From: Laurent Pinchart Date: Sun, 2 Mar 2014 19:09:48 +0000 (+0100) Subject: drm/cma: Use dma_mmap_writecombine() to mmap buffer X-Git-Tag: firefly_0821_release~176^2~4105^2~9 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=b65e64f7ccd40762fbd26b24414966d0437e7591;p=firefly-linux-kernel-4.4.55.git drm/cma: Use dma_mmap_writecombine() to mmap buffer The GEM CMA helpers uses a custom mmap implementation based on remap_pfn_range(). While this works when the buffer DMA and physical addresses are identical, it fails to take IOMMU into account and tries to mmap the buffer to userspace using the DMA virtual address instead of the physical address. This results in mapping random physical pages when the device is behind an IOMMU. Use the DMA mapping dma_mmap_writecombine() function instead. Signed-off-by: Laurent Pinchart Tested-by: Philipp Zabel Signed-off-by: Dave Airlie --- diff --git a/drivers/gpu/drm/drm_gem_cma_helper.c b/drivers/gpu/drm/drm_gem_cma_helper.c index 2c07cb9550ef..fbb9df6becb0 100644 --- a/drivers/gpu/drm/drm_gem_cma_helper.c +++ b/drivers/gpu/drm/drm_gem_cma_helper.c @@ -234,8 +234,17 @@ static int drm_gem_cma_mmap_obj(struct drm_gem_cma_object *cma_obj, { int ret; - ret = remap_pfn_range(vma, vma->vm_start, cma_obj->paddr >> PAGE_SHIFT, - vma->vm_end - vma->vm_start, vma->vm_page_prot); + /* + * Clear the VM_PFNMAP flag that was set by drm_gem_mmap(), and set the + * vm_pgoff (used as a fake buffer offset by DRM) to 0 as we want to map + * the whole buffer. + */ + vma->vm_flags &= ~VM_PFNMAP; + vma->vm_pgoff = 0; + + ret = dma_mmap_writecombine(cma_obj->base.dev->dev, vma, + cma_obj->vaddr, cma_obj->paddr, + vma->vm_end - vma->vm_start); if (ret) drm_gem_vm_close(vma);