Hi Christoph ,
On Wed, Nov 28, 2018 at 1:10 PM Christoph Hellwig hch@infradead.org wrote:
/** dma_sync_sg_*() flush the physical pages, so point* sg->dma_address to the physical ones for the right behavior.*/for_each_sg(msm_obj->sgt->sgl, s, msm_obj->sgt->nents, i)sg_dma_address(s) = sg_phys(s);I'm sorry, but this is completely bogus and not acceptable.
The only place that is allowed to initialize sg_dma_address is dma_map_sg. If the default dma ops don't work for your setup we have major a problem and need to fix the dma api / iommu integration instead of hacking around it.
Thanks for reviewing this change.
From what I understand the things in drm, we don't use the default
iommu-dma domain for drm devices. Rather we allocate a new iommu domain, and therefore we can't use the default dma ops. Hence we need separate dma_sync_sg*() to flush/invalidate the cache. For this we need to initialize the sg's addresses.
Please correct me if my understanding is incomplete.
Best regards Vivek
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