Parameter - no.
Parameter: yes.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20161231112012.29263-2-chris@chris-wilson.co.uk

The read of the page pin count and the bind count are unordered,
presenting races in the assert and it firing off incorrectly. Prevent
this by restricting the assert to the vma bind/unbind routines where we
have local cpu ordering between the two.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20161231112012.29263-1-chris@chris-wilson.co.uk

Remove the IS_PLATFORM() macros from intel_dump_pipe_config() and split
that logic in platform specific implementations inside the dpll code,
accessed through a platform independent interface.

v2: Rebase.
Signed-off-by: NAnder Conselvan de Oliveira <ander.conselvan.de.oliveira@intel.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch> (v1)
Link: http://patchwork.freedesktop.org/patch/msgid/1483024933-3726-7-git-send-email-ander.conselvan.de.oliveira@intel.com

The documentation for most of the non-static members and structs were
missing. Fix that.

v2: Fix typos (Durga)

v3: Rebase.
    Fix make docs warnings.
    Document more.

v4: capitilize CRTC; say that the prepare hook is a nop if the DPLL is
    already enabled; link to struct intel_dpll_hw_state from @hw_state
    field in struct intel_shared_dpll_state; reorganize DPLL flags; link
    intel_shared_dpll_state to other structs and functions. (Daniel)
Signed-off-by: NAnder Conselvan de Oliveira <ander.conselvan.de.oliveira@intel.com>
Reviewed-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1483024933-3726-6-git-send-email-ander.conselvan.de.oliveira@intel.com

The hook is called from intel_prepare_shared_dpll(). The name doesn't
make sense after all the changes to modeset code. So just call it
prepare.
Signed-off-by: NAnder Conselvan de Oliveira <ander.conselvan.de.oliveira@intel.com>
Reviewed-by: NDurgadoss R <durgadoss.r@intel.com>
Reviewed-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1483024933-3726-5-git-send-email-ander.conselvan.de.oliveira@intel.com

Struct intel_shared_dpll_config is used to hold the state of the DPLL in
the "atomic" sense, so call it state like everything else atomic.

v2: Rebase
Signed-off-by: NAnder Conselvan de Oliveira <ander.conselvan.de.oliveira@intel.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch> (v1)
Link: http://patchwork.freedesktop.org/patch/msgid/1483024933-3726-4-git-send-email-ander.conselvan.de.oliveira@intel.com

The function intel_shared_dpll_commit() performs the equivalent of
drm_atomic_helper_swap_state() for the shared dpll state, which is not
handled by the helpers. So make it do a full swap of the state and
rename it for consistency.

v2: Fix typo in the commit message. (Durga)
v3: Rebase.
v4: Swap the states instead of just renaming the function. (Daniel)
Signed-off-by: NAnder Conselvan de Oliveira <ander.conselvan.de.oliveira@intel.com>
Reviewed-by: Durgadoss R <durgadoss.r@intel.com> (v2)
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch> (v3)
Link: http://patchwork.freedesktop.org/patch/msgid/1483024933-3726-3-git-send-email-ander.conselvan.de.oliveira@intel.com

While the details of getting a shared dpll are wrapped by
intel_get_shared_dpll(), the release was still hand rolled into the
modeset code. Fix that by creating an entry point for releasing the
pll and move that code there.

v2: Take old_dpll from crtc->state instead of crtc_state. (CI)
Signed-off-by: NAnder Conselvan de Oliveira <ander.conselvan.de.oliveira@intel.com>
Reviewed-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1483024933-3726-2-git-send-email-ander.conselvan.de.oliveira@intel.com

Add an assertion to the plain i915_ggtt_offset() to double check that
any offset we hand to the GuC is outside of its unmappable ranges.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161224193146.4402-1-chris@chris-wilson.co.ukReviewed-by: NDaniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>

Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

The context has to obey the same offset requirements as the ring,
so we can re-use the same bias value we computed for the ring instead of
unconditionally using GUC_WOPCM_TOP.
Suggested-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NDaniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/1482537382-28584-2-git-send-email-daniele.ceraolospurio@intel.comReviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>

GuC will validate the ring offset and fail if it is in the
[0, GUC_WOPCM_TOP) range. The bias is conditionally applied only
if GuC loading is enabled (we can't check for guc submission enabled as
in other cases because HuC loading requires this fix).

