Exynos GEM objects contains an array of pointers to the pages, which the
allocated buffer consists of. Till now the code used some hacks (like
relying on DMA-mapping internal structures or using ARM-specific
dma_to_pfn helper) to build this array. This patch fixes this by adding
proper call to dma_get_sgtable_attrs() and using the acquired scatter-list
to construct needed array. This approach is more portable (work also for
ARM64) and finally fixes the layering violation that was present in this
code.
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>
Struct of gem object in exynos_drm driver is struct exynos_drm_gem_obj.
It's too long and we can know its meaning of name without _obj postfix.
We use several names to variable name of gem object for exynos_drm -
exynos_gem_obj, gem_obj and obj. Especially "obj" name can cause
misunderstanding with variable name "obj" of struct drm_gem_object.
This will clean about name of gem object for exynos_drm as follows.
s/struct exynos_drm_gem_obj/struct exynos_drm_gem
s/exynos_gem_obj or gem_obj or obj/exynos_gem
Signed-off-by: Joonyoung Shim <jy0922.shim@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>
The exynos_drm_gem_mmap_buffer() is not used outside so make it static.
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>
Don't create a fake mmap offset in exynos_drm_gem_dumb_map_offset. If
not, it will call drm_gem_create_mmap_offset whenever user requests
DRM_IOCTL_MODE_MAP_DUMB ioctl.
Signed-off-by: Joonyoung Shim <jy0922.shim@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>
The drm_gem_object_release() function already performs this cleanup,
so there is no reason to do it explicitly.
Signed-off-by: Joonyoung Shim <jy0922.shim@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>
The beginning of statement in function is next line of a brace.
Signed-off-by: Joonyoung Shim <jy0922.shim@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>
By if statment, some function callings are written twice. It needs
several line feed by indentation in if statment. Make to one function
calling from outside if statment.
Signed-off-by: Joonyoung Shim <jy0922.shim@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>
The exynos_drm_gem_init() is used only in exynos_drm_gem.c file. Make it
static and don't export it.
Signed-off-by: Joonyoung Shim <jy0922.shim@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>
They will be freed right or was freed already, so NULL assignment is
unnecessary.
Signed-off-by: Joonyoung Shim <jy0922.shim@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>
When obj->import_attach is existed, code calling drm_prime_gem_destroy()
was removed from commit 67e93c808b ("drm/exynos: stop copying sg
table"), and it's a fault.
The drm_prime_gem_destroy() is cleanup function which GEM drivers need
to call when they use drm_gem_prime_import() to import dma-bufs, so
exynos-drm driver using drm_gem_prime_import() needs calling
drm_prime_gem_destroy().
Signed-off-by: Joonyoung Shim <jy0922.shim@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>
There is no guarantee that DMA addresses are the same as physical
addresses, but dma_to_pfn() knows how to convert a dma_addr_t to a PFN
which can then be converted to a struct page.
Suggested-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Joonyoung Shim <jy0922.shim@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>
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Merge tag 'media/v4.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media
Pull media updates from Mauro Carvalho Chehab:
"A series of patches that move part of the code used to allocate memory
from the media subsystem to the mm subsystem"
[ The mm parts have been acked by VM people, and the series was
apparently in -mm for a while - Linus ]
* tag 'media/v4.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media:
[media] drm/exynos: Convert g2d_userptr_get_dma_addr() to use get_vaddr_frames()
[media] media: vb2: Remove unused functions
[media] media: vb2: Convert vb2_dc_get_userptr() to use frame vector
[media] media: vb2: Convert vb2_vmalloc_get_userptr() to use frame vector
[media] media: vb2: Convert vb2_dma_sg_get_userptr() to use frame vector
[media] vb2: Provide helpers for mapping virtual addresses
[media] media: omap_vout: Convert omap_vout_uservirt_to_phys() to use get_vaddr_pfns()
[media] mm: Provide new get_vaddr_frames() helper
[media] vb2: Push mmap_sem down to memops
Convert g2d_userptr_get_dma_addr() to pin pages using get_vaddr_frames().
This removes the knowledge about vmas and mmap_sem locking from exynos
driver. Also it fixes a problem that the function has been mapping user
provided address without holding mmap_sem.
