Currently we print all pipe underruns on GMCH platforms. Hook up the
same logic we use on PCH platforms where we disable the underrun
reporting after the first underrun.

Underruns don't actually generate interrupts themselves on GMCH
platforms, we just can detect them whenever we service other
interrupts. So we don't have any enable bits to worry about. We just
need to remember to clear the underrun status when enabling underrun
reporting.

Note that the underrun handling needs to be moved to the non-locked
pipe_stats[] loop in the interrupt handlers to avoid having to rework
the locking in intel_set_cpu_fifo_underrun_reporting().
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: NPaulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Forgot to convert to using the refclk variable when I added refclk
readout support, and Paulo noticed the resulting calculation was off due
to the way p & r are stored.
Reported-by: NPaulo Zanoni <przanoni@gmail.com>
Signed-off-by: NJesse Barnes <jbarnes@virtuousgeek.org>
Reviewed-by: NPaulo Zanoni <paulo.r.zanoni@intel.com>
Tested-by: NPaulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

This statenment became false here:

commit 4fc688ce
Author: Jesse Barnes <jbarnes@virtuousgeek.org>
Date:   Fri Nov 2 11:14:01 2012 -0700

    drm/i915: protect RPS/RC6 related accesses (including PCU) with a new mutex
Signed-off-by: NBen Widawsky <ben@bwidawsk.net>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Now that we have DDI support, we can check these all the time.
Signed-off-by: NJesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Read out and calculate the port and pixel clocks on DDI configs as well.
This means we have to grab the DP divider values and look at the port
mapping to figure out which clock select reg to read out.

v2: do the work from ddi_get_config (Ville)
v3: check WRPLL reference clock (Ville)
    add additional SPLL freqs (Ville)
    clean up port/crtc clock calc (Ville)
    fix up crtc_clock conditionals (Ville)
    drop superfluous dp_get_m_n from get_config (Ville)
Signed-off-by: NJesse Barnes <jbarnes@virtuousgeek.org>
Reviewed-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

We need a bit more flexibility here in the future, bits get shuffled
around.

v2: more descriptive commit message (Jani Nikula)
Reviewed-by: NJani Nikula <jani.nikula@intel.com>
Signed-off-by: NDamien Lespiau <damien.lespiau@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

So it's easier to compare what we program with the documentation, not
having to jump at all.
Signed-off-by: NDamien Lespiau <damien.lespiau@intel.com>
Reviewed-by: NJani Nikula <jani.nikula@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Also, move that computation outside of the for loop that tries 5 times,
this value doesn't change between tries.
Signed-off-by: NDamien Lespiau <damien.lespiau@intel.com>
Reviewed-by: NJani Nikula <jani.nikula@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

A tiny clean-up to allow better code separation between platforms.

v2: Fix comment placement (put in in i9xx_get_aux_clock_divider()) and
    nuke the outdated PCH eDP comment (Jani Nikula)
Signed-off-by: NDamien Lespiau <damien.lespiau@intel.com>
Reviewed-by: NJani Nikula <jani.nikula@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Since
commit ee1452d7
Author: Jani Nikula <jani.nikula@intel.com>
Date:   Fri Sep 20 15:05:30 2013 +0300

    drm/i915: assume all GM45 Acer laptops use inverted backlight PWM

failed and was later reverted in
commit be505f64
Author: Alexander van Heukelum <heukelum@fastmail.fm>
Date:   Sat Dec 28 21:00:39 2013 +0100

    Revert "drm/i915: assume all GM45 Acer laptops use inverted backlight PWM"

fix the individual broken machine instead.

Note to backporters:

http://patchwork.freedesktop.org/patch/17837/

is the patch you want for 3.13 and older.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=54171
Reference: http://mid.gmane.org/DUB115-W7628C7C710EA51AA110CD4A5000@phx.gbl
CC: stable@vger.kernel.org
Signed-off-by: NJani Nikula <jani.nikula@intel.com>
Reviewed-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
[danvet: Patch mangling for 3.14 plus adding the link to the original
for 3.13.]
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

It's unused, and nowadays specifying unknown parameters no longer
prevents modules from being loaded.
Signed-off-by: NJani Nikula <jani.nikula@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

For HSW+ platforms, enable the 5.4Ghz (HBR2) link rate for devices that support it. The
sink device must report that is supports Displayport 1.2 and the HBR2 bit rate in the
DPCD in order to use HBR2.
Signed-off-by: NTodd Previte <tprevite@gmail.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Group the sprite register writes a bit tighter. We want to write
the registers atomically, and so doing the base address/offset
artihmetic within the critical section is pointless when it can
all be done beforehand.
Reviewed-by: NJesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Currently we're doing the reset handling a bit late, and we're doing
it both in the driver load code and on resume. This makes it unusable
for e.g. resetting the panel power sequence state like Paulo wants to.

