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>

0 files changed, 0 insertions, 0 deletions