This reverts

commit 047fe6e6
Author: David Weinehall <david.weinehall@linux.intel.com>
Date:   Tue Aug 4 16:55:52 2015 +0300

    drm/i915: Allow parsing of variable size child device entries from VBT

That commit is not valid for v4.2, however it will be valid for v4.3. It
was simply queued too early.

The referenced regressing commit is just fine until the size of struct
common_child_dev_config changes, and that won't happen until
v4.3. Indeed, the expected size checks here rely on the increased size
of the struct, breaking new platforms.

Fixes: 047fe6e6 ("drm/i915: Allow parsing of variable size child device entries from VBT")
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: David Weinehall <david.weinehall@linux.intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: NJani Nikula <jani.nikula@intel.com>

VBT version 196 increased the size of common_child_dev_config. The parser
code assumed that the size of this structure would not change.

The modified code now copies the amount needed based on the VBT version,
and emits a debug message if the VBT version is unknown (too new);
since the struct config block won't shrink in newer versions it should
be harmless to copy the maximum known size in such cases, so that's
what we do, but emitting the warning is probably sensible anyway.

In the longer run it might make sense to modify the parser code to
use a version/feature mapping, rather than hardcoding things like this,
but for now the variants are fairly managable.

This fixes a regression introduced in

commit 90e4f159
Author: Ville Syrjälä <ville.syrjala@linux.intel.com>
Date:   Wed Mar 25 18:45:58 2015 +0200

    drm/i915: Fix the VBT child device parsing for BSW

since we're hitting a DRM_ERROR on older platforms with this.

v2: Stricter size checks
Signed-off-by: NDavid Weinehall <david.weinehall@linux.intel.com>
[danvet: Fixup format string.]
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Add one explicit discard of __iomem address space qualifier in
validate_vbt(), and respect it otherwise. This adds clarity in the code,
and reduces the sparse warnings from the module to just one.

Quoting Daniel, "The vbt really is plain old memory. Except that it's
reserved in the e820 table as something special and hence treated as io
range by the kernel. But it is memory, hence casting away the __iomem is
imo the right approach."
Signed-off-by: NJani Nikula <jani.nikula@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Improve clarity. No functional changes.
Signed-off-by: NJani Nikula <jani.nikula@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

We never pass a non-NULL vbt to validate_vbt, and we can safely expect
the callers to not change.
Signed-off-by: NJani Nikula <jani.nikula@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Make input and output of validate_vbt const, and fix the fallout. We
shouldn't modify the VBT, so make the compiler help us here.

v2: use pointer arithmetics on void* to simplify (Ville)
Signed-off-by: NJani Nikula <jani.nikula@intel.com>
Reviewed-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Make input and output of find_section const, and fix the fallout. We
shouldn't modify the VBT, so make the compiler help us here.
Signed-off-by: NJani Nikula <jani.nikula@intel.com>
Reviewed-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

This provides an option to override the value set by VBT
for selecting edp Vswing Pre-emph setting table.

v2: Adding comment about this being a temporary workaround and
making the parameter read-only (Jani)
v3: Changing mode to 0400 instead of 0 (Jani)

https://bugs.freedesktop.org/show_bug.cgi?id=89554Signed-off-by: NSonika Jindal <sonika.jindal@intel.com>
Reviewed-by: NJani Nikula <jani.nikula@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Recent BSW VBT has a VBT child device size 37 bytes instead of the 33
bytes our code assumes. This means we fail to parse the VBT and thus
fail to detect eDP ports properly and just register them as DP ports
instead.

Fix it up by using the reported child device size from the VBT instead
of assuming it matches out struct defintions.

The latest spec I have shows that the child device size should be 36
bytes for rev >= 195, however on my BSW the size is actually 37 bytes.
And our current struct definition is 33 bytes.

Feels like the entire VBT parses would need to be rewritten to handle
changes in the layout better, but for now I've decided to do just the
bare minimum to get my eDP port back.

Cc: Vijay Purushothaman <vijay.a.purushothaman@linux.intel.com>
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: NDamien Lespiau <damien.lespiau@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

This will be helpful for adding future platforms. It is better to keep
the information in the single point of truth (the table) instead of
duplicating it into the validity function.

