Adding Enable and Disable PSR functionalities. This includes setting the
PSR configuration over AUX, sending SDP VSC DIP over the eDP PIPE config,
enabling PSR in the sink via DPCD register and finally enabling PSR on
the host.

This patch is based on initial PSR code by Sateesh Kavuri and Kumar Shobhit
but in a different implementation.

v2: * moved functions around and changed its names.
    * removed VSC DIP unset from disable.
    * remove FBC wa.
    * don't mask LSPS anymore.
    * incorporate new crtc usage after a rebase.
v3: Make a clear separation between Sink (Panel) and Source (HW) enabling.
v4: Fix identation and other style issues raised by checkpatch (by Paulo).
v5: Changes according to Paulo's review:
    static on write_vsc;
    avoid using dp_to_dev when already calling dp_to_dig_port;
    remove unecessary TP default time setting;
    remove unecessary interrupts disabling;
    remove unecessary wait_for_vblank when disabling psr;
v6: remove unecessary wait_for_vblank when writing vsc;
v7: adding setup once function to avoid unnecessarily write to vsc
    and set debug_ctl every time we enable or disable psr.

Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
Credits-by: NSateesh Kavuri <sateesh.kavuri@intel.com>
Credits-by: NShobhit Kumar <shobhit.kumar@intel.com>
Signed-off-by: NRodrigo Vivi <rodrigo.vivi@gmail.com>
Reviewed-by: NPaulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: NShobhit Kumar <shobhit.kumar@intel.com>
[danvet: Apply Paulo's suggestion for unconditionally clearing the
control register when writing the DIP.]
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Prep patch for reuse aux_clock_divider with EDP_PSR_AUX_CTL setup.
Reviewed-by: NPaulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: NRodrigo Vivi <rodrigo.vivi@gmail.com>
Reviewed-by: NShobhit Kumar <shobhit.kumar@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

v2: reuse of just created is_edp_psr and put it at right place.
v3: move is_edp_psr above intel_edp_disable
v4: remove parentheses. Noticed by Paulo.
Reviewed-by: NPaulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: NJani Nikula <jani.nikula@intel.com>
Signed-off-by: NShobhit Kumar <shobhit.kumar@intel.com>
Signed-off-by: NRodrigo Vivi <rodrigo.vivi@gmail.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Formerly: "drm/i915: Create VMAs (part 1)"

In a previous patch, the notion of a VM was introduced. A VMA describes
an area of part of the VM address space. A VMA is similar to the concept
in the linux mm. However, instead of representing regular memory, a VMA
is backed by a GEM BO. There may be many VMAs for a given object, one
for each VM the object is to be used in. This may occur through flink,
dma-buf, or a number of other transient states.

Currently the code depends on only 1 VMA per object, for the global GTT
(and aliasing PPGTT). The following patches will address this and make
the rest of the infrastructure more suited

v2: s/i915_obj/i915_gem_obj (Chris)

v3: Only move an object to the now global unbound list if there are no
more VMAs for the object which are bound into a VM (ie. the list is
empty).

v4: killed obj->gtt_space
some reworks due to rebase

v5: Free vma on error path (Imre)

v6: Another missed vma free in i915_gem_object_bind_to_gtt error path
(Imre)
Fixed vma freeing in stolen preallocation (Imre)
Signed-off-by: NBen Widawsky <ben@bwidawsk.net>
Reviewed-by: NImre Deak <imre.deak@intel.com>
[danvet: Squash in fixup from Ben to not deref a non-existing vma in
set_cache_level, reported by Chris.]
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

The odds of this happening are *extremely* unlikely.
Reported-by: NImre Deak <imre.deak@intel.com>
Signed-off-by: NBen Widawsky <ben@bwidawsk.net>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Shamelessly manipulated out of Daniel :-)
"When moving the lists around explain that the active/inactive stuff is
used by eviction when we run out of address space, so needs to be
per-vma and per-address space. Bound/unbound otoh is used by the
shrinker which only cares about the amount of memory used and not one
bit about in which address space this memory is all used in. Of course
to actual kick out an object we need to unbind it from every address
space, but for that we have the per-object list of vmas."

v2: Leave the bound list as a global one. (Chris, indirectly)

v3: Rebased with no i915_gtt_vm. In most places I added a new *vm local,
since it will eventually be replaces by a vm argument.
Put comment back inline, since it no longer makes sense to do otherwise.

v4: Rebased on hangcheck/error state movement
Signed-off-by: NBen Widawsky <ben@bwidawsk.net>
Reviewed-by: NImre Deak <imre.deak@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

After we plumb our code to support multiple address spaces (VMs), there
are a few situations where we want to be able to traverse the list of
all address spaces in the system. Cases like eviction, or error state
collection are obvious example.

v2: Delete the global link instead of the list head. While this in and
of itself shouldn't be really be a problem, doing this allows us to WARN
on an non-empty list, which is a problem. (Daniel)
Signed-off-by: NBen Widawsky <ben@bwidawsk.net>
Reviewed-by: NImre Deak <imre.deak@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Every address space should support object allocation. It therefore makes
sense to have the allocator be part of the "superclass" which GGTT and
PPGTT will derive.