Acked-by: Inki Dae <inki.dae@samsung.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
The struct exynos_drm_gem_obj can have fields of the struct
exynos_drm_gem_buf then don't need to use exynos_drm_buf.c file.
Signed-off-by: Joonyoung Shim <jy0922.shim@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>
The dma-buf codes of exynos drm is almost same with prime helpers. A
difference is that consider DMA_NONE when import dma-buf, but it's wrong
and we don't consider it any more, so we can use prime interface.
Signed-off-by: Joonyoung Shim <jy0922.shim@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>
The function roundup_gem_size can be merged in exynos_drm_gem_create.
Signed-off-by: Joonyoung Shim <jy0922.shim@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>
The function update_vm_cache_attr can be merged in exynos_drm_gem_mmap.
Signed-off-by: Joonyoung Shim <jy0922.shim@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>
The function check_gem_flags is too simple, so it's better to move codes
in each consumer functions.
Signed-off-by: Joonyoung Shim <jy0922.shim@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>
Already struct exynos_drm_gem_buf has pages of the buffer, so we don't
need to copy from sg table of the buffer to sg table of dma-buf
attachment, just can make sg table from pages of the buffer.
Signed-off-by: Joonyoung Shim <jy0922.shim@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>
The exynos_drm_gem_map_buf can be merged in exynos_drm_gem_fault.
Signed-off-by: Joonyoung Shim <jy0922.shim@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>
There is no reason to use mutex locking in pagefault handler.
Signed-off-by: Joonyoung Shim <jy0922.shim@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>
The convert_to_vm_err_msg is called just once by exynos_drm_gem_fault,
so it's simple not to use the function.
Signed-off-by: Joonyoung Shim <jy0922.shim@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>
Already struct exynos_drm_gem_buf has pages of the buffer when buffer is
created, so just can use pages in page fault handler, we don't have to
make sgtable of the buffer. But this needs to construct pages of the
buffer that is imported from dma-buf prime.
Signed-off-by: Joonyoung Shim <jy0922.shim@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>
This patch removes DRM_EXYNOS_GEM_MMAP ictrl feature specific
to Exynos drm and instead uses drm generic mmap.
We had used the interface specific to Exynos drm to do mmap directly,
not to use demand paging which maps each page with physical memory
at page fault handler. We don't need the specific mmap interface
because the drm generic mmap which uses vm offset manager stuff can
also do mmap directly.
This patch makes a userspace region to be mapped with whole physical
memory region allocated by userspace request when mmap system call is
requested.
Changelog v2:
- do not set VM_IO, VM_DONTEXPEND and VM_DONTDUMP. These flags were already
set by drm_gem_mmap
- do not include <linux/anon_inodes.h>, which isn't needed anymore.
Signed-off-by: Inki Dae <inki.dae@samsung.com>
'exynos_gem_obj' is not used in the function. Remove it.
Signed-off-by: Sachin Kamat <sachin.kamat@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>
Allow to allocate non-contigous buffers when iommu is enabled.
Currently, it tries to allocates contigous buffer which consistently
fail for large buffers and then fall back to non contigous. Apart
from being slow, this implementation is also very noisy and fills
the screen with alloc fail logs.
Signed-off-by: Rahul Sharma <Rahul.Sharma@samsung.com>
Reviewed-by: Sachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: Inki Dae <inki.dae@samsung.com>
Pull drm updates from Dave Airlie:
"Been a bit busy, first week of kids school, and waiting on other trees
to go in before I could send this, so its a bit later than I'd
normally like.
Highlights:
- core:
timestamp fixes, lots of misc cleanups
- new drivers:
bochs virtual vga
- vmwgfx:
major overhaul for their nextgen virt gpu.
- i915:
runtime D3 on HSW, watermark fixes, power well work, fbc fixes,
bdw is no longer prelim.
- nouveau:
gk110/208 acceleration, more pm groundwork, old overlay support
- radeon:
dpm rework and clockgating for CIK, pci config reset, big endian
fixes
- tegra:
panel support and DSI support, build as module, prime.