Instead of adding yet another single-use callback shuffle things
around:
- Output handling code is responsible to reset/init all state on its
  own at driver load time.
- We call the reset functions much earlier, before we start using any
  of the modeset code.

Compared to Paulo's new ->resume callback the only difference in
placement is that ->reset is still called without dev->struct_mutex
held. Which is imo a feature.

v2: Rebase on top of the now merge dinq.

Cc: Paulo Zanoni <przanoni@gmail.com>
Reviewed-by: NPaulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Because we already do the wait in software: see
ironlake_wait_backlight_on and ironlake_edp_wait_backlight_off.

For the "backlight on" delay, even BSpec says we need to program 0x1
to PP_ON_DELAYS 12:0.

For the "backlight off" delay, if we don't do the same thing, when we
call ironlake_wait_panel_off we'll end up waiting for the it again.

On my machine the off delay is 200ms, so we save this amount of time
whenever we disable the panel (e.g, suspend).
Signed-off-by: NPaulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: NJesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

I forgot to set new_config and new_enabled appropriately in the load
detect code. Fix it up.

v2: Handle the other error path in intel_get_load_detect_pipe() too (Imre)
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: NImre Deak <imre.deak@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Not sure anyone cares about this information. I suppose most people
would just look at /proc/interrupts instead.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Acked-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

irq_received is used as a boolean in i965_irq_handler(), so make it
bool. This also makes i965_irq_handler() closer to i915_irq_handler().
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Reviewd-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Add intel_hpd_irq_uninstall() which will cancel the hotplug re-enable
timer.

Also s/i915_reenable_hotplug_timer_func/intel_hpd_irq_reenable/
Suggested-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Function ironlake_wait_panel_off should just wait for the power off
delay, while function ironlake_wait_panel_power_cycle should wait for
the panel cycle (that's required after we turn the panel off, before
we enable it again).

The problem is that, currently, ironlake_wait_panel_off is waiting not
just for the panel to be off, but also for the power cycle delay and
the backlight off delay. This function relies on the PP_STATUS bits
3:0, which are not documented and not supposed to be used. A quick
analysis of the values we get while waiting quickly shows that power
off is reached while bits 3:0 are still 0x1, and the time it takes to
become 0x0 is the power cycle delay.

On my system with backlight off delay of 200ms, power down delay of
50ms and power cycle delay of 500ms, this is what I get:
 - Start waiting with value 0x80000008, timestamp 6.429364.
 - Jumps to 0xa0000003, timestamp 6.431360 (time waited: 0.001996)
 - Jumps to 0xa0000002, timestamp 6.631277 (time waited: 0.201913)
 - Jumps to 0x08000001, timestamp 6.681258 (time waited: 0.251894)
 - Jumps to 0x00000000, timestamp 7.192012 (time waited: 0.762648)

As you can see, ironlake_wait_panel_off is sleeping 760ms instead of
the expected 50ms: the first 200ms matches the backlight off delay
(which we should already have waited for!), then the 50ms for the real
panel off delay, then the 500ms for the panel power cycle.

This patch makes is look just at bits 31 and 29:28, which will ignore
the panel power cycle.

And just to be clear: this saves 500ms on my system every time we
disable the panel. But we can still save 200ms more (the backlight off
delay) on the next patches.
Signed-off-by: NPaulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: NJesse Barnes <jbarnes@virtuougseek.org>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

I like how the macros are nicely column-aligned, so we can properly
compare what each macro waits for, but a column full of zeroes doesn't
really help anything: it just makes the lines bigger, and they're
already way past 80 columns. I imagine this column was used in the
past, but IMHO now we can get rid of it.
Signed-off-by: NPaulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: NJesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

They now also work on vlv, which has the regs somewhere else. And
daring a glance into the looking glass it seems like this
functionality will continue to work the same for the next few hardware
platforms.

So it's better to just remove that misleading prefix and have a bit
shorter code for better readability.

The only exceptions are the panel/backlight functions shared with
intel_ddi.c, those get an intel_ prefix.

While at it make the vdd_on/off functions static.

And one straggler was missing the edp_ in the name, so make everything
neatly OCD.

Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: NJani Nikula <jani.nikula@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

The eDP spec defines some points where after you do action A, you have
to wait some time before action B. The thing is that in our driver
action B does not happen exactly after action A, but we still use
msleep() calls directly. What this patch does is that we record the
timestamp of when action A happened, then, just before action B, we
look at how much time has passed and only sleep the remaining amount
needed.

