The driver only uses even dividers for hsdiv when pclk >= 100MHz, as odd
dividers can create uneven duty cycle. However, while this holds true
for some dividers like DISPC's LCK and PCK dividers, it is not actually
true for hsdiv.

hsdiv always produces even duty cycle, so the constraint can be removed.
Signed-off-by: NTomi Valkeinen <tomi.valkeinen@ti.com>
Acked-by: NLaurent Pinchart <laurent.pinchart@ideasonboard.com>

The current driver doesn't expose any of the CRTC HW properties like
background color or transparency key, and sets them at CRTC enable time.

Refactor this into a separate function and call that function from
omap_crtc_atomic_flush(). This is the behavior we want when the
properties can be configured, so this patch makes it easier to add
patches later which implement those properties.
Signed-off-by: NTomi Valkeinen <tomi.valkeinen@ti.com>

DRA7 errata i886 (FPDLink PLL Unlocks With Certain SoC PLL M/N Values)
says that FPDLink is sensitive to jitter on the vout clock, and that low
PLL M and N values result in more jitter than high M and N values.

This patch implements a workaround for the problem by changing the PLL
setup to search for clocks starting from high M and N values, instead of
low values. This should not cause any functional change, and only
reduces the jitter.
Signed-off-by: NTomi Valkeinen <tomi.valkeinen@ti.com>
Reviewed-by: NLaurent Pinchart <laurent.pinchart@ideasonboard.com>

drm-misc for 4.12:

Core:
- Removed some fb subsampling dimension checks from core (Ville)
- Some MST slot cleanup (Dhinakaran)
- Extracted drm_debugfs.h & drm_ioctl.h from drmP.h (Daniel)
- Added drm_atomic_helper_shutdown() to compliment suspend/resume counterparts
  (Daniel)
- Pipe context through legacy modeset to remove legacy_backoff nasties (Daniel)
- Cleanups around vblank as well as allowing lockless counter reads (Chris W.)
- VGA Switcheroo added to MAINTAINERS with Lukas Wunner as reviewer (Lukas)

Drivers:
- Enhancements to rockchip driver probe (Jeffy) and dsi (Chris Z.)
- Thunderbolt external GPU awareness added (Lukas)

* tag 'drm-misc-next-2017-03-31' of git://anongit.freedesktop.org/git/drm-misc: (63 commits)
  apple-gmux: Don't switch external DP port on 2011+ MacBook Pros
  drm/nouveau: Don't register Thunderbolt eGPU with vga_switcheroo
  drm/amdgpu: Don't register Thunderbolt eGPU with vga_switcheroo
  drm/radeon: Don't register Thunderbolt eGPU with vga_switcheroo
  PCI: Recognize Thunderbolt devices
  MAINTAINERS: Add Lukas Wunner as reviewer for vga_switcheroo
  drm: Fix locking gotcha in page_flip ioctl
  drm: Clarify the role of plane_state argument to drm_simple update().
  drm: Clear e after kfree in drm_mode_page_flip_ioctl
  drm: Convert cmpxchg(bool) back to a two step operation
  drm/bridge: ti-tfp410: support hpd via gpio
  drm: use .hword to represent 16-bit numbers
  Revert unrelated part of "drm: simplify the locking in the GETCRTC ioctl"
  drm: Fixup failure paths in drm_atomic_helper_set_config
  drm: Peek at the current counter/timestamp for vblank queries
  drm: Refactor vblank sequence number comparison
  drm: vblank cannot be enabled if dev->irq_enabled is false
  drm: Mark up accesses of vblank->enabled outside of its spinlock
  drm: Make the decision to keep vblank irq enabled earlier
  drm/atomic-helper: Remove the backoff hack from set_config
  ...

This series enables atomic mode set for vmwgfx.  A number of features and
larger fixes are also included.

