As the request is only valid during the same global reset epoch, we can
record the current reset_counter when constructing the request and reuse
it when waiting upon that request in future. This removes a very hairy
atomic check serialised by the struct_mutex at the time of waiting and
allows us to transfer those waits to a central dispatcher for all
waiters and all requests.

PS: With per-engine resets, we obviously cannot assume a global reset
epoch for the requests - a per-engine epoch makes the most sense. The
challenge then is how to handle checking in the waiter for when to break
the wait, as the fine-grained reset may also want to requeue the
request (i.e. the assumption that just because the epoch changes the
request is completed may be broken - or we just avoid breaking that
assumption with the fine-grained resets).
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/1460565315-7748-7-git-send-email-chris@chris-wilson.co.uk

In the reset_counter, we use two bits to track a GPU hang and reset. The
low bit is a "reset-in-progress" flag that we set to signal when we need
to break waiters in order for the recovery task to grab the mutex. As
soon as the recovery task has the mutex, we can clear that flag (which
we do by incrementing the reset_counter thereby incrementing the gobal
reset epoch). By clearing that flag when the recovery task holds the
struct_mutex, we can forgo a second flag that simply tells GEM to ignore
the "reset-in-progress" flag.

The second flag we store in the reset_counter is whether the
reset failed and we consider the GPU terminally wedged. Whilst this flag
is set, all access to the GPU (at least through GEM rather than direct mmio
access) is verboten.

PS: Fun is in store, as in the future we want to move from a global
reset epoch to a per-engine reset engine with request recovery.
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/1460565315-7748-6-git-send-email-chris@chris-wilson.co.uk

If we, when we store the reset_counter for the operation, we ensure that
it is not in a wedged or in the middle of a reset, we can then assert that
if any reset occurs the reset_counter must change. Later we can just
compare the operation's reset epoch against the current counter to see
if we need to abort the operation (to handle the hang).
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/1460565315-7748-5-git-send-email-chris@chris-wilson.co.uk

This is principally a little bit of syntatic sugar to hide the
atomic_read()s throughout the code to retrieve the current reset_counter.
It also provides the other utility functions to check the reset state on the
already read reset_counter, so that (in later patches) we can read it once
and do multiple tests rather than risk the value changing between tests.

v2: Be more strict on converting existing i915_reset_in_progress() over to
the more verbose i915_reset_in_progress_or_wedged().
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/1460565315-7748-4-git-send-email-chris@chris-wilson.co.uk

Currently there is a #define to enable extra BUG_ON for debugging
requests and associated activities. I want to expand its use to cover
all of GEM internals (so that we can saturate the code with asserts).
We can add a Kconfig option to make it easier to enable - with the usual
caveats of not enabling unless explicitly requested.
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/1460565315-7748-3-git-send-email-chris@chris-wilson.co.uk

Separate out the layers of includes (linux, drm, intel, i915) so that it
is a little easier to order our definitions between our multiple
reentrant headers. A couple of headers needed fixes to make them more
standalone (forgotten includes, forward declarations etc).
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/1460565315-7748-2-git-send-email-chris@chris-wilson.co.uk

Our driver compiles clean (nowadays thanks to 0day) but for me, at least,
it would be beneficial if the compiler threw an error rather than a
warning when it found a piece of suspect code. (I use this to
compile-check patch series and want to break on the first compiler error
in order to fix the patch.)

v2: Kick off a new "Debugging" submenu for i915.ko

At this point, we applied it to the kernel and promptly kicked it out
again as it broke buildbots (due to a compiler warning on 32bits):

commit 908d759b
Author: Daniel Vetter <daniel.vetter@ffwll.ch>
Date:   Tue May 26 07:46:21 2015 +0200

    Revert "drm/i915: Force clean compilation with -Werror"

v3: Avoid enabling -Werror for allyesconfig/allmodconfig builds, using
COMPILE_TEST as a suitable proxy suggested by Andrew Morton. (Damien)
Only make the option available for EXPERT to reinforce that the option
should not be casually enabled.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Damien Lespiau <damien.lespiau@intel.com>
Reviewed-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1460565315-7748-1-git-send-email-chris@chris-wilson.co.uk

With gen9+ the edram capabilities are defined so
that we can calculate the edram (ellc) size accordingly.

