diff options
| author | Daniel Vetter <daniel.vetter@ffwll.ch> | 2023-04-04 14:19:32 +0200 |
|---|---|---|
| committer | Daniel Vetter <daniel.vetter@ffwll.ch> | 2024-01-08 14:01:50 +0100 |
| commit | e44977aeeddd98813161adba4df24132a9601427 (patch) | |
| tree | 30e5499776678d3803ad6c6970d807634f37336c | |
| parent | 8136fd6b763ea20cbee782d85363f27c64fb3139 (diff) | |
drm/dma-helpers: Don't change vma flags
This code was added in b65e64f7ccd4 ("drm/cma: Use
dma_mmap_writecombine() to mmap buffer"), but does not explain why
it's needed.
It should be entirely unnecessary, because remap_pfn_range(), which is
what the various dma_mmap functiosn are built on top of, does already
unconditionally adjust the vma flags:
https://elixir.bootlin.com/linux/v6.1-rc6/source/mm/memory.c#L2518
More importantly, it does uncondtionally set VM_PFNMAP, so clearing
that does not make much sense.
Patch motived by discussions around enforcing VM_PFNMAP semantics for
all dma-buf users, where Thomas asked why dma helpers will work with
that dma_buf_mmap() contract.
FIXME: There are dma implementations which don't set VM_PFNMAP. This
is a can of worms.
References: https://lore.kernel.org/dri-devel/5c3c8d4f-2c06-9210-b00a-4d0ff6f6fbb7@suse.de/
Cc: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Cc: Dave Airlie <airlied@redhat.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Cc: "Christian König" <christian.koenig@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
| -rw-r--r-- | drivers/gpu/drm/drm_gem_dma_helper.c | 6 |
1 files changed, 2 insertions, 4 deletions
diff --git a/drivers/gpu/drm/drm_gem_dma_helper.c b/drivers/gpu/drm/drm_gem_dma_helper.c index 870b90b78bc4..d1f2a358f441 100644 --- a/drivers/gpu/drm/drm_gem_dma_helper.c +++ b/drivers/gpu/drm/drm_gem_dma_helper.c @@ -525,12 +525,10 @@ int drm_gem_dma_mmap(struct drm_gem_dma_object *dma_obj, struct vm_area_struct * int ret; /* - * 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. + * Set the vm_pgoff (used as a fake buffer offset by DRM) to 0 as we + * want to map the whole buffer. */ vma->vm_pgoff -= drm_vma_node_start(&obj->vma_node); - vm_flags_mod(vma, VM_DONTEXPAND, VM_PFNMAP); if (dma_obj->map_noncoherent) { vma->vm_page_prot = vm_get_page_prot(vma->vm_flags); |