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,