I don't see why we couldn't use the HPLL watermarks on g4x. So let's
enable them. Let's assume a 35 usec memory latency for the HPLL mode.
That's roughly what PNV uses.

Based on the behaviour of the ELK box I have 35 usec is probably
overkill. Actually all the current latency values used seem overkill as
I can reduce them pretty drastically before I start to see underruns.
But let's play things a bit safe for now.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170421181432.15216-14-ville.syrjala@linux.intel.comReviewed-by: NMaarten Lankhorst <maarten.lankhorst@linux.intel.com>

Implement proper two stage watermark programming for g4x. As with
other pre-SKL platforms, the watermark registers aren't double
buffered on g4x. Hence we must sequence the watermark update
carefully around plane updates.

The code is quite heavily modelled on the VLV/CHV code, with some
fairly significant differences due to the different hardware
architecture:
* g4x doesn't use inverted watermark values
* CxSR actually affects the watermarks since it controls memory self
  refresh in addition to the max FIFO mode
* A further HPLL SR mode is possible with higher memory wakeup
  latency
* g4x has FBC2 and so it also has FBC watermarks
* max FIFO mode for primary plane only (cursor is allowed, sprite is not)
* g4x has no manual FIFO repartitioning
* some TLB miss related workarounds are needed for the watermarks

Actually the hardware is quite similar to ILK+ in many ways. The
most visible differences are in the actual watermakr register
layout. ILK revamped that part quite heavily whereas g4x is still
using the layout inherited from earlier platforms.

Note that we didn't previously enable the HPLL SR on g4x. So in order
to not introduce too many functional changes in this patch I've not
actually enabled it here either, even though the code is now fully
ready for it. We'll enable it separately later on.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170421181432.15216-13-ville.syrjala@linux.intel.comReviewed-by: NMaarten Lankhorst <maarten.lankhorst@linux.intel.com>

The documentation I've seen doesn't actually specify which watermarks
need the TLB miss w/a. Currently we only apply the w/a to the normal
watermarks for both primary and cursor planes. Since the documentation
doesn't explicitly say anything I'm going to assume that the w/a should
equally apply to the SR/HPLL watermarks. So let's do that.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170421181432.15216-12-ville.syrjala@linux.intel.comReviewed-by: NMaarten Lankhorst <maarten.lankhorst@linux.intel.com>

All platforms until SKL compute their watermarks essentially
using the same method1/small buffer and method2/large buffer
formulas. Most just open code it in slightly different ways.
Let's pull it all into common helpers. This makes it a little
easier to spot the actual differences.

While at it try to add some docs explainign what the formulas
are trying to do.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170421181432.15216-11-ville.syrjala@linux.intel.comReviewed-by: NMaarten Lankhorst <maarten.lankhorst@linux.intel.com>

Pull the g4x TLB miss w/a calculation into a small helper.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170421181432.15216-10-ville.syrjala@linux.intel.comReviewed-by: NMaarten Lankhorst <maarten.lankhorst@linux.intel.com>

The g4x watermark TLB miss workaround requires that we bump up the
watermark by the difference between 8 full lines and the FIFO size.
Unfortunately the way we compute it at the moment ignores the size
of the pixels. The code also used the primary plane width as the
cursor width when computing the TLB miss w/a for the cursor.
Let's fix both problems.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170421181432.15216-9-ville.syrjala@linux.intel.comReviewed-by: NMaarten Lankhorst <maarten.lankhorst@linux.intel.com>

The watermark code for the old platforms (g4x and older) uses the
primary plane cpp when computing cursor watermarks. To keep the fix
simple let's just hardcode cpp=4 for the cursor on those platforms
since that's all we support.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170421181432.15216-8-ville.syrjala@linux.intel.comReviewed-by: NMaarten Lankhorst <maarten.lankhorst@linux.intel.com>

Add some documentation explaining what CxSR actually is.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170421181432.15216-7-ville.syrjala@linux.intel.comReviewed-by: NMaarten Lankhorst <maarten.lankhorst@linux.intel.com>

The magic numbers 0,1,2 aren't all that interesting for users perhaps.
Since we know what these watermark levels mean for VLV/CHV let's print
their names.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170421181432.15216-6-ville.syrjala@linux.intel.comReviewed-by: NMaarten Lankhorst <maarten.lankhorst@linux.intel.com>

We'll be wanting to share some of these watermark structures on g4x,
so let's rename them to have a g4x_ prefix instead of vlv_.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170421181432.15216-5-ville.syrjala@linux.intel.comReviewed-by: NMaarten Lankhorst <maarten.lankhorst@linux.intel.com>

