Start converting over from the byte count to its semantic macro, either
we want to allocate the size of a physical page in main memory or we
want the size of a virtual page in the GTT. 4096 could mean either, but
PAGE_SIZE and I915_GTT_PAGE_SIZE are explicit and should help improve
code comprehension and future changes. In the future, we may want to use
variable GTT page sizes and so have the challenge of knowing which
hardcoded values were used to represent a physical page vs the virtual
page.

v2: Look for a few more 4096s to convert, discover IS_ALIGNED().
v3: 4096ul paranoia, make fence alignment a distinct value of 4096, keep
bdw stolen w/a as 4096 until we know better.
v4: Add asserts that i915_vma_insert() start/end are aligned to GTT page
sizes.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/20170110144734.26052-1-chris@chris-wilson.co.ukReviewed-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>

It has been some time since i915_gem_engine_cleanup was only called from
the module unload path, and now it is only called when the GPU is
wedged. Mika complained that the name is confusing, especially in light
of the existence of i915_gem_cleanup_engines().
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170110172246.27297-5-chris@chris-wilson.co.uk

Similarly to a normal reset, after we mark the GPU as wedged (completely
fubar and no more requests can be executed), set the error status on all
the in flight requests.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170110172246.27297-4-chris@chris-wilson.co.uk

Let userspace know if its request was resubmitted due to it being
executed at the time of a global reset. In this case, the reset was for
a guilty request on another engine, and this request was an innocent
victim that will be re-executed upon restarting. However, since it was
running at the time of the reset, we can not guarantee that it suffered
no ill-effects from the reset (e.g. some context state may be lost, or
some self-modifying fragment shaders will be restarted from the final
state not their initial state), to let userspace know that it has been
corrupted set a special value on the fence->error, -EAGAIN.

If the request does hang on resubmission, the error will be overwritten
with -EIO.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170110172246.27297-3-chris@chris-wilson.co.uk

The struct dma_fence carries a status field exposed to userspace by
sync_file. This is inspected after the fence is signaled and can convey
whether or not the request completed successfully, or in our case if we
detected a hang during the request (signaled via -EIO in
SYNC_IOC_FILE_INFO).

v2: Mark all cancelled requests as failed.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170110172246.27297-2-chris@chris-wilson.co.uk

Always reset the requests of the guilty context, including the hung
request that we tell the hardware to skip. This should help if the
reprogram fails entirely, but more importantly makes the guilty path
more uniform (and simplifies the subsequent patch to tweak the cancelled
requests).
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170110172246.27297-1-chris@chris-wilson.co.uk

Use drm_accurate_vblank_count so we have the full 32 bit to represent
the frame counter and userspace has a simpler way of knowing when the
counter wraps around.
Signed-off-by: NTomeu Vizoso <tomeu.vizoso@collabora.com>
Reviewed-by: NEmil Velikov <emil.velikov@collabora.com>
Reviewed-by: NRobert Foss <robert.foss@collabora.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20170110134305.26326-3-tomeu.vizoso@collabora.com

The core provides now an ABI to userspace for generation of frame CRCs,
so implement the ->set_crc_source() callback and reuse as much code as
possible with the previous ABI implementation.

When handling the pageflip interrupt, we skip 1 or 2 frames depending on
the HW because they contain wrong values. For the legacy ABI for
generating frame CRCs, this was done in userspace but now that we have a
generic ABI it's better if it's not exposed by the kernel.

v2:
    - Leave the legacy implementation in place as the ABI implementation
      in the core is incompatible with it.
v3:
    - Use the "cooked" vblank counter so we have a whole 32 bits.
    - Make sure we don't mess with the state of the legacy CRC capture
      ABI implementation.
v4:
    - Keep use of get_vblank_counter as in the legacy code, will be
      changed in a followup commit.

v5:
    - Skip first frame or two as it's known that they contain wrong
      data.
    - A few fixes suggested by Emil Velikov.

v6:
    - Rework programming of the HW registers to preserve previous
      behavior.

v7:
    - Address whitespace issue.
    - Added a comment on why in the implementation of the new ABI we
      skip the 1st or 2nd frames.

