We need to be extremely careful inside i915_request_await_start() as it
needs to walk the list of requests in the foreign timeline with very
little protection. As we hold our own timeline mutex, we can not nest
inside the signaler's timeline mutex, so all that remains is our RCU
protection. However, to be safe we need to tell the compiler that we may
be traversing the list only under RCU protection, and furthermore we
need to start declaring requests as elements of the timeline from their
construction.

Fixes: 9ddc8ec0 ("drm/i915: Eliminate the trylock for awaiting an earlier request")
Fixes: 6a79d848

 ("drm/i915: Lock signaler timeline while navigating")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200227085723.1961649-11-chris@chris-wilson.co.uk

Check that we can recover if the LRC is totally corrupted. Based on a
very simple theory that anything that can be adjusted via the context
(i.e. on behalf of the user), should be under the purview of the
per-engine-reset.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200227085723.1961649-13-chris@chris-wilson.co.uk

Record the LRC registers before/after a preemption event to ensure that
the first context sees nothing from the second client; at least in the
normal per-context register state.

References: https://gitlab.freedesktop.org/drm/intel/issues/1233
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200227085723.1961649-12-chris@chris-wilson.co.uk

Pull the final atomic_dec of vm->open (marking the vm as closed)
underneath the same vm->mutex as used to close it. This is required to
correctly serialise with attempting to reuse the vma as the vm is closed
by a second thread.

References: 00de702c

 ("drm/i915: Check that the vma hasn't been closed before we insert it")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200227085723.1961649-10-chris@chris-wilson.co.uk

As we drop the engine-pm on retiring, that may happen while there are
still CS events in the buffer. As such we cannot assert the engine is
still active on reset, until we know that the current request is still
in flight.

Closes: https://gitlab.freedesktop.org/drm/intel/issues/1338
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Andi Shyti <andi.shyti@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200227204727.2009346-1-chris@chris-wilson.co.uk

Still chasing the mystery of the stray idle flush, let's ensure that the
heartbeat does not run at the same time as our test and confuse us.

References: https://gitlab.freedesktop.org/drm/intel/issues/541
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Andi Shyti <andi.shyti@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200227085723.1961649-8-chris@chris-wilson.co.uk

Attaching to the i915_active barrier is a two stage process, and a flush
is only effective when the barrier is activation. Thus it is possible
for us to see a barrier, and attempt to flush, only for our flush to
have no effect. As such, before attempting to activate signaling on the
fence we need to double check it is a fence!

Fixes: d13a3177

 ("drm/i915: Flush idle barriers when waiting")
Closes: https://gitlab.freedesktop.org/drm/intel/issues/1333
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Andi Shyti <andi.shyti@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200227085723.1961649-1-chris@chris-wilson.co.uk

On TGL, bits 2-4 in the GGTT PTE are not ignored anymore and are
instead used for some extra VT-d capabilities. We don't (yet?) have
support for those capabilities, but, given that we shared the pte_encode
function betweed GGTT and PPGTT, we still set those bits to the PPGTT
PPAT values. The DMA engine gets very confused when those bits are
set while the iommu is enabled, leading to errors. E.g. when loading
the GuC we get:

[    9.796218] DMAR: DRHD: handling fault status reg 2
[    9.796235] DMAR: [DMA Write] Request device [00:02.0] PASID ffffffff fault addr 0 [fault reason 02] Present bit in context entry is clear
[    9.899215] [drm:intel_guc_fw_upload [i915]] *ERROR* GuC firmware signature verification failed

To fix this, just have dedicated gen8_pte_encode function per type of
gtt. Also, explicitly set vm->pte_encode for gen8_ppgtt, even if we
don't use it, to make sure we don't accidentally assign it to the GGTT
one, like we do for gen6_ppgtt, in case we need it in the future.

Reported-by: "Sodhi, Vunny" <vunny.sodhi@intel.com>
Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20200226185657.26445-1-daniele.ceraolospurio@intel.com

Wa_1608008084 is an additional WA that applies to writes on FF_MODE2
register. We can't read it back either from CPU or GPU. Since the other
bits should be 0, recommendation to handle Wa_1604555607 is to actually
just write the timer value.

Do a write only and don't try to read it, neither before or after
the WA is applied.