* 'drm-vmwgfx-next' of git://people.freedesktop.org/~syeh/repos_linux: (22 commits)
  drm/vmwgfx: Properly check display/scanout surface size
  drm/vmwgfx: Support topology greater than texture size
  drm/vmwgfx: Define an overlaid handle_close ioctl.
  drm/vmwgfx: Re-implement the stream resource as a simple resource.
  drm/vmwgfx: Introduce a simple resource type
  drm/vmwgfx: Revert "drm/vmwgfx: Replace numeric parameter like 0444 with macro"
  drm/vmwgfx: Fix LDU X blank screen until mode change issue
  drm/vmwgfx: Skipping fbdev fb pinning for ldu
  drm/vmwgfx: Explicityly track screen target width and height
  drm/vmwgfx: Turn on DRIVER_ATOMIC flag
  drm/vmwgfx: Switch over to internal atomic API for SOU and LDU
  drm/vmwgfx: Switch over to internal atomic API for STDU
  drm/vmwgfx: Fixes to vmwgfx_fb
  drm/vmwgfx: Add and connect atomic state object check/commit
  drm/vmwgfx: Add and connect connector helper function
  drm/vmwgfx: Add and connect plane helper functions
  drm/vmwgfx: Add and connect CRTC helper functions
  drm/vmwgfx: Connector atomic state
  drm/vmwgfx: Plane atomic state
  drm/vmwgfx: CRTC atomic state
  ...

The scanout surface size is the smaller of max texture size and
max STDU size.
Signed-off-by: NSinclair Yeh <syeh@vmware.com>
Reviewed-by: NThomas Hellstrom <thellstrom@vmware.com>

Most of the display servers today use a single surface to represent the
entire desktop even if it's stretched across multiple screens.

For vmwgfx with STDU, the maximum surface size is limited to the
maximum texture size on the host.  On a 2D VM, this limits our
ability to support configurations with more than one 4K monitor.

To get past this limitation, we will now allow using a large DMA buf
as the framebuffer, and take care of blitting contents from this DMA buf
to the display buffer.
Signed-off-by: NSinclair Yeh <syeh@vmware.com>
Reviewed-by: NThomas Hellstrom <thellstrom@vmware.com>

Instead of providing an ioctl for each handle type, provide a single
handle_close ioctl, and reuse the UNREF_DMABUF ioctl.
Signed-off-by: NThomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: NSinclair Yeh <syeh@vmware.com>

Provide and document a reference implementation.
Signed-off-by: NThomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: NSinclair Yeh <syeh@vmware.com>

The callbacks we need to provide to many resources are very similar, so
provide a simple resource type with a number of helpers for these
callbacks.
Signed-off-by: NThomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: NSinclair Yeh <syeh@vmware.com>

This reverts commit 2d8e60e8 ("drm/vmwgfx: Replace numeric
parameter like 0444 with macro")

The commit belongs to the series of 1285 patches sent to LKML on
2016-08-02, it changes the representation of file permissions from the
octal value "0600" to "S_IRUSR | S_IWUSR".

The general consensus was that the changes does not increase
readability, quite the opposite; 0600 is easier to parse mentally than
S_IRUSR | S_IWUSR.

It also causes argument inconsistency, due to commit 04319d89
("drm/vmwgfx: Add an option to change assumed FB bpp") that added
another call to module_param_named() where the permissions are written
as 0600.
Signed-off-by: NØyvind A. Holm <sunny@sunbase.org>
Reviewed-by: NSinclair Yeh <syeh@vmware.com>

vmw_ldu_crtc_helper_commit() is not called if
drm_atomic_crtc_needs_modeset() decides nothing related to CRTC timing has
changed.

So a better place for this code is in vmw_ldu_primary_plane_atomic_update()
since we will need to update ld->fb every time the FB is updated.
Signed-off-by: NSinclair Yeh <syeh@vmware.com>
Reviewed-by: NThomas Hellstrom <thellstrom@vmware.com>

Pinning fbdev's FB at the start of VRAM prevents X from pinning
its FB.  Since for ldu, the fb would be pinned anyway during a
mode set, just skip pinning it in fbdev.

