We hit this a lot with i915 and although we'd like to engineer things to hit
it a lot less, this commit at least makes it consume a few less cycles.

from something containing
movzwl 0x0(%rip),%r10d
to
add    %r8,%rdx

I only noticed it while using perf to profile something else.
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NDave Airlie <airlied@redhat.com>

The SH Mobile LCD controller (LCDC) DRM driver supports the main
graphics plane in RGB and YUV formats, as well as the overlay planes (in
alpha-blending mode only).

Only flat panel outputs using the parallel interface are supported.
Support for SYS panels, HDMI and DSI is currently not implemented.
Signed-off-by: NLaurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: NSascha Hauer <s.hauer@pengutronix.de>

Signed-off-by: NLaurent Pinchart <laurent.pinchart@ideasonboard.com>

This patchset introduces a set of helper function for implementing the KMS
framebuffer layer for drivers which use the DRM GEM CMA helper function.
Signed-off-by: NLars-Peter Clausen <lars@metafoo.de>
Tested-by: NSascha Hauer <s.hauer@pengutronix.de>
Acked-by: NSascha Hauer <s.hauer@pengutronix.de>
[Make DRM_KMS_CMA_HELPER a boolean Kconfig option]
Signed-off-by: NLaurent Pinchart <laurent.pinchart@ideasonboard.com>

Many embedded drm devices do not have a IOMMU and no dedicated
memory for graphics. These devices use CMA (Contiguous Memory
Allocator) backed graphics memory. This patch provides helper
functions to be able to share the code. The code technically does
not depend on CMA as the backend allocator, the name has been chosen
because CMA makes for a nice, short but still descriptive function
prefix.
Signed-off-by: NSascha Hauer <s.hauer@pengutronix.de>
Tested-by: NLars-Peter Clausen <lars@metafoo.de>
[Make DRM_GEM_CMA_HELPER a boolean Kconfig option]
Signed-off-by: NLaurent Pinchart <laurent.pinchart@ideasonboard.com>

This goes back to

commit c1c7af60
Author: Jesse Barnes <jbarnes@virtuousgeek.org>
Date:   Thu Sep 10 15:28:03 2009 -0700

    drm/i915: force mode set at lid open time

It was used to fix an issue on a i915GM based Thinkpad X41, which
somehow clobbered the modeset state at lid close time. Since then
massive amounts of things changed: Tons of fixes to the modeset
sequence, OpRegion support, better integration with the acpi code.
Especially OpRegion /should/ allow us to control the display hw
cooperatively with the firmware, without the firmware clobbering the
hw state behind our backs.

So it's dubious whether we still need this.

The second issue is that it's unclear who's responsibility it actually
is to restore the mode - Chris Wilson suggests to just emit a hotplug
event and let userspace figure things out.

The real reason I've stumbled over this is that the new modeset code
breaks drm_helper_resume_force_mode - it OOPSes derefing a NULL vfunc
pointer. The reason this wasn't caught in testing earlier is that in

commit c9354c85
Author: Linus Torvalds <torvalds@linux-foundation.org>
Date:   Mon Nov 2 09:29:55 2009 -0800

    i915: fix intel graphics suspend breakage due to resume/lid event
    confusion

logic was added to _not_ restore the modeset state after a resume. And
since most machines are configured to auto-suspend on lid-close, this
neatly papered over the issue.

Summarizing, this shouldn't be required on any platform supporting
OpRegion. And none of the really old machines I have here seem to
require it either. Hence I'm inclined to just rip it out.

But in case that there are really firmwares out there that clobber the
hw state, replace it with a call to intel_modset_check_state. This
will ensure that we catch any issues as soon as they happen.

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Acked-by: NJesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

While reworking the modeset sequence, this got lost in

commit 25c5b266
Author: Daniel Vetter <daniel.vetter@ffwll.ch>
Date:   Sun Jul 8 22:08:04 2012 +0200

    drm/i915: implement new set_mode code flow

I've noticed this because some Xorg versions seem to set up a new mode
with every crtc at (0,0) and then pan to the right multi-monitor
setup. And since some hacks of mine added more calls to mode_set using
the stored crtc->x/y my multi-screen setup blew up.
Reviewed-by: NJesse Barnes <jbarnes@virtuousgeek.org>
Signed-Off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Limit printing bad edid information at one time per connector.
Connector that are connected to a bad monitor/kvm will likely
stay connected to the same bad monitor/kvm and it makes no
sense to keep printing the bad edid message.
Signed-off-by: NJerome Glisse <jglisse@redhat.com>
Reviewed-by: NAdam Jackson <ajax@redhat.com>
Signed-off-by: NDave Airlie <airlied@redhat.com>