Fixes: ff690b21

 ("drm/i915/tgl: Implement Wa_1604555607")
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: José Roberto de Souza <jose.souza@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200224191258.15668-1-lucas.demarchi@intel.com

Looks like the pipe rounding mode bit has moved from PIPE_CHICKEN to
PIPE_MISC on tgl. Frob the new location.

Bspec does still document the old bits as well, so I left the code
for them as is until we get clarification from the hw folks on
whether the old bits still do something useful.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200226163054.9509-1-ville.syrjala@linux.intel.com
Reviewed-by: José Roberto de Souza <jose.souza@intel.com>

This register was placed in the middle of the PP_STATUS definition
instead of together with the PP_CONTROL where it should. Since it's not
used and there are no current plans to use it, just remove the
definition.

v2: remove the define rather than moving it.

Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190308232321.30168-1-lucas.demarchi@intel.com

The implicit "dev_priv" local variable use has been a long-standing pain
point in the register access macros I915_READ(), I915_WRITE(),
POSTING_READ(), I915_READ_FW(), and I915_WRITE_FW().

Replace the sole remaining I915_WRITE() in i915_drv.c with
intel_uncore_write(), although it might be better to keep the entire
file void of direct register access.

No functional changes.

Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200225111509.21879-3-jani.nikula@intel.com

The implicit "dev_priv" local variable use has been a long-standing pain
point in the register access macros I915_READ(), I915_WRITE(),
POSTING_READ(), I915_READ_FW(), and I915_WRITE_FW().

Replace them with the corresponding uncore register accessors
intel_uncore_read(), intel_uncore_write(), intel_uncore_posting_read(),
intel_uncore_read_fw(), and intel_uncore_write_fw().

Rename dev_priv to i915 while at it.

No functional changes.

Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200225111509.21879-2-jani.nikula@intel.com

The DRAM related routines are pretty isolated from the rest of the
i915_drv.c, split it out to a separate file. Put the eDRAM stuff in the
same bag, and rename the visible functions to have intel_dram_
prefix. Do some benign whitespace fixes and dev_priv -> i915 conversions
while at it.

Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200225111509.21879-1-jani.nikula@intel.com

The #include has been splattered all over the place, but there are
precious few places, all .c files, that actually need it.

v2: remove leftover double newlines

Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200225133131.3301-1-jani.nikula@intel.com

On Tiger Lake we do not support source keying in the pixel formats P010,
P012, P016.

v2: Move WA to end of function. Create helper function for format
check. Less verbose debugging messaging.

v3: whitespace

v4(MattR):
 - Actually return EINVAL to reject this combination.
 - Pass format parameter as u32.
 - Make test TGL-specific for now.
 - Switch to per-device logging.
 - Shorten/simplify comment.

Bspec: 52890
Cc: Matt Roper <matthew.d.roper@intel.com>
Cc: Manasi Navare <manasi.d.navare@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Matt Atwood <matthew.s.atwood@intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200224223651.3801646-1-matthew.d.roper@intel.com
Reviewed-by: José Roberto de Souza <jose.souza@intel.com>

On gen12, we no longer need to disable DC5/DC6 when when PG2 is in use
(which translates to cases where we're using VDSC on pipe A).

Bspec: 49193
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Cc: José Roberto de Souza <jose.souza@intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200220231843.3127468-1-matthew.d.roper@intel.com
Reviewed-by: José Roberto de Souza <jose.souza@intel.com>

gvt-next-2020-02-26

- Enable VFIO edid for all platform (Zhenyu)
- Code cleanup for attr group and unused vblank complete (Zhenyu, Julian)
- Make gvt oblivious of kvmgt data structures (Julian)
- Make WARN* drm specific (Pankaj)

Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
From: Zhenyu Wang <zhenyuw@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200226103840.GD10413@zhen-hp.sh.intel.com

skl_ddb_allocation_overlaps() num_entries hass been passed as
INTEL_NUM_PIPES, it should be I915_MAX_PIPES.

v2:
- Rebased.

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Anshuman Gupta <anshuman.gupta@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200224124004.26712-8-anshuman.gupta@intel.com

Add a WARN_ON for a disabled pipe in pipe_mask at
intel_get_crtc_for_pipe() function.

v2:
- Use drm_WARN_ON instead of WARN_ON.