Since our maximum address space size is only 2GB we're not yet able to
avoid doing allocation/eviction; but we'd hope one day this becomes
almost irrelvant.

v2: Rebased
Signed-off-by: NBen Widawsky <ben@bwidawsk.net>
Reviewed-by: NImre Deak <imre.deak@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

The GTT and PPGTT can be thought of more generally as GPU address
spaces. Many of their actions (insert entries), state (LRU lists), and
many of their characteristics (size) can be shared. Do that.

The change itself doesn't actually impact most of the VMA/VM rework
coming up, it just fits in with the grand scheme of abstracting the GPU
VM operations. GGTT will usually be a special case where we either know
an object must be in the GGTT (dislay engine, workarounds, etc.).

The scratch page is left as part of the VM (even though it's currently
shared with the ppgtt code) because in the future when we have Full
PPGTT, I intend to create a separate scratch page for each.

v2: Drop usage of i915_gtt_vm (Daniel)
Make cleanup also part of the parent class (Ben)
Modified commit msg
Rebased

v3: Properly share scratch page (Imre)
Finish commit message (Daniel, Imre)
Signed-off-by: NBen Widawsky <ben@bwidawsk.net>
Reviewed-by: NImre Deak <imre.deak@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

To run hangcheck in near future.
Signed-off-by: NMika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: NBen Widawsky <ben@bwidawsk.net>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

The intent of the check is made more clear if we use the proper name for
0 here.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NMika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: NBen Widawsky <ben@bwidawsk.net>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

The default context is always supported (as it contains the global
hangcheck stats) and the contexts for hangcheck are not limited
to any ring.

References: https://bugs.freedesktop.org/show_bug.cgi?id=65845Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NMika Kuoppala <mika.kuoppala@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

intel_enable_rc6() is used to check if we can compute the RC6 residency
in the sysfs code. Disable this for platforms older than Ironlake.
Signed-off-by: NDamien Lespiau <damien.lespiau@intel.com>
Reviewed-by: NPaulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Signed-off-by: NDamien Lespiau <damien.lespiau@intel.com>
Reviewed-by: NPaulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Signed-off-by: NDamien Lespiau <damien.lespiau@intel.com>
Reviewed-by: NPaulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

v2: Put the comment a bit closer to the actual write (Paulo Zanoni)
Reviewed-by: NPaulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: NDamien Lespiau <damien.lespiau@intel.com>
[danvet: Fix space before tab.]
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

We also wait for that blank on other platforms but the w/a doesn't
apply there. Not an issue at all.
Signed-off-by: NDamien Lespiau <damien.lespiau@intel.com>
Reviewed-by: NPaulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

At the moment we have the following interrupt enabling sequence:
1. irq preinstall hook
2. enabling the interrupt handler and calling irq postinstall hook
3. enable rps interrupts from the async work

And the folliwing disable sequence:
1. disabling the interrupt handler and calling the uninstall hook
2. disabling the rps interrupt

Since the postinstall hook now always sets up PMIIR, PMIER and PMIMR
to known-good states there no way for an interrupt to sneak in in the
enable sequence, so we can reinstate the WARN lost in

commit eda63ffb
Author: Ben Widawsky <ben@bwidawsk.net>
Date:   Tue May 28 19:22:26 2013 -0700

    drm/i915: Add PM regs to pre/post install

Note that there's some room for future cleanups since most of the
interrupt register clearing in the disable function is rather
redundant. But that's better done in follow-up patches, if at all.

Cc: Ben Widawsky <ben@bwidawsk.net>
Reviewed-by: NBen Widawsky <ben@bwidawsk.net>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

The VECS enabling required some changes to how rps interrupts are
enabled/disabled since VECS interrupts are handling with the PM
interrupt registers.

But now that the pre/postinstall sequences is identical for all
platforms with rps support (snb, ivb, hsw, vlv) we can also use the
exact same sequence to actually enable the rps interrupts. Strictly
speaking using spinlocks is overkill on snb/ivb & vlv since they have
no VECS ring, but imo that's more than made up by the common code.