- armada, omap, gma500, rcar, exynos, mgag200, cirrus, ast:
fixes
- msm:
hdmi support for mdp5"
* 'drm-next' of git://people.freedesktop.org/~airlied/linux: (595 commits)
drm/nouveau: resume display if any later suspend bits fail
drm/nouveau: fix lock unbalance in nouveau_crtc_page_flip
drm/nouveau: implement hooks for needed for drm vblank timestamping support
drm/nouveau/disp: add a method to fetch info needed by drm vblank timestamping
drm/nv50: fill in crtc mode struct members from crtc_mode_fixup
drm/radeon/dce8: workaround for atom BlankCrtc table
drm/radeon/DCE4+: clear bios scratch dpms bit (v2)
drm/radeon: set si_notify_smc_display_change properly
drm/radeon: fix DAC interrupt handling on DCE5+
drm/radeon: clean up active vram sizing
drm/radeon: skip async dma init on r6xx
drm/radeon/runpm: don't runtime suspend non-PX cards
drm/radeon: add ring to fence trace functions
drm/radeon: add missing trace point
drm/radeon: fix VMID use tracking
drm: ast,cirrus,mgag200: use drm_can_sleep
drm/gma500: Lock struct_mutex around cursor updates
drm/i915: Fix the offset issue for the stolen GEM objects
DRM: armada: fix missing DRM_KMS_FB_HELPER select
drm/i915: Decouple GPU error reporting from ring initialisation
...
This patch resolves potential deadlock issue that can be incurred
by changing file->f_op and filp->private_data to exynos specific
mapper ops and gem object temporarily.
To resolve this issue, this patch creates a new anon file dedicated
to exynos specific mmaper, and making it used instead of existing one.
Signed-off-by: Inki Dae <inki.dae@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
All drivers embed gem-objects into their own buffer objects. There is no
reason to keep drm_gem_object_alloc(), gem->driver_private and
->gem_init_object() anymore.
New drivers are highly encouraged to do the same. There is no benefit in
allocating gem-objects separately.
Cc: Dave Airlie <airlied@gmail.com>
Cc: Alex Deucher <alexdeucher@gmail.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Rob Clark <robdclark@gmail.com>
Cc: Inki Dae <inki.dae@samsung.com>
Cc: Ben Skeggs <skeggsb@gmail.com>
Cc: Patrik Jakobsson <patrik.r.jakobsson@gmail.com>
Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
To address the case where physically contiguous memory
MAY NOT be a mandatory requirement for framebuffer for
the application calling exynos_drm_gem_dumb_create,
the patch adds a feature to get non physically contiguous
memory for framebuffer, if physically contiguous memory
allocation fails and if IOMMU is supported.
Signed-off-by: Vikas Sajjan <vikas.sajjan@linaro.org>
Signed-off-by: Arun Kumar <arun.kk@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>
This is the 2nd attempt, I've always been a bit dissatisified with the
tricky nature of the first one:
http://lists.freedesktop.org/archives/dri-devel/2012-July/025451.html
The issue is that the flink ioctl can race with calling gem_close on
the last gem handle. In that case we'll end up with a zero handle
count, but an flink name (and it's corresponding reference). Which
results in a neat space leak.
In my first attempt I've solved this by rechecking the handle count.
But fundamentally the issue is that ->handle_count isn't your usual
refcount - it can be resurrected from 0 among other things.
For those special beasts atomic_t often suggest way more ordering that
it actually guarantees. To prevent being tricked by those hairy
semantics take the easy way out and simply protect the handle with the
existing dev->object_name_lock.
With that change implemented it's dead easy to fix the flink vs. gem
close reace: When we try to create the name we simply have to check
whether there's still officially a gem handle around and if not refuse
to create the flink name. Since the handle count decrement and flink
name destruction is now also protected by that lock the reace is gone
and we can't ever leak the flink reference again.
Outside of the drm core only the exynos driver looks at the handle
count, and tbh I have no idea why (it's just for debug dmesg output
luckily).
I've considered inlining the drm_gem_object_handle_free, but I plan to
add more name-like things (like the exported dma_buf) to this scheme,
so it's clearer to leave the handle freeing in its own function.
This is exercised by the new gem_flink_race i-g-t testcase, which on
my snb leaks gem objects at a rate of roughly 1k objects/s.
v2: Fix up the error path handling in handle_create and make it more
robust by simply calling object_handle_unreference.
v3: Fix up the handle_unreference logic bug - atomic_dec_and_test
retursn 1 for 0. Oops.
v4: Squash in inlining of drm_gem_object_handle_reference as suggested
by Dave Airlie and add a note that we now have a testcase.