Rename the VLV/CHV max_level->num_levels helper to have an intel_
prefix since it's not VLV/CHV specific and I'll want to use it on
other platforms as well.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170421181432.15216-4-ville.syrjala@linux.intel.comReviewed-by: NMaarten Lankhorst <maarten.lankhorst@linux.intel.com>

Seeing the display FIFO sizes at driver load time doesn't really provide
anything useful for us, so let's just drop the debug message. One can
always use eg. intel_watermarks to dump out the hardware settings prior
to loading the driver.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170421181432.15216-3-ville.syrjala@linux.intel.comReviewed-by: NMaarten Lankhorst <maarten.lankhorst@linux.intel.com>

Rename some of the vlv wm functions to reflect the fact that they
operate on the "raw" watermarks.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170421181432.15216-2-ville.syrjala@linux.intel.comReviewed-by: NMaarten Lankhorst <maarten.lankhorst@linux.intel.com>

This looks like a left-over from enabling work. The spec defines
CH7017_LVDS_PLL_FEEDBACK_DEFAULT_RESERVED as reserved set, so follow
this in the programming.

v2:
- Follow the spec to set CH7017_LVDS_PLL_FEEDBACK_DEFAULT_RESERVED.
  (Ville)

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: NImre Deak <imre.deak@intel.com>
Reviewed-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1494408113-379-7-git-send-email-imre.deak@intel.com

On GEN8+ (not counting CHV) the calculation can in theory result in an
incorrect sign extension with all upper bits set. In practice this is
unlikely to happen since it would require 4GB of stolen memory set
aside. For consistency still prevent the sign extension explicitly
everywhere.
Signed-off-by: NImre Deak <imre.deak@intel.com>
Reviewed-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1494408113-379-6-git-send-email-imre.deak@intel.com

An error from intel_get_pipe_from_connector() would mean a bug somewhere
else, but we still should check for it to prevent some other more
obscure bug later.

v2:
- Fall back to a reasonable default instead of bailing out in case of
  error. (Jani)
v3:
- Fix s/PIPE_INVALID/INVALID_PIPE/ typo. (Jani)
v4:
- Fix bogus bracing around WARN() condition. (Ville)

Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: NImre Deak <imre.deak@intel.com>
Reviewed-by: NJani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1494408113-379-5-git-send-email-imre.deak@intel.com

Even though an error from these functions isn't fatal we still want to
have a diagnostic message about it.

v2:
- Don't do assignments in if statements. (Jani)

Cc: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: NImre Deak <imre.deak@intel.com>
Reviewed-by: NJani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1494408113-379-4-git-send-email-imre.deak@intel.com

The current code assumes that 'enhancements' won't change in case of an
error, but this isn't guaranteed. Fix things by treating any error as a
lack of the given capability.

v2:
- Remove the now redundant init of enhancements. (Ville)

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: NImre Deak <imre.deak@intel.com>
Reviewed-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1494408113-379-3-git-send-email-imre.deak@intel.com

The assumptions of these users of drm_dp_dpcd_readb() is that the passed
in output buffer won't change in case of error, but this isn't
guaranteed. Fix this by treating any error as the lack of the given
capability.

In case of DP_SINK_DEVICE_AUX_FRAME_SYNC_CAP an error would leave the
buffer uninitialized even with the above assumption.
Signed-off-by: NImre Deak <imre.deak@intel.com>
Reviewed-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1494408113-379-2-git-send-email-imre.deak@intel.com

The current code looks like a typo, the specification calls for setting
bits 31:24 to 0x8C, while preserving bits 23:0. Fix things accordingly.

I'm not aware of the typo causing a real problem, so the fix is only for
consistency.

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: NImre Deak <imre.deak@intel.com>
Reviewed-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1494408113-379-1-git-send-email-imre.deak@intel.com

The assumption is that the registers offsets are
identical as with skl. Also all the published
kbl firmwares support the debug registers. So
let kbl show the debug counts.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=100975
Cc: Imre Deak <imre.deak@intel.com>
Signed-off-by: NMika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: NImre Deak <imre.deak@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1494324322-28193-1-git-send-email-mika.kuoppala@intel.com

In order to allow use of e.g. forcewake_domains in a other feature headers
included from the top of i915_drv.h, move all uncore related definitions
into their own header.

v2: move __mask_next_bit macro to utils header (Mika)
Signed-off-by: NMichal Wajdeczko <michal.wajdeczko@intel.com>
Suggested-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Mika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: NMika Kuoppala <mika.kuoppala@intel.com>
Signed-off-by: NMika Kuoppala <mika.kuoppala@intel.com>

Use memdup_user_nul() helper instead of open-coding to simplify the
code.
Signed-off-by: NGeliang Tang <geliangtang@gmail.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/6baf3aa45d0b5e0fd016b508bac905ebf8443aac.1493779294.git.geliangtang@gmail.com

Turns out our skills in decoding the CLKCFG register weren't good
enough. On this particular elk the answer we got was 400 MHz when
in reality the clock was running at 266 MHz, which then caused us
to program a bogus AUX clock divider that caused all AUX communication
to fail.