v9:
    - Add stub for intel_crtc_set_crc_source.

v12:
    - Rebased.
    - Remove stub for intel_crtc_set_crc_source and instead set the
      callback to NULL (Jani Nikula).

v15:
    - Rebased.
Signed-off-by: NTomeu Vizoso <tomeu.vizoso@collabora.com>
Reviewed-by: NEmil Velikov <emil.velikov@collabora.com>
Reviewed-by: NRobert Foss <robert.foss@collabora.com>

irq
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20170110134305.26326-2-tomeu.vizoso@collabora.com

Expose an interface for changing the tiling and stride on an object,
that includes the complexity of checking for conflicting bindings and
fence registers.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170110121045.27144-2-chris@chris-wilson.co.uk

Make it clear that these functions are the user entry points for
the tiling/fence registers.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170110121045.27144-1-chris@chris-wilson.co.uk

The VMA is later clipped against the vm_area_struct before insertion of
the faulting PTE so we are free to create the partial view as we desire.
If we use the object as the extents rather than the area, this partial
can then be used for other areas.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170110095633.6612-2-chris@chris-wilson.co.uk

In order to reuse the partial view for selftesting, extract the common
function for computing the view.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170110095633.6612-1-chris@chris-wilson.co.uk

Commit cc3f90f0 ("drm/i915/glk: Reuse broxton code for geminilake")
missed a few of occurences of IS_BROXTON() that should have been
coverted to IS_GEN9_LP().

v2: Cite the right commit. (Ander)

Fixes: cc3f90f0 ("drm/i915/glk: Reuse broxton code for geminilake")
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Ander Conselvan de Oliveira <ander.conselvan.de.oliveira@intel.com>
Cc: Daniel Vetter <daniel.vetter@intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: intel-gfx@lists.freedesktop.org
Signed-off-by: NMichel Thierry <michel.thierry@intel.com>
Signed-off-by: NTomasz Lis <tomasz.lis@intel.com>
Signed-off-by: NAnder Conselvan de Oliveira <ander.conselvan.de.oliveira@intel.com>
Reviewed-by: Tomasz Lis <tomasz.lis@intel.com> (v1)
Reviewed-by: NRodrigo Vivi <rodrigo.vivi@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1483973495-15138-1-git-send-email-ander.conselvan.de.oliveira@intel.com

Besides having the DMC firmware in place and loaded let's
handle runtime suspend and dc9 as we do for Broxton.

Cc: Ander Conselvan de Oliveira <ander.conselvan.de.oliveira@intel.com>
Signed-off-by: NRodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: NAnder Conselvan de Oliveira <ander.conselvan.de.oliveira@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1481902946-18593-2-git-send-email-ander.conselvan.de.oliveira@intel.com

This patch loads the DMC on GLK. There is a single
firmware image for all steppings on a GLK.

Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: NAnusha Srivatsa <anusha.srivatsa@intel.com>
Reviewed-by: NRodrigo Vivi <rodrigo.vivi@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1481902946-18593-1-git-send-email-ander.conselvan.de.oliveira@intel.com

Rename i915_gem_get_ggtt_size() and i915_gem_get_ggtt_alignment() to
i915_gem_fence_size() and i915_gem_fence_alignment() respectively to
better match usage. Similarly move the pair of functions into
i915_gem_tiling.c next to the fence restrictions.
Suggested-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170109161613.11881-6-chris@chris-wilson.co.ukReviewed-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>

Restricting the fence to the end of the previous tile-row breaks access
to the final portion of the object. On gen2/3 we employed lazy fencing
to pad out the fence with scratch page to provide access to the tail,
and now we also pad out the object on gen4+ we can apply the same fix.