Cc: Dave Airlie <airlied@gmail.com>
Cc: Inki Dae <inki.dae@samsung.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Dave Airlie <airlied@redhat.com>
All the gem based kms drivers really want the same function to
destroy a dumb framebuffer backing storage object.
So give it to them and roll it out in all drivers.
This still leaves the option open for kms drivers which don't use GEM
for backing storage, but it does decently simplify matters for gem
drivers.
Acked-by: Inki Dae <inki.dae@samsung.com>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Intel Graphics Development <intel-gfx@lists.freedesktop.org>
Cc: Ben Skeggs <skeggsb@gmail.com>
Reviwed-by: Rob Clark <robdclark@gmail.com>
Cc: Alex Deucher <alexdeucher@gmail.com>
Acked-by: Patrik Jakobsson <patrik.r.jakobsson@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Use the new vma manager instead of the old hashtable. Also convert all
drivers to use the new convenience helpers. This drops all the
(map_list.hash.key << PAGE_SHIFT) non-sense.
Locking and access-management is exactly the same as before with an
additional lock inside of the vma-manager, which strictly wouldn't be
needed for gem.
v2:
- rebase on drm-next
- init nodes via drm_vma_node_reset() in drm_gem.c
v3:
- fix tegra
v4:
- remove duplicate if (drm_vma_node_has_offset()) checks
- inline now trivial drm_vma_node_offset_addr() calls
v5:
- skip node-reset on gem-init due to kzalloc()
- do not allow mapping gem-objects with offsets (backwards compat)
- remove unneccessary casts
Cc: Inki Dae <inki.dae@samsung.com>
Cc: Rob Clark <robdclark@gmail.com>
Cc: Dave Airlie <airlied@redhat.com>
Cc: Thierry Reding <thierry.reding@gmail.com>
Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
Acked-by: Patrik Jakobsson <patrik.r.jakobsson@gmail.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Dave Airlie <airlied@gmail.com>
The exynos_drm_gem_create() only calls drm_gem_object_release()
when exynos_drm_alloc_buf() is failed, and exynos_gem_obj remains
as a leak, which is allocated in exynos_drm_gem_init().
So this patch fixes it not to remain as a leak.
Signed-off-by: YoungJun Cho <yj44.cho@samsung.com>
Signed-off-by: Seung-Woo Kim <sw0312.kim@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>
vm_mmap function returns unsigned long so addr type should be unsigned long.
a pointer or address variable is required to use unsigned long or uint64_t
type for 64bits address support.
So this patch makes sure that addr has unsigned long type and also
exynos_drm_gem_mmap_ioctl returns correct error type.
Signed-off-by: Inki Dae <inki.dae@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
This patch removes tracking log functions which were used to debug
in the early development stage and are not so important as were.
So remove them for code clean up.
Signed-off-by: YoungJun Cho <yj44.cho@samsung.com>
Signed-off-by: Seung-Woo Kim <sw0312.kim@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>
This patch removes the use of dumb flags from driver.
As Dave pointed out, the dumb flags are not driver specific
so this should be removed from driver.
Signed-off-by: Inki Dae <inki.dae@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
This patch adds a new function to get gem buffer size. And this
funtion could be used for g2d driver or others can get gem buffer
size to check if the buffer is valid or not.
Signed-off-by: Inki Dae <inki.dae@samsung.com>
Signed-off-by: Kyungmin Park <inki.dae@samsung.com>
This patch fixes wrong pointer access issue to filp->f_op and
filp->private_data.
The exynos_drm_gem_mmap_ioctl() changes filp->f_op and
filp->private_data temporarily and restore them to use
original ones in exynos_drm_gem_mmap_buffer() but there
was no lock between the changing and the restoring so
wrong pointer access to filp->f_op and filp->private_data
was induced by vm close callback.
So this patch uses mutex lock properly to resolve this issue.
Signed-off-by: YoungJun Cho <yj44.cho@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
This patch changes file license to GPL
Most of exynos files had been copied from some random
file and not updated correctly. So this patch corrects
the file license.
Signed-off-by: Inki Dae <inki.dae@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Changelog v3:
just code cleanup.
Changelog v2:
fix argument to dma_mmap_attr function.