While at it, add dev_priv parameter to the function, also to prepare for
adding future platform support.
Signed-off-by: NJani Nikula <jani.nikula@intel.com>
Reviewed-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Rename intel_gmbus_is_port_valid to intel_gmbus_is_valid_pin, and rename
port parameters to pin as well. This matches usage all around, as
usually a pin is passed to the validity check function. No functional
changes.
Signed-off-by: NJani Nikula <jani.nikula@intel.com>
Reviewed-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

The specs refer to pin pairs. Start moving towards using pin rather than
port all around to avoid confusion. No functional changes.
Signed-off-by: NJani Nikula <jani.nikula@intel.com>
Reviewed-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

v2: Adding VBT version check for low_vswing field, and correcting parsing

v3: (Damien)
 - Restrain the scope of the 'vswing' variable
 - Use the more idiomatic "ev_priv->vbt.edp_low_vswing = vswing == 0;"
  instead of if (foo) var = true; else var = false;
 - Shorten edp_vswing_premph_setting to edp_vswing_premph to fit in 80 chars
 - Add the version from which the edp_vswing_premph field is valid in the
  struct definition

Reviewed-by: Satheeshakrishna M <satheeshakrishna.m@intel.com> (v2)
Signed-off-by: NSonika Jindal <sonika.jindal@intel.com>
Signed-off-by: NDamien Lespiau <damien.lespiau@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

This reverts commit 371abae8.

This data seems unreliable and causing many issues and blocking other
teams and feature implementation. Safest way is to revert that for now.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=88081
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=88039
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=87671
Cc: Vandana Kannan <vandana.kannan@intel.com>
Cc: Deepak M <m.deepak@intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Ben Widawsky <ben@bwidawsk.net>
Cc: Kristian Høgsberg <hoegsberg@gmail.com>
Signed-off-by: NRodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: NJani Nikula <jani.nikula@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

LFP brighness control from the VBT block 43 indicates which
controller is used for brightness.
LFP1 brightness control method:
Bit 7-4 = This field controller number of the brightnes controller.
0 = Controller 0
1 = Controller 1
2 = Controller 2
3 = Controller 3
Others = Reserved
Bits 3-0 = This field specifies the brightness control pin to be used on the
platform.
0 = PMIC pin is used for brightness control
1 = LPSS PWM is used for brightness control
2 = Display DDI is used for brightness control
3 = CABC method to control brightness
Others = Reserved

Adding the above fields in dev_priv->vbt and corresponding changes in
parse_backlight()

v2: Jani's review comments addressed
	- Move PWM definitions to intel_bios.h
	- Moving vbt_version to intel_vbt_data
	- Rename brightness to bl_ctrl_data
	- Logging just control_pin instead of string
	- Avoid adding vbt_version in dev_priv
	- Since only DDI option is available as of now, let control pin DDI
	affect dev_priv->vbt.backlight.present

v3: Jani's review comments addressed
	- Drop control_pin
	- Use bdb->version
	- set controller to 0 instead of using control pin define
	- check controller bounds
	- remove superfluous changes in intel_parse_bios
Signed-off-by: NDeepak M <m.deepak@intel.com>
Signed-off-by: NVandana Kannan <vandana.kannan@intel.com>
Reviewed-by: NJani Nikula <jani.nikula@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

PSR (aka SRD) block is defined at VBT and currently being used.
Mainly/At-least to configure the amount of idle_frames require to get
back to PSR Entry.
Signed-off-by: NRodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: NDurgadoss R <durgadoss.r@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Rename the defines to have levels instead of values for vswing and
pre-emph levels as the values may differ in other scenarios like low vswing of
eDP1.4 where the values are different.

Done using following cocci patch for each define:
@@
@@

 # define DP_TRAIN_VOLTAGE_SWING_400     (0 << 0)
+ # define DP_TRAIN_VOLTAGE_SWING_LEVEL_0     (0 << 0)

...
Signed-off-by: NSonika Jindal <sonika.jindal@intel.com>
Reviewed-by: NDamien Lespiau <damien.lespiau@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

The __init annotations for the DMI callback functions are wrong as this
code can be called even after the module has been initialized, e.g. like
this:

  # echo 1 > /sys/bus/pci/devices/0000:00:02.0/remove
  # modprobe i915
  # echo 1 > /sys/bus/pci/rescan

The first command will remove the PCI device from the kernel's device
list so the second command won't see it right away. But as it registers
a PCI driver it'll see it on the third command. If the system happens to
match one of the DMI table entries we'll try to call a function in long
released memory and generate an Oops, at best.