Fixes: af1a7301 ("drm/i915: Only fence tiled region of object.")
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170109161613.11881-5-chris@chris-wilson.co.uk

The fence size/alignment is a combination of the vma size plus object
tiling parameters. Those parameters are rarely changed, making the fence
size/alignemnt roughly constant for the lifetime of the VMA. We can
simplify subsequent calculations by precalculating the size/alignment
required for GGTT vma taking fencing into account (with an update if we
do change the tiling or stride).
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170109161613.11881-4-chris@chris-wilson.co.uk

All of these conditions are prechecked by i915_tiling_ok() before we
allow setting the tiling/stride on the object and so we should never
fail asserting those conditions before writing the register.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170109161613.11881-3-chris@chris-wilson.co.uk

Ensure the view occupies the full tile row so that reads/writes into the
VMA do not escape (via fenced detiling) into neighbouring objects - we
will pad the object with scratch pages to satisfy the fence. This
applies the lazy-tiling we employed on gen2/3 to gen4+.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170109161613.11881-2-chris@chris-wilson.co.uk

Computing the tile row size of a tiled object (for use with fence
registers) is repeated, so extract it to a common helper.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/20170109161613.11881-1-chris@chris-wilson.co.ukReviewed-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>

Now that it's obvious what the helpers do, we can simplify the code
somewhat by using them when clearing the pdpe/pml4e with the relevant
scratch entry.

Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NMatthew Auld <matthew.auld@intel.com>
Reviewed-by: NMichał Winiarski <michal.winiarski@intel.com>
Signed-off-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161213160512.7008-1-matthew.auld@intel.com

The function name gen8_setup_page_directory_pointer is misleading, and
only serves to confuse the reader, it's not setting up a pdp, but
rather encoding a specific pml4e with a given pdp.

Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NMatthew Auld <matthew.auld@intel.com>
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>

The function name gen8_setup_page_directory is misleading, and only
serves to confuse the reader, it's not setting up a pd, but rather
encoding a specific pdpe with a given pd.

Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NMatthew Auld <matthew.auld@intel.com>
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>

Removing MMU configuration flag from DRM make few automatic
build failed when they answer yes to all flags.

Add asm/vga.h file on Blackfin architecture to not broke compilation.
Signed-off-by: NBenjamin Gaignard <benjamin.gaignard@linaro.org>
Fixes: 62a0d98a ("drm: allow to use mmuless SoC")
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1483789151-6603-1-git-send-email-benjamin.gaignard@linaro.org

The integer returned by the unload hook is ignored by the drm core, so
let's make it void.

This patch was created using the following Coccinelle semantic script
(except for the declaration and comment in drm_drv.h):

Compile-tested only.

// <smpl>
@ get_name @
struct drm_driver drv;
identifier fn;
@@
drv.unload = fn;

@ replace_type @
identifier get_name.fn;
@@
- int
+ void
fn (...)
{
...
}

@ remove_return_param @
identifier get_name.fn;
@@
void fn (...)
{
<...
if (...)
return
- ...
;
...>
 }

@ drop_final_return @
identifier get_name.fn;
@@
void fn (...)
{
...

- return 0;
}
// </smpl>
Suggested-by: NDaniel Vetter <daniel.vetter@intel.com>
Signed-off-by: NGabriel Krisman Bertazi <krisman@collabora.co.uk>
Acked-by: Christian König <christian.koenig@amd.com>.
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20170106175731.29196-1-krisman@collabora.co.uk

Add a bit more document for function drm_crtc_from_index() to cross
link it with drm_crtc_from_index(), and explain that the function is
useful in vblank code.

While at it, add cross link comment for drm_plane_from_index() as well.
Signed-off-by: NShawn Guo <shawn.guo@linaro.org>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1483779131-19935-1-git-send-email-shawnguo@kernel.org

drm_pick_cmdline_mode width and height parameters are useless.
Just remove them.

Cc: Daniel Vetter <daniel.vetter@intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Signed-off-by: NVincent Abriou <vincent.abriou@st.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1483721084-20278-2-git-send-email-vincent.abriou@st.com

Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

So they can figure out what is the optimal number of pages
that can be contingously stitched together without fear of
bounce buffer.