- use pages instead of kvaddr because kvaddr is 0 with
DMA_ATTR_NO_KERNEL_MAPPING.
Changelog v1:
When gem allocation is requested, kernel space mapping isn't needed.
But if need, such as console framebuffer, the physical pages would be
mapped with kernel space though vmap function.
Signed-off-by: Inki Dae <inki.dae@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Changelog v2:
Removed redundant check for invalid sgl.
Added check for valid page_offset in the beginning of exynos_drm_gem_map_buf.
Changelog v1:
The 'pages' structure is not required since we can use the 'sgt'. Even for
CONTIG buffers, a SGT is created (which will have just one sgl). This SGT
can be used during mmap instead of 'pages'. The 'page_size' element of the
structure is also not used anywhere and is removed.
This patch also fixes a memory leak where the 'pages' structure was being
allocated during gem buffer allocation but not being freed during deallocate.
Signed-off-by: Prathyush K <prathyush.k@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Changelog v3:
use drm_file's file object instead of gem object's
- gem object's file represents the shmem storage so
process-unique file object should be used instead.
Changelog v2:
call mutex_lock before drm_vm_open_locked is called.
Changelog v1:
This patch makes it takes a reference to gem object when
specific gem mmap is requested. For this, it sets
dev->driver->gem_vm_ops to vma->vm_ops.
And this patch is based on exynos-drm-next-iommu branch of
git://git.kernel.org/pub/scm/linux/kernel/git/daeinki/drm-exynos
Signed-off-by: Inki Dae <inki.dae@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
This patch adds userptr feautre for G2D module.
The userptr means user space address allocated by malloc().
And the purpose of this feature is to make G2D's dma able
to access the user space region.
To user this feature, user should flag G2D_BUF_USRPTR to
offset variable of struct drm_exynos_g2d_cmd and fill
struct drm_exynos_g2d_userptr with user space address
and size for it and then should set a pointer to
drm_exynos_g2d_userptr object to data variable of struct
drm_exynos_g2d_cmd. The last bit of offset variable is used
to check if the cmdlist's buffer type is userptr or not.
If userptr, the g2d driver gets user space address and size
and then gets pages through get_user_pages().
(another case is counted as gem handle)
Below is sample codes:
static void set_cmd(struct drm_exynos_g2d_cmd *cmd,
unsigned long offset, unsigned long data)
{
cmd->offset = offset;
cmd->data = data;
}
static int solid_fill_test(int x, int y, unsigned long userptr)
{
struct drm_exynos_g2d_cmd cmd_gem[5];
struct drm_exynos_g2d_userptr g2d_userptr;
unsigned int gem_nr = 0;
...
g2d_userptr.userptr = userptr;
g2d_userptr.size = x * y * 4;
set_cmd(&cmd_gem[gem_nr++], DST_BASE_ADDR_REG |
G2D_BUF_USERPTR,
(unsigned long)&g2d_userptr);
...
}
int main(int argc, char **argv)
{
unsigned long addr;
...
addr = malloc(x * y * 4);
...
solid_fill_test(x, y, addr);
...
}
And next, the pages are mapped with iommu table and the device
address is set to cmdlist so that G2D's dma can access it.
As you may know, the pages from get_user_pages() are pinned.
In other words, they CAN NOT be migrated and also swapped out.
So the dma access would be safe.
But the use of userptr feature has performance overhead so
this patch also has memory pool to the userptr feature.
Please, assume that user sends cmdlist filled with userptr
and size every time to g2d driver, and the get_user_pages
funcion will be called every time.
The memory pool has maximum 64MB size and the userptr that
user had ever sent, is holded in the memory pool.
This meaning is that if the userptr from user is same as one
in the memory pool, device address to the userptr in the memory
pool is set to cmdlist.
And last, the pages from get_user_pages() will be freed once
user calls free() and the dma access is completed. Actually,
get_user_pages() takes 2 reference counts if the user process
has never accessed user region allocated by malloc(). Then, if
the user calls free(), the page reference count becomes 1 and
becomes 0 with put_page() call. And the reverse holds as well.
This means how the pages backed are used by dma and freed.
This patch is based on "drm/exynos: add iommu support for g2d",
https://patchwork.kernel.org/patch/1629481/
Signed-off-by: Inki Dae <inki.dae@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Marek Szyprowski