Fix this by removing the bogus annotation.

Modpost should have caught that one but it ignores section reference
mismatches from the .rodata section. :/

Fixes: 25e341cf ("drm/i915: quirk away broken OpRegion VBT")
Fixes: 8ca4013d ("CHROMIUM: i915: Add DMI override to skip CRT...")
Fixes: 425d244c ("drm/i915: ignore LVDS on intel graphics systems...")
Signed-off-by: NMathias Krause <minipli@googlemail.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Duncan Laurie <dlaurie@chromium.org>
Cc: Jarod Wilson <jarod@redhat.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>	# Can modpost be fixed?
Cc: stable@vger.kernel.org
Signed-off-by: NJani Nikula <jani.nikula@intel.com>

This patch fix spelling typo in printk within vairous
part of the code.
Signed-off-by: NMasanari Iida <standby24x7@gmail.com>
Acked-by: NRandy Dunlap <rdunlap@infradead.org>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

The knowledge about the HDMI/DVI DDI translation table was scattered
around.
  - info->hdmi_level_shift was initialized with 6, the index of the 800
    mV, 0dB translation
  - A check on the VBT value was done to ensure it wasn't overflowing
    the translation table (< 0xC)
  - The actual programming was done in intel_ddi.c

As we need to change that knowledge for Broadwell, let's gather
everything into one place.
Signed-off-by: NDamien Lespiau <damien.lespiau@intel.com>
Reviewed-by: NPaulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

This particular nasty presented itself while trying to register the
intelfb device (intel_fbdev.c). During the process of registering the device
the driver will disable the crtc via i9xx_crtc_disable. These will
also disable the panel using the generic mipi panel functions in
dsi_mod_vbt_generic.c. The stale MIPI generic data sequence pointers would
cause a crash within those functions. However, all of this is happening
while console_lock is held from do_register_framebuffer inside fbcon.c. Which
means that you got kernel log and just the device appearing to reboot/hang for
no apparent reason.

The fault started from the FB_EVENT_FB_REGISTERED event using the
fb_notifier_call_chain call in fbcon.c.

This regression has been introduced in

commit d3b542fc
Author: Shobhit Kumar <shobhit.kumar@intel.com>
Date:   Mon Apr 14 11:00:34 2014 +0530

    drm/i915: Add parsing support for new MIPI blocks in VBT

Cc: Shobhit Kumar <shobhit.kumar@intel.com>
Signed-off-by: NRafael Barbalho <rafael.barbalho@intel.com>
Reviewed-by: NShobhit Kumar <shobhit.kumar@intel.com>
[danvet: Add regression citation.]
Cc: stable@vger.kernel.org
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Reviewed-by: NJesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: NJani Nikula <jani.nikula@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Apparently there are Apple laptops with magic smoke for a VBIOS, which
we fail to find and use. Default to having and setting up backlight in
this case.

This fixes a regression introduced by
commit c675949e
Author: Jani Nikula <jani.nikula@intel.com>
Date:   Wed Apr 9 11:31:37 2014 +0300

    drm/i915: do not setup backlight if not available according to VBT

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=77831Reported-and-tested-by: NMatteo Cypriani <mcy@lm7.fr>
Cc: stable@vger.kernel.org # 3.15+
Reviewed-by: NImre Deak <imre.deak@intel.com>
Signed-off-by: NJani Nikula <jani.nikula@intel.com>

It seems by default the VBT has MIPI configuration block as well. The
Generic driver will assume always MIPI if MIPI configuration block is found.
This is causing probelm when actually there is eDP. Fix this by looking
into general definition block which will have device configurations. From here
we can figure out what is the LFP type and initialize MIPI only if MIPI
is found.

v2: Addressed review comments by Damien
    - Moved PORT definitions to intel_bios.h and renamed as DVO_PORT_MIPIA
    - renamed is_mipi to has_mipi and moved definition as suggested
    - Check has_mipi inside parse_mipi and intel_dsi_init insted of outside

v3: Make has_mipi as a bitfield as suggested
Signed-off-by: NShobhit Kumar <shobhit.kumar@intel.com>
Reviewed-by: NDamien Lespiau <damien.lespiau@intel.com>
[danvet: fold in conditions to pack everything neatly below 80 chars.]
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Use defines, do not set anything if VBT has values unknown to us.
Reviewed-by: NDamien Lespiau <damien.lespiau@intel.com>
Signed-off-by: NJani Nikula <jani.nikula@intel.com>