We also expose an mechanism for sub-users of SWIOTLB API, such
as Xen-SWIOTLB to set the max segment value. And lastly
if swiotlb=force is set (which mandates we bounce buffer everything)
we set max_segment so at least we can bounce buffer one 4K page
instead of a giant 512KB one for which we may not have space.
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reported-and-Tested-by: NJuergen Gross <jgross@suse.com>

As we now use a deferred free queue for objects, simply retiring the
active objects is not enough to immediately free them and recover their
mmap space - we must now also drain the freed object list.

Fixes: fbbd37b3 ("drm/i915: Move object release to a freelist + worker"
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: <drm-intel-fixes@lists.freedesktop.org>
Link: http://patchwork.freedesktop.org/patch/msgid/20170106152240.5793-3-chris@chris-wilson.co.ukReviewed-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>

If the DMA remap fails, one cause can be that we have too many objects
pinned in a small remapping table, such as swiotlb. (DMA remapping does
not trigger the shrinker by itself on its normal failure paths.)  So try
purging all other objects (using i915_gem_shrink_all(), sparing our own
pages as we have yet to assign them to the obj->pages) and try again. If
there are no pages to reclaim (and consequently no pages to unmap), the
shrinker will report 0 and we fail with -ENOSPC as before.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170106152240.5793-2-chris@chris-wilson.co.uk

Since commit fe115628 ("drm/i915: Implement pwrite without
struct-mutex") the lowlevel pwrite calls are now called without the
protection of struct_mutex, but pwrite_phys was still asserting that it
held the struct_mutex and later tried to drop and relock it.

Fixes: fe115628 ("drm/i915: Implement pwrite without struct-mutex")
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: <drm-intel-fixes@lists.freedesktop.org>
Link: http://patchwork.freedesktop.org/patch/msgid/20170106152240.5793-1-chris@chris-wilson.co.ukReviewed-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>

The kernel context (dev_priv->kernel_context) is unique in that it is
not associated with any user filp - it is the only one with
ctx->file_priv == NULL. This is a simpler test than comparing it against
dev_priv->kernel_context which involves some pointer dancing.

In checking that this is true, we notice that the gvt context is
allocating itself a i915_hw_ppgtt it doesn't use and not flagging that
its file_priv should be invalid.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170106152013.24684-5-chris@chris-wilson.co.uk

Replace a few more open-coded overflow checks with the macro.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170106152013.24684-4-chris@chris-wilson.co.uk

Stolen memory is a hardware resource of known size, so use an accurate
fixed integer type rather than the ambiguous variable size_t. This was
motivated by the next patch spotting inconsistencies in our types.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170106152013.24684-3-chris@chris-wilson.co.uk

Though we know the hw is limited to keeping stolen memory inside the
first 4GiB, it is clearer to the reader that we are handling physical
address if we use phys_addr_t to refer to the base of stolen memory.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170106152013.24684-2-chris@chris-wilson.co.uk

In order to silence sparse:

../drivers/gpu/drm/i915/i915_gpu_error.c:200:39: warning: Using plain integer as NULL pointer

add a helper to check whether we have sse4.1 and that the desired
alignment is valid for acceleration.

v2: Explain the macros and split the two use cases between
i915_has_memcpy_from_wc() and i915_can_memcpy_from_wc().
Reported-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170106152013.24684-1-chris@chris-wilson.co.uk

Each time new data has being added in CRC list inform reader by calling
wake_up_interruptible().
This should avoid to do it in all drivers.
Signed-off-by: NBenjamin Gaignard <benjamin.gaignard@linaro.org>
Cc: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: NTomeu Vizoso <tomeu.vizoso@collabora.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1483694104-25627-1-git-send-email-benjamin.gaignard@linaro.org

Some SoC without MMU have display driver where a drm/kms driver
could be implemented.

Before doing such kind of thing drm/kms must allow to use mmuless devices.
This patch propose to remove MMU configuration flag and add a cma helper
function to help implementing mmuless display driver

version 4:
- add documentation about drm_gem_cma_get_unmapped_area()
- stub it MMU case
Signed-off-by: NBenjamin Gaignard <benjamin.gaignard@linaro.org>
[danvet: Use recommended struct member references in kernel-doc.]
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1483521177-21794-4-git-send-email-benjamin.gaignard@linaro.org