If we have just completed a WC write, we must ensure that the WCB (Write
Combining Buffer) is flushed out to main memory before we can expect to
see the results. This is especially important when mixing WC with GTT as
the physical paths are different and cachelines are not naturally flushed.

Testcase: igt/drv_selftests/live_coherency #gdg
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180706115402.18547-1-chris@chris-wilson.co.uk

If the GPU is irrecoverably wedged, we can not execute any requests
making testing execlists (request execution) pointless. Skip!

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Matthew Auld <matthew.auld@intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180706114510.18467-1-chris@chris-wilson.co.uk

If the HW (or driver) doesn't support logical contexts, don't pretend we
gain anything from trying to execute GPU commands with them. At best it
reports -ENODEV, which is an unhelpful failure that we should just skip.

v2: Be more specific and check the driver/engine caps for logical (HW)
context support.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Matthew Auld <matthew.auld@intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180706101923.28548-1-chris@chris-wilson.co.uk

Avoid looking at the magical engines[RCS] to decide if the HW and driver
supports logical contexts, and instead record that knowledge during
initialisation.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Matthew Auld <matthew.auld@intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180706101442.21279-1-chris@chris-wilson.co.uk

We can simplify the encoder's get_power_domains() hook by calling it
only if the encoder is active. That way the hook can return its power
domains unconditionally without checking the active state by calling
encoder::get_hw_state(). This get_hw_state() query is in fact
redundant since it's already done by intel_modeset_readout_hw_state()
setting the encoder's crtc or leaving it NULL accordingly. Let's use
this fact to decide if the encoder is active.

While at it clarify the comment in intel_ddi_get_power_domains() about
primary vs. fake MST encoders and make sure we never do an incorrect
encoder->dig_port cast for fake MST encoders.

Suggested-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180705122654.17072-1-imre.deak@intel.com

This interface is deprecated, and has been replaced by the upstream
drm crc interface.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Tomi Sarvela <tomi.p.sarvela@intel.com>
Cc: Petri Latvala <petri.latvala@intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Acked-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180628072303.14175-1-maarten.lankhorst@linux.intel.com

If the GPU is terminally wedged we cannot submit any requests into a
context, completely unfulfilling our purpose of doing so. As this
expectedly fails, skip over the test.

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/20180706065332.15214-9-chris@chris-wilson.co.uk

We test the GPU handling of huge pages by submitting requests that write
into a huge page, but if the GPU is irrecoverably wedged we cannot
submit any requests. As the test expectedly fails, skip over it.

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/20180706065332.15214-8-chris@chris-wilson.co.uk

If the GPU is irrecoverably wedged, we cannot submit any requests and so
cannot make the GTT busy in order to test evicting active objects. As
this expectedly fails, skip over the test.

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/20180706065332.15214-7-chris@chris-wilson.co.uk

If the GPU is irrecoverably wedged, we cannot submit any request and
therefore cannot query the register state of the context (which is done
using the GPU command stream). So skip over the test as it expectedly
fails.

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/20180706065332.15214-6-chris@chris-wilson.co.uk

If the GPU is irrecoverably wedge, we cannot submit any request and so
all of the request selftests will expectedly fail. Skip over them.

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/20180706065332.15214-5-chris@chris-wilson.co.uk

If the GPU is wedged, we cannot make the object busy as trying to
submit a request will generate -EIO. Skip to the end of the test.

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/20180706065332.15214-4-chris@chris-wilson.co.uk

If the GPU is irrecoverably broken, we can not use it to dirty memory
and check for cache coherency with the CPU. All we can do is simply skip
over the GPU subtests and focus on the CPU domains (WC, WB) cache
management.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=107127
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/20180706065332.15214-3-chris@chris-wilson.co.uk

As we keep VMA around until the object is destroyed, when testing
partial tiling we instantiate many, many VMA (as the object is huge
allowing for many different partial regions). We test elsewhere our
handling of populating large objects with a full set of VMA and checking
we can retrieve them afterwards, but in this test we incur the cost of
flushing all VMA after every GTT write, dramatically slowing down the
test.

