Make it clear that these functions are the user entry points for
the tiling/fence registers.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170110121045.27144-1-chris@chris-wilson.co.uk

Rename i915_gem_get_ggtt_size() and i915_gem_get_ggtt_alignment() to
i915_gem_fence_size() and i915_gem_fence_alignment() respectively to
better match usage. Similarly move the pair of functions into
i915_gem_tiling.c next to the fence restrictions.
Suggested-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170109161613.11881-6-chris@chris-wilson.co.ukReviewed-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>

The fence size/alignment is a combination of the vma size plus object
tiling parameters. Those parameters are rarely changed, making the fence
size/alignemnt roughly constant for the lifetime of the VMA. We can
simplify subsequent calculations by precalculating the size/alignment
required for GGTT vma taking fencing into account (with an update if we
do change the tiling or stride).
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/20170109161613.11881-4-chris@chris-wilson.co.uk

Ensure the view occupies the full tile row so that reads/writes into the
VMA do not escape (via fenced detiling) into neighbouring objects - we
will pad the object with scratch pages to satisfy the fence. This
applies the lazy-tiling we employed on gen2/3 to gen4+.
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/20170109161613.11881-2-chris@chris-wilson.co.uk

99% of the time we access i915_address_space->dev we want the i915
device and not the drm device, so let's store the drm_i915_private
backpointer instead. The only real complication here are the inlines
in i915_vma.h where drm_i915_private is not yet defined and so we have
to choose an alternate path for our asserts.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161129095008.32622-1-chris@chris-wilson.co.ukReviewed-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>

And a little bit of cascaded function prototype changes.
Signed-off-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>

commit bc0629a7 ("drm/i915: Track pages pinned due to swizzling
quirk") fixed one problem, but revealed a whole lot more. The root cause
of the pin count mismatch for the swizzle quirk (for L-shaped memory on
gen3/4) was that we were incrementing the pages_pin_count upon getting
the backing pages but then overwriting the pages_pin_count to set it to
1 afterwards. With a little bit of adjustment to satisfy the GEM_BUG_ON
sanitychecks, the fix is to replace the explicit atomic_set with an
atomic_inc.

v2: Consistently use atomics (not mix atomics and helpers) within the
lowlevel get_pages routines. This makes the atomic operations much
clearer.

Fixes: 1233e2db ("drm/i915: Move object backing storage manipulation")
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161104103001.27643-1-chris@chris-wilson.co.ukReviewed-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>

If we have a tiled object and an unknown CPU swizzle pattern, we pin the
pages to prevent the object from being swapped out (and us corrupting
the contents as we do not know the access pattern and so cannot convert
it to linear and back to tiled on reuse). This requires us to remember
to drop the extra pinning when freeing the object, or else we trigger
warnings about the pin leak. In commit fbbd37b3 ("drm/i915: Move
object release to a freelist + worker"), the object free path was
deferred to a worker, but the unpinning of the quirk, along with marking
the object as reclaimable, was left on the immediate path (so that if
required we could reclaim the pages under memory pressure as early as
possible). However, this split introduced a bug where the pages were no
longer being unpinned if they were marked as unneeded.