This patch removes a unused struct psb_intel_connector

Sparse gives a warning:
drivers/gpu/drm/gma500/cdv_intel_hdmi.c:142:30: warning:
	unused variable ‘psb_intel_connector’ [-Wunused-variable]
Signed-off-by: NEmil Goode <emilgoode@gmail.com>
Signed-off-by: NDave Airlie <airlied@redhat.com>

The memory return by kzalloc() or kmem_cache_zalloc() has already
be set to zero, so remove useless memset(0).
Signed-off-by: NWei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: NDave Airlie <airlied@redhat.com>

The current logic for probing ddc is limited to
2 blocks (256 bytes), this patch adds support
for the 4 block (512) data.

To do this, a single 8-bit segment index is
passed to the display via the I2C address 30h.
Data from the selected segment is then immediately
read via the regular DDC2 address using a repeated
I2C 'START' signal.
Signed-off-by: NShirish S <s.shirish@samsung.com>
Reviewed-by: NJean Delvare <jdelvare@suse.de>
Reviewed-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: NVille Syrjala <ville.syrjala@linux.intel.com>
Signed-off-by: NDave Airlie <airlied@redhat.com>

Since arch/arm/include/asm/pgtable.h contains:

#define io_remap_pfn_range(vma,from,pfn,size,prot) \
                remap_pfn_range(vma, from, pfn, size, prot)

there is no point treating ARM as a special case in distinguishing
between remap_pfn_range() and io_remap_pfn_range().
Signed-off-by: NRobert P. J. Day <rpjday@crashcourse.ca>
Signed-off-by: NDave Airlie <airlied@redhat.com>

Signed-off-by: NAndy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: NDave Airlie <airlied@redhat.com>

There are two slightly different pieces of code for HDMI VSDB
detection. Unify the code into a single helper function.

Also fix a bug where drm_detect_hdmi_monitor() would stop looking
for the HDMI VSDB after the first vendor specific block is found,
whether or not that block happened to be the HDMI VSDB. The
standard allows for any number of vendor specific blocks to be
present.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: NAdam Jackson <ajax@redhat.com>
Signed-off-by: NDave Airlie <airlied@redhat.com>

The length of HDMI VSDB must be at least 5 bytes. Other than the minimum,
nothing else about the length is specified. Check the length before
accessing any additional field beyond the minimum length.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: NAdam Jackson <ajax@redhat.com>
Signed-off-by: NDave Airlie <airlied@redhat.com>

Make sure drm_detect_hdmi_monitor() and drm_detect_monitor_audio() don't
access beyond the extension block.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: NAdam Jackson <ajax@redhat.com>
Signed-off-by: NDave Airlie <airlied@redhat.com>

At the moment, there is an inconsistency in the way modes are named.
Modes with timings parsed from the EDID information will call
drm_mode_set_name(), which will name the mode using this form:

	<horizontal-res>x<vertical-res><interlace-char>

eg, 1920x1080i for an interlaced mode, or 1920x1080 for a progressive
mode.

However, timings parsed using the tables in drm_edid_modes.h do not
have the 'i' suffix.  You are left to deduce that they're interlaced
from xrandr's output by the lower vertical refresh frequencies.

This patch changes the interlaced mode names in drm_edid_modes.h to
follow the style set by drm_mode_set_name(), which makes it clear
in xrandr which modes are interlaced and which are not (as xrandr
groups the refresh rates on a line according to the name field.)
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>
Reviewed-by: NAlex Deucher <alexander.deucher@amd.com>
Reviewed-by: NAdam Jackson <ajax@redhat.com>
Signed-off-by: NDave Airlie <airlied@redhat.com>

DRM users should be able to create/destroy/manage dumb- and frame-buffers
without DRM_MASTER. These ioctls do not affect modesetting so there is no
reason to protect them by drm-master. Particularly, destroying buffers
should always be possible as a client has only access to buffers that they
created. Hence, there is no reason to prevent a client from destroying the
buffers, considering a simple close() would destroy them, anyway.

Furthermore, a display-server currently cannot shutdown correctly if it
does not have DRM_MASTER. If some other display-server becomes active (or
the kernel console), then the background display-server is unable to
destroy its buffers.
Under special curcumstances (like monitor reconfiguration) this might even
happen during runtime.
Signed-off-by: NDavid Herrmann <dh.herrmann@googlemail.com>
Signed-off-by: NDave Airlie <airlied@redhat.com>

Yet again a case where the fb helper is too intimate with the crtc
helper and calls a crtc helepr function directly instead of going
through the interface vtable.