This is not the best solution, but since ldu is not used much
anymore, it seems like a reasonable workaround.
Signed-off-by: NSinclair Yeh <syeh@vmware.com>
Reviewed-by: NThomas Hellstrom <thellstrom@vmware.com>

We can no longer make the assumption that vmw_stdu_update_st() will
be called when there's a valid display surface attached.  So
instead of using display_srf for width and height, make a record of
these paremeters when the screen target is first defined.
Signed-off-by: NSinclair Yeh <syeh@vmware.com>
Reviewed-by: NThomas Hellstrom <thellstrom@vmware.com>

Now that the legacy path has been tested, turn on the
DRIVER_ATOMIC flag so user mode driver can start going through
the Atomic path.
Signed-off-by: NSinclair Yeh <syeh@vmware.com>
Reviewed-by: NThomas Hellstrom <thellstrom@vmware.com>
Acked-by: NDaniel Vetter <daniel@ffwll.ch>

Switch over to internal atomic API.  This completes the atomic
internal atomic switch for all the Display Units.
Signed-off-by: NSinclair Yeh <syeh@vmware.com>
Signed-off-by: NThomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: NThomas Hellstrom <thellstrom@vmware.com>

Switch over to using internal atomic API for mode set.

This removes the legacy set_config API, replacing it with
drm_atomic_helper_set_config().  The DRM helper will use various
vmwgfx-specific atomic functions to set a mode.

DRIVER_ATOMIC capability flag is not yet set, so the user mode
will still use the legacy mode set IOCTL.

v2:
* Avoid a clash between page-flip pinning and setcrtc pinning, modify
the page-flip code to use the page-flip helper and the atomic callbacks.
To enable this, we will need to add a wrapper around atomic_commit.

* Add vmw_kms_set_config() to work around vmwgfx xorg driver bug
Signed-off-by: NSinclair Yeh <syeh@vmware.com>
Signed-off-by: NThomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: NThomas Hellstrom <thellstrom@vmware.com>

1.  When unsetting a mode, num_connector should be set to zero
2.  The pixel_format field needs to be initialized as newer DRM internal
    functions checks this field
3.  Take the drm_modeset_lock_all() because vmw_fb_kms_detach() can
    change current mode
Signed-off-by: NSinclair Yeh <syeh@vmware.com>
Reviewed-by: NThomas Hellstrom <thellstrom@vmware.com>

This connects the main state object check and commit function.

v2
* Use drm_atomic_helper_commit() rather than a vmwgfx-specific one
Signed-off-by: NSinclair Yeh <syeh@vmware.com>
Signed-off-by: NThomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: NThomas Hellstrom <thellstrom@vmware.com>
Acked-by: NDaniel Vetter <daniel@ffwll.ch>

These helpers won't be called until we flip on the atomic support
flag or set drm_crtc_funcs->set_config to using the atomic
helper.

v2
Use drm_atomic_helper_best_encoder() rather than a vmwgfx-specific one
Signed-off-by: NSinclair Yeh <syeh@vmware.com>
Reviewed-by: NThomas Hellstrom <thellstrom@vmware.com>
Acked-by: NDaniel Vetter <daniel@ffwll.ch>

Refactor previous FB and cursor plane update code into their
atomic counterparts: check, update, prepare, cleanup, and disable.

These helpers won't be called until we flip on the atomic support
flag or set drm_crtc_funcs->set_config to using the atomic
helper.

v2:
* Removed unnecessary pinning of cursor surface
* Added a few function headers

v3:
* Set clip region equal to the destination region
* Fixed surface pinning policy
* Enable SVGA mode in vmw_sou_primary_plane_prepare_fb
Signed-off-by: NSinclair Yeh <syeh@vmware.com>
Signed-off-by: NThomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: NThomas Hellstrom <thellstrom@vmware.com>

Atomic mode set requires us to refactor existing vmw_stdu_crtc_set_config
code into sections that check the validity of the new mode, and sections
that actually program the hardware state.

vmw_du_crtc_atomic_check() takes CRTC-related checking code.  In a later
patch, vmw_du_primary_plane_atomic_check() will take framebuffer-related
checking code.

These helpers won't be called until we flip on the atomic support
flag or set drm_crtc_funcs->set_config to using the atomic
helper.

v2:
* The state->num_connector is actually the total number of potential
  connectors, not just the one associated with the display unit.
  The proper one to check is ->connector_mask.