Note that there are undefined combinations for some subset of
edram capability bits. Return the closest size for undefined indexes.
Even if we get it wrong with beginning of future gen enabling, the size
information is currently only used for boot message and in debugfs entry.

v2: Use function instead of hard to read macro (Daniel)
v3: s/INTEL_INFO/INTEL_GEN (Matthew)
Signed-off-by: NMika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: NMatthew Auld <matthew.auld@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1460557604-7126-2-git-send-email-mika.kuoppala@intel.com

Store the edram capabilities instead of only the size of
edram. This is preparatory patch to allow edram size calculation
based on edram capability bits for gen9+. With gen9 the
edram is behind llc and is a separate entity. With hsw/bdw
it was more of a victim cache for LLC so the name 'eLLC' might
be warranted. Regardless, rename all mentions of eLLC to EDRAM to
clear the confusion.

v2: return bytes for edram size (Chris)
    s/eLLC/eDRAM in output if we are gen > 8

v3: rebase, INTEL_GEN (Chris)
Signed-off-by: NMika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>

For gen9 onwards, eDRAM is a true memory side cache. So
there is no need to program idi hash mask as it is for eLLC
only.

v2: INTEL_GEN (Chris), s/has/hash (Matthew)
Signed-off-by: NMika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: NMatthew Auld <matthew.auld@intel.com>

The whole file is ignored on CONFIG_ACPI=n.
Reviewed-by: NAnder Conselvan de Oliveira <conselvan2@gmail.com>
Signed-off-by: NJani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1460127589-8357-1-git-send-email-jani.nikula@intel.com

We started to use PIPE_CONTROL to write render ring seqno in order to
combat seqno write vs interrupt generation problems. This was introduced
by commit 7c17d377 ("drm/i915: Use ordered seqno write interrupt
generation on gen8+ execlists").

On gen8+ size of PIPE_CONTROL with Post Sync Operation should be
6 dwords. When we're using older 5-dword variant it's possible to
observe inconsistent values written by PIPE_CONTROL with Post
Sync Operation from user batches, resulting in rendering corruptions.

v2: Fix BAT failures
v3: Comments on alignment and thrashing high dword of seqno (Chris)
v4: Updated commit msg (Mika)

Testcase: igt/gem_pipe_control_store_loop/*-qword-write
Issue: VIZ-7393
Cc: stable@vger.kernel.org
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@intel.com>
Cc: Abdiel Janulgue <abdiel.janulgue@linux.intel.com>
Signed-off-by: NMichał Winiarski <michal.winiarski@intel.com>
Reviewed-by: NMika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Tested-by: NAbdiel Janulgue <abdiel.janulgue@linux.intel.com>
Signed-off-by: NMika Kuoppala <mika.kuoppala@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1460469115-26002-1-git-send-email-michal.winiarski@intel.com

Experiments with heaven 4.0 benchmark and skylake gt3e (rev 0xa)
suggest that WaForceContextSaveRestoreNonCoherent is needed for all
revs. Extending this to all revs cures a gpu hang with rev 0xa when
running heaven4.0 gpu benchmark.

We have been here before, with problems enabling gt4e and extending
up to revision F0 instead of false claims of bspec of E0 only. See
commit <e238659d> ("drm/i915/skl: Default to noncoherent access
up to F0"). In retrospect we should have covered this with this big
blanket back then already, as E0 vs F0 discrepancy was suspicious
enough.

Previously the WaForceEnableNonCoherent has been tied to
context non-coherence, atleast in relevant hsds. So keep this tie
and extended this alongside.

Cc: Abdiel Janulgue <abdiel.janulgue@linux.intel.com>
Cc: Ben Widawsky <benjamin.widawsky@intel.com>
Cc: Timo Aaltonen <tjaalton@ubuntu.com>
Cc: stable@vger.kernel.org
Reported-by: NMike Lothian <mike@fireburn.co.uk>
References: https://bugs.freedesktop.org/show_bug.cgi?id=93491Signed-off-by: NMika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: NBen Widawsky <benjamin.widawsky@intel.com>
Tested-by: NTimo Aaltonen <tjaalton@ubuntu.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1459860977-27751-2-git-send-email-mika.kuoppala@intel.com

For all gt3 and gt4 skylake variants, extend the usage of
WaRsDisableCoarsePowerGating for all revisions. Without this
gt3 and gt4 skylakes up to atleast rev 0xa can gpu hang or
system hang.

