This is required to get fbcon probing to work on new connectors,
callers should acquire the mode config lock before calling these.
Reviewed-by: NTodd Previte <tprevite@gmail.com>
Signed-off-by: NDave 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: NDaniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: NThierry Reding <treding@nvidia.com>
Signed-off-by: NDave Airlie <airlied@redhat.com>

Some drivers need to be able to have a perfect race-free fbcon setup.
Current drivers only enable hotplug processing after the call to
drm_fb_helper_initial_config which leaves a tiny but important race.

This race is especially noticable on embedded platforms where the
driver itself enables the voltage for the hdmi output, since only then
will monitors (after a bit of delay, as usual) respond by asserting
the hpd pin.

Most of the infrastructure is already there with the split-out
drm_fb_helper_init. And drm_fb_helper_initial_config already has all
the required locking to handle concurrent hpd events since

commit 53f1904b
Author: Daniel Vetter <daniel.vetter@ffwll.ch>
Date:   Thu Mar 20 14:26:35 2014 +0100

    drm/fb-helper: improve drm_fb_helper_initial_config locking

The only missing bit is making drm_fb_helper_hotplug_event save
against concurrent calls of drm_fb_helper_initial_config. The only
unprotected bit is the check for fb_helper->fb.

With that drivers can first initialize the fb helper, then enabel
hotplug processing and then set up the initial config all in a
completely race-free manner. Update kerneldoc and convert i915 as a
proof of concept.

Feature requested by Thierry since his tegra driver atm reliably boots
slowly enough to misses the hotplug event for an external hdmi screen,
but also reliably boots to quickly for the hpd pin to be asserted when
the fb helper calls into the hdmi ->detect function.

Cc: Thierry Reding <treding@nvidia.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: NThierry Reding <treding@nvidia.com>
Signed-off-by: NDave Airlie <airlied@redhat.com>

The following list empty check is unnecessary because we would still do nothing
real and return 'val' if my_list is empty.

if (list_empty(&my_list))
	return val;

list_for_each_entry(pos, &my_list, member) {
	...
}

return val;

This patch removes the unnecessary check in drm_fb_helper_debug_enter().
Signed-off-by: NLiu Ying <Ying.Liu@freescale.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

The variable info->fix.type_aux is set to zero twice in the function
drm_fb_helper_fill_fix().  This patch removes one redundant.
Signed-off-by: NLiu Ying <Ying.Liu@freescale.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

All drm_fb_helper_restore_fbdev_mode() call sites, save one, do the same
locking.  Simplify this into drm_fb_helper_restore_fbdev_mode_unlocked().
Signed-off-by: NRob Clark <robdclark@gmail.com>
Reviewed-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: NDave Airlie <airlied@redhat.com>

For atomic, it will be quite necessary to not need to care so much
about locking order.  And 'state' gives us a convenient place to stash a
ww_ctx for any sort of update that needs to grab multiple crtc locks.

Because we will want to eventually make locking even more fine grained
(giving locks to planes, connectors, etc), split out drm_modeset_lock
and drm_modeset_acquire_ctx to track acquired locks.

Atomic will use this to keep track of which locks have been acquired
in a transaction.

v1: original
v2: remove a few things not needed until atomic, for now
v3: update for v3 of connection_mutex patch..
v4: squash in docbook
v5: doc tweaks/fixes
Signed-off-by: NRob Clark <robdclark@gmail.com>
Reviewed-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: NDave Airlie <airlied@redhat.com>

Generated using semantic patch:

@@
expression E;
@@

- drm_get_connector_name(E)
+ E->name

[airlied: regenerated]
Acked-by: NDavid Herrmann <dh.herrmann@gmail.com>
Signed-off-by: NJani Nikula <jani.nikula@intel.com>
Signed-off-by: NDave Airlie <airlied@redhat.com>

Fix a few trivial typos in the framebuffer helper documentation.
Signed-off-by: NThierry Reding <treding@nvidia.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Commit 62ff94a5 "drm/crtc-helper: remove LOCKING from kerneldoc"
causes drm_helper_crtc_in_use() and drm_helper_encoder_in_use() to
complain loudly during a kernel panic or sysrq processing. This is
caused by nobody acquiring the modeset lock in these code paths.