References: https://bugs.freedesktop.org/show_bug.cgi?id=107130
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/20180706065332.15214-2-chris@chris-wilson.co.uk

Having found the error causing the IGT test to fail, downgrade the
verbose logging so that we stop flooding the syslogs as we deliberately
provoke it many thousands of time during selftests.

References: 10195b1e

 ("drm/i915: Show vma allocator stack when in doubt")
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/20180706065332.15214-1-chris@chris-wilson.co.uk

This patch defines AUX lane registers for PORT_PCS_DW1,
PORT_TX_DW2, PORT_TX_DW4, PORT_TX_DW5 used during
dsi enabling.

v2: Review comments from Jani N:
    - Define _ICL_PORT_PCS_DW1_AUX_A for consistency
    - Three spaces for bitfield definition.

Signed-off-by: Madhav Chauhan <madhav.chauhan@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1530798591-2077-8-git-send-email-madhav.chauhan@intel.com

To save power, unused lanes should be powered
down using the bitfield of PORT_CL_DW10.

v2: Review comments from Jani N
    - Put default label next to case 4
    - Include the shifts in the macros

Signed-off-by: Madhav Chauhan <madhav.chauhan@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1530798591-2077-7-git-send-email-madhav.chauhan@intel.com

This register used to power down individual lanes for
DDI/DSI ports. Bitfields to power up/down various
combinations of lanes are also added in this patch.

v2: Review comments from Jani N
    - Use override instead of "override" for bitfields
    - Define mask for override bitfield
    - Define PWR_DOWN_LN* macros shifted in place
v3: Correct PWR_DOWN_LN_MASK value (Jani N)

Signed-off-by: Madhav Chauhan <madhav.chauhan@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1530798591-2077-6-git-send-email-madhav.chauhan@intel.com

This patch configures mode of operation for DSI
and enable DDI IO power by configuring power well.

v2: Use for_each_dsi_port() for power get (Jani N)

Signed-off-by: Madhav Chauhan <madhav.chauhan@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1530798591-2077-5-git-send-email-madhav.chauhan@intel.com

This patch defines DSI IO mode control register and it's bits
used while enabling IO power for DSI.

Signed-off-by: Madhav Chauhan <madhav.chauhan@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1530798591-2077-4-git-send-email-madhav.chauhan@intel.com

Escape Clock is used for LP communication across the DSI
Link. To achieve the constant frequency of the escape clock
from the variable DPLL frequency output, a variable divider(M)
is needed. This patch programs the same.

v2: (Jani N) Don't end line with "(".

Signed-off-by: Madhav Chauhan <madhav.chauhan@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1530798591-2077-3-git-send-email-madhav.chauhan@intel.com

Use the more customary order of latest platform first, and don't bother
with an if in the last branch.

Cc: Madhav Chauhan <madhav.chauhan@intel.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Madhav Chauhan <madhav.chauhan@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180705132509.12881-3-jani.nikula@intel.com

Avoid confusion with the functions to be added for the new ICL or gen 11
DSI implementation by renaming the current DSI functions. While at it,
permutate the words in the function names to make them all start with
"vlv_dsi" or "vlv_dsi_pll" etc.

Reduce the platform abstractions in the PLL file while at it, moving the
checks to vlv_dsi.c instead, where we typically already have the
necessary if ladders.

Leave the static functions as-is for now; they could be renamed later if
needed.

No functional changes.

v2: use "gen7" prefix.

v3: use "vlv" and "bxt" prefixes, reduce the abstractions.

References: https://patchwork.freedesktop.org/series/44823/
Cc: Madhav Chauhan <madhav.chauhan@intel.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Madhav Chauhan <madhav.chauhan@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180705132509.12881-2-jani.nikula@intel.com

Starting from ICL or gen 11 we have a new DSI block which requires
completely different programming from the current implementation. Having
them in the same file would be confusing. Rename the current DSI and DSI
PLL implementation files as vlv_dsi.c and vlv_dsi_pll.c.

No functional changes.

v2: use "gen7" prefix.

v3: use "vlv" prefix.