Sadly the docs are now in bit heaven, so the fix will have to be based
on empirical evidence. Using another elk machine I was able to frob
the FSB frequency from the BIOS and see how it affects the CLKCFG
register. The machine seesm to use a frequency of 266 MHz by default,
and fortunately it still boot even with the 50% CPU overclock that
we get when we bump the FSB up to 400 MHz.

It turns out the actual FSB frequency and the register have no real
link whatsoever. The register value is based on some straps or something,
but fortunately those too can be configured from the BIOS on this board,
although it doesn't seem to respect the settings 100%. In the end I was
able to derive the following relationship:

BIOS FSB / strap | CLKCFG
-------------------------
200              | 0x2
266              | 0x0
333              | 0x4
400              | 0x4

So only the 200 and 400 MHz cases actually match how we're currently
decoding that register. But as the comment next to some of the defines
says, we have been just guessing anyway.

So let's fix things up so that at least the 266 MHz case will work
correctly as that is actually the setting used by both the buggy
machine and my test machine.

The fact that 333 and 400 MHz BIOS settings result in the same register
value is a little disappointing, as that means we can't tell them apart.
However, according to the gmch datasheet for both elk and ctg 400 Mhz is
not even a supported FSB frequency, so I'm going to make the assumption
that we should decode it as 333 MHz instead.

Cc: stable@vger.kernel.org
Cc: Tomi Sarvela <tomi.p.sarvela@intel.com>
Reported-by: NTomi Sarvela <tomi.p.sarvela@intel.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=100926Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170504181530.6908-1-ville.syrjala@linux.intel.comAcked-by: NJani Nikula <jani.nikula@intel.com>
Tested-by: NTomi Sarvela <tomi.p.sarvela@intel.com>

Typically, there is space available within the ring and if not we have
to wait (by definition a slow path). Rearrange the code to reduce the
number of branches and stack size for the hotpath, accomodating a slight
growth for the wait.

v2: Fix the new assert that packets are not larger than the actual ring.
v3: Make the parameters unsigned as well to make usage.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NMika Kuoppala <mika.kuoppala@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170504130846.4807-3-chris@chris-wilson.co.uk

Some callers immediately want to know the current ring->space after
calling intel_ring_update_space(), which we can freely provide via the
return parameter.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170504130846.4807-2-chris@chris-wilson.co.uk

Exploit the power-of-two ring size to compute the space across the
wraparound using a mask rather than a if. Convert to unsigned integers
so the operation is well defined.

References: https://bugs.freedesktop.org/show_bug.cgi?id=99671Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: NMika Kuoppala <mika.kuoppala@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170504130846.4807-1-chris@chris-wilson.co.uk

Since unifying ringbuffer/execlist submission to use
engine->pin_context, we ensure that the intel_ring is available before
we start constructing the request. We can therefore move the assignment
of the request->ring to the central i915_gem_request_alloc() and not
require it in every engine->request_alloc() callback. Another small step
towards simplification (of the core, but at a cost of handling error
pointers in less important callers of engine->pin_context).

v2: Rearrange a few branches to reduce impact of PTR_ERR() on gcc's code
generation.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Oscar Mateo <oscar.mateo@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Reviewed-by: NOscar Mateo <oscar.mateo@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170504093308.4137-1-chris@chris-wilson.co.uk

Since kmap allows us to block we can pin the pages and use our normal
page lookup routine making the implementation simple, or as some might
say quick and dirty.

Testcase: igt/drv_selftest/dmabuf
Testcase: igt/prime_rw
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170503202517.16797-1-chris@chris-wilson.co.uk

Backmerge the main drm-next pull to sync up.

