This way the driver can decide if it is valuable to evict a BO or not.
The current implementation is added as default to all existing drivers.
v2: fix some typos found during internal testing
Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
We get 1 warning when building kernel with W=1:
drivers/gpu/drm/bochs/bochs_kms.c:181:5: warning: no previous prototype for 'bochs_connector_get_modes' [-Wmissing-prototypes]
In fact, this function is only used in the file in which it is
declared and don't need a declaration, but can be made static.
So this patch marks it 'static'.
Signed-off-by: Baoyou Xie <baoyou.xie@linaro.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1474788334-11007-1-git-send-email-baoyou.xie@linaro.org
The qemu stdvga can be configured with a wide range of video memory,
from 1 MB to 256 MB (default is 16 MB). In case it is configured
with only 1 or 2 MB it isn't really usable with bochsdrm, due to
depths other than 32bpp not being supported so that isn't enough
memory for a reasonable sized framebuffer. So skip the device
and let vgacon or vesafb+fbcon handle the it.
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Rather than using "struct file*", use "struct drm_file*" as tag VM tag for
BOs. This will pave the way for "struct drm_file*" without any "struct
file*" back-pointer.
Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20160901124837.680-3-dh.herrmann@gmail.com
Lots of drivers don't properly compile without this when CONFIG_FB=n.
It's kinda a hack, but since CONFIG_FB doesn't stub any fucntions when
it's disabled I think it makes sense to add it to drm_fb_helper.h.
Long term we probably need to rethink all the logic to unload firmware
framebuffer drivers, at least if we want to be able to move away from
CONFIG_FB and fbcon.
v2: Unfortunately just stubbing out remove_conflicting_framebuffers in
drm_fb_helper.h upset gcc about static vs. non-static declarations, so
a new wrapper it needs to be. Means more churn :(
Cc: Tobias Jakobi <tjakobi@math.uni-bielefeld.de>
Cc: Noralf Trønnes <noralf@tronnes.org>
Cc: tomi.valkeinen@ti.com
Cc: dh.herrmann@gmail.com
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1470847958-28465-2-git-send-email-daniel.vetter@ffwll.ch
Backmerge drm-next to be able to apply Chris' connector_unregister_all
cleanup (need latest i915 and sun4i state for that).
Also there's a trivial conflict in ttm_bo.c that git rerere fails to
remember.
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
The drm_gem_object_unreference_unlocked() function tests whether
its argument is NULL and then returns immediately.
Thus the test around the call is not needed.
This issue was detected by using the Coccinelle software.
Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1e3a8c0d-e737-f092-727e-af7e3810b8dc@users.sourceforge.net
It's pointless to only call the default implementation.
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
drm_gem_object_lookup() has never required the drm_device for its file
local translation of the user handle to the GEM object. Let's remove the
unused parameter and save some space.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: dri-devel@lists.freedesktop.org
Cc: Dave Airlie <airlied@redhat.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
[danvet: Fixup kerneldoc too.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
This allows fine grained control for the driver where to add a BO into the LRU.
v2: fix typo in comment
Reviewed-by: Sinclair Yeh <syeh@vmware.com>
Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Not used any more.
Reviewed-by: Sinclair Yeh <syeh@vmware.com>
Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Only really needed for fbdev emulation at 8bpp. And bochs doesn't do
that. And either way bochs only does 32bit rgb, so this is all pretty
much wasted dead code.
The only consideration is that we need to not set up any gamma size
either.
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Dave Airlie <airlied@redhat.com>
Reviewed-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1459331485-28376-5-git-send-email-daniel.vetter@ffwll.ch
Pull drm updates from Dave Airlie:
"This is the main drm pull request for 4.6 kernel.
Overall the coolest thing here for me is the nouveau maxwell signed
firmware support from NVidia, it's taken a long while to extract this
from them.
I also wish the ARM vendors just designed one set of display IP, ARM
display block proliferation is definitely increasing.
Core:
- drm_event cleanups
- Internal API cleanup making mode_fixup optional.
- Apple GMUX vga switcheroo support.
- DP AUX testing interface
Panel:
- Refactoring of DSI core for use over more transports.
New driver:
- ARM hdlcd driver
i915:
- FBC/PSR (framebuffer compression, panel self refresh) enabled by default.
- Ongoing atomic display support work
- Ongoing runtime PM work
- Pixel clock limit checks
- VBT DSI description support
- GEM fixes
- GuC firmware scheduler enhancements
amdkfd:
- Deferred probing fixes to avoid make file or link ordering.
amdgpu/radeon:
- ACP support for i2s audio support.