With this change, I am able to save about 5-20ms (out of the total
200ms) of the backlight_off delay and completely skip the 1ms
backlight_on delay. The 600ms vdd_off delay doesn't happen during
normal usage anymore due to a previous patch.

v2: - Rename ironlake_wait_jiffies_delay to intel_wait_until_after and
      move it to intel_display.c
    - Fix the msleep call: diff is in jiffies
v3: - Use "tmp_jiffies" so we don't need to worry about the value of
      "jiffies" advancing while we're doing the math.
v4: - Rename function again.
    - Move function to i915_drv.h.
    - Store last_power_cycle at edp_panel_off too.
    - Use msecs_to_jiffies_timeout, then replace the msleep with an
      open-coded version that avoids the extra +1 jiffy.
    - Try to add units to every variable name so we don't confuse
      jiffies with milliseconds.
Signed-off-by: NPaulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: NJani Nikula <jani.nikula@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Our driver has two different ways of waiting for panel power
sequencing delays. One of these ways is through
ironlake_wait_panel_status, which implicitly uses the values written
to our registers. The other way is through the functions that call
intel_wait_until_after, and on this case we do direct msleep() calls
on the intel_dp->xxx_delay variables.

Function intel_dp_init_panel_power_sequencer is responsible for
initializing the _delay variables and deciding which values we need to
write to the registers, but it does not write these values to the
registers. Only at intel_dp_init_panel_power_sequencer_registers we
actually do this write.

Then problem is that when we call intel_dp_i2c_init, we will get some
I2C calls, which will trigger a VDD enable, which will make use of the
panel power sequencing registers and the _delay variables, so we need
to have both ready by this time. Today, when this happens, the _delay
variables are zero (because they were not computed) and the panel
power sequence registers contain whatever values were written by the
BIOS (which are usually correct).

What this patch does is to make sure that function
intel_dp_init_panel_power_sequencer is called earlier, so by the time
we call intel_dp_i2c_init, the _delay variables will already be
initialized. The actual registers won't contain their final values,
but at least they will contain the values set by the BIOS.

The good side is that we were reading the values, but were not using
them for anything (because we were just skipping the msleep(0) calls),
so this "fix" shouldn't fix any real existing bugs. I was only able to
identify the problem because I added some debug code to check how much
time time we were saving with my previous patch.

Regression introduced by:
    commit ed92f0b2
    Author: Paulo Zanoni <paulo.r.zanoni@intel.com>
    Date:   Wed Jun 12 17:27:24 2013 -0300
        drm/i915: extract intel_edp_init_connector

v2: - Rewrite commit message.
Reviewed-by: NJesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: NPaulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

This was forgotten in

commit 565ee389
Author: Jani Nikula <jani.nikula@intel.com>
Date:   Wed Nov 13 12:56:29 2013 +0200

    drm/i915: do not save/restore backlight registers in KMS

Since the confusion was likely due to the duplicated definition for
this pci config register, let's unify that, too.

Cc: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: NJani Nikula <jani.nikula@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Atm, we don't print these events for all platforms and for VLV/G4X we
also print them for DP AUX completion events which is unnecessary spam.
Fix both issues.
Signed-off-by: NImre Deak <imre.deak@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Those are two distinct concepts. Just use a comment to remind us to
remove that W/A at some point.
Signed-off-by: NDamien Lespiau <damien.lespiau@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

crtc->new_config is only relevant for pipes that are going to be active
post-modeset. Set the pointer to NULL for all pipes that are going to
be disabled. This is done to help catch bugs where some piece of code
would go looking at crtc->new_config even if the data there is stale.

v2: Clear new_config in disable_crtc_nofb() too (Imre)
Suggested-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: NImre Deak <imre.deak@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

If the first modeset operation fails, we will attempt to restore the
previous configuration that we read out from the hardware. But as we
don't yet reconstruct the framebuffer information, we end up calling
the modeset code with an enabled crtc but with fb==NULL. This will
lead to an oops within the modeset code.

Check for NULL fb when restoring the configuration, and instead of
oopsing simply disable the pipe.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: NImre Deak <imre.deak@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

On VLV we need to compute the new cdclk before we've updated the current
state. The code achieved that in a somewhat complex way. Now that we
have new_enabled and new_config, we can simplify the code quite a bit.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: NImre Deak <imre.deak@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Add a new_config pointer to intel_crtc which will point to the new pipe
config for said crtc while intel_crtc.config will still contain the old
config during first parts of the modeset operation. This is a step
towards having the entire new state available during the compute phase,
so that we can make accurate decisions about global resource usage.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: NImre Deak <imre.deak@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Add 'new_enabled' to intel_crtc and precompute it alongside new_encoder
and new_crtc. This will allow making decisions about shared resources
that are affected by the set of active pipes, before we've clobbered
anything for real.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: NImre Deak <imre.deak@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

This reverts commit 446f2545.

I've left the masking in the pageflip code since that seems to be some
useful piece of preemptive robustness.