* Add the check to only allow plane state to be the same as crtc state
  (Thanks to mlankhorst)

* Make sure to turn on SVGA mode before using VRAM.  SVGA mode is
  disabled in master_drop if dbdev is not running.

v3:
* Moved dot clock override to crtc_atomic_check
Signed-off-by: NSinclair Yeh <syeh@vmware.com>
Signed-off-by: NThomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: NThomas Hellstrom <thellstrom@vmware.com>
Acked-by: NDaniel Vetter <daniel@ffwll.ch>

Add connector handling functions. Start tracking is_implicity in
the connector state.  Eventually, this field should be tracked
exclusively in a connector state.

Now that plane and connector states have been created, we can also
activate the code that use CRTC state.
Signed-off-by: NSinclair Yeh <syeh@vmware.com>
Reviewed-by: NThomas Hellstrom <thellstrom@vmware.com>

Add plane state handling functions.

We have to keep track of a few plane states so we cannot use the
DRM helper for this.

Created vmw_plane_state along with functions to reset, duplicate,
and destroty it.

v2
* Removed cursor clean up special case
Signed-off-by: NSinclair Yeh <syeh@vmware.com>
Reviewed-by: NThomas Hellstrom <thellstrom@vmware.com>
Acked-by: NDaniel Vetter <daniel@ffwll.ch>

Create and Add CRTC state.  We currently do not track any properties
or custom states so we can technically use the DRM helpers.  Creating
this code just to make potential future additions easier.

Most of the new code will be compiled but not enabled until
plane/connector state handling code is also in place.

This is the first of a series to enable atomic mode set for vmwgfx.

The atomic enabling effort was done in collaboration with Thomas
Hellstrom and the VMware Graphics Team.
Signed-off-by: NSinclair Yeh <syeh@vmware.com>
Reviewed-by: NThomas Hellstrom <thellstrom@vmware.com>

Universal support is prerequisite for atomic mode set.

Explicitly create planes for the cursor and the primary FB.  With
a functional cursor plane, the DRM will no longer use the legacy
cursor_set2 and cursor_move entry points.
Signed-off-by: NSinclair Yeh <syeh@vmware.com>
Signed-off-by: NThomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: NThomas Hellstrom <thellstrom@vmware.com>

This field is not being used anymore
Signed-off-by: NSinclair Yeh <syeh@vmware.com>
Reviewed-by: NThomas Hellstrom <thellstrom@vmware.com>

New stuff for 4.12:
- Preliminary vega10 support
- Support for multi-level page tables
- GPU sensor stuff for mesa
- job tracing improvements
- PRT support for sparse buffers
- Additional SR-IOV improvements
- ttm improvements
- misc bug fixes and code cleanups

* 'drm-next-4.12' of git://people.freedesktop.org/~agd5f/linux: (315 commits)
  drm/amdgpu: Fix 32bit x86 compilation warning
  drm/amdgpu: just disallow reading untouched registers
  drm/amdgpu: remove duplicate allowed reg CP_CPF_BUSY_STAT
  drm/amdgpu/soc15: enable psp block for SRIOV
  drm/amdgpu/soc15: bypass pp block for vf
  drm/amdgpu/psp: add check sOS sign
  drm/amd/amdgpu: Correct ring wptr address in debugfs (v2)
  drm/amdgpu: Fix multi-level page table bugs for large BOs v3
  drm/amdgpu: Fix Vega10 VM initialization
  drm/amdgpu: Make max_pfn 64-bit
  drm/amdgpu: drop GB_GPU_ID from the golden settings
  drm/amdgpu: fix vm pte pde flags to 64-bit for sdma (v3)
  drm/amd/amdgpu: fix Tonga S3 resume hang on rhel6.8
  drm/ttm: decrease ttm bo priority number
  drm/amd/amdgpu: fix performance drop when VRAM pressure
  drm/amdgpu: Couple small warning fixes
  drm/amdgpu: Clean up GFX 9 VM fault messages
  drm/amdgpu: Register UTCL2 as a source of VM faults
  drm/amdgpu/soc15: drop support for reading some registers
  drm/amdgpu/soc15: return cached values for some registers (v2)
  ...

On MacBook Pros introduced 2011 and onward, external DP ports are
combined DP/Thunderbolt ports that are no longer fully switchable
between GPUs, they can only be driven by the discrete GPU.

