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Date: Wed, 1 Nov 2017 14:14:19 +0000 From: Liviu Dudau <Liviu.Dudau@....com> To: Brian Starkey <brian.starkey@....com> Cc: Mali DP Maintainers <malidp@...s.arm.com>, Daniel Vetter <daniel.vetter@...el.com>, David Airlie <airlied@...ux.ie>, DRI-devel <dri-devel@...ts.freedesktop.org>, LKML <linux-kernel@...r.kernel.org>, Jani Nikula <jani.nikula@...ux.intel.com>, Sean Paul <seanpaul@...omium.org>, Liviu Dudau <liviu.dudau@....com> Subject: [PATCH] drm: gem_cma_helper.c: Allow importing of contiguous scatterlists with nents > 1 drm_gem_cma_prime_import_sg_table() will fail if the number of entries in the sg_table > 1. However, you can have a device that uses an IOMMU engine and can map a discontiguous buffer with multiple entries that have consecutive sg_dma_addresses, effectively making it contiguous. Allow for that scenario by testing the entries in the sg_table for contiguous coverage. Reviewed-by: Brian Starkey <brian.starkey@....com> Signed-off-by: Liviu Dudau <liviu.dudau@....com> --- Hi, This patch is the only change I need in order to be able to use existing IOMMU domain infrastructure with the Mali DP driver. I have tested the patch and I know it works correctly for my setup, but I would like to get some comments on whether I am on the right path or if CMA really wants to see an sg_table with only one entry. Best regards, Liviu drivers/gpu/drm/drm_gem_cma_helper.c | 22 ++++++++++++++++++++-- 1 file changed, 20 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/drm_gem_cma_helper.c b/drivers/gpu/drm/drm_gem_cma_helper.c index 020e7668dfaba..43b179212052d 100644 --- a/drivers/gpu/drm/drm_gem_cma_helper.c +++ b/drivers/gpu/drm/drm_gem_cma_helper.c @@ -482,8 +482,26 @@ drm_gem_cma_prime_import_sg_table(struct drm_device *dev, { struct drm_gem_cma_object *cma_obj; - if (sgt->nents != 1) - return ERR_PTR(-EINVAL); + if (sgt->nents != 1) { + /* check if the entries in the sg_table are contiguous */ + dma_addr_t next_addr = sg_dma_address(sgt->sgl); + struct scatterlist *s; + unsigned int i; + + for_each_sg(sgt->sgl, s, sgt->nents, i) { + /* + * sg_dma_address(s) is only valid for entries + * that have sg_dma_len(s) != 0 + */ + if (!sg_dma_len(s)) + continue; + + if (sg_dma_address(s) != next_addr) + return ERR_PTR(-EINVAL); + + next_addr = sg_dma_address(s) + sg_dma_len(s); + } + } /* Create a CMA GEM buffer. */ cma_obj = __drm_gem_cma_create(dev, attach->dmabuf->size); -- 2.14.3
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