Note that the default context is processed before enable_guc_loading is
sanitized, so we might still apply the bias to its ring even if it is
not needed.

v2: compute the value during ctx init and pass it to
    intel_ring_pin (Chris), updated commit message
Signed-off-by: NDaniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Arkadiusz Hiler <arkadiusz.hiler@intel.com>
Cc: Anusha Srivatsa <anusha.srivatsa@intel.com>
Cc: Michał Winiarski <michal.winiarski@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1482537382-28584-1-git-send-email-daniele.ceraolospurio@intel.comReviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>

As the fence may be signaled concurrently from an interrupt on another
device, it is possible for the list of requests on the timeline to be
modified as we walk it. Take both (the context's timeline and the global
timeline) locks to prevent such modifications.

Fixes: 80b204bc ("drm/i915: Enable multiple timelines")
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: <drm-intel-fixes@lists.freedesktop.org>
Reviewed-by: NMika Kuoppala <mika.kuoppala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161223145804.6605-10-chris@chris-wilson.co.uk

When creating a partial VMA assert that it first fits with the parent
object, and that if it covers the whole of the parent a normal view was
created instead.
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/20161223145804.6605-5-chris@chris-wilson.co.uk

As trimming the sg table is merely an optimisation that gracefully fails
if we cannot allocate a new table, we do not need to report the failure
either.

Fixes: 0c40ce13 ("drm/i915: Trim the object sg table")
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161223145804.6605-4-chris@chris-wilson.co.uk

When we teardown the backing storage for the phys object, we copy from
the coherent contiguous block back to the shmemfs object, clflushing as
we go. Trying to clflush the invalid sg beforehand just oops and would
be redundant (due to it already being coherent, and clflushed
afterwards).
Reported-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: <drm-intel-fixes@lists.freedesktop.org>
Reviewed-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161223145804.6605-3-chris@chris-wilson.co.uk

The idle work handler is self-arming - if it detects that it needs to
run again it will queue itself from its work handler. Take greater care
when trying to drain the idle work, and double check that it is flushed.

The free worker has a similar issue where it is armed by an RCU task
which may be running concurrently with us.

This should hopefully help with the sporadic WARN_ON(dev_priv->gt.awake)
from i915_gem_suspend.

v2: Reuse drain_freed_objects.
v3: Don't try to flush the freed objects from the shrinker, as it may be
underneath the struct_mutex already.
v4: do while and comment upon the excess rcu_barrier in drain_freed_objects
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/20161223145804.6605-2-chris@chris-wilson.co.uk

Since commit db6c2b41 ("drm/i915: Store the vma in an rbtree under
the object") the vma are once again sorted into GGTT first, then ppGTT
so that the typical case of walking the GGTT vma can stop as soon as we
find a non-ppGTT. Apply that optimisation.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Reviewed-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161223145804.6605-1-chris@chris-wilson.co.uk

Now that we're disabling L2 clock gating MI_OVERLAY_OFF actually works
on 830, so let's use it.

v2: Nuke the unused dev_priv variable
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161222195222.9618-1-ville.syrjala@linux.intel.comReviewed-by: NChris Wilson <chris@chris-wilson.co.uk>

On enable intel_dsi_enable() directly calls intel_enable_dsi_pll(),
make intel_dsi_disable() also directly call intel_disable_dsi_pll(),
rather then hiding the call in intel_dsi_clear_device_ready(),
no functional changes.
Signed-off-by: NHans de Goede <hdegoede@redhat.com>
Reviewed-by: NJani Nikula <jani.nikula@intel.com>
Signed-off-by: NJani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161201202925.12220-7-hdegoede@redhat.com

The upper bits of the vsync width, vsync offset and hsync width
were not parsed from the VBT. Parse these fields in this patch.

V2: Renamed lvds dvo timing structure members and code identation
fix (Jani's review comments)
V3: Corrected commit message, used "from the VBT"
Signed-off-by: NVincente Tsou <vincente.tsou@intel.com>
Signed-off-by: NMadhav Chauhan <madhav.chauhan@intel.com>
Reviewed-by: NJani Nikula <jani.nikula@intel.com>
Signed-off-by: NJani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1482430993-3265-1-git-send-email-madhav.chauhan@intel.com

BSpec says:
"Overlay Clock Gating Must be Disabled: Overlay & L2 Cache clock gating
must be disabled in order to prevent device hangs when turning off overlay.SW
must turn off Ovrunit clock gating (6200h) and L2 Cache clock gating (C8h)."

We only turned off the overlay clock gating (due to lack of docs I
presume). After a bit of experimentation it looks like the the magic
C8h register lives in the PCI config space of device 0, and the magic
bit appears to be bit 2. Or at the very least this eliminates the GPU
death after MI_OVERLAY_OFF.

L2 clock gating seems to save ~80mW, so let's keep it on unless we need
to actually use the overlay.