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Anshuman Gupta <anshuman.gupta@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200224124004.26712-7-anshuman.gupta@intel.com

intel_plane_fb_max_stride should return the max stride of
primary plane for first available pipe in intel device info
pipe_mask.
Similarly glk_force_audio_cdclk() should also use the first
available CRTC instead of pipe 'A' crtc to force the cdclk
changes.

changes since RFC:
- Introduced a helper to get first intel_crtc intel_get_first_crtc. [Ville]
v1:
- Used intel_get_first_crtc() instead of PIPE_A crtc in
  glk_force_audio_cdclk(). [Ville]

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Anshuman Gupta <anshuman.gupta@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200224124004.26712-6-anshuman.gupta@intel.com

Skip the transcoder whose pipe is disabled while
initializing transcoder error state in 3 non-contiguous
display pipe system.

v2:
- Don't skip EDP_TRANSCODER error state. [Ville]
- Use a helper has_transcoder(). [Ville]
v3:
- Removed DSI transcoder case from has_transcoder(),
  and few other cosmetic changes. [Ville]

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Anshuman Gupta <anshuman.gupta@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200224124004.26712-4-anshuman.gupta@intel.com

we can't have (pipe == crtc->index) assumption in
driver in order to support 3 non-contiguous
display pipe system.

FIXME: Remove the WARN_ON(drm_crtc_index(&crtc->base) != crtc->pipe)
when we will fix all such assumption.

changes since RFC:
- Added again removed (pipe == crtc->index) WARN_ON.
- Pass drm_crtc_index instead of intel pipe in order to
  call drm_handle_vblank().
v2:
- Used drm_crtc_handle_vblank()/drm_crtc_wait_one_vblank()
  instead of drm_handle_vblank/drm_wait_one_vblank(). [Jani]
- Introduced intel_handle_vblank() helper to avoid sprinkle
  of intel_crtc across irq_handlers. [Ville]
v3:
- Moved intel_handle_vblank() from header to i915_irq.c. [Ville]

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Anshuman Gupta <anshuman.gupta@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200224124004.26712-3-anshuman.gupta@intel.com

It should not be assumed that a disabled display pipe will be
always last the pipe.
for_each_pipe() should iterate over I915_MAX_PIPES and check
for the disabled pipe and skip that pipe so that it should not
initialize the intel crtc for any disabled pipes.

Due to changes in for_each_pipe() macro, it requires to handle
the below compilation error.
"suggest explicit braces to avoid ambiguous ‘else’
[-Werror=dangling-else]"

v2:
- Cosmetic changes, removed unwanted parentheses. [Ville]

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Anshuman Gupta <anshuman.gupta@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200224124004.26712-2-anshuman.gupta@intel.com

Split inte_modeset_init() to parts before and after irq install, to
facilitate further cleanup. The error paths are a mess, otherwise no
functional changes.

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200224120828.22105-1-jani.nikula@intel.com

We no longer need or use it as we subclass struct drm_device in our
struct drm_i915_private, and can always use to_i915() to get at
i915. Stop assigning the pointer to catch anyone trying to add new users
for ->dev_private.

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Dale B Stimson <dale.b.stimson@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200224113312.13674-1-jani.nikula@intel.com

Check the user's flags on the struct file before deciding whether or not
to stall before submitting a request. This allows us to reasonably
cheaply honour O_NONBLOCK without checking at more critical phases
during request submission.

Suggested-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Steve Carbonari <steven.carbonari@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200225192206.1107336-3-chris@chris-wilson.co.uk

No good reason why we must always use a static ringsize, so let
userspace select one during construction.

Link: https://github.com/intel/compute-runtime/pull/261
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Steve Carbonari <steven.carbonari@intel.com>
Reviewed-by: Janusz Krzysztofik <janusz.krzysztofik@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200225192206.1107336-2-chris@chris-wilson.co.uk

If we do find ourselves with an idle barrier inside our active while
waiting, attempt to flush it by emitting a pulse using the kernel
context.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Steve Carbonari <steven.carbonari@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200225192206.1107336-1-chris@chris-wilson.co.uk

Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

Some DSI and VBT pending patches from Hans will apply
cleanly and with less ugly conflicts if they are rebuilt
on top of other patches that recently landed on drm-next.

Reference: https://patchwork.freedesktop.org/series/70952/
Cc: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

We cannot assert the fence is not yet changed as the next thread may
change it prior to acquiring our lock.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200225082233.274530-1-chris@chris-wilson.co.uk

Tidy up after a call to eb_parse() if a later bind fails.