Iirc I've merged this patch under the assumption that the BIOS leaves
some random gunk in the lower bits and gets unhappy if we trample on
them. We have quite a few case like this, so this made sense.

Now I've just learned that there's actual hardware features bits in
the low 12 bits, and the kernel needs to preserve them to allow a
userspace blob to do its job. Given Dave Airlie's clear stance on
userspace blob drivers I've quickly chatted with him and he doesn't
seem too happy. So let's revert this.

If there are indeed bits that we must preserve in this range then we
can ressurrect this patch, but with proper documentation for those
bits supplied. And we probably also need to think a bit about
interactions with our driver.

Cc: Armin Reese <armin.c.reese@intel.com>
Cc: Jesse Barnes <jbarnes@virtuousgeek.org>
Cc: Dave Airlie <airlied@linux.ie>
Reviewed-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Add new definitions for hotplug live status bits for VLV2 since they're
in reverse order from the gen4x ones.

Changelog:
- Restored gen4 bit definitions
- Added new definitions for VLV2
- Added platform check for IS_VALLEYVIEW() in dp_detect to use the correct
  bit defintions
- Replaced a lost trailing brace for the added switch()
Signed-off-by: NTodd Previte <tprevite@gmail.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=73951
[danvet: Switch to _VLV postfix instead of prefix and regroupg
comments again so that the g4x warning is right next to those defines.
Also add a _G4X suffix for those special ones. Also cc stable.]
Cc: stable@vger.kernel.org
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Nothing's changed here; we just need to bump the generation check.
Signed-off-by: NKenneth Graunke <kenneth@whitecape.org>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Since an old pageflip will keep its scanout buffer object pinned until
it has executed its unpin task on the common workqueue, we can clog up
our GGTT with stale pinned objects. As we cannot flush those workqueues
without dropping our locks, we have to resort to falling back to
userspace and telling them to repeat the operation in order to have a
chance to run our workqueues and free up the required memory. If we
fail, then we are forced to report ENOSPC back to userspace causing the
operation to fail and best-case scenario is that it introduces temporary
corruption.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NJon Bloomfield <jon.bloomfield@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

On older generations (gen2, gen3) the GPU requires fences for many
operations, such as blits. The display hardware also requires fences for
scanouts and this leads to a situation where an arbitrary number of
fences may be pinned by old scanouts following a pageflip but before we
have executed the unpin workqueue. This is unpredictable by userspace
and leads to random EDEADLK when submitting an otherwise benign
execbuffer. However, we can detect when we have an outstanding flip and
so cause userspace to wait upon their completion before finally
declaring that the system is starved of fences. This is really no worse
than forcing the GPU to stall waiting for older execbuffer to retire and
release their fences before we can reallocate them for the next
execbuffer.

v2: move the test for a pending fb unpin to a common routine for
later reuse during eviction

Reported-and-tested-by: dimon@gmx.net
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=73696Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NJon Bloomfield <jon.bloomfield@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Atm after a failed link training we disable the DP port. This can happen
during a modeset-enable or a DP link re-establishment. The latter can be
a problem and we shouldn't disable the DP port, see the previous patch for
the reasoning. In the former case the right thing would be to disable
the DP port, but also the rest of the pipe.

As a stop-gap solution leave the DP port enabled in both cases. It is an
improvement on its own (avoiding HW lock ups) and the proper solution
for the first case requires a bigger change, so let's keep that on the
TODO list.

v2:
- fix explanation of change impact (Chris)
Suggested-by: NDaniel Vetter <daniel@ffwll.ch>
Signed-off-by: NImre Deak <imre.deak@intel.com>
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Currently if the DP link is lost (either because of a hot unplug, or
failed link status check) we disable the DP port, but leave the rest
of the pipe running. This is incompatible with the modeset disabling
sequence of some platforms/configurations. At least this is the case for
DP ports on the CPU as opposed to PCH.

Atm we'll also get a warning when we do a modeset disable after the
above link lost event, since we expect the DP port to be enabled at this
point (see the bugzilla ticket for the related dmesg).

Note that with this patch we'll still end up disabling the port, thanks
to the HPD uevent and subsequent modeset disable.

See also the next patch fixing the other half of this issue.

Solution suggested by Ville.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=70570Signed-off-by: NImre Deak <imre.deak@intel.com>
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

My 855gm doesn't register the intel backlight but it still ends up
calling the backlight code to enable/disable the backlight via the
LVDS code. This leads to some WARNs due to backlight.max being 0.

Let's have intel_panel_enable_backlight() and intel_panel_disable_backlight()
check whether there's a backlight present or not.

Also move the backlight.present check from asle_set_backlight() into
intel_panel_set_backlight() for some extra symmetry.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: NJani Nikula <jani.nikula@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>