[  231.800401] WARNING: CPU: 1 PID: 90 at drivers/gpu/drm/i915/i915_gem.c:4275 __i915_gem_free_objects+0x326/0x3c0 [i915]
[  231.800403] WARN_ON(i915_gem_object_has_pinned_pages(obj))
[  231.800405] Modules linked in:
[  231.800406]  snd_hda_intel i915 snd_hda_codec_generic mei_me snd_hda_codec coretemp snd_hwdep mei lpc_ich snd_hda_core snd_pcm e1000e ptp pps_core [last unloaded: i915]
[  231.800426] CPU: 1 PID: 90 Comm: kworker/1:4 Tainted: G     U          4.9.0-rc2-CI-CI_DRM_1780+ #1
[  231.800428] Hardware name: LENOVO 7465CTO/7465CTO, BIOS 6DET44WW (2.08 ) 04/22/2009
[  231.800456] Workqueue: events __i915_gem_free_work [i915]
[  231.800459]  ffffc9000034fc80 ffffffff8142dd65 ffffc9000034fcd0 0000000000000000
[  231.800465]  ffffc9000034fcc0 ffffffff8107e4e6 000010b300000001 0000000000001000
[  231.800469]  ffff88011d3db740 ffff880130ef0000 0000000000000000 ffff880130ef5ea0
[  231.800474] Call Trace:
[  231.800479]  [<ffffffff8142dd65>] dump_stack+0x67/0x92
[  231.800484]  [<ffffffff8107e4e6>] __warn+0xc6/0xe0
[  231.800487]  [<ffffffff8107e54a>] warn_slowpath_fmt+0x4a/0x50
[  231.800491]  [<ffffffff811d12ac>] ? kmem_cache_free+0x2dc/0x340
[  231.800520]  [<ffffffffa009ef36>] __i915_gem_free_objects+0x326/0x3c0 [i915]
[  231.800548]  [<ffffffffa009effe>] __i915_gem_free_work+0x2e/0x50 [i915]
[  231.800552]  [<ffffffff8109c27c>] process_one_work+0x1ec/0x6b0
[  231.800555]  [<ffffffff8109c1f6>] ? process_one_work+0x166/0x6b0
[  231.800558]  [<ffffffff8109c789>] worker_thread+0x49/0x490
[  231.800561]  [<ffffffff8109c740>] ? process_one_work+0x6b0/0x6b0
[  231.800563]  [<ffffffff8109c740>] ? process_one_work+0x6b0/0x6b0
[  231.800566]  [<ffffffff810a2aab>] kthread+0xeb/0x110
[  231.800569]  [<ffffffff810a29c0>] ? kthread_park+0x60/0x60
[  231.800573]  [<ffffffff818164a7>] ret_from_fork+0x27/0x40

Moving to a separate flag for tracking the quirked pin is overkill for
the bug (since we only have to interchange the two tests in
i915_gem_free_object) but it does reduce a complicated test on all
objects and provide a sanitycheck for uncommon code paths.

Fixes: fbbd37b3 ("drm/i915: Move object release to a freelist + worker")
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Reviewed-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161101100317.11129-2-chris@chris-wilson.co.uk

Having moved the locked phase of freeing an object to a separate worker,
we can now declare to the core that we only need the unlocked variant of
driver->gem_free_object, and can use the simple unreference internally.
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/20161028125858.23563-20-chris@chris-wilson.co.uk

We want to hide the latency of releasing objects and their backing
storage from the submission, so we move the actual free to a worker.
This allows us to switch to struct_mutex freeing of the object in the
next patch.

Furthermore, if we know that the object we are dereferencing remains valid
for the duration of our access, we can forgo the usual synchronisation
barriers and atomic reference counting. To ensure this we defer freeing
an object til after an RCU grace period, such that any lookup of the
object within an RCU read critical section will remain valid until
after we exit that critical section. We also employ this delay for
rate-limiting the serialisation on reallocation - we have to slow down
object creation in order to prevent resource starvation (in particular,
files).

v2: Return early in i915_gem_tiling() ioctl to skip over superfluous
work on error.
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/20161028125858.23563-19-chris@chris-wilson.co.uk

Break the allocation of the backing storage away from struct_mutex into
a per-object lock. This allows parallel page allocation, provided we can
do so outside of struct_mutex (i.e. set-domain-ioctl, pwrite, GTT
fault), i.e. before execbuf! The increased cost of the atomic counters
are hidden behind i915_vma_pin() for the typical case of execbuf, i.e.
as the object is typically bound between execbufs, the page_pin_count is
static. The cost will be felt around set-domain and pwrite, but offset
by the improvement from reduced struct_mutex contention.
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/20161028125858.23563-14-chris@chris-wilson.co.uk