References: https://patchwork.freedesktop.org/series/44823/
Cc: Madhav Chauhan <madhav.chauhan@intel.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Madhav Chauhan <madhav.chauhan@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180705132509.12881-1-jani.nikula@intel.com

If the GPU is irrecoverably wedged on startup, it means that it failed
on initialisation and we have already tried to reset it but failed. We
can ignore all further testing, as it is already dead. Failing early,
prevents us from slowly failing in our endeavours later and timing out.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180705150214.28316-1-chris@chris-wilson.co.uk

i915_gem_detect_bit_6_swizzle() tries to hide unknown swizzling from
userspace (and ourselves) leaving us with the only clue inside
i915->quirks & QUIRK_PIN_SWIZZLED_PAGES. If we see this bit set, it
means that we really have no clue as to what the swizzle pattern is
being used in any one page and so cannot compute what the reference
value should be in our tiling selftests. We have to skip the test.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=107133
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180705171523.18462-1-chris@chris-wilson.co.uk

The return value is a bool so we can just return the result of
the biwise AND. The compiler will take care of the rest.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180621174658.18823-1-ville.syrjala@linux.intel.com
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>

There's no magic bit0 in MI_BB_START for gen3, it's the same dword length
parameter as elsewhere and needs to be zero.

v2: Same bug in both live_requests and live_hanghcheck.

References: https://bugs.freedesktop.org/show_bug.cgi?id=107132
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20180705154756.5533-1-chris@chris-wilson.co.uk
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

In preparation to enabling -Wimplicit-fallthrough, mark switch cases
where we are expecting to fall through.

Addresses-Coverity-ID: 141432
Addresses-Coverity-ID: 141433
Addresses-Coverity-ID: 141434
Addresses-Coverity-ID: 141435
Addresses-Coverity-ID: 141436
Addresses-Coverity-ID: 1357360
Addresses-Coverity-ID: 1357403
Addresses-Coverity-ID: 1357433
Addresses-Coverity-ID: 1392622
Addresses-Coverity-ID: 1415273
Addresses-Coverity-ID: 1435752
Addresses-Coverity-ID: 1441500
Addresses-Coverity-ID: 1454596
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180628223541.GA17665@embeddedor.com

This patch adds the new registers and corresponding bit definitions
which will be used for programming/enable DSI PLL.

v2: Review comments from Jani N
    - Fix spaces while defining ICL_ESC_CLK_DIV_MASK
    - Define shift and mask for bitfields.

Signed-off-by: Madhav Chauhan <madhav.chauhan@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1530795727-28644-2-git-send-email-madhav.chauhan@intel.com

Use i915_address_space_init() rather than open-code it inside
mock_ppgtt() as we will forget to keep it in sync.

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/20180705065653.20449-3-chris@chris-wilson.co.uk

We can now use the full release mechanism (i915_ppgtt_put) for our local
ppgtt allocation in igt_ppgtt_alloc.

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/20180705065653.20449-2-chris@chris-wilson.co.uk

No longer used and can be removed. One less global that currently
demands struct_mutex protection.

References: e9e7dc41

 ("drm/i915/gtt: Make gen6 page directories evictable")
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/20180705065653.20449-1-chris@chris-wilson.co.uk

Currently, the wc-stash used for providing flushed WC pages ready for
constructing the page directories is assumed to be protected by the
struct_mutex. However, we want to remove this global lock and so must
install a replacement global lock for accessing the global wc-stash (the
per-vm stash continues to be guarded by the vm).

We need to push ahead on this patch due to an oversight in hastily
removing the struct_mutex guard around the igt_ppgtt_alloc selftest. No
matter, it will prove very useful (i.e. will be required) in the near
future.

v2: Restore the onstack stash so that we can drop the vm->mutex in
future across the allocation.
v3: Restore the lost pagevec_init of the onstack allocation, and repaint
function names.
v4: Reorder init so that we don't try and use i915_address_space before
it is ininitialised.