Hence this just unifies the vlv code with the snb-hsw code which
matched exactly before the VECS enabling. See

commit eda63ffb
Author: Ben Widawsky <ben@bwidawsk.net>
Date:   Tue May 28 19:22:26 2013 -0700

    drm/i915: Add PM regs to pre/post install

and

commit 4848405c
Author: Ben Widawsky <ben@bwidawsk.net>
Date:   Tue May 28 19:22:27 2013 -0700

    drm/i915: make PM interrupt writes non-destructive

for why the gen6 code (shared between snb, ivb and hsw) needed to be
changed originally.

v3: Improve the commit message to more clearly spell out why we want
to unify the code and what exactly changes.

Cc: Paulo Zanoni <przanoni@gmail.com>
Cc: Ben Widawsky <ben@bwidawsk.net>
Reviewed-by: NBen Widawsky <ben@bwidawsk.net>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Again extract a common helper. For the postinstall hook things are a
bit more complicated since we have more cases on ilk-hsw/vlv here.

But since vlv was clearly broken by failing to initialize
dev_priv->gt_irq_mask correctly the shared code is clearly justified.

Also kill the PMIER setting in the async rps enable work. I should
have been save, but also clearly looked rather fragile. PMIER setup is
now all down in the irq pre/postinstall hooks.

With this we now have the usual interrupt register sequence for GT/PM
irq registers:

- IER is setup once with all the interrupts we ever need in the
  postinstall hook and never touched again. Exceptions are SDEIER,
  which is touched in the preinstall hook (when the irq handler isn't
  enabled) and then only from the irq handler. And DEIER/VLV_IER with
  is used in the irq handler but also written to once in the
  postinstall hook. But since that write is essentially what enables
  the interrupt and we should always have MSI interrupts we should be
  save. In case we ever have non-MSI interrupts we'd be screwed.

- IIR is cleared in the postinstall hook before we enable/unmask the
  respective interrupt sources. Hence we can't steal an interrupt
  event an accidentally trigger the spurious interrupt logic in the
  core kernel. Note that after some discussion with Ben Widawsky we
  think that we actually should clear the IIR registers in the
  preinstall hook. But doing that is a much larger patch series.

- IMR regs are (usually) all masked off. Those are the only regs
  changed at runtime, which is all protected by dev_priv->irq_lock.

This unification also kills the cargo-culted read-modify-write PM
register setup for VECS. Interrupt setup is done without userspace
being able to interfere, so we better know what values we want to put
into those registers. RMW cycles otoh are really good at papering over
races, until stuff magically blows up and no one has a clue why.

v2: Touch the gen6+ PM interrupt registers only on gen6+.

v3: Improve the commit message to more clearly spell out why we want
to unify the code and what exactly changes.

Cc: Ben Widawsky <ben@bwidawsk.net>
Cc: Paulo Zanoni <przanoni@gmail.com>
Reviewed-by: NBen Widawsky <ben@bwidawsk.net>
[danvet: Add a comment to explain why the l3 parity interrupt is
special.]
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Since the addition of VECS we have a slightly different enable
sequence for PM interrupts on ivb/hsw vs snb and vlv. Usually that
will end up in hard to track down surprises.

Hence unifiy things and since we have copies of this code in 3 places
now, extract it into its own little helper.

Note that this changes the irq preinstall sequence a bit for snb and
vlv: We now also clear the PM registers in the preinstall hook, in
addition to the PM register clearing/setup already done when actually
enabling rps. So this doesn't fix a bug but simply unifies the code
across all platforms. After the postinstall hook is similarly unified
we can rip out the then redundant PM interrupt setup from the rps
code.

v3: Rebase on top of the retained double-GTIIR clearing. Also
resurrect the masking/disabling of the gen6+ PM interrupts as spotted
by Ben Widaswky.

v4: Move the DE interrupt reset code out of gen5_gt_irq_preinstall
back to ironlake_irq_preinstall where it really belongs. Spotted by
Paulo.

v3: Improve the commit message to more clearly spell out why we want
to unify the code and what exactly changes.

Cc: Paulo Zanoni <przanoni@gmail.com>
Reviewed-by: NBen Widawsky <ben@bwidawsk.net>
[danvet: s/GT/PM/ to fix up a comment which Ben spotted while
reviewing.]
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

To make users life a little easier figuring out what they have on their
system.