This fixes console blanking in drm/i915 with the new i915-specific
modeset code.
Reported-by: NJesse Barnes <jbarnes@virtuousgeek.org>
Tested-by: NJesse Barnes <jbarnes@virtuousgeek.org>
Acked-by: NDave Airlie <airlied@gmail.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Now that we have solid modeset state tracking and checking code in
place, we can do the Full Monty also after dpms calls.
Reviewed-by: NJesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

... let's see whether this catches anything earlier and I can track
down a few bugs.

v2: Add more checks and also add DRM_DEBUG_KMS output so that it's
clear which connector/encoder/crtc is being checked atm. Which proved
rather useful for debugging ...

v3: Add a WARN in the common encoder dpms function, now that also
modeset changes properly update the dpms state ...

v4: Properly add a short explanation for each WARN, to avoid the need
to correlate dmesg lines with source lines accurately. Suggested by
Chris Wilson.

v5: Also dump (expected, found) for state checks (or wherever it's not
apparent from the test what exactly mismatches with expectations).
Again suggested by Chris Wilson.

v6: Due to an issue reported by Paulo Zanoni I've noticed that the
encoder checking is by far not as strict as it could and should be.
Improve this.
Reviewed-by: NJesse Barnes <jbarnes@virtuousgeek.org>
Signed-Off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Since this only calls crtc helper functions, of which a shocking
amount are NULL.

Now the curious thing is how the new modeset code worked with this
function call still present:

Thanks to the hw state readout and the suspend fixes to properly
quiescent the register state, nothing is actually enabled at resume
(if the bios doesn't set up anything). Which means resume_force_mode
doesn't actually do anything and hence nothing blows up at resume
time.

The other reason things do work is that the fbcon layer has it's own
resume notifier callback, which restores the mode. And thanks to the
force vt switch at suspend/resume, that then forces X to restore it's
own mode.

Hence everything still worked (as long as the bios doesn't enable
anything). And we can just kill the call to resume_force_mode.

The upside of both this patch and the preceeding patch to quiescent
the modeset state is that our resume path is much simpler:
- We now longer restore bogus register values (which most often would
  enable the backlight a bit and a few ports), causing flickering.
- We now longer call resume_force_mode to restore a mode that the
  fbcon layer would overwrite right away anyway.
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

We need this to avoid confusing the hw state readout code with the cpt
pch plls at resume time: We'd read the new pipe state (which is
disabled), but still believe that we have a life pll connected to that
pipe (from before the suspend). Hence properly disable pipes to clear
out all the residual state.

This has the neat side-effect that we don't enable ports prematurely
by restoring bogus state from the saved register values.
Reviewed-by: NJesse Barnes <jbarnes@virtuousgeek.org>
Signed-Off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

With this change we can (finally!) rip out a few of the temporary hacks
and clean up a few other things:
- Kill intel_crtc_prepare_encoders, now unused.
- Kill the hacks in the crtc_disable/enable functions to always call the
  encoder callbacks, we now always call the crtc functions with the right
  encoder -> crtc links.
- Also push down the crtc->enable, encoder and connector dpms state
  updates. Unfortunately we can't add a WARN in the crtc_disable
  callbacks to ensure that the crtc is always still enabled when
  disabling an output pipe - the crtc sanitizer of the hw readout path
  can hit this when it needs to disable an active pipe without any
  enabled outputs.
- Only call crtc->disable if the pipe is already enabled - again avoids
  running afoul of the new WARN.

v2: Copy&paste our own version of crtc_in_use, too.

v3: We need to update the dpms an encoder->connectors_active states,
too.

v4: I've forgotten to kill the unconditional encoder->disable calls in
the crtc_disable functions.

v5: Rip out leftover debug printk.

v6: Properly clear intel_encoder->connectors_active. This wasn't
properly cleared when disabling an encoder because it was no longer on
the new connector list, but the crtc was still enabled (i.e. switching
the encoder of an active crtc). Reported by Jani Nikula.

v7: Don't clobber the encoder->connectors_active state of untouched
encoders. Since X likes to first disable all outputs with dpms off
before setting a new framebuffer, this hit a few warnings. Reported by
Paulo Zanoni.

v8: Kill the now stale comment warning that intel_crtc->active is not
always updated at the right times.
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Now that set_mode also disables crtcs and expects it's new
configuration in the staged output links we need to adjust the load
detect code a bit.
Reviewed-by: NJesse Barnes <jbarnes@virtuousgeek.org>
Signed-Off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