Be we read and chase pointers from the VBT, it is prudent to make sure
that those accesses are wholly contained within the MMIO region, or else
we may cause a kernel panic during boot.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NRodrigo Vivi <rodrigo.vivi@gmail.com>
Reviewed-by: NShobhit Kumar <shobhit.kumar@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Make sure that the whole BDB section is within the MMIO region prior to
accessing it contents. That we don't read outside of the secion is left
up to the individual section parsers.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NRodrigo Vivi <rodrigo.vivi@gmail.com>
Reviewed-by: NShobhit Kumar <shobhit.kumar@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

This cleans up the checkpatch errors for the merged commit -

commit d3b542fc
Author: Shobhit Kumar <shobhit.kumar@intel.com>
Date:   Mon Apr 14 11:00:34 2014 +0530

    drm/i915: Add parsing support for new MIPI blocks in VBT
Signed-off-by: NShobhit Kumar <shobhit.kumar@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

The parser extracts the config block(#52) and sequence(#53) data
and store in private data structures.

v2: Address review comments by Jani
    - adjust code for the structure changes for bdb_mipi_config
    - add boundry and buffer overflow checks as suggested
    - use kmemdup instead of kmalloc and memcpy

v3: More strict check while parsing VBT
    - Ensure that at anytime we do not go beyond sequence block
      while parsing
    - On unknown element fail the whole parsing

v4: Style changes and spell check mostly as suggested by Jani
Signed-off-by: NShobhit Kumar <shobhit.kumar@intel.com>
Reviewed-by: NJani Nikula <jani.nikula@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

The only supported types are none and PWM. Other values are obsolete or
reserved, don't add them.
Tested-by: NKamal Mostafa <kamal@canonical.com>
Tested-by: NMartin <bugs@mrvanes.com>
Tested-by: jrg.otte@gmail.com
Reviewed-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: NJani Nikula <jani.nikula@intel.com>

This patch reads the DRRS support and Mode type from VBT fields.
The read information will be stored in VBT struct during BIOS
parsing. The above functionality is needed for decision making
whether DRRS feature is supported in i915 driver for eDP panels.
This information helps us decide if seamless DRRS can be done
at runtime to support certain power saving features. This patch
was tested by setting necessary bit in VBT struct and merging
the new VBT with system BIOS so that we can read the value.

v2: Incorporated review comments from Chris Wilson
Removed "intel_" as a prefix for DRRS specific declarations.

v3: Incorporated Jani's review comments
Removed function which deducts drrs mode from panel_type. Modified some
print statements. Made changes to use DRRS_NOT_SUPPORTED as 0 instead of -1.

v4: Incorporated Jani's review comments.
Modifications around setting vbt drrs_type.
Signed-off-by: NPradeep Bhat <pradeep.bhat@intel.com>
Signed-off-by: NVandana Kannan <vandana.kannan@intel.com>
Acked-by: NJesse Barnes <jbarnes@virtuousgeek.org>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
[danvet: Drop the misleading/redundant comment about the added drrs
field in the vbt struct as discussed with Jani on irc.]
Reviewed-by: NJani Nikula <jani.nikula@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

MIPI Block #52 which provides configuration details for the MIPI panel
including dphy settings as per panel and tcon specs

Block #53 gives information on panel enable sequences

v2: Address review comemnts from Jani
    - Move panel ids from intel_dsi.h to intel_bios.h
    - bdb_mipi_config structure improvements for cleaner code
    - Adding units for the pps delays, all in ms
    - change data structure to be more cleaner and simple

v3: Corrected the unit for pps delays as 100us
Signed-off-by: NShobhit Kumar <shobhit.kumar@intel.com>
Reviewed-by: NJani Nikula <jani.nikula@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

With 20+ module parameters, I think referring to them via a struct
improves clarity over just having a bunch of globals. While at it, move
the parameter initialization and definitions into a new file
i915_params.c to reduce clutter in i915_drv.c.