Also let's move the OVRUNIT clock gating to the same place since we can,
and 845 supposedly doesn't need it.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1481131693-27993-11-git-send-email-ville.syrjala@linux.intel.comAcked-by: NChris Wilson <chris@chris-wilson.co.uk>

Extract the primary plane pixel format via plane state when setting up
the overlay colorkey.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1481131693-27993-10-git-send-email-ville.syrjala@linux.intel.comReviewed-by: NChris Wilson <chris@chris-wilson.co.uk>

Use two-dimensional arrays and named initializers to make the
overlay filter coefficient tables easier to parse for humans.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1481131693-27993-9-git-send-email-ville.syrjala@linux.intel.comReviewed-by: NChris Wilson <chris@chris-wilson.co.uk>

The formula in Bspec for computing the overlay SWIDTHSW is overly
obfuscated. Simplify the formula to something that's easily parsed by
humans.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1481131693-27993-8-git-send-email-ville.syrjala@linux.intel.comReviewed-by: NChris Wilson <chris@chris-wilson.co.uk>

Check pipe config gmch_pfit.control instead of using intel_panel_fitter_pipe()
to figure out if the pipe for the overlay is using the panel fitter.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1481131693-27993-7-git-send-email-ville.syrjala@linux.intel.comReviewed-by: NChris Wilson <chris@chris-wilson.co.uk>

Replace the use of crtc->mode.h/vdisplay with the more appropriate
config->pipe_src_w/h.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1481131693-27993-6-git-send-email-ville.syrjala@linux.intel.comReviewed-by: NChris Wilson <chris@chris-wilson.co.uk>

Do the overlay frontbuffer tracking properly so that it matches
the state of the overlay on/off/continue requests.

One slight problem is that intel_frontbuffer_flip_complete()
may get delayed by an arbitrarily liong time due to the fact that
the overlay code likes to bail out when a signal occurs. So the
flip may not get completed until the ioctl is restarted. But fixing
that would require bigger surgery, so I decided to ignore it for now.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1481131693-27993-5-git-send-email-ville.syrjala@linux.intel.comReviewed-by: NChris Wilson <chris@chris-wilson.co.uk>

The vma will be NULL if the overlay was previously off, so
dereferencing it will oops. Check for NULL before doing that.

Cc: stable@vger.kernel.org
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Fixes: 9b3b7841 ("drm/i915/overlay: Use VMA as the primary tracker for images")
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1481131693-27993-2-git-send-email-ville.syrjala@linux.intel.comReviewed-by: NChris Wilson <chris@chris-wilson.co.uk>

The i915_gem_active stuff doesn't like a NULL ->retire hook, but
the overlay code can set it to NULL. That obviously ends up oopsing.
Fix it by introducing a new helper to assign the retirement callback
that will switch out the NULL function pointer with
i915_gem_retire_noop.

Cc: stable@vger.kernel.org
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Fixes: 0d9bdd88 ("drm/i915: Convert intel_overlay to request tracking")
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/20161207175647.10018-1-chris@chris-wilson.co.uk

Initialize overlay->last_flip properly instead of leaving it zeroed.

Cc: stable@vger.kernel.org
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Fixes: 0d9bdd88 ("drm/i915: Convert intel_overlay to request tracking")
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161221144547.27319-1-ville.syrjala@linux.intel.com

Trying to determine the pixel rate of the pipe can't be done until we
know the clock, which means it can't be done until the encoder
.get_config() hooks have been called. So let's move the min_pixclk[]
stuff to the end of intel_modeset_readout_hw_state() when we actually
have gathered all the required infromation.

Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Mika Kahola <mika.kahola@intel.com>
Cc: Ander Conselvan de Oliveira <ander.conselvan.de.oliveira@intel.com>
Fixes: 565602d7 ("drm/i915: Do not acquire crtc state to check clock during modeset, v4.")
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161220153902.15621-1-ville.syrjala@linux.intel.comReviewed-by: NAnder Conselvan de Oliveira <conselvan2@gmail.com>
Reviewed-by: NMaarten Lankhorst <maarten.lankhorst@linux.intel.com>

Apparently some VLV BIOSen like to leave the VDD force bit enabled
even for power seqeuncers that aren't properly hooked up to any
port. That will result in a imbalance in the AUX power domain
refcount when we stat to use said power sequencer as edp_panel_vdd_on()
will not grab the power domain reference if it sees that the VDD is
already on.

To fix this let's make sure we turn off the VDD force bit when we
initialize the power sequencer registers. That is, unless it's
being done from the init path since there we are actually
initializing the registers for the current power sequencer and
we don't want to turn VDD off needlessly as that would require
waiting for the power cycle delay before we turn it back on.