Chris also pointed out that

commit ade0b0c9
Author: Chris Wilson <chris@chris-wilson.co.uk>
Date:   Sat Apr 22 09:15:37 2017 +0100

    drm/i915: Confirm the request is still active before adding it to the await

is double-applied in the git merge, so make sure we get this right.
Signed-off-by: NDaniel Vetter <daniel.vetter@intel.com>

Now that everything is in place let's register a PCM device for
each port of the display engine. This will make it possible to
actually output audio to multiple displays at the same time. And
it avoids modesets on unrelated displays from clobbering up the
ELD and whatnot for the display currently doing the playback.

v2: Add a PCM per port instead of per pipe
v3: Fix off by one error with port numbers (Pierre-Louis)
    Fix .notify_audio_lpe() prototype (Pierre-Louis)

Cc: Takashi Iwai <tiwai@suse.de>
Cc: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170427160231.13337-12-ville.syrjala@linux.intel.comReviewed-by: NTakashi Iwai <tiwai@suse.de>

To allow multiple PCM devices to be registered for the LPE audio card,
split the private data into card and PCM specific chunks. For now we'll
stick to just one PCM device as before.

v2: Rework to do a pcm device per port instead of per pipe

Cc: Takashi Iwai <tiwai@suse.de>
Cc: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170427160231.13337-11-ville.syrjala@linux.intel.comReviewed-by: NTakashi Iwai <tiwai@suse.de>

In preparation for register a PCM device for each pipe adjust
link up the ctl elements with the corresponding PCM device.

Cc: Takashi Iwai <tiwai@suse.de>
Cc: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170427160231.13337-10-ville.syrjala@linux.intel.comReviewed-by: NTakashi Iwai <tiwai@suse.de>

Split the LPE audio platform data into a port specific
chunk and device specific chunk. Eventually we'll have
a port specific chunk for each port, but for now we'll
stick to just one.

We'll also get rid of the intel_hdmi_lpe_audio_eld structure
which doesn't seem to have any real reason to exist.

v2: Organize per port instead of per pipe

Cc: Takashi Iwai <tiwai@suse.de>
Cc: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170427160231.13337-9-ville.syrjala@linux.intel.comReviewed-by: NTakashi Iwai <tiwai@suse.de>

Shuffle the arguments to intel_lpe_audio_notify() around a bit. Pipe
and port being the most important things, so let's put the first, and
thre rest can come in as is. Also constify the eld argument.

Cc: Takashi Iwai <tiwai@suse.de>
Cc: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170427160231.13337-8-ville.syrjala@linux.intel.comReviewed-by: NTakashi Iwai <tiwai@suse.de>

We can determine that the pipe was shut down from pipe<0, so there's
no point in duplicating that information as 'hdmi_connected'.

v2: Use pipe<0 instead of port<0 as we'll want to do per-port
    PCM devices later
    Initialize pipe to -1 to inidicate inactive initial state

Cc: Takashi Iwai <tiwai@suse.de>
Cc: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170427160231.13337-7-ville.syrjala@linux.intel.comReviewed-by: NTakashi Iwai <tiwai@suse.de>

There's no need to distinguish between the DP link rate and HDMI TMDS
clock for the purposes of the LPE audio. Both are actually the same
thing more or less, which is the link symbol clock. So let's just
call the thing ls_clock and simplify the code.

Cc: Takashi Iwai <tiwai@suse.de>
Cc: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170427160231.13337-6-ville.syrjala@linux.intel.comReviewed-by: NTakashi Iwai <tiwai@suse.de>

The pending_notify flag in the LPE audio platform data is pointless,
actually unused. So let's kill it off.

v2: Fix typo in patch subject

Cc: Takashi Iwai <tiwai@suse.de>
Cc: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170427160231.13337-5-ville.syrjala@linux.intel.comReviewed-by: NTakashi Iwai <tiwai@suse.de>

vlv_display_irq_postinstall() enables the LPE audio interrupts
regardless of whether the LPE audio irq chip has masked/unmasked
them. Also the irqchip masking/unmasking doesn't consider the state
of the display power well or the device, and hence just leads to
dmesg spew when it tries to access the hardware while it's powered
down.

If the current way works, then we don't need to do anything in the
mask/unmask hooks. If it doesn't work, well, then we'd need to properly
track whether the irqchip has masked/unmasked the interrupts when
we enable display interrupts. And the mask/unmask hooks would need
to check whether display interrupts are even enabled before frobbing
with he registers.

So let's just assume the current way works and neuter the mask/unmask
hooks. Also clean up vlv_display_irq_postinstall() a bit and stop
it from trying to unmask/enable the LPE C interrupt on VLV since it
doesn't exist.

Cc: Takashi Iwai <tiwai@suse.de>
Cc: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170427160231.13337-4-ville.syrjala@linux.intel.comReviewed-by: NTakashi Iwai <tiwai@suse.de>

Clear the notify function pointer in the platform data before we tear
down the driver. Otherwise i915 would end up calling a stale function
pointer and possibly explode.

Cc: stable@vger.kernel.org
Cc: Takashi Iwai <tiwai@suse.de>
Cc: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170427160231.13337-3-ville.syrjala@linux.intel.comReviewed-by: NTakashi Iwai <tiwai@suse.de>