From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754701AbdKAOOb (ORCPT ); Wed, 1 Nov 2017 10:14:31 -0400 Received: from fw-tnat.cambridge.arm.com ([217.140.96.140]:12530 "EHLO cam-smtp0.cambridge.arm.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754625AbdKAOOa (ORCPT ); Wed, 1 Nov 2017 10:14:30 -0400 From: Liviu Dudau To: Brian Starkey Cc: Mali DP Maintainers , Daniel Vetter , David Airlie , DRI-devel , LKML , Jani Nikula , Sean Paul , Liviu Dudau Subject: [PATCH] drm: gem_cma_helper.c: Allow importing of contiguous scatterlists with nents > 1 Date: Wed, 1 Nov 2017 14:14:19 +0000 Message-Id: <20171101141419.3180-1-Liviu.Dudau@arm.com> X-Mailer: git-send-email 2.14.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 Signed-off-by: Liviu Dudau --- 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