Wrap the stolen memory related struct drm_i915_private members (dsm,
dsm_reserved, and stolen_usable_size) together in a a new struct
i915_dsm.
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230116173422.1858527-1-jani.nikula@intel.com

Add intel_de_read64_2x32() wrapper for the uncore version of the same,
and use it to read the high and low frame registers. Avoid duplicating
code for existing helpers.

The slight functional difference is checking that the entire high
register remains the same across two reads, instead of just the part
we're interested in. This should be of no consequence. (Unless those
bits function as a PRNG.)

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/33853549adff82045b95af527e14cfdff5712470.1673873708.git.jani.nikula@intel.com

Use the intel_de_* functions for display registers.

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Arun R Murthy <arun.r.murthy@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/ecfac5ebddcb46be1ddf2e34e52648fbf9fa4ca6.1673873708.git.jani.nikula@intel.com

cpt_verify_modeset() is roughly the same as
intel_wait_for_pipe_scanline_moving(). Assume it's close enough.

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Arun R Murthy <arun.r.murthy@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/bf26763caaad25f3dfcf6f8e468421f93fb99646.1673873708.git.jani.nikula@intel.com

Reduce clutter in intel_display.c by moving the scanline moving/stopped
wait functions to intel_vblank.[ch].

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Arun R Murthy <arun.r.murthy@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/3613b8c22e5022ebf61ab942e6bc81b717e8f520.1673873708.git.jani.nikula@intel.com

The vblank/scanline code is fairly isolated in i915_irq.c. Split it out
to new intel_vblank.[ch].

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/3e3e9016f5135dccae5110c291ba048567622e7a.1673873708.git.jani.nikula@intel.com

Add 4th pipe and extend TGL Wa_16013835468 to support ADLP, MTL and
DG2 and all TGL steppings.

BSpec: 54369, 55378, 66624

v3:
 - commit message modified
v2:
 - apply for PSR1 as well
 - remove stepping information from comments

Cc: Matt Roper <matthew.d.roper@intel.com>
Cc: José Roberto de Souza <jose.souza@intel.com>
Cc: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
Signed-off-by: Mika Kahola <mika.kahola@intel.com>
Signed-off-by: Jouni Högander <jouni.hogander@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230105065637.2063311-1-jouni.hogander@intel.com

Drop the redundant sub-directory from #includes under display/. Group
and sort the results.

v2: Rebase
Reviewed-by: Arun R Murthy <arun.r.murthy@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230104153258.453431-1-jani.nikula@intel.com

Using DEFINE_SIMPLE_ATTRIBUTE macro with the debugfs_create_file()
function adds the overhead of introducing a proxy file operation
functions to wrap the original read/write inside file removal protection
functions. This adds significant overhead in terms of introducing and
managing the proxy factory file operations structure and function
wrapping at runtime.
As a replacement, a combination of DEFINE_DEBUGFS_ATTRIBUTE macro paired
with debugfs_create_file_unsafe() is suggested to be used instead.  The
DEFINE_DEBUGFS_ATTRIBUTE utilises debugfs_file_get() and
debugfs_file_put() wrappers to protect the original read and write
function calls for the debug attributes. There is no need for any
runtime proxy file operations to be managed by the debugfs core.
Following coccicheck make command helped identify this change:

make coccicheck M=drivers/gpu/drm/i915/ MODE=patch COCCI=./scripts/coccinelle/api/debugfs/debugfs_simple_attr.cocci
Signed-off-by: Deepak R Varma <drv@mailo.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/5d26e924ec8dea21925c77fa79a2bf2a34cef705.1673451705.git.drv@mailo.com

Using DEFINE_SIMPLE_ATTRIBUTE macro with the debugfs_create_file()
function adds the overhead of introducing a proxy file operation
functions to wrap the original read/write inside file removal protection
functions. This adds significant overhead in terms of introducing and
managing the proxy factory file operations structure and function
wrapping at runtime.
As a replacement, a combination of DEFINE_DEBUGFS_ATTRIBUTE macro paired
with debugfs_create_file_unsafe() is suggested to be used instead.  The
DEFINE_DEBUGFS_ATTRIBUTE utilises debugfs_file_get() and
debugfs_file_put() wrappers to protect the original read and write
function calls for the debug attributes. There is no need for any
runtime proxy file operations to be managed by the debugfs core.
Following coccicheck make command helped identify this change:

make coccicheck M=drivers/gpu/drm/i915/ MODE=patch COCCI=./scripts/coccinelle/api/debugfs/debugfs_simple_attr.cocci
Signed-off-by: Deepak R Varma <drv@mailo.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/9e08dd1b5fabf3e4f54dda27dd1d6ea1dbe6c542.1673451705.git.drv@mailo.com

Add all the know DSB instruction opcodes.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221216003810.13338-12-ville.syrjala@linux.intel.comReviewed-by: Animesh Manna <animesh.manna@intel.com>

The caller should more or less know how many DSB commands it
wants to emit into the command buffer, so allow it to specify
the size of the command buffer rather than having the low level
DSB code guess it.