Ideally, I'd really like to report LLC size, but it turned out to be a
bit of a pain. Maybe I'll revisit it in the future.
Signed-off-by: NBen Widawsky <ben@bwidawsk.net>
Reviewed-by: NRodrigo Vivi <rodrigo.vivi@gmail.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

DRI clients really should be using MOCS to get fine grained streaming
cache controls. With that note, I *hope* that this patch doesn't improve
performance overwhelmingly, because if it does - it means there is a
problem elsewhere.

In any case, the kernel, and old userspace should get some benefit from
this, so let's do it. eLLC is always a good default, and really not
using it is the special case for MOCS.

References: http://www.intel.com/newsroom/kits/restricted/ha$well!/pdfs/4th_Gen_Intel_Core_PressBriefing_5-29.pdf (page 57)
Signed-off-by: NBen Widawsky <ben@bwidawsk.net>
Reviewed-by: NRodrigo Vivi <rodrigo.vivi@gmail.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

The eLLC cannot be determined by PCIID because as far as we know, even
machines supporting eLLC may not have it enabled, or fused off or
whatever. It's possible this isn't actually true, and at that point we
can switch to a DEV_INFO flag instead.

I've defined everything where the docs are clear, and left the rest as
magic.

But we need it before we set the pte_encode function pointers, which
happens really early, in gtt_init.

The problem with just doing the normal sequence earlier is we don't have
the ability to use forcewake until after the pte functions have been set
up.

Since all solutions are somewhat ugly (barring rewriting all the init
ordering), I've opted to do the detection really early, and the enabling
later - since the register to detect doesn't require forcewake.
Signed-off-by: NBen Widawsky <ben@bwidawsk.net>
[danvet: Move dev_priv->ellc_size away from the dri1 dungeon to a nice
place right next to the l3 parity stuff. Also squash in the follow-up
commit to read out the eLLC size a bit earlier.]
Reviewed-by: NRodrigo Vivi <rodrigo.vivi@gmail.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

The EDRAM present register isn't really defined in the docs. It just
says check to see if it's set to 1. So I haven't defined the 1 value not
knowing what it actually means.
Signed-off-by: NBen Widawsky <ben@bwidawsk.net>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

The cacheability controls have changed, and the bits have been
rearranged in general.

Note that age 0 is the oldest (most likely to get evicted) and age 3
is the youngest (most likely to stick around for a bit). We've picked
0 for no reason, but atm it shouldn't matter anyway (since we don't
yet try to differentiate between different objects).

v2: Remove comments for snb/ivb cache leves, that's a separate change.

v3: Resolve conflicts due to patch series reordering.

v4: Rebased on top of Kenneth Graunke's ->pte_encode refactoring.

v5: Removed eLLC bits for separate patch.

In the internal repository this was:
Signed-off-by: NBen Widawsky <ben@bwidawsk.net>
Signed-off-by: NKenneth Graunke <kenneth@whitecape.org>
Reviewed-by: NDamien Lespiau <damien.lespiau@intel.com>
[danvet: Add comment about cache ages as requested by Ben provoked due
to a question from Damien.]
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Toghether with the hw state readout this should catch cases where we
don't properly updated the pll state (either in sw or hw). At least
for the shared dpll code the equivalent tricke helped a lot in
catching bugs.

Also rename the function prefix, it's not a generic piece of
infrastructure.
Reviewed-by: NImre Deak <imre.deak@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Bspec for the "DPLL HDMI multiplier" field says:

"Restriction : The DPLL must be enabled and stable before setting these bits.
These bits must be programmed after DPLL_SEL is programmed."

There is apparently no restriction on programming the DPLL_SEL
register wrt the DPLL. So let's just move that up before we enable the
pch dpll.
Reviewed-by: NImre Deak <imre.deak@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

No need to call the ->pre_pll_enable hook twice if we don't enable the
dpll too early. This should make Jani a bit less grumpy.

v2: Rebase on top of the newly-colored BUG_ONs.

v3: Reinstate the lost write of the DPLL_MD register, spotted by Imre.

Cc: Imre Deak <imre.deak@intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: NImre Deak <imre.deak@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Move error state generation and stringification to it's
own compilation unit. Sysfs also uses this so it can't be
under CONFIG_DEBUG_FS

This fixes a regression introduced in

commit ef86ddce
Author: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Date:   Thu Jun 6 17:38:54 2013 +0300

    drm/i915: add error_state sysfs entry

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=66814Signed-off-by: NMika Kuoppala <mika.kuoppala@intel.com>
Reported-by: Nkbuild test robot <fengguang.wu@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

If intel_sdvo_get_value() fails here, val is unitialized and the cross
check will compare the pipe config multiplier with a bogus value.