This seems to be the symptom of a few neat bugs, hence be more
obnoxious when this fails.
Reviewed-by: NJesse Barnes <jbarnes@virtuousgeek.org>
Signed-Off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Because that's what it is. Unfortunately we can't rip this out because
the fb helper has an incetious relationship with the crtc helper - it
likes to call disable_unused_functions, among other things.
Reviewed-by: NJesse Barnes <jbarnes@virtuousgeek.org>
Signed-Off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

This requires a few changes
- We still need a noop function for crtc->disable, becuase the fb
  helper is a bit too intimate with the crtc helper.
- We need to clear crtc->fb ourselves in intel_crtc_disable now that
  we no longer rely on the helper's disable_unused_functions to do
  that.
- We need to split out the sare update code, becuase the crtc code
  can't call update_dpms any more, it needs to disable the crtc
  unconditionally. This is because we now keep onto the encoder ->
  crtc mapping of the (still) active output pipe configuration.
- To check that we really disable a crtc that still has encoders,
  insert a WARN_ON(!enabled) in the crtc disable function.
- Lastly, we need to walk over all crtcs to update their enabled state
  after having called commit_output_state - for all disabled crtcs the
  crtc helper code has done that for us previously.

v2: Update connector dpms and encoder->connectors_active after
disabling the crtc, too.

v3: Noop-out intel_encoder_disable. Similarly to the crtc disable
callback used by the crtc helper code we can't simply remove all these
encoder callbacks: The fb helper (which we still use) has a rather
incetious relationship with the crtc helper code ...
Reviewed-by: NJesse Barnes <jbarnes@virtuousgeek.org>
Signed-Off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

... using the pipe masks from the previous patch.

Well, not quite:
- We still need to call the disable_unused_functions helper, until
  we've moved the call to commit_output_state further down and
  adjusted intel_crtc_disable a bit. The next patch will do that.
- Because we don't support (yet) mode changes on more than one crtc at
  a time, some of the modeset_pipes checks are a bit hackish - but
  that only needs fixing once we incorporate global modeset support.
Reviewed-by: NJesse Barnes <jbarnes@virtuousgeek.org>
Signed-Off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

This is definetely a bit more generic than currently required, but if
we keep track of all crtcs that need to be disabled/enable (because
they loose an encoder or something similar), crtcs that get completely
disabled and those that we need to do an actual mode change nicely
prepares us for global modeset operations on multiple crtcs.

The only big thing missing here would be a global resource allocation
step (for e.g. pch plls), which would equally frob these bitmasks if
e.g. a crtc only needs a new pll. Or if we need to enable dithering on
an another pipe due to bandwidth constrains somewhere.

These masks aren't yet put to use in this patch, this will follow in the
next one.

v2-v5: Fix up the computations for good (hopefully).

v6: Fixup a confusion reported by Damien Lespiau: I've conserved the
(imo braindead) behaviour of the crtc helper to disable _any_
disconnected outputs if we do a modeset, even when that newly disabled
connector isn't connected to the crtc being changed by the modeset.

The effect of that is that we could disable an arbitrary number of
unrelated crtcs, which I haven't taken into account when writing this
code. Fix this up.
Reviewed-by: NJesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

- Use the check_cloned helper from the previous patch.
- Use encoder->new_crtc to check crtc properties.

v2: Kill the double negation with s/!non_cloned/is_cloned, suggested
by Jesse Barnes.
Reviewed-by: NJesse Barnes <jbarnes@virtuousgeek.org>
Signed-Off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

The "is this encoder cloned" check will be reused by the lvds encoder,
hence exract it.

v2: Be a bit more careful about that we need to check the new, staged
ouput configuration in the check_non_cloned helper ...

v3: Kill the double negation with s/!non_cloned/is_cloned/, suggested
by Jesse Barnes.
Reviewed-by: NJesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

While at it, adjust a few things:
- Only assigng the new mode to crtc->mode right before calling the
  mode_set callbacks - none of the previous callbacks depend upon
  this, they all use the mode argument (as they should).
- Check encoder->new_crtc instead of the current crtc to check whether
  the encoder will be used. This prepares for moving the staged output
  committing further down in the sequence. Follow-on patches will fix
  up individual ->mode_fixup callbacks (only tv and lvds are affected
  though).
Reviewed-by: NJesse Barnes <jbarnes@virtuousgeek.org>
Signed-Off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

It's rather pointless to compute crtc->enabled twice right away ;-)

The only thing we really have to be careful about is that we frob the
dpms state only after a successful modeset and when we've actually
haven't just disabled the crtc.