This patch fixes this by trying to acquire the modeset lock for each
FB helper that's forced to kernel mode. If the lock can't be acquired,
it's likely that somebody else is performing a modeset. However, doing
another modeset concurrently might make things even worse, so the safe
option is to simply bail out in that case.
Reviewed-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: NDavid Herrmann <dh.herrmann@gmail.com>
Signed-off-by: NThierry Reding <treding@nvidia.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Currently drm_pick_cmdline_mode() doesn't care about the interlace
when the given mode line has no "i" suffix.  That is, when there are
multiple entries for the same resolution, an interlace mode might be
picked up just depending on the assigned order, and there is no way to
exclude it.

This patch changes the logic for the mode selection, to prefer the
noninterlace mode unless the interlace mode is explicitly given.
When no matching mode is found, it still tries the interlace mode as
fallback.
Signed-off-by: NTakashi Iwai <tiwai@suse.de>
Reviewed-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: NDave Airlie <airlied@redhat.com>

Now that CRTC's have a primary plane, there's no need to track the
framebuffer in the CRTC.  Replace all references to the CRTC fb with the
primary plane's fb.

This patch was generated by the Coccinelle semantic patching tool using
the following rules:

        @@ struct drm_crtc C; @@
        -   (C).fb
        +   C.primary->fb

        @@ struct drm_crtc *C; @@
        -   (C)->fb
        +   C->primary->fb

v3: Generate patch via coccinelle.  Actual removal of crtc->fb has been
    moved to a subsequent patch.

v2: Fixup several lingering crtc->fb instances that were missed in the
    first patch iteration.  [Rob Clark]
Signed-off-by: NMatt Roper <matthew.d.roper@intel.com>
Reviewed-by: NRob Clark <robdclark@gmail.com>

The DRM core currently only tracks "overlay"-style planes.  Start
refactoring the plane handling to allow other plane types (primary and
cursor) to also be placed on the DRM plane list.

v2: Add drm_for_each_legacy_plane() iterator to smooth transition
    of drivers with plane loops.
Signed-off-by: NMatt Roper <matthew.d.roper@intel.com>
Reviewed-by: NRob Clark <robdclark@gmail.com>

The locking in drm_fb_helper_initial_config is a bit troublesome for a
few reasons:

- We can't just wrap the entire function up into modeset locks since
  the fbdev registration might call down into fbcon code, which then
  through our ->set_par implementation needs to be able to grab all
  modeset locks. So we'd have a neat deadlock.

- This implies though that all current callers don't hold any modeset
  locks by necessity, so we have free reign to grab any modeset locks
  we need to grab.

- The private state of the fbdev helper doesn't need any protection
  through locks, since once we have the fbdev registered it is mostly
  invariant or protected through the modeset locking in ->set_par and
  other callbacks. We can fully rely on driver having non-racy setup
  sequences here. For the initial config computation we actually may
  not grab locks since drivers which provide their own magic sauce
  (like i915) might need to grab locks themselves.

- We should grab locks though when we probe outputs. Currently there's
  not much risk, but already now userspace could start poking at sysfs
  files and so probe concurrently. I expect that in the future driver
  init will be much more async, and since probing is really
  time-consuming this is a prime candidate.

- We must not hold any crtc->mutex locks while calling probe functions
  since those might need to lock a crtc for e.g. load detection. i915
  is such a driver.

Also it's the probing calls which hit upon piles of new locking
asserts I've recently added in

commit 62ff94a5
Author: Daniel Vetter <daniel.vetter@ffwll.ch>
Date:   Thu Jan 23 22:18:47 2014 +0100

    drm/crtc-helper: remove LOCKING from kerneldoc

and

commit 63951385
Author: Daniel Vetter <daniel.vetter@ffwll.ch>
Date:   Thu Jan 23 15:14:15 2014 +0100

    drm/doc: Repleace LOCKING kerneldoc sections in drm_modes.c

Hence the right fix is to grab the mode_config mutex, but only that
and only right around the probe calls.

It seems to be sufficient to shut up all the locking WARNINGs I see on
i915 and nouveau in drm_fb_helper_initial_config.
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Tested-by: NThierry Reding <treding@nvidia.com>
Signed-off-by: NDave Airlie <airlied@redhat.com>

Since we cannot make sure the 'max_conn_count' will always be none
zero from the users, and then if max_conn_count equals to zero, the
kcalloc() will return ZERO_SIZE_PTR, which equals to ((void *)16).