Instead, only set encoder_pixel_multiplier when the sdvo command has
been successful. The cross check will compare the pipe config value with
0 otherwise.

v2: Do the cross check with the initial value of encoder_pixel_multiplier (0)
if the sdvo command fails (and thus keep the warning) (Daniel Vetter)
Signed-off-by: NDamien Lespiau <damien.lespiau@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Came accross two open coding of for_each_pipe(), might as well use the
macro.
Signed-off-by: NDamien Lespiau <damien.lespiau@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

The code to handle it is broken - there's simply no code to clear CS
parser errors on gen5+. And behold, for all the other rings we also
don't enable it!

Leave the handling code itself in place just to be consistent with the
existing mess though. And in case someone feels like fixing it all up.

This has been errornously enabled in

commit 12638c57
Author: Ben Widawsky <ben@bwidawsk.net>
Date:   Tue May 28 19:22:31 2013 -0700

    drm/i915: Enable vebox interrupts

Cc: Damien Lespiau <damien.lespiau@intel.com>
Cc: Ben Widawsky <ben@bwidawsk.net>
Reviewed-by: NBen Widawsky <ben@bwidawsk.net>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

With the simplified locking there's no reason any more to keep the
refcounts seperate.

v2: Readd the lost comment that ring->irq_refcount is protected by
dev_priv->irq_lock.
Reviewed-by: NBen Widawsky <ben@bwidawsk.net>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Now that the rps interrupt locking isn't clearly separated (at elast
conceptually) from all the other interrupt locking having a different
lock stopped making sense: It protects much more than just the rps
workqueue it started out with. But with the addition of VECS the
separation started to blurr and resulted in some more complex locking
for the ring interrupt refcount.

With this we can (again) unifiy the ringbuffer irq refcounts without
causing a massive confusion, but that's for the next patch.

v2: Explain better why the rps.lock once made sense and why no longer,
requested by Ben.
Reviewed-by: NBen Widawsky <ben@bwidawsk.net>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

And kill the comment about it. Queueing work is a barrier type event,
no amount of locking will help in ordering things (as long as we queue
the work after having updated all relevant data structures). Also, the
queue_work works itself as a sufficient memory barrier.

Again on the surface this is just a tiny micro-optimization to reduce
the hold-time of dev_priv->irq_lock. But the better reason is that it
reduces superficial locking and so makes it clearer what we actually
need for correctness.
Reviewed-by: NBen Widawsky <ben@bwidawsk.net>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

The if (pm_iir & ~GEN6_PM_RPS_EVENTS) check was redunandant. Otoh
adding a check for rps events allows us to avoid the spinlock grabbing
for VECS interrupts.

v2: Drop misplaced hunk which now moved to the right patch.
Reviewed-by: NBen Widawsky <ben@bwidawsk.net>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Since we only have one interrupt handler and interrupt handlers are
non-reentrant.

To drive the point really home give them all an _irq_handler suffix.

This is a tiny micro-optimization but even more important it makes it
clearer what locking we actually need. And in case someone screws this
up: lockdep will catch hardirq vs. other context deadlocks.

v2: Fix up compile fail.
Reviewed-by: NPaulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: NBen Widawsky <ben@bwidawsk.net>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

It's racy: There's no guarantee that we won't walk this code (due to a
pch fifo underrun interrupt) while someone is changing the pointers
around.

The only reason we do this is to use the righ crtc for the pch fifo
underrun accounting. But we never expose this to userspace, so
essentially no one really cares if we use the "wrong" crtc.

So let's just rip it out.

With this patch fifo underrun code will always use crtc A for tracking
underruns on the (only) pch transcoder on LPT.

v2: Add a big comment explaining what's going on. Requested by Paulo.

v3: Fixup spelling in comment as spotted by Paulo.

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

Same treatment as for SERR_INT: If we clear only the bit for the pipe
we're enabling (but unconditionally) then we can always check for
possible underruns after having disabled the interrupt. That way pipe
underruns won't be lost, but at worst only get reported in a delayed
fashion.

v2: The same logic bug as in the SERR handling change also existed
here. The same bugfix of only reporting missed underruns when the
error interrupt was masked applies, too.

v3: Do the same fixes as for the SERR handling that Paulo suggested in
his review:
- s/%i/%c/ fix in the debug output
- move the DE_ERR_INT_IVB read into the respective if block

Cc: Paulo Zanoni <przanoni@gmail.com>
Reviewed-by: NPaulo Zanoni <paulo.r.zanoni@intel.com>
[danvet: Fix up the checkpatch bikeshed Paulo noticed.]
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>