- Command Submission/GPU scheduler/GPUVM optimisations
- Initial GPU reset support for amdgpu
vmwgfx:
- Support for DX10 gen mipmaps
- Pageflipping and other fixes.
exynos:
- Exynos5420 SoC support for FIMD
- Exynos5422 SoC support for MIPI-DSI
nouveau:
- GM20x secure boot support - adds acceleration for Maxwell GPUs.
- GM200 support
- GM20B clock driver support
- Power sensors work
etnaviv:
- Correctness fixes for GPU cache flushing
- Better support for i.MX6 systems.
imx-drm:
- VBlank IRQ support
- Fence support
- OF endpoint support
msm:
- HDMI support for 8996 (snapdragon 820)
- Adreno 430 support
- Timestamp queries support
virtio-gpu:
- Fixes for Android support.
rockchip:
- Add support for Innosilicion HDMI
rcar-du:
- Support for 4 crtcs
- R8A7795 support
- RCar Gen 3 support
omapdrm:
- HDMI interlace output support
- dma-buf import support
- Refactoring to remove a lot of legacy code.
tilcdc:
- Rewrite of pageflipping code
- dma-buf support
- pinctrl support
vc4:
- HDMI modesetting bug fixes
- Significant 3D performance improvement.
fsl-dcu (FreeScale):
- Lots of fixes
tegra:
- Two small fixes
sti:
- Atomic support for planes
- Improved HDMI support"
* 'drm-next' of git://people.freedesktop.org/~airlied/linux: (1063 commits)
drm/amdgpu: release_pages requires linux/pagemap.h
drm/sti: restore mode_fixup callback
drm/amdgpu/gfx7: add MTYPE definition
drm/amdgpu: removing BO_VAs shouldn't be interruptible
drm/amd/powerplay: show uvd/vce power gate enablement for tonga.
drm/amd/powerplay: show uvd/vce power gate info for fiji
drm/amdgpu: use sched fence if possible
drm/amdgpu: move ib.fence to job.fence
drm/amdgpu: give a fence param to ib_free
drm/amdgpu: include the right version of gmc header files for iceland
drm/radeon: fix indentation.
drm/amd/powerplay: add uvd/vce dpm enabling flag to fix the performance issue for CZ
drm/amdgpu: switch back to 32bit hw fences v2
drm/amdgpu: remove amdgpu_fence_is_signaled
drm/amdgpu: drop the extra fence range check v2
drm/amdgpu: signal fences directly in amdgpu_fence_process
drm/amdgpu: cleanup amdgpu_fence_wait_empty v2
drm/amdgpu: keep all fences in an RCU protected array v2
drm/amdgpu: add number of hardware submissions to amdgpu_fence_driver_init_ring
drm/amdgpu: RCU protected amd_sched_fence_release
...
Introduce PCI_VENDOR/PCI_SUBVENDOR/PCI_SUBDEVICE defines to replace the
constants scattered in the kernel already used to detect QEMU.
They are defined in the QEMU codebase per docs/specs/pci-ids.txt.
Signed-off-by: Robin H. Johnson <robbat2@gentoo.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Takashi Iwai <tiwai@suse.de>
Reviewed-by: Gerd Hoffmann <kraxel@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Previously a negative pipe caused a special case to be triggered for
drivers that didn't have proper VBLANK support. The trigger for this
special case is now independent of the pipe, so the correct CRTC index
can now be stored in events.
v2: convert to use drm_crtc_send_vblank_event()
Cc: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1450178476-26284-3-git-send-email-boris.brezillon@free-electrons.com
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Done with coccinelle for the most part. However, it thinks '...' is
part of the semantic patch, so I put an 'int DOTDOTDOT' placeholder
in its place and got rid of it with sed afterwards.
@@
identifier dev, encoder, funcs;
@@
int drm_encoder_init(struct drm_device *dev,
struct drm_encoder *encoder,
const struct drm_encoder_funcs *funcs,
int encoder_type
+ ,const char *name, int DOTDOTDOT
)
{ ... }
@@
identifier dev, encoder, funcs;
@@
int drm_encoder_init(struct drm_device *dev,
struct drm_encoder *encoder,
const struct drm_encoder_funcs *funcs,
int encoder_type
+ ,const char *name, int DOTDOTDOT
);
@@
expression E1, E2, E3, E4;
@@
drm_encoder_init(E1, E2, E3, E4
+ ,NULL
)
v2: Add ', or NULL...' to @name kernel doc (Jani)
Annotate the function with __printf() attribute (Jani)
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1449670818-2966-1-git-send-email-ville.syrjala@linux.intel.com
Drivers shouldn't clobber the passed in addfb ioctl parameters.
i915 was doing just that. To prevent it from happening again,
pass the struct around as const, starting all the way from
internal_framebuffer_create().