More specifically, the Main Link pins (which transport the actual video
and audio streams) are soldered to the discrete GPU, whereas the AUX
Channel pins are switchable. Because the integrated GPU is missing the
Main Link, external displays appear to it as phantoms which fail to
link-train.

Force the AUX channel to the discrete GPU on these models to avoid any
confusion. Document the switching policy implemented by this commit.
Acked-by: NAndy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: NLukas Wunner <lukas@wunner.de>
Link: http://patchwork.freedesktop.org/patch/msgid/4d1fcc92d1960049e2cff997fbd2d74e45e84e49.1489145162.git.lukas@wunner.de

An external Thunderbolt GPU can neither drive the laptop's panel nor be
powered off by the platform, so there's no point in registering it with
vga_switcheroo.  In fact, when the external GPU is runtime suspended,
vga_switcheroo will cut power to the internal discrete GPU, resulting in
a lockup.

Cc: Ben Skeggs <bskeggs@redhat.com>
Acked-by: NAlex Deucher <alexander.deucher@amd.com>
Signed-off-by: NLukas Wunner <lukas@wunner.de>
Link: http://patchwork.freedesktop.org/patch/msgid/8e733152b13e7c14501ad5af45c1c5c736584111.1489145162.git.lukas@wunner.de

An external Thunderbolt GPU can neither drive the laptop's panel nor be
powered off by the platform, so there's no point in registering it with
vga_switcheroo.  In fact, when the external GPU is runtime suspended,
vga_switcheroo will cut power to the internal discrete GPU, resulting in
a lockup.  Moreover AMD's Windows driver special-cases Thunderbolt as
well.
Acked-by: NAlex Deucher <alexander.deucher@amd.com>
Signed-off-by: NLukas Wunner <lukas@wunner.de>
Link: http://patchwork.freedesktop.org/patch/msgid/701a8e89ce8ac39734736ab779558b6a4042a19e.1489145162.git.lukas@wunner.de

An external Thunderbolt GPU can neither drive the laptop's panel nor be
powered off by the platform, so there's no point in registering it with
vga_switcheroo.  In fact, when the external GPU is runtime suspended,
vga_switcheroo will cut power to the internal discrete GPU, resulting in
a lockup.  Moreover AMD's Windows driver special-cases Thunderbolt as
well.
Acked-by: NAlex Deucher <alexander.deucher@amd.com>
Signed-off-by: NLukas Wunner <lukas@wunner.de>
Link: http://patchwork.freedesktop.org/patch/msgid/72d8a9645aece3eff44e116303f0fec8be061c88.1489145162.git.lukas@wunner.de

Detect on probe whether a PCI device is part of a Thunderbolt controller.
Intel uses a Vendor-Specific Extended Capability (VSEC) with ID 0x1234
on such devices.  Detect presence of this VSEC and cache it in a newly
added is_thunderbolt bit in struct pci_dev.

Also, add a helper to check whether a given PCI device is situated on a
Thunderbolt daisy chain (i.e., below a PCI device with is_thunderbolt
set).

The necessity arises from the following:

* If an external Thunderbolt GPU is connected to a dual GPU laptop,
  that GPU is currently registered with vga_switcheroo even though it
  can neither drive the laptop's panel nor be powered off by the
  platform.  To vga_switcheroo it will appear as if two discrete
  GPUs are present.  As a result, when the external GPU is runtime
  suspended, vga_switcheroo will cut power to the internal discrete GPU
  which may not be runtime suspended at all at this moment.  The
  solution is to not register external GPUs with vga_switcheroo, which
  necessitates a way to recognize if they're on a Thunderbolt daisy
  chain.

* Dual GPU MacBook Pros introduced 2011+ can no longer switch external
  DisplayPort ports between GPUs.  (They're no longer just used for DP
  but have become combined DP/Thunderbolt ports.)  The driver to switch
  the ports, drivers/platform/x86/apple-gmux.c, needs to detect presence
  of a Thunderbolt controller and, if found, keep external ports
  permanently switched to the discrete GPU.

v2: Make kerneldoc for pci_is_thunderbolt_attached() more precise,
    drop portion of commit message pertaining to separate series.
    (Bjorn Helgaas)

