From 59f39bfa6553d598cb22f694d45e89547f420d85 Mon Sep 17 00:00:00 2001
From: Robin Murphy <robin.murphy@arm.com>
Date: Wed, 13 Oct 2021 10:36:54 -0400
Subject: drm/cma-helper: Set VM_DONTEXPAND for mmap
Git-commit: 59f39bfa6553d598cb22f694d45e89547f420d85
Patch-mainline: v5.17-rc5
References: bsc#1152472

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.

[Alyssa: Update commit message.]

Fixes: c40069cb7bd6 ("drm: add mmap() to drm_gem_object_funcs")
Acked-by: Daniel Vetter <daniel@ffwll.ch>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211013143654.39031-1-alyssa@rosenzweig.io
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
---
 drivers/gpu/drm/drm_gem_cma_helper.c |    1 +
 1 file changed, 1 insertion(+)

--- a/drivers/gpu/drm/drm_gem_cma_helper.c
+++ b/drivers/gpu/drm/drm_gem_cma_helper.c
@@ -277,6 +277,7 @@ static int drm_gem_cma_mmap_obj(struct d
 	 * the whole buffer.
 	 */
 	vma->vm_flags &= ~VM_PFNMAP;
+	vma->vm_flags |= VM_DONTEXPAND;
 	vma->vm_pgoff = 0;
 
 	ret = dma_mmap_wc(cma_obj->base.dev->dev, vma, cma_obj->vaddr,