Fixes: 1f6f0023

 ("drm/i915/selftests: Drop struct_mutex around lowlevel pggtt allocation")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180704185518.4193-1-chris@chris-wilson.co.uk

For whatever reason we only unmask and enable the master error
interrut on gen4. With the EIR handling fixed let's do that
on gen2/3 as well.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180611200258.27121-4-ville.syrjala@linux.intel.com
Reviewed-by: Imre Deak <imre.deak@intel.com>

Adjust the EIR clearing to cope with the edge triggered IIR
on i965/g4x. To guarantee an edge in the ISR master error bit
we temporarily mask everything in EMR. As some of the EIR bits
can't even be directly cleared we also borrow a trick from
i915_clear_error_registers() and permanently mask any bit that
remains high. No real thought given to how we might unmask them
again once the cause for the error has been clered. I suppose
on pre-g4x GPU reset will reinitialize EMR from scratch.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180611200258.27121-3-ville.syrjala@linux.intel.com
Reviewed-by: Imre Deak <imre.deak@intel.com>

Just like with PIPESTAT, the edge triggered IIR on i965/g4x
also causes problems for hotplug interrupts. To make sure
we don't get the IIR port interrupt bit stuck low with the
ISR bit high we must force an edge in ISR. Unfortunately
we can't borrow the PIPESTAT trick and toggle the enable
bits in PORT_HOTPLUG_EN as that act itself generates hotplug
interrupts. Instead we just have to loop until we've cleared
PORT_HOTPLUG_STAT, or we just give up and WARN.

v2: Don't frob with PORT_HOTPLUG_EN

Cc: stable@vger.kernel.org
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180614175625.1615-1-ville.syrjala@linux.intel.com
Reviewed-by: Imre Deak <imre.deak@intel.com>

For a ppgtt that we are constructing, there is no struct_mutex
dependence so skip it. In the process, also ping the scheduler
frequently to try and avoid the NMI watchdog.

v2: gen6 requires struct_mutex to clean up (currently)

Suggested-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
References: https://bugs.freedesktop.org/show_bug.cgi?id=107094
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180703135331.12265-1-chris@chris-wilson.co.uk

live_gtt is a very slow test to run, simply because it tries to allocate
and use as much as the 48b address space as possibly can and in the
process will try to own all of the system memory. This leads to resource
exhaustion and CPU starvation; the latter impacts us when the NMI
watchdog declares a task hung due to a mutex contention with ourselves.
This we can prevent by releasing the struct_mutex and forcing our
i915/rcu workers to run, and in particular flushing the freed object
worker that is the cause for concern.

References: https://bugs.freedesktop.org/show_bug.cgi?id=107094
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180703101829.7360-1-chris@chris-wilson.co.uk

The PIPEDSL freezes on PSR entry and if PSR hasn't fully exited, then
the pipe_update_start call schedules itself out to check back later.

On ChromeOS-4.4 kernel, which is fairly up-to-date w.r.t drm/i915 but
lags w.r.t core kernel code, hot plugging an external display triggers
tons of "potential atomic update errors" in the dmesg, on *pipe A*. A
closer analysis reveals that we try to read the scanline 3 times and
eventually timeout, b/c PSR hasn't exited fully leading to a PIPEDSL
stuck @ 1599. This issue is not seen on upstream kernels, b/c for *some*
reason we loop inside intel_pipe_update start for ~2+ msec which in this
case is more than enough to exit PSR fully, hence an *unstuck* PIPEDSL
counter, hence no error. On the other hand, the ChromeOS kernel spends
~1.1 msec looping inside intel_pipe_update_start and hence errors out
b/c the source is still in PSR.

Regardless, we should wait for PSR exit (if PSR is disabled, we incur
a ~1-2 usec penalty) before reading the PIPEDSL, b/c if we haven't
fully exited PSR, then checking for vblank evasion isn't actually
applicable.

v4: Comment explaining psr_wait after enabling VBL interrupts (DK)

v5: CAN_PSR() to handle platforms that don't support PSR.

v6: Handle local_irq_disable on early return (Chris)

Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Signed-off-by: Tarun Vyas <tarun.vyas@intel.com>
Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180627200250.1515-2-tarun.vyas@intel.com