(가) 쓴 글: > 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> Acked-by : Inki Dae <inki.dae@samsung.com> Thanks, Inki Dae > --- > drivers/gpu/drm/exynos/exynos_drm_g2d.c | 10 +++++----- > 1 file changed, 5 insertions(+), 5 deletions(-) > > diff --git a/drivers/gpu/drm/exynos/exynos_drm_g2d.c b/drivers/gpu/drm/exynos/exynos_drm_g2d.c > index fcee33a43aca..7014a8cd971a 100644 > --- a/drivers/gpu/drm/exynos/exynos_drm_g2d.c > +++ b/drivers/gpu/drm/exynos/exynos_drm_g2d.c > @@ -395,8 +395,8 @@ static void g2d_userptr_put_dma_addr(struct g2d_data *g2d, > return; > > out: > - dma_unmap_sg(to_dma_dev(g2d->drm_dev), g2d_userptr->sgt->sgl, > - g2d_userptr->sgt->nents, DMA_BIDIRECTIONAL); > + dma_unmap_sgtable(to_dma_dev(g2d->drm_dev), g2d_userptr->sgt, > + DMA_BIDIRECTIONAL, 0); > > pages = frame_vector_pages(g2d_userptr->vec); > if (!IS_ERR(pages)) { > @@ -511,10 +511,10 @@ static dma_addr_t *g2d_userptr_get_dma_addr(struct g2d_data *g2d, > > g2d_userptr->sgt = sgt; > > - if (!dma_map_sg(to_dma_dev(g2d->drm_dev), sgt->sgl, sgt->nents, > - DMA_BIDIRECTIONAL)) { > + ret = dma_map_sgtable(to_dma_dev(g2d->drm_dev), sgt, > + DMA_BIDIRECTIONAL, 0); > + if (ret) { > DRM_DEV_ERROR(g2d->dev, "failed to map sgt with dma region.\n"); > - ret = -ENOMEM; > goto err_sg_free_table; > } > >
diff --git a/drivers/gpu/drm/exynos/exynos_drm_g2d.c b/drivers/gpu/drm/exynos/exynos_drm_g2d.c index fcee33a43aca..7014a8cd971a 100644 --- a/drivers/gpu/drm/exynos/exynos_drm_g2d.c +++ b/drivers/gpu/drm/exynos/exynos_drm_g2d.c @@ -395,8 +395,8 @@ static void g2d_userptr_put_dma_addr(struct g2d_data *g2d, return; out: - dma_unmap_sg(to_dma_dev(g2d->drm_dev), g2d_userptr->sgt->sgl, - g2d_userptr->sgt->nents, DMA_BIDIRECTIONAL); + dma_unmap_sgtable(to_dma_dev(g2d->drm_dev), g2d_userptr->sgt, + DMA_BIDIRECTIONAL, 0); pages = frame_vector_pages(g2d_userptr->vec); if (!IS_ERR(pages)) { @@ -511,10 +511,10 @@ static dma_addr_t *g2d_userptr_get_dma_addr(struct g2d_data *g2d, g2d_userptr->sgt = sgt; - if (!dma_map_sg(to_dma_dev(g2d->drm_dev), sgt->sgl, sgt->nents, - DMA_BIDIRECTIONAL)) { + ret = dma_map_sgtable(to_dma_dev(g2d->drm_dev), sgt, + DMA_BIDIRECTIONAL, 0); + if (ret) { DRM_DEV_ERROR(g2d->dev, "failed to map sgt with dma region.\n"); - ret = -ENOMEM; goto err_sg_free_table; }
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/exynos/exynos_drm_g2d.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-)