Cc: Abdiel Janulgue <abdiel.janulgue@linux.intel.com>
Cc: Ben Widawsky <benjamin.widawsky@intel.com>
Cc: Timo Aaltonen <tjaalton@ubuntu.com>
Cc: <stable@vger.kernel.org>
Reported-by: NMikael Djurfeldt <mikael@djurfeldt.com>
References: https://bugs.freedesktop.org/show_bug.cgi?id=94161Signed-off-by: NMika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: NBen Widawsky <benjamin.widawsky@intel.com>
Tested-by: NTimo Aaltonen <tjaalton@ubuntu.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1459860977-27751-1-git-send-email-mika.kuoppala@intel.com

Sudden realization:

$ grep -ho "INTEL_INFO([^)]*)->[a-zA-Z0-9_]*" *.[ch] | sed 's/.*->//' |\
  sort | uniq -c | sort -rn | head -5
  446 gen
   24 num_pipes
   10 ring_mask
    9 color
    4 subslice_per_slice
Acked-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NJani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1460022497-29304-1-git-send-email-jani.nikula@intel.com

We can use the new pin/lazy unpin API for simplicity
and more performance in the execlist submission paths.

v2:
  * Fix error handling and convert more users.
  * Compact some names for readability.

v3:
  * intel_lr_context_free was not unpinning.
  * Special case for GPU reset which otherwise unbalances
    the HWS object pages pin count by running the engine
    initialization only (not destructors).

v4:
  * Rebased on top of hws setup/init split.
Signed-off-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/1460472042-1998-1-git-send-email-tvrtko.ursulin@linux.intel.com
[tursulin: renames: s/hwd/hws/, s/obj_addr/vaddr/]
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>

Split the hardware status page into setup and initialisation,
where setup means setting up the driver state to support the
engine, and initialization means programming the hardware
with the before set up state.

This way the design matches the design of the engine setup/init
code which is split in the same fashion and it enables the
stages to be used in a balanced fashion (engine setup - hws
setup, engine init - hws init).

This will enable the upcoming improvements to slot in without
any kludges on the GPU reset path.
Signed-off-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Suggested-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>

Check whether the DPLL is even enabled before readoing out the dividers
and trying to derive port_clock on CHV. We already did this on VLV.

Also remove the comment "MIPI" comment from the VLV code since we call
this function whenever the pipe is enabled.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1458052809-23426-9-git-send-email-ville.syrjala@linux.intel.comReviewed-by: NJani Nikula <jani.nikula@intel.com>

pgm_ratios in stored as a register value in pipe config, so let's dump
this one as hex as well.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1458052809-23426-15-git-send-email-ville.syrjala@linux.intel.comReviewed-by: NJani Nikula <jani.nikula@intel.com>

Use the proper refclock frequency (100MHz) when reading out the
current DSI clock on CHV.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1458052809-23426-13-git-send-email-ville.syrjala@linux.intel.comReviewed-by: NJani Nikula <jani.nikula@intel.com>

On VLV at least, the BIOS may leave the DSI PLL enabled in some wonky
state where it just refuses to lock. Simply disabling the PLL before
reconfiguring it is not enough to fix it, but power gating the PLL
prior to reconfiguring does work.

This happens on BYT FFRD8 when booting with HDMI connected so the DSI
display will not be lit up by the BIOS.

Also we can remove the code for BXT that disables the PLL before
enabling it again.

v2: s/vlv/intel/ since BXT made thing generic
v3: Remove the BXT disable PLL before enable trick
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1458052809-23426-11-git-send-email-ville.syrjala@linux.intel.comAcked-by: NJani Nikula <jani.nikula@intel.com>

All the values in the DSI PLL LFSR seed table fit into 9bits, so change
the type to u16 from u32 to save a bit of space.

 drivers/gpu/drm/i915/i915.ko:
-.rodata                        90824
+.rodata                        90760
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1458052809-23426-10-git-send-email-ville.syrjala@linux.intel.comReviewed-by: NJani Nikula <jani.nikula@intel.com>

Enable the unclaimd register detection stuff on vlv/chv since we've now
fixed the known problems during suspend.

This reverts commit c81eeea6.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1460382992-28728-11-git-send-email-ville.syrjala@linux.intel.comReviewed-by: NImre Deak <imre.deak@intel.com>

DPINVGTT lives inside the disp2d power well so we can't frob it unless
we know the power well is active. Let's this stuff into
vlv_display_irq_reset() which is only called at the right times so that
we don't get unclaimed register access errors.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=94164Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1460382992-28728-10-git-send-email-ville.syrjala@linux.intel.comReviewed-by: NImre Deak <imre.deak@intel.com>

The registers frobbed by vlv_init_display_clock_gating() libve inside
the disp2d power well, so frobbing them while the power well is down
results in unclaimed register access warning (and of course the values
won't stick). Let's do this setup after we know the power well is
enabled.