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Since David Herrmann's mmap vma manager rework we don't need to grab
dev->struct_mutex any more to prevent races when looking up the mmap
offset. Drop it and instead don't forget to use the unref_unlocked
variant (since the drm core still cares).
Reviewed-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Use the newly created wrapper drm_fb_helper functions instead of calling
core fbdev functions directly. They also simplify the fb_info creation.
v3:
- Don't touch remove_conflicting_framebuffers
v2:
- remove unused variable device in bochsfb_create
Cc: David Airlie <airlied@linux.ie>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Archit Taneja <architt@codeaurora.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Make drm_fb_helper_initial_config() return an int rather than a bool so
that the error can be properly propagated. While at it, update drivers
to propagate errors further rather than just ignore them.
v2:
- cirrus: No cleanup is required, the top-level cirrus_driver_load()
will do it as part of cirrus_driver_unload() in its cleanup path.
Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Patrik Jakobsson <patrik.r.jakobsson@gmail.com>
Cc: Rob Clark <robdclark@gmail.com>
Cc: Tomi Valkeinen <tomi.valkeinen@ti.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Christian König <christian.koenig@amd.com>
Cc: Ben Skeggs <bskeggs@redhat.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Patrik Jakobsson <patrik.r.jakobsson@gmail.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
[danvet: Squash in simplification patch from kbuild.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
The ->load_lut() callback is optional, therefore a dummy implementation
is not needed.
Cc: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Implement crtc page_flip callback for bochsdrm. The qemu stdvga has no
vblank signaling, so we have to fake it. We do so by instantly calling
drm_send_vblank_event. Tested with kmscon.
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Remove the mapping offset from the bo backing the fbdev framebuffer.
Wire up fbdev mmap function to map the backing bo using ttm_fbdev_mmap.
With that patch in place mmap(/dev/fb0) works as expected.
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Recently (qemu 2.2+) the qemu stdvga got a register to switch the vga
framebuffer endianness. This patch adds code to explicitly set the
endianness of the framebuffer. In most cases this has no effect as
the default is guest architecture endianness. It is needed though in
case a architecture supports both big and little endian, i.e. for
ppc64le.
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Just a bit of OCD cleanup on headers - this function isn't the core
interface any more but just a helper for drivers who haven't yet
transitioned to universal planes. Put the declaration at the right
spot and sprinkle necessary #includes over all drivers.
Maybe this helps to encourage driver maintainers to do the switch.
v2: Fix #include ordering for tegra, reported by 0-day builder.
v3: Include required headers, reported by Thierry.
Cc: Matt Roper <matthew.d.roper@intel.com>
Cc: Thierry Reding <treding@nvidia.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Sean Paul <seanpaul@chromium.org>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Pull drm updates from Dave Airlie:
"This is the main git pull for the drm,
I pretty much froze major pulls at -rc5/6 time, and haven't had much
fallout, so will probably continue doing that.
Lots of changes all over, big internal header cleanup to make it clear
drm features are legacy things and what are things that modern KMS
drivers should be using. Also big move to use the new generic fences
in all the TTM drivers.
core:
atomic prep work,
vblank rework changes, allows immediate vblank disables
major header reworking and cleanups to better delinate legacy
interfaces from what KMS drivers should be using.
cursor planes locking fixes
ttm:
move to generic fences (affects all TTM drivers)
ppc64 caching fixes
radeon:
userptr support,
uvd for old asics,
reset rework for fence changes
better buffer placement changes,
dpm feature enablement
hdmi audio support fixes
intel:
Cherryview work,
180 degree rotation,
skylake prep work,
execlist command submission
full ppgtt prep work
cursor improvements
edid caching,
vdd handling improvements
nouveau:
fence reworking
kepler memory clock work
gt21x clock work
fan control improvements
hdmi infoframe fixes
DP audio
ast:
ppc64 fixes
caching fix
rcar:
rcar-du DT support
ipuv3:
prep work for capture support
msm:
LVDS support for mdp4, new panel, gpu refactoring
exynos:
exynos3250 SoC support, drop bad mmap interface,
mipi dsi changes, and component match support"
* 'drm-next' of git://people.freedesktop.org/~airlied/linux: (640 commits)
drm/mst: rework payload table allocation to conform better.
drm/ast: Fix HW cursor image
drm/radeon/kv: add uvd/vce info to dpm debugfs output
drm/radeon/ci: add uvd/vce info to dpm debugfs output
drm/radeon: export reservation_object from dmabuf to ttm
drm/radeon: cope with foreign fences inside the reservation object
drm/radeon: cope with foreign fences inside display
drm/core: use helper to check driver features
drm/radeon/cik: write gfx ucode version to ucode addr reg
drm/radeon/si: print full CS when we hit a packet 0
drm/radeon: remove unecessary includes
drm/radeon/combios: declare legacy_connector_convert as static
drm/radeon/atombios: declare connector convert tables as static
drm/radeon: drop btc_get_max_clock_from_voltage_dependency_table
drm/radeon/dpm: drop clk/voltage dependency filters for BTC
drm/radeon/dpm: drop clk/voltage dependency filters for CI
drm/radeon/dpm: drop clk/voltage dependency filters for SI
drm/radeon/dpm: drop clk/voltage dependency filters for NI
drm/radeon: disable audio when we disable hdmi (v2)
drm/radeon: split audio enable between eg and r600 (v2)
...
v2: Don't forget git add, noticed by David.