This fixes the following kind of warnings:
WARNING: CPU: 0 PID: 123 at ../drivers/gpu/drm/i915/intel_runtime_pm.c:1455 intel_display_power_put+0x13a/0x170 [i915]()
WARN_ON(!power_domains->domain_use_count[domain])
...

v2: Fix typos in comment (David)

Cc: stable@vger.kernel.org
Cc: Matwey V. Kornilov <matwey.kornilov@gmail.com>
Tested-by: NMatwey V. Kornilov <matwey.kornilov@gmail.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=98695Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161220165117.24801-1-ville.syrjala@linux.intel.comReviewed-by: NDavid Weinehall <david.weinehall@linux.intel.com>

There is at least one APL based system using port A in DP mode
(connecting to an on-board DP->VGA adaptor). Atm we'll configure port A
unconditionally as eDP which is incorrect in this case. Fix this by
relying on the VBT DDI port 'internal port' flag instead on all ports on
DDI platforms. For now chicken out from using VBT for port A before
GEN9.

v2:
- Move the DDI port info lookup to intel_bios_is_port_edp() (David, Jani)
- Use the DDI port info on all DDI platforms starting from port B.

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: David Weinehall <david.weinehall@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com> (v1)
Reviewed-by: NDavid Weinehall <david.weinehall@linux.intel.com>
Signed-off-by: NImre Deak <imre.deak@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1482315444-24750-1-git-send-email-imre.deak@intel.com

when num_pipes is zero, it indicates there is no display and HDMI
audio doesn't exist.

v2: Move the check from caller to callee for consistency.

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Signed-off-by: NElaine Wang <elaine.wang@intel.com>
Reviewed-by: NJani Nikula <jani.nikula@intel.com>
Signed-off-by: NJani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1482142746-21663-1-git-send-email-elaine.wang@intel.com

v2: Addressed Jani's Review comments (renamed bit field macros)
Signed-off-by: NDeepak M <m.deepak@intel.com>
Signed-off-by: NMadhav Chauhan <madhav.chauhan@intel.com>
Reviewed-by: NJani Nikula <jani.nikula@intel.com>
Signed-off-by: NJani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1481792500-30863-2-git-send-email-madhav.chauhan@intel.com

This macro got useless after commit 8d9c20e1
"drm/i915: Remove .is_mobile field from platform struct"

that removed is_mobile split from VLV definition.
Also this was never reused on any following platform.

So let's clean up a bit here.

Cc: Carlos Santa <carlos.santa@intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: NRodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1482184508-18346-1-git-send-email-rodrigo.vivi@intel.com

Don't even tell the mm allocator to handle the first page of stolen on
the affected platforms. This means that we won't inherit the FB in
case the BIOS decides to put it at the start of stolen. But the BIOS
should not be putting it at the start of stolen since it's going to
get corrupted. I suppose the bug here is that some pixels at the very
top of the screen will be corrupted, so it's not exactly easy to
notice.

We have confirmation that the first page of stolen does actually get
corrupted, so I really think we should do this in order to avoid any
possible future headaches, even if that means losing BIOS framebuffer
inheritance. Let's not use the HW in a way it's not supposed to be
used.

Notice that now ggtt->stolen_usable_size won't reflect the ending
address of the stolen usable range anymore, so we have to fix the
places that rely on this. To simplify, we'll just use U64_MAX.

v2: don't even put the first page on the mm (Chris)
v3: drm_mm_init() takes size instead of end as argument (Ville)
v4: add a comment explaining the reserved ranges (Chris)
    use 0 for start and U64_MAX for end when possible (Chris)

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=94605
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NPaulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/1481808235-27607-1-git-send-email-paulo.r.zanoni@intel.com

BSpec got updated and this workaround is now listed as standard
required programming for all subsequent projects. This is confirmed to
fix Skylake screen flickering issues (probably caused by the fact that
we initialized a ring in the first page of stolen, but I didn't 100%
confirm this theory).

v2: this is the patch that fixes the screen flickering, document it.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=94605
Cc: stable@vger.kernel.org
Tested-by: NDominik Klementowski <dominik232@gmail.com>
Signed-off-by: NPaulo Zanoni <paulo.r.zanoni@intel.com>
Acked-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1481727338-9901-1-git-send-email-paulo.r.zanoni@intel.com

In commit 0c40ce13 ("drm/i915: Trim the object sg table"), we expect
to copy exactly orig_st->nents across and allocate the table thusly.
The copy loop should therefore end with the new_sg being NULL.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161219124346.550-2-chris@chris-wilson.co.ukReviewed-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>