It's also worth noting that DSPCLK_GATE_D and CBR1_VLV lose their state
when the power well goes down, but fortunately the values we've been
writing are actually the reset defaults.

MI_ARB_VLV actually retains its value even if the power well was turned
off, we just can't access it while the power well is down.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=94164Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1460382992-28728-9-git-send-email-ville.syrjala@linux.intel.comReviewed-by: NImre Deak <imre.deak@intel.com>

We expect vlv_display_irq_reset() to have been called prior to
vlv_display_irq_postinstall() so let's WARN if that isn't the case.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1460382992-28728-8-git-send-email-ville.syrjala@linux.intel.comReviewed-by: NImre Deak <imre.deak@intel.com>

Replace the hand rolled IMR/IER setup in vlv_display_irq_postinstall()
with GEN5_IRQ_INIT(). Also rename the iir_mask to enable_mask to avoid
consusion since we no longer deal with IIR here.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1460382992-28728-7-git-send-email-ville.syrjala@linux.intel.comReviewed-by: NImre Deak <imre.deak@intel.com>

For a bit of extra paranoia make sure the display irqs are all cleared
before we enabled them when turning on the power well. This should
really be the case already since the power well was off which resets
everything.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1460382992-28728-6-git-send-email-ville.syrjala@linux.intel.comReviewed-by: NImre Deak <imre.deak@intel.com>

Reshuffle the code a bit to move the vlv/chv display irq functions away
from the main irq hooks, next to the other sub (de,gt,etc.) hooks.

v2: Rebased due to changes in vlv_display_irq_reset()
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Imre Deak <imre.deak@intel.com> (v1)
Link: http://patchwork.freedesktop.org/patch/msgid/1460476604-2035-1-git-send-email-ville.syrjala@linux.intel.com

During runtime PM we'll be reinitializing interrupt support from the
ground up. However since the display power well will be off at that
time, well end up with a ton of unclaimed register accesses from the
display irq setup. Since we turned off the power well already before
runtime suspend, we've flagged display irqs as disabled during runtime
PM transitions. So we can just check that flag to see if we should do
skip display irqs during irq setup.

During driver load display irqs will be flagged as enabled since we've
turned on the power well already, however the power well code will have
skipped the display irq setup since irq support as a whole wasn't yet
enabled when the power well was enabled. So we'll want to do the display
irq setup in that case.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=94164Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1460382992-28728-4-git-send-email-ville.syrjala@linux.intel.comReviewed-by: NImre Deak <imre.deak@intel.com>

The vlv/chv display irq setup was a bit of mess after I ran out of steam
when working on it last. Fix it up so that we just have a _reset() and
_postinstall() hooks for the display irqs, and use those consistently.

v2: Clear out pipestat_irq_mask[] and PIPE_FIFO_UNDERRUN_STATUS in
    vlv_display_irq_reset() (Imre)
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Imre Deak <imre.deak@intel.com> (v1)
Link: http://patchwork.freedesktop.org/patch/msgid/1460476574-1921-1-git-send-email-ville.syrjala@linux.intel.com

No clue what this is supposed to achieve. I think it's been there since
the very beginning, so presumably some kind of kludge for very early
silicon. Let's just throw it out.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1460382992-28728-2-git-send-email-ville.syrjala@linux.intel.comReviewed-by: NImre Deak <imre.deak@intel.com>

The underruns we were seeing when enabling eDP port A on ILK seem to
have been caused by prematurely clearing the LP1+ watermark values when
disabling LP1+ watermarks. Now that the watermarks are handled
properly, we can rip out the underrun suppression around the port A
enable.

We still need to worry about the underruns on FDI when enabling
the eDP PLL. But as Bspec tells us, we can avoid that by a vblank
wait on the pipe driving FDI just prior to enabling the eDP PLL.

Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1459536799-18109-4-git-send-email-ville.syrjala@linux.intel.comReviewed-by: NPatrik Jakobsson <patrik.jakobsson@linux.intel.com>

Once again ILK is unhappy if we clear out the LP1+ watermark levels
outright, and instead we must disable the levels we don't want while
still leaving the actual programmed watermark levels intact.

Fixes underruns on the already enabled pipe when programming watermarks
while enabling the second pipe.

Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Matt Roper <matthew.d.roper@intel.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=93787Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1459536799-18109-3-git-send-email-ville.syrjala@linux.intel.comReviewed-by: NPatrik Jakobsson <patrik.jakobsson@linux.intel.com>

Take a bigger hammer to the underrun suppression on ILK. Instead of
trying to suppress them at specific points in the modeset sequence just
silence them across the entire sequence. This gets rid of some underruns
at least on my ILK. Note that this changes SNB and IVB to follow the
same approach just to keep the code less convoluted. The difference is
that on those platforms we won't suppress CPU underruns for port A since
it doesn't seem to be necessary.

My ILK has port A eDP and two PCH HDMI ports, so I can't be sure this is
as effective on other PCH port types. Perhaps we still need some of
Daniel's extra vblank waits [2]?

I've still been able to trigger an underrun on the other pipe, but
fixing that perhaps needs the LP1+ disable trick I implemented here [1]
which never got merged.

A few details which hamper stress testing on my ILK are that sometimes
the PCH transcoder gets messed up and refuses to shut down, and sometimes
even the panel power sequencer apparently gets stuck on the always on
position.

[1] https://lists.freedesktop.org/archives/intel-gfx/2014-March/041317.html
[2] https://lists.freedesktop.org/archives/intel-gfx/2016-January/086397.html

v2: Add a note that we also get underruns when enabling PCH ports

Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch> (v1)
Link: http://patchwork.freedesktop.org/patch/msgid/1459536799-18109-2-git-send-email-ville.syrjala@linux.intel.comReviewed-by: NPatrik Jakobsson <patrik.jakobsson@linux.intel.com>

Rather than blindly waking up all forcewake domains on command
submission, we can teach each engine what is (or are) the correct
one to take.

On platforms with multiple forcewake domains like VLV, CHV, SKL
and BXT, this has the potential of lowering the GPU and CPU
power use and submission latency.

To implement it we add a function named
intel_uncore_forcewake_for_reg whose purpose is to query which
forcewake domains need to be taken to read or write a specific
register with raw mmio accessors.

These enables the execlists engine setup  to query which
forcewake domains are relevant per engine on the currently
running platform.

v2:
  * Kerneldoc.
  * Split from intel_uncore.c macro extraction, WARN_ON,
    no warns on old platforms. (Chris Wilson)

v3:
  * Single domain per engine, mention all registers,
    bi-directional function and a new name, fix handling
    of gen6 and gen7 writes. (Chris Wilson)
Signed-off-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/1460468251-14069-1-git-send-email-tvrtko.ursulin@linux.intel.com

Chris Wilson points out that we can remove them from the array
since they are always written to with raw accessors.
Signed-off-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>

Knowledge of which register per platform belonds in which
forcewake domain was embedded in the MMIO accessors themselves.

Extract it into standalone macros so they can be used from
new code in the following patches.

This causes GCC to compile some of the MMIO accessors slightly
differently and grows the code a tiny amount. But none of the
growth is on the fast-path so it does not matter hugely.

Affected sizes before:

00000000000026f0 00000000000001a5 t gen6_read16
0000000000002390 00000000000001a5 t gen6_read32
00000000000028a0 00000000000001a5 t gen6_read64

00000000000061d0 000000000000019e t gen8_write16
0000000000006510 000000000000019d t gen8_write32
0000000000006370 000000000000019d t gen8_write64
00000000000021f0 000000000000019d t gen8_write8

Affected sizes after:

0000000000002840 00000000000001aa t gen6_read16
00000000000024e0 00000000000001a9 t gen6_read32
00000000000029f0 00000000000001a9 t gen6_read64

0000000000004f20 00000000000001b5 t gen8_write16
0000000000004ba0 00000000000001b4 t gen8_write32
00000000000050e0 00000000000001b4 t gen8_write64
0000000000004d60 00000000000001b4 t gen8_write8

Other MMIO accessors are not affected in size.
Signed-off-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Acked-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>

On platforms with multiple forcewake domains it seems more efficient
to request all desired ones and then to wait for acks to avoid
needlessly serializing on each domain.

v2: Rebase.
Signed-off-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/1460045074-1006-1-git-send-email-tvrtko.ursulin@linux.intel.com

As the vast majority of users do not use the domain id variable,
we can eliminate it from the iterator and also change the latter
using the same principle as was recently done for for_each_engine.

For a couple of callers which do need the domain mask, store it
in the domain array (which already has the domain id), then both
can be retrieved thence.

Result is clearer code and smaller generated binary, especially
in the tight fw get/put loops. Also, relationship between domain
id and mask is no longer assumed in the macro.

v2: Improve grammar in the commit message and rename the
    iterator to for_each_fw_domain_masked for consistency.
    (Dave Gordon)
Signed-off-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NDave Gordon <david.s.gordon@intel.com>