Cc: David Herrmann <dh.herrmann@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Acked-by: David Herrmann <dh.herrmann@gmail.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Really, the legacy buffer api should be dead, especially for all these
newfangled drivers. I suspect this is copypasta from the transitioning
days, which probably originated in radeon.
Cc: "Christian König" <christian.koenig@amd.com>
Cc: David Herrmann <dh.herrmann@gmail.com>
Cc: Rashika <rashika.kheria@gmail.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Fabian Frederick <fabf@skynet.be>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Alexandre Courbot <acourbot@nvidia.com>
Cc: Maarten Lankhorst <maarten.lankhorst@canonical.com>
Cc: Christian Engelmayer <cengelma@gmx.at>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Reviewed-by: David Herrmann <dh.herrmann@gmail.com>
Acked-by: Ben Skeggs <bskeggs@redhat.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
One step closer to dropping all the drm_bus_* code:
Add a driver->set_busid() callback and make all drivers use the generic
helpers. Nouveau is the only driver that uses two different bus-types with
the same drm_driver. This is totally broken if both buses are available on
the same machine (unlikely, but lets be safe). Therefore, we create two
different drivers for each platform during module_init() and set the
set_busid() callback respectively.
Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
Reviewed-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
This allows us to more fine grained specify where to place the buffer object.
v2: rebased on drm-next, add bochs changes as well
Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
We should prefer `struct pci_device_id` over `DEFINE_PCI_DEVICE_TABLE` to
meet kernel coding style guidelines. This issue was reported by checkpatch.
A simplified version of the semantic patch that makes this change is as
follows (http://coccinelle.lip6.fr/):
// <smpl>
@@
identifier i;
declarer name DEFINE_PCI_DEVICE_TABLE;
initializer z;
@@
- DEFINE_PCI_DEVICE_TABLE(i)
+ const struct pci_device_id i[]
= z;
// </smpl>
[bhelgaas: add semantic patch]
Signed-off-by: Benoit Taine <benoit.taine@lip6.fr>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Regular nightly randconfig build testing discovered these warnings:
drivers/gpu/drm/bochs/bochs_drv.c💯12: warning: 'bochs_pm_suspend' defined but not used [-Wunused-function]
drivers/gpu/drm/bochs/bochs_drv.c:117:12: warning: 'bochs_pm_resume' defined but not used [-Wunused-function]
Fix these by adding the same condition that SET_SYSTEM_SLEEP_PM_OPS()
uses.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Dave Airlie <airlied@redhat.com>
The final parameter to ttm_bo_reserve() is a pointer, therefore callers
should use NULL instead of 0.
Fixes a bunch of sparse warnings of this type:
warning: Using plain integer as NULL pointer
Signed-off-by: Thierry Reding <treding@nvidia.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
To implement hotplug detection in a race-free manner, drivers must call
drm_kms_helper_poll_init() before hotplug events can be triggered. Such
events can be triggered right after any of the encoders or connectors
are initialized. At the same time, if the drm_fb_helper_hotplug_event()
helper is used by a driver, then the poll helper requires some parts of
the FB helper to be initialized to prevent a crash.
At the same time, drm_fb_helper_init() requires information that is not
necessarily available at such an early stage (number of CRTCs and
connectors), so it cannot be used yet.
Add a new helper, drm_fb_helper_prepare(), that initializes the bare
minimum needed to allow drm_kms_helper_poll_init() to execute and any
subsequent hotplug events to be processed properly.
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
There's no need for this to be modifiable. Make it const so that it can
be put into the .rodata section.
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Acked-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Dave Airlie <airlied@redhat.com>
The ->gem_free_object never gets called with a NULL pointer, the check
is redundant. Also checking after the upcast allows compilers to elide
it anyway.
Noticed while chasing coverity reports, somehow this one here was not
flagged.
Reviewed-by: David Herrmann <dh.herrmann@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
ttm_bo_unref unconditionally calls kref_put on it's argument, so the
thing can't be NULL without already causing Oopses.
Spotted by coverity.
Reviewed-by: David Herrmann <dh.herrmann@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>