The plan is to make obtaining the backing storage for the object avoid
struct_mutex (i.e. use its own locking). The first step is to update the
API so that normal users only call pin/unpin whilst working on the
backing storage.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161028125858.23563-12-chris@chris-wilson.co.uk

We can remove the false coupling between RPM and struct mutex by the
observation that we can use the RPM wakeref as the barrier around user
mmap access. That is as we tear down the user's PTE atomically from
within rpm suspend and then to fault in new PTE requires the rpm
wakeref, means that no user access is possible through those PTE without
RPM being awake. Having made that observation, we can then remove the
presumption of having to take rpm outside of struct_mutex and so allow
fine grained acquisition of a wakeref around hw access rather than
having to remember to acquire the wakeref early on.

v2: Rejig placement of the new intel_runtime_pm_get() to be as tight
as possible around the GTT pread/pwrite.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Imre Deak <imre.deak@intel.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: NDaniel Vetter <daniel@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20161024124218.18252-2-chris@chris-wilson.co.uk

Saves 1416 bytes of .rodata strings.

v2: Add parantheses around dev_priv. (Ville Syrjala)
Signed-off-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: NDavid Weinehall <david.weinehall@linux.intel.com>
Acked-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: NJani Nikula <jani.nikula@linux.intel.com>
Acked-by: NChris Wilson <chris@chris-wilson.co.uk>
Acked-by: NMaarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1476352990-2504-1-git-send-email-tvrtko.ursulin@linux.intel.com

Saves 4472 bytes of .rodata strings.

v2: Add parantheses around dev_priv. (Ville Syrjala)
Signed-off-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: NDavid Weinehall <david.weinehall@linux.intel.com>
Acked-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: NJani Nikula <jani.nikula@linux.intel.com>
Acked-by: NChris Wilson <chris@chris-wilson.co.uk>
Acked-by: NMaarten Lankhorst <maarten.lankhorst@linux.intel.com>

In order to handle tiled partial GTT mmappings, we need to associate the
fence with an individual vma.

v2: A couple of silly drops replaced spotted by Joonas
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/20160818161718.27187-21-chris@chris-wilson.co.uk

By moving map-and-fenceable tracking from the object to the VMA, we gain
fine-grained tracking and the ability to track individual fences on the VMA
(subsequent patch).
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/20160818161718.27187-16-chris@chris-wilson.co.uk

Treat the VMA as the primary struct responsible for tracking bindings
into the GPU's VM. That is we want to treat the VMA returned after we
pin an object into the VM as the cookie we hold and eventually release
when unpinning. Doing so eliminates the ambiguity in pinning the object
and then searching for the relevant pin later.

v2: Joonas' stylistic nitpicks, a fun rebase.
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/1471254551-25805-27-git-send-email-chris@chris-wilson.co.uk

v2: Rename functions to suit their more active role
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/1471254551-25805-14-git-send-email-chris@chris-wilson.co.uk

In the previous commit, we moved the obj->tiling_mode out of a bitfield
and into its own integer so that we could safely use READ_ONCE(). Let us
now repair some of that damage by sharing the tiling_mode with its
companion, the fence stride.

v2: New magic
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/1470388464-28458-18-git-send-email-chris@chris-wilson.co.uk

Through the GTT interface to the fence registers, we can only handle
linear, X and Y tiling. The more esoteric tiling patterns are ignored.
Document that the tiling ABI only supports upto Y tiling, and reject any
attempts to set a tiling mode other than NONE, X or Y.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Reviewed-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1470388464-28458-17-git-send-email-chris@chris-wilson.co.uk

Since we are not concerned with userspace racing itself with set-tiling
(the order is indeterminant even if we take a lock), then we can safely
read back the single obj->tiling_mode and do the static lookup of
swizzle mode without having to take a lock.

get-tiling is reasonably frequent due to the back-channel passing around
of tiling parameters in DRI2/DRI3.