Hooray for convoluted interfaces ...
Reviewed-by: NJesse Barnes <jbarnes@virtuousgeek.org>
Signed-Off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Originally this has been introduced in

commit 6eebd6bb
Author: Chris Wilson <chris@chris-wilson.co.uk>
Date:   Mon Nov 28 21:10:05 2011 +0000

    drm: Fix lack of CRTC disable for drm_crtc_helper_set_config(.fb=NULL)

With the improvements of the output state staging and no longer
overwriting crtc->fb before the hw state is updated we can now handle
crtc disabling as part of the normal modeset sequence.
Reviewed-by: NJesse Barnes <jbarnes@virtuousgeek.org>
Signed-Off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Passing in the old fb, having overwritten the current fb, leads to
some neatly convoluted code. It's much simpler if we defer the
crtc->fb update to the place that updates the hw, in pipe_set_base.
This way we also don't need to restore anything in case something
fails - we only update crtc->fb once things have succeeded.

The real reason for this change is that now we keep the old fb
assigned to crtc->fb, which allows us to finally move the crtc disable
case into the common low-level set_mode function in the next patch.

Also don't clobber crtc->x and crtc->y, we neatly pass these down the
callchain already. Unfortunately we can't do the same with crtc->mode,
because that one is being used in the mode_set callbacks.

v2: Don't restore the drm_crtc object any more on failed modesets,
since we've lose an fb reference otherwise. Also (and this is the
reason this has been found), this totally confused the modeset state
tracking, since it clobbers crtc->enabled. Issue reported by Paulo
Zanoni.

v3: Rip out the entire crtc saving into struct intel_set_config, not
just the restoring part.
Reviewed-by: NJesse Barnes <jbarnes@virtuousgeek.org>
Signed-Off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

This is the core of the new modeset logic.

The current code which is based upon the crtc helper code first
updates all the link of the new display pipeline and then calls the
lower-level set_mode function to execute the required callbacks to get
there. The issue with this approach is that for disabling we need to
know the _current_ display pipe state, not the new one.

Hence we need to stage the new state of the display pipe and only
update it once we have disabled the current configuration and before we
start to update the hw registers with the new configuration.

This patch here just prepares the ground by switching the new output
state computation to these staging pointers. To make it clearer,
rename the old update_output_state function to stage_output_state.

A few peculiarities:
- We're also calling the set_mode function at various places to update
  properties. Hence after a successfule modeset we need to stage the
  current configuration (for otherwise we might fall back again). This
  happens automatically because as part of the (successful) modeset we
  need to copy the staged state to the real one. But for the hw
  readout code we need to make sure that this happens, too.
- Teach the new staged output state computation code the required
  smarts to handle the disabling of outputs. The current code handles
  this in a special case, but to better handle global modeset changes
  covering more than one crtc, we want to do this all in the same
  low-level modeset code.
- The actual modeset code is still a bit ugly and wants to know the new
  crtc->enabled state a bit early. Follow-on patches will clean that
  up, for now we have to apply the staged output configuration early,
  outside of the set_mode functions.
- Improve/add comments in stage_output_state.

Essentially all that is left to do now is move the disabling code into
set_mode and then move the staged state update code also into
set_mode, at the right place between disabling things and calling the
mode_set callbacks for the new configuration.

v2: Disabling a crtc works by passing in a NULL mode or fb, userspace
doesn't hand in the list of connectors. We therefore need to detect
this case manually and tear down all the output links.

v3: Properly update the output staging pointers after having read out
the hw state.

v4: Simplify the code, add more DRM_DEBUG_KMS output and check a few
assumptions with WARN_ON. Essentially all things that I've noticed
while debugging issues in other places of the code.

v4: Correctly disable the old set of connectors when enabling an
already enabled crtc on a new set of crtc. Reported by Paulo Zanoni.
Reviewed-by: NJesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

We actually only touch the connector -> encoder and encoder -> crtc
linking. So it's enough to just save/restore that.

While at it, also switch to kcalloc to allocate these arrays (omission
in the commit message spotted by Jesse Barnes).
Reviewed-by: NJesse Barnes <jbarnes@virtuousgeek.org>
Signed-Off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Because they all are, the ioctl command never calls us with any of
these violated. Also drop a equally pointless empty debug message (and
also in set_cursor, while we're at it).

With all these changes, intel_crtc_set_config is neatly condensed down
to it's essence, the actual modeset code (or fb update calling code)

v2: The fb helper code is actually stretching ->set_config semantics a bit,
it calls it with set->mode == NULL but set->fb != NULL.
Reviewed-by: NJesse Barnes <jbarnes@virtuousgeek.org>
Signed-Off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Otherwise we'll set_fb complains pretty loudly if we the crtc is off
and userspace moves the NULL fb around a bit. Yeah, this actually
happens in the wild ...
Reviewed-by: NJesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>