So this patch fix this with just doing the 'max_conn_count' zero check
in the front of drm_fb_helper_init().
Signed-off-by: NXiubo Li <Li.Xiubo@freescale.com>
CC: Jani Nikula <jani.nikula@linux.intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Use drm_fb_helper_restore_fbdev_mode() in drm_fb_helper_set_par() to
make sure extra planes get disabled whenever fbcon takes over.

Otherwise the code in drm_fb_helper_set_par() was already doing the
exact same thing as drm_fb_helper_restore_fbdev_mode(), so this doesn't
change the behaviour in any other way.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

There's a neat FIXME asking whether this is really need. I'd
say really no.
Reviewed-by: NAlex Deucher <alexander.deucher@amd.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

This allows drivers to use them in custom initial_config functions.
Signed-off-by: NJesse Barnes <jbarnes@virtuousgeek.org>
Acked-by: NDave Airlie <airlied@gmail.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Sometimes we want to disable all the screens on a system, because that
will allow the graphics card to be put into low-power states. The
problem is that, for example, while all screens are disabled, if we
get a hotplug interrupt, fbcon will decide to set a mode instead of
keeping everything disabled, which will remove us from our low power
states.

Let's assume that if there's a DRM master, it will be able to do
whatever is appropriate when we get the hotplug.

This problem can be reproduced by the runtime PM test program from
intel-gpu-tools: we disable all the screens so the graphics device can
be put into D3, then something triggers a hotplug interrupt, fbcon
sets a mode and breaks our test suite. The problem can be reproduced
more easily by the "i2c" subtest.

Other approaches considered for the problem:
    - Return "false" if "bound == 0" and the caller of
      drm_fb_helper_is_bound is a hotplug handler. This would break
      the case where the machine boots with no outputs connected, then
      the user plugs a monitor.
    - Add a new IOCTL to force fbcon to not set modes. This would keep
      all the current applications behaving the same, but adding a new
      IOCTL is not always the greatest idea.
    - Return false only if "dev->primary->master && bound == 0". This
      was my first implementation, but Chris suggested we should do
      the check irrespective of the "bound" variable.

Thanks to Daniel Vetter for the investigation, ideas and the
implementation of the hotplug alternative.

v2: - Do the check first, irrespective of "bound".
    - Cc dri-devel

Cc: dri-devel@lists.freedesktop.org
Credits-to: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: NPaulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: NDavid Herrmann <dh.herrmann@gmail.com>
Signed-off-by: NDave Airlie <airlied@redhat.com>

For drivers which might want to disable fbdev legacy support.

Select the new option in all drivers for now, so this shouldn't result
in any change. Drivers need some work anyway to make fbdev support
optional (if they have it implemented, that is), so the recommended
way to expose this is by adding per-driver options. At least as long
as most drivers don't support disabling the fbdev support.

v2: Update for new drm drivers msm and rcar-du. Note that Rob's msm
driver can already take advantage of this, which allows us to build
msm without any fbdev depencies in the kernel!

v3: Move the MODULE_* stuff from the fbdev helper file to
drm_crtc_helper.c.

Cc: David Herrmann <dh.herrmann@gmail.com>
Cc: Rob Clark <robdclark@gmail.com>
Reviewed-by: NRob Clark <robdclark@gmail.com>
Acked-by: NDave Airlie <airlied@linux.ie>
Reviewed-by: NChon Ming Lee <chon.ming.lee@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

This reverts commit 928c2f0c.

This patch double applied, two checks for the price of one.
Signed-off-by: NDave Airlie <airlied@redhat.com>

Signed-off-by: NDamien Lespiau <damien.lespiau@intel.com>
Signed-off-by: NDave Airlie <airlied@redhat.com>

Signed-off-by: NDamien Lespiau <damien.lespiau@intel.com>
Signed-off-by: NDave Airlie <airlied@redhat.com>

Signed-off-by: NDamien Lespiau <damien.lespiau@intel.com>
Signed-off-by: NDave Airlie <airlied@redhat.com>

Otherwise the system will burn even brighter and worse, leave the user
wondering what's going on exactly.

