From: Robin Murphy robin.murphy@arm.com
drm_gem_cma_mmap() cannot assume every implementation of dma_mmap_wc() will end up calling remap_pfn_range() (which happens to set the relevant vma flag, among others), so in order to make sure expectations around VM_DONTEXPAND are met, let it explicitly set the flag like most other GEM mmap implementations do.
This avoids repeated warnings on a small minority of systems where the display is behind an IOMMU, and has a simple driver which does not override drm_gem_cma_default_funcs. Arm hdlcd is an in-tree affected driver. Out-of-tree, the Apple DCP driver is affected; this fix is required for DCP to be mainlined.
Signed-off-by: Robin Murphy robin.murphy@arm.com Reviewed-and-tested-by: Alyssa Rosenzweig alyssa@rosenzweig.io --- drivers/gpu/drm/drm_gem_cma_helper.c | 1 + 1 file changed, 1 insertion(+)
diff --git a/drivers/gpu/drm/drm_gem_cma_helper.c b/drivers/gpu/drm/drm_gem_cma_helper.c index d53388199f34..63e48d98263d 100644 --- a/drivers/gpu/drm/drm_gem_cma_helper.c +++ b/drivers/gpu/drm/drm_gem_cma_helper.c @@ -510,6 +510,7 @@ int drm_gem_cma_mmap(struct drm_gem_object *obj, struct vm_area_struct *vma) */ vma->vm_pgoff -= drm_vma_node_start(&obj->vma_node); vma->vm_flags &= ~VM_PFNMAP; + vma->vm_flags |= VM_DONTEXPAND;
cma_obj = to_drm_gem_cma_obj(obj);