Apart from the ill-named i915_enable_rc6, i915_enable_fbc and
i915_enable_ppgtt parameters, for which we lose the "i915_" prefix
internally, the module parameters now look the same both on the kernel
command line and in code. For example, "i915.modeset".

The downsides of the change are losing static on a couple of variables
and not having the initialization and module_param_named() right next to
each other. On the other hand, all module parameters are now defined in
one place at i915_params.c. Plus you can do this to find all module
parameter references:

$ git grep "i915\." -- drivers/gpu/drm/i915

v2:
- move the definitions into a new file
- s/i915_params/i915/
- make i915_try_reset i915.reset, for consistency
Signed-off-by: NJani Nikula <jani.nikula@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

We don't actually do anything with the information yet, but parse and
log what's in the VBT.
Signed-off-by: NJani Nikula <jani.nikula@intel.com>
Signed-off-by: NRodrigo Vivi <rodrigo.vivi@gmail.com>
Reviewed-by: NRodrigo Vivi <rodrigo.vivi@gmail.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Store the SSC refclock frequency in kHz to get more accuracy. Currently
we're pretending that 66 MHz is ~66000 kHz, when in fact it is actually
~66667 kHz. By storing the less rounded kHz value we get a much better
accuracy for out pixel clock calculations.

Cc: Bruno Prémont <bonbons@linux-vserver.org>
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Tested-by: NBruno Prémont <bonbons@linux-vserver.org>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

We had been using a DMI table workaround to select the right
frequency for devices, but this is fragile and must be updated
with every new platform.

Instead the default case when VBT is missing is changed to use
120MHz clock for LVDS SSC for these generations.

The docs for 2010-Core, SandyBridge, and IvyBridge all indicate
that the reference frequency for LVDS is 120MHz:

"2010 Core"
http://intellinuxgraphics.org/IHD_OS_Vol3_Part3r2.pdf
page 38
Reference Frequency: 120MHz for CRT and LVDS.  100MHz for the FDI.

"2011 SandyBridge"
http://intellinuxgraphics.org/documentation/SNB/IHD_OS_Vol3_Part3.pdf
page 33
Reference Frequency: 120MHz for CRT, HDMI, LVDS.  100MHz for the FDI.

"2012 IvyBridge"
http://intellinuxgraphics.org/documentation/IVB/IHD_OS_Vol3_Part4.pdf
page 27
Reference Frequency: 120 MHz for CRT, HDMI, LVDS, 100MHz for the FDI.
Signed-off-by: NDuncan Laurie <dlaurie@chromium.org>
[olof: Fixup for recent base, switched from if/else to single call]
Signed-off-by: NOlof Johansson <olof@lixom.net>
Reviewed-by: NRodrigo Vivi <rodrigo.vivi@gmail.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

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>

It only controls the setting of the vbt.edp_support variable, which in
turn only controls one debug output plus can also force-disable the
lvds output.

Since the value only restricted this logic to mobile ilk there's the
slight risk that this will break lvds on desktop ilk or on snb/ivb
platforms. But with the vbt it's better when we know what's going on
here, so let's rip it out and see what happens.

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

There's no reason to init a DP connector if the encoder just supports
HDMI: we'll just waste hundreds and hundreds of cycles trying to do DP
AUX transactions to detect if there's something there. Same goes for a
DP connector that doesn't support HDMI, but I'm not sure these
actually exist.

v2: - Use bit fields
    - Remove useless identation level
    - Replace DRM_ERROR with DRM_DEBUG_KMS
Signed-off-by: NPaulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@gmail.com> (v1)
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Our code makes a lot of assumptions regarding what each DDI port
actually supports, and the VBT should tell us what is really happening
in the hardware. So parse the information provided by the VBT and
check if any of our assumptions is wrong.

Our driver also has a history of not really trusting the VBT, so a
WARN here could mean that:
 a) our coding assumptions are wrong
 b) the VBT is wrong
 c) we're incorrectly parsing the VBT
 d) the checks are wrong

But I really hope we won't ever trigger any of those WARNs.

v2: Don't check the redundant "Capabilities" field from byte 24 since
    it doesn't seem to be used.
v3: Rebase
v4: Replace WARN with DRM_DEBUG_KMS
Signed-off-by: NPaulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@gmail.com> (v2)
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>