v2: Make tiling_mode a full unsigned int so that we can trivially use it
with READ_ONCE(). Separating it out into manual control over the flags
field was too noisy for a simple patch. Note that we could use the lower
bits of obj->stride for the tiling mode.
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/1470388464-28458-16-git-send-email-chris@chris-wilson.co.uk

For consistency, internal functions should take drm_i915_private rather
than drm_device. Now that we are subclassing drm_device, there are no
more size wins, but being consistent is its own blessing.
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/1470324762-2545-12-git-send-email-chris@chris-wilson.co.uk

In order to be consistent with other address space functions, we want to
pass around 64-bit sizes, even though all known global GTT are limited
to 4GiB. Similarly, we are trying to be consistent in using the _ggtt_
nomenclature when referring to the special global GTT.

v2: Update docs to consistently state "global GTT".
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/1470324762-2545-11-git-send-email-chris@chris-wilson.co.uk

The future annotations will track the locking used for access to ensure
that it is always sufficient. We make the preparations now to present
the API ahead and to make sure that GCC can eliminate the unused
parameter.

Before:	6298417 3619610  696320 10614347         a1f64b vmlinux
After:	6298417 3619610  696320 10614347         a1f64b vmlinux
(with i915 builtin)
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/1470293567-10811-12-git-send-email-chris@chris-wilson.co.uk

In the future, we will want to add annotations to the i915_gem_active
struct. The API is thus expanded to hide direct access to the contents
of i915_gem_active and mediated instead through a number of helpers.
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/1470293567-10811-11-git-send-email-chris@chris-wilson.co.uk

In the next patch, request tracking is made more generic and for that we
need a new expanded struct and to separate out the logic changes from
the mechanical churn, we split out the structure renaming into this
patch.

v2: Writer's block. Add some spiel about why we track requests.
v3: Now i915_gem_active.
v4: Now with i915_gem_active_set() for attaching to the active request.
v5: Use i915_gem_active_set() from inside the retirement handlers
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/1470293567-10811-10-git-send-email-chris@chris-wilson.co.uk

Whilst this ultimately wraps kref_put_mutex(), our goal here is the
lockless variant, so keep the _unlocked() suffix until we need it no
more.

s/drm_gem_object_unreference_unlocked/i915_gem_object_put_unlocked/
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/1469005202-9659-7-git-send-email-chris@chris-wilson.co.ukReviewed-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1469017917-15134-6-git-send-email-chris@chris-wilson.co.uk

Ultimately wraps kref_put(), so adopt its nomenclature for consistency
with other subsystems.

s/drm_gem_object_unreference/i915_gem_object_put/
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/1469005202-9659-6-git-send-email-chris@chris-wilson.co.ukReviewed-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1469017917-15134-5-git-send-email-chris@chris-wilson.co.uk

For symmetry with a forthcoming i915_gem_object_get() and
i915_gem_object_put().
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/1469005202-9659-4-git-send-email-chris@chris-wilson.co.ukReviewed-by: NDave Gordon <david.s.gordon@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1469017917-15134-3-git-send-email-chris@chris-wilson.co.uk

Since we now subclass struct drm_device, we can save pointer dances by
noting the equivalence of struct drm_device and struct drm_i915_private,
i.e. by using to_i915().

   text    data     bss     dec     hex filename
1073824    4562     416 1078802  107612 drivers/gpu/drm/i915/i915.ko
1068976    4562     416 1073954  106322 drivers/gpu/drm/i915/i915.ko

Created by the coccinelle script:

@@
expression E;
identifier p;
@@
- struct drm_i915_private *p = E->dev_private;
+ struct drm_i915_private *p = to_i915(E);
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NDave Gordon <david.s.gordon@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1467628477-25379-1-git-send-email-chris@chris-wilson.co.uk

drm_gem_object_lookup() has never required the drm_device for its file
local translation of the user handle to the GEM object. Let's remove the
unused parameter and save some space.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: dri-devel@lists.freedesktop.org
Cc: Dave Airlie <airlied@redhat.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
[danvet: Fixup kerneldoc too.]
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

This way optimization from a previous patch works even better.

v2: Rebase.
Signed-off-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NJani Nikula <jani.nikula@intel.com>

Only has one user and is nothing more than a shim on top of
i915_vma_unbind, so let's just get rid of it.

Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Suggested-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Signed-off-by: NMatthew Auld <matthew.auld@intel.com>
Signed-off-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1461842691-27575-1-git-send-email-matthew.auld@intel.com

After fixing the same issue in the set_caching IOCTL and Chris' request
to check out the possibilities for an improved RPM ref handling I
noticed that we have the same issue in the set_tiling IOCTL. Fix this
up.I didn't see any bug reports about this one, but the GTT unbind
operation on this path accesses the HW, which needs the ref.
Signed-off-by: NImre Deak <imre.deak@intel.com>
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/1447092986-11165-1-git-send-email-imre.deak@intel.com

The old style of memory interleaving swizzled upto the end of the
first even bank of memory, and then used the remainder as unswizzled on
the unpaired bank - i.e. swizzling is not constant for all memory. This
causes problems when we try to migrate memory and so the kernel prevents
migration at all when we detect L-shaped inconsistent swizzling.
However, this issue also extends to userspace who try to manually detile
into memory as the swizzling for an individual page is unknown (it
depends on its physical address only known to the kernel), userspace
cannot correctly swizzle.

Note that this is a new attempt for the previously merged one,
reverted in

commit d82c0ba6
Author: Daniel Vetter <daniel.vetter@ffwll.ch>
Date:   Tue Jul 14 12:29:27 2015 +0200

    Revert "drm/i915: Declare the swizzling unknown for L-shaped configurations"

This is cc: stable since we need it to fix up troubles with wc cpu
mmaps that userspace recently started to use widely.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=91105Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: stable@vger.kernel.org
[danvet: Add note about previous (failed attempt).]
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Chris rightfully suggested that documenting fences without documenting
the BO tiling tracking doesn't make much sense, so fix that.

The important bit to stress here (since it lead to some confusion) is
the GEM doesn't really care about tiling. Except for a few select cases
where the kernel needs to manage something that userspace can't take
care of: Namely the limited number of fences and fixing up swizzling,
although we still fail at the later.

v2: Move the low-level tiling/swizzling functions and kerneldoc to
i915_gem_fence.c and leave only the userspace interface here.
Suggested by Chris.

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NDaniel Vetter <daniel.vetter@intel.com>

It fits more with the low-level fence code, and this move leaves only
the userspace tiling ioctl handling in i915_gem_tiling.c.
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>
Signed-off-by: NDaniel Vetter <daniel.vetter@intel.com>

This reverts commit 19ee835c.

It breaks existing old userspace which doesn't handle UNKNOWN
swizzling correct. Yes UNKNOWN was a thing back in 2009 and probably
still is on some other platforms, but it still pretty clearly broke
the testers machine. If we want this we need to extend the ioctl with
new paramters that only new userspace looks at.

Cc: Harald Arnesen <harald@skogtun.org>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reported-by: NHarald Arnesen <harald@skogtun.org>
Cc: stable@vger.kernel.org
Signed-off-by: NDaniel Vetter <daniel.vetter@intel.com>

The old style of memory interleaving swizzled upto the end of the
first even bank of memory, and then used the remainder as unswizzled on
the unpaired bank - i.e. swizzling is not constant for all memory. This
causes problems when we try to migrate memory and so the kernel prevents
migration at all when we detect L-shaped inconsistent swizzling.
However, this issue also extends to userspace who try to manually detile
into memory as the swizzling for an individual page is unknown (it
depends on its physical address only known to the kernel), userspace
cannot correctly swizzle objects.

v2: Mark the global swizzling as unknown rather than adjust the value
reported to userspace.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=91105Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: stable@vger.kernel.org
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>