Since we already have a panic handler which will (try) to restore the
entire fbdev console mode, we can just bail out.  Inspired by a patch from
Konstantin Khlebnikov.  The callchain leading to this, cut&pasted from
Konstantin's original patch:

callstack:
panic()
bust_spinlocks(1)
unblank_screen()
vc->vc_sw->con_blank()
fbcon_blank()
fb_blank()
info->fbops->fb_blank()
drm_fb_helper_blank()
drm_fb_helper_dpms()
drm_modeset_lock_all()
mutex_lock(&dev->mode_config.mutex)

Note that the entire locking in the fb helper around panic/sysrq and kdbg
is ...  non-existant.  So we have a decent change of blowing up
everything.  But since reworking this ties in with funny concepts like the
fbdev notifier chain or the impressive things which happen around
console_lock while oopsing, I'll leave that as an exercise for braver
souls than me.
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Cc: Konstantin Khlebnikov <khlebnikov@openvz.org>
Cc: Dave Airlie <airlied@gmail.com>
Reviewed-by: NRob Clark <robdclark@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NDave Airlie <airlied@redhat.com>

Check whether the crtc provides the load_lut callback before calling it.
This allows the driver to provide the hook only for those CRTCs that
actually have the hardware support for it.

Also check whether the driver provided the fb_helper gamma_set/gamma_get
hooks. It's a driver bug if it allows non-truecolor fbdev visuals w/o
these hooks, but auditing all the drivers is too tedious. So just slap
a big WARN_ON() there and bail out before things start to explode.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: NDave Airlie <airlied@gmail.com>

Perform the drm_fb_helper_is_bound() check to avoid clobbering the
display palette of some other KMS client.

While at it, fix up the locking by grabbing all modeset locks for the
duration of the fb_setcmap operation.

v2: Make a note of the locking changes in the commit message
Reviewed-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: NDave Airlie <airlied@gmail.com>

Cursors and plane can obscure whatever fbdev wants to show the user.
Disable them all in drm_fb_helper_restore_fbdev_mode.

After the cursors and planes have been disabled, user space needs to
explicitly re-enable them to make them visible again.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: NDave Airlie <airlied@gmail.com>

Driver's and ->fill_modes functions are allowed to grab crtc mutexes
(for e.g. load detect). Hence we need to first only grab the general
kms mutex, and only in a second step grab all locks to do the
modesets.

This prevents a deadlock on my gm45 in the tv load detect code called
by drm_helper_probe_single_connector_modes.
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: NDave Airlie <airlied@redhat.com>

Rather than building a config which may or may not work, let the driver
build an initial fb config.  This allows the driver to use the BIOS boot
configuration for example, displaying kernel messages and the initial fb
console on the same outputs the BIOS lit up at boot time.  If that
fails, the driver can still fall back the same way as the core.
Signed-off-by: NJesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: dri-devel@lists.freedesktop.org
Acked-by: NDave Airlie <airlied@gmail.com>
Reviewed-by: NImre Deak <imre.deak@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Otherwise the system will burn even brighter and worse, leave the user
wondering what's going on exactly.

Since we already have a panic handler which will (try) to restore the
entire fbdev console mode, we can just bail out. Inspired by a patch
from Konstantin Khlebnikov. The callchain leading to this, cut&pasted
from Konstantin's original patch:

callstack:
panic()
bust_spinlocks(1)
unblank_screen()
vc->vc_sw->con_blank()
fbcon_blank()
fb_blank()
info->fbops->fb_blank()
drm_fb_helper_blank()
drm_fb_helper_dpms()
drm_modeset_lock_all()
mutex_lock(&dev->mode_config.mutex)

Note that the entire locking in the fb helper around panic/sysrq and
kdbg is ... non-existant. So we have a decent change of blowing up
everything. But since reworking this ties in with funny concepts like
the fbdev notifier chain or the impressive things which happen around
console_lock while oopsing, I'll leave that as an exercise for braver
souls than me.

v2: Drop the -EBUSY return value I've copied, we don't need it since
the we'll take care of things ourselves anyway.

Cc: Konstantin Khlebnikov <khlebnikov@openvz.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
References: https://patchwork.kernel.org/patch/1878181/Reviewed-by: NRob Clark <robdclark@gmail.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Now that the fbdev helper interface for drivers is trimmed down,
update the kerneldoc for all the remaining exported functions.

I've tried to beat the DocBook a bit by reordering the function
references a bit into a more sensible ordering. But that didn't work
out at all. Hence just extend the in-code DOC: section a bit.