Closes: https://gitlab.freedesktop.org/drm/intel/issues/1312
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200225082233.274530-4-chris@chris-wilson.co.uk

When vgpu ptr is unavailable, the drm_WARN* can hang the whole system
due to the drm pointer is NULL. This patch fixes this issue by using
WARN directly which won't care about the drm pointer.

Fixes: 12d58619

 ("drm/i915/gvt: Make WARN* drm specific where vgpu ptr is available")
Signed-off-by: Tina Zhang <tina.zhang@intel.com>
Reviewed-by: Zhenyu Wang <zhenyuw@linux.intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20200225053527.8336-1-tina.zhang@intel.com

Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

Full-ppgtt on gen7 is proving to be highly unstable and not robust.

Closes: https://gitlab.freedesktop.org/drm/intel/issues/694
Fixes: 3cd6e886

 ("drm/i915/gen7: Re-enable full-ppgtt for ivb & hsw")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Dave Airlie <airlied@redhat.com>
Acked-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200224101120.4024481-1-chris@chris-wilson.co.uk

Commit 60c6a14b ("drm/i915/display: Force the state compute phase
once to enable PSR") was forcing the state compute too earlier
causing errors because not everything was initialized, so here
moving to the end of i915_driver_modeset_probe() when the display is
all initialized.

Also fixing the place where it disarm the force probe as during the
atomic check phase errors could happen like the ones due locking and
it would cause PSR to never be enabled if that happens.
Leaving the disarm to the atomic commit phase, intel_psr_enable() or
intel_psr_update() will be called even if the current state do not
allow PSR to be enabled.

v2: Check if intel_dp is null in intel_psr_force_mode_changed_set()
v3: Check intel_dp before get dev_priv
v4:
- renamed intel_psr_force_mode_changed_set() to
intel_psr_set_force_mode_changed()
- removed the set parameter from intel_psr_set_force_mode_changed()
- not calling intel_psr_set_force_mode_changed() from
intel_psr_enable/update(), directly setting it after the same checks
that intel_psr_set_force_mode_changed() does
- moved intel_psr_set_force_mode_changed() arm call to
i915_driver_modeset_probe() as it is a better for a PSR call, all the
functions calls happening between the old and the new function call
will cause issue

Fixes: 60c6a14b

 ("drm/i915/display: Force the state compute phase once to enable PSR")
Closes: https://gitlab.freedesktop.org/drm/intel/issues/1151
Tested-by: Ross Zwisler <zwisler@google.com>
Reported-by: Ross Zwisler <zwisler@google.com>
Cc: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Anshuman Gupta <anshuman.gupta@intel.com>
Reviewed-by: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200221212635.11614-1-jose.souza@intel.com

One should use drm_connector_list_iter_end() rather than
drm_connector_list_iter_begin() to terminate the connector
iteration.

Cc: Manasi Navare <manasi.d.navare@intel.com>
Cc: Uma Shankar <uma.shankar@intel.com>
Closes: https://gitlab.freedesktop.org/drm/intel/issues/1278
Fixes: e24bcd34

 ("drm/i915/dp: Add all tiled and port sync conns to modeset")
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200221154310.14858-1-ville.syrjala@linux.intel.com
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Uma Shankar <uma.shankar@intel.com>

$(CC) with $(CFLAGS_GCOV) assumes the output filename with .gcno suffix
appended is writable. This is not the case when the output filename is
/dev/null:

  HDRTEST drivers/gpu/drm/i915/display/intel_frontbuffer.h
/dev/null:1:0: error: cannot open /dev/null.gcno
  HDRTEST drivers/gpu/drm/i915/display/intel_ddi.h
/dev/null:1:0: error: cannot open /dev/null.gcno
make[5]: *** [../drivers/gpu/drm/i915/Makefile:307:
drivers/gpu/drm/i915/display/intel_ddi.hdrtest] Error 1
make[5]: *** Waiting for unfinished jobs....
make[5]: *** [../drivers/gpu/drm/i915/Makefile:307:
drivers/gpu/drm/i915/display/intel_frontbuffer.hdrtest] Error 1

Filter out $(CFLAGS_GVOC) from the header test $(c_flags) as they don't
make sense here anyway.

References: http://lore.kernel.org/r/d8112767-4089-4c58-d7d3-2ce03139858a@infradead.org
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Fixes: c6d4a099

 ("drm/i915: reimplement header test feature")
Cc: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200221105414.14358-1-jani.nikula@intel.com