Cc: Andreas Noever <andreas.noever@gmail.com>
Cc: Michael Jamet <michael.jamet@intel.com>
Cc: Tomas Winkler <tomas.winkler@intel.com>
Cc: Amir Levy <amir.jer.levy@intel.com>
Acked-by: NBjorn Helgaas <bhelgaas@google.com>
Signed-off-by: NLukas Wunner <lukas@wunner.de>
Link: http://patchwork.freedesktop.org/patch/msgid/0ab165a4a35c0b60f29d4c306c653ead14fcd8f9.1489145162.git.lukas@wunner.de

I've been contributing to vga_switcheroo for the past two years and by
now am fairly familiar with it, so danvet suggested that I add myself
as reviewer.

While at it, add missing file pattern for vga_switcheroo.h + vgaarb.h
to the DRM and DRM-MISC sections such that get_maintainer.pl returns
dri-devel@ and the drm-misc maintainers.
Suggested-and-acked-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: NLukas Wunner <lukas@wunner.de>
Link: http://patchwork.freedesktop.org/patch/msgid/ff2320a0790d039e714cf352cf32ec16fa370627.1490623913.git.lukas@wunner.de

We want to lock the primary plane, not the cursor (which might be
optional). Real bad case of copy-paste fail, unfortunately our CI
didn't catch that because i915 does have a cursor plane.
Reported-by: NEric Anholt <eric@anholt.net>
Fixes: 29dc0d1d ("drm: Roll out acquire context for the page_flip ioctl")
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Sean Paul <seanpaul@chromium.org>
Signed-off-by: NDaniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170330204831.8225-1-daniel.vetter@ffwll.chTested-by: NEric Anholt <eric@anholt.net>
Reviewed-by: NHarry Wentland <harry.wentland@amd.com>

drivers/gpu/drm/amd/amdgpu/mmhub_v1_0.c:187:2: warning: right shift count >= width of type [enabled by default]
drivers/gpu/drm/amd/amdgpu/gfxhub_v1_0.c:173:2: warning: right shift count >= width of type [enabled by default]
drivers/gpu/drm/amd/amdgpu/vega10_ih.c:106:3: warning: right shift count >= width of type [enabled by default]

v2: Add a space between "&" and "0xff"

Reported by: kbuild-all@01.org
Signed-off-by: NAlex Xie <AlexBin.Xie@amd.com>
Reviewed-by: NChristian König <christian.koenig@amd.com>
Reviewed-by: NAlex Deucher <alexander.deucher@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>

Like the atomic update hook it's wrapping, the plane_state is the old
one, and the new one is in plane->state.  Both msxfb and tinydrm use
it correctly, but I mistook it for the new state in pl111 due to its
naming.
Signed-off-by: NEric Anholt <eric@anholt.net>
Link: http://patchwork.freedesktop.org/patch/msgid/20170320233615.5242-3-eric@anholt.netReviewed-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Not sure what the original intention was here, but returning a random piece of
kernel memory to userspace because we didn't set the value at all is clearly
not a good idea.

This patch disallows reading the register and returns
a proper error code instead.
Signed-off-by: NChristian König <christian.koenig@amd.com>
Acked-by: NAlex Deucher <alexander.deucher@amd.com>
Acked-by: NTom St Denis <tom.stdenis@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>

Remove duplicate mmCP_CPF_BUSY_STAT from the allowed registers.
Signed-off-by: NChristian König <christian.koenig@amd.com>
Reviewed-by: NAlex Deucher <alexander.deucher@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>

With the explicit retry loop static analyzers get confused by the
control flow and believe that e could be accessed after kfree. That's
not possible, but it's non-obvious, so let's clear it to NULL.

We already cleared e = NULL at the top of the function, so this is all
in line.

Cc: Julia Lawall <julia.lawall@lip6.fr>
Reported-by: NJulia Lawall <julia.lawall@lip6.fr>
Fixes: 29dc0d1d ("drm: Roll out acquire context for the page_flip ioctl")
Cc: Harry Wentland <harry.wentland@amd.com>
Cc: Daniel Vetter <daniel.vetter@intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Sean Paul <seanpaul@chromium.org>
Reviewed-by: NHarry Wentland <harry.wentland@amd.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170330133253.29500-1-daniel.vetter@ffwll.ch