Also remove the LOCKING: sections - especially for the setup functions
they're totally bogus. But that's not a documentation problem, but
simply an artifact of the current rather hazardous locking around drm
init and even more so around fbdev setup ...

v2: Some further improvements:
- Also add documentation for drm_fb_helper_single_add_all_connectors,
  Dave Airlie didn't want me to kill this one from the fb helper
  interface.
- Update docs for drm_fb_helper_fill_var/fix - they should be used
  from the driver's ->fb_probe callback to setup the fbdev info
  structure.
- Clarify what the ->fb_probe callback should all do - it needs to
  setup both the fbdev info and allocate the drm framebuffer used as
  backing storage.
- Add basic documentaation for the drm_fb_helper_funcs driver callback
  vfunc.

v3: Implement clarifications Laurent Pinchart suggested in his review.

v4: Fix another mispelling Laurent spotted.

Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: NLaurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

No need to check whether we've allocated a new fb since we're not
always doing that. Also, we always need to register the fbdev and add
it to the panic notifier.
Reviewed-by: NRob Clark <robdclark@gmail.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

The idea behind calling down into the driver's ->fb_probe function on each
hotplug seems to be able to reallocate the backing storage (if e.g. a screen
with higher resolution gets added). But that requires quite a bit of work in the
fb helper itself, since currently we limit new screens to the currently
allocated fb. An no kms driver supports fbdev fb resizing.

So don't bother and start to simplify the code by calling drm_fb_helper_set_par
directly from the fbdev hotplug function, since that's the only thing left in
drm_fb_helper_single_fb_probe which does not concern itself with fb allocation
and initial setup. Follow-on patches will streamline the initial setup
code.
Reviewed-by: NRob Clark <robdclark@gmail.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

While doing the modeset rework for drm/i915 I've noticed that the fb
helper is very liberal with the semantics of the ->set_config
interface:
- It doesn't bother clearing stale modes (e.g. when unplugging a
  screen).
- It unconditionally sets the fb, even if no mode will be set on a
  given crtc.
- The initial setup is a bit fun since we need to pick crtcs to decide
  the desired fb size, but also should set the modeset->fb pointer.
  Explain what's going on in the fixup code after the fb is allocated.

The crtc helper didn't really care, but the new i915 modeset
infrastructure did, so I've had to add a bunch of special-cases to
catch this.

Fix this all up and enforce the interface by converting the checks in
drm/i915/intel_display.c to BUG_ONs.

v2: Fix commit message spell fail spotted by Rob Clark.
Reviewed-by: NRob Clark <robdclark@gmail.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

This should be done in the drivers for two reasons:
- it gets in the way of fastboot efforts
- it links the fb helpers with the crtc helpers instead of going
  through the real interface vfuncs, forcing i915 to fake all the
  ->disable callbacks used by the crtc helper to avoid ugly Oopsen

v2: Resolve conflicts since drivers still call
drm_fb_helper_single_add_all_connectors.
Reviewed-by: NRob Clark <robdclark@gmail.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Not called by anyone, and really, shouldn't be. Drivers are supposed
either drm_fb_helper_initial_config or drm_fb_helper_hotplug_event.
Originally this was done differently, but is now consolidated in the
helper functions and no longer done by drivers directly.
Reviewed-by: NRob Clark <robdclark@gmail.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

It doesn't even show up in any header files and only used iternally.
Originally it was (ab)used to restore the fbcon on lastclose, but that
died with

commit e8e7a2b8
Author: Dave Airlie <airlied@redhat.com>
Date:   Thu Apr 21 22:18:32 2011 +0100

    drm/i915: restore only the mode of this driver on lastclose (v2)
Reviewed-by: NRob Clark <robdclark@gmail.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

It's only used internally for the sysrq and panic handlers provided by
the drm fb helper implementation. Hence just inline it, kill the
export and remove the confusing kerneldoc. Driver's are supposed to
call drm_fb_helper_restore_fbdev_mode on lastclose.

Note that locking is totally fubar - the sysrq case doesn't take any
locks at all. The panic handler probably shouldn't take any locks
since it'll only make things worse. Otoh it's probably better to
switch things over to the atomic modeset callbacks (and disable the
panic handler for those drivers which don't implement it).

But that's both better done in separate patches.
Reviewed-by: NRob Clark <robdclark@gmail.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

... it's required. Fix up exynos and the cma helper, and add a
corresponding WARN_ON to drm_fb_helper_restore_fbdev_mode.

Note that tegra calls the fbdev cma helper restore function also from
it's driver-load callback. Which is a bit against current practice,
since usually the call is only from ->lastclose, and initial setup is
done by drm_fb_helper_initial_config.

Also add the relevant drm DocBook entry.

v2: Add promised WARN to restore_fbdev_mode.
Reviewed-by: NRob Clark <robdclark@gmail.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>