Technically we can emit as many as 134+1033 (for adl+ degamma +
10bit gamma) register writes but thanks to the DSB indexed register
write command we get significant space savings so the current size
estimate of 8KiB (~1024 DSB commands) is sufficient for now.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221216003810.13338-11-ville.syrjala@linux.intel.comReviewed-by: Animesh Manna <animesh.manna@intel.com>

Move the DSB tail cacheline alignment to a helper. No need to pollute
the caller with mundane details like this.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221216003810.13338-10-ville.syrjala@linux.intel.comReviewed-by: Animesh Manna <animesh.manna@intel.com>

The DSB indexed register write insturction is purely an internal
DSB implementation detail, no reason why the caller should have to
know about it. So let's just have the caller emit blind register
writes let the DSB code convert things to an indexed write if/when
multiple writes occur to the same register offset in a row.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221216003810.13338-9-ville.syrjala@linux.intel.comReviewed-by: Animesh Manna <animesh.manna@intel.com>

Currently intel_dsb_indexed_reg_write() just assumes the previous
instructions is also an indexed register write, and thus only
checks the register offset. Make the check more robust by
actually checking the instruction opcode as well.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221216003810.13338-8-ville.syrjala@linux.intel.comReviewed-by: Animesh Manna <animesh.manna@intel.com>

Extract a small helper to emit a DSB intstruction. Should
become useful if/when we need to start emitting other
instructions besides register writes.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221216003810.13338-7-ville.syrjala@linux.intel.comReviewed-by: Animesh Manna <animesh.manna@intel.com>

Pull the DSB command buffer size checks into a small helper so
we don't have repeat the same thing multiple times.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221216003810.13338-6-ville.syrjala@linux.intel.comReviewed-by: Animesh Manna <animesh.manna@intel.com>

free_pos is in dwords, DSB_BUF_SIZE in bytes. Directly
comparing the two is nonsense. Fix it up, and make sure
we also account for the 8byte alignment requirement for
each instruction, and also assume that each instruction
normally eats two dwords.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221216003810.13338-5-ville.syrjala@linux.intel.comReviewed-by: Animesh Manna <animesh.manna@intel.com>

Every DSB instruction has to be 8byte aligned. Make sure
that is the case for the non-indexed register writes as well.
The way this could end up unaligned is we emitted an odd
number of indexed register writes beforehand.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221216003810.13338-4-ville.syrjala@linux.intel.comReviewed-by: Animesh Manna <animesh.manna@intel.com>

No point in having these wrappers for a simple DSB_CTRL write.
Inline them into intel_dsb_commit().
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221216003810.13338-3-ville.syrjala@linux.intel.comReviewed-by: Animesh Manna <Animesh.manna@intel.com>

We don't want to keep random bits set in DSB_CTRL. Stop the
harmful RMW.

Also flip the reverse & around to appease my ocd.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221216003810.13338-2-ville.syrjala@linux.intel.comReviewed-by: Animesh Manna <animesh.manna@intel.com>

The error message suggests that the height of the src rect must be at
least 1. Reject source with height of 0.

Cc: stable@vger.kernel.org
Signed-off-by: Drew Davenport <ddavenport@chromium.org>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221226225246.1.I15dff7bb5a0e485c862eae61a69096caf12ef29f@changeid

Defeature Display Interlace support.
Support for interlace modes is removed from Gen 12 onwards.
Pruning the interlace modes for HDMI for Display >=12.
Bspec: 50490

v2: Add check for both DP and HDMI. (Ville)
Get rid of redundant check for interlace mode in modevalid. (Ville)

v3: Simplify the condition to avoid interlace modes. (Jani)
Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Uma Shankar <uma.shankar@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230105124125.1129653-1-ankit.k.nautiyal@intel.com

Since the DP/HDMI connector do not set connector->doublescan_allowed,
the doublescan modes will get automatically filtered during
drm_helper_probe_single_connector_modes().

Therefore check for double scan modes is not required and is dropped
from modevalid functions for both DP and HDMI.
Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Uma Shankar <uma.shankar@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221017143038.1748319-2-ankit.k.nautiyal@intel.com

The max source and destination limits for scalers in MTL have changed.
Use the new values accordingly.
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Signed-off-by: Animesh Manna <animesh.manna@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Reviewed-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
Signed-off-by: Radhakrishna Sripada <radhakrishna.sripada@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221223130509.43245-3-luciano.coelho@intel.com

In newer hardware versions (i.e. display version >= 14), the second
scaler doesn't support vertical scaling.

The current implementation of the scaling limits is simplified and
only occurs when the planes are created, so we don't know which scaler
is being used.

In order to handle separate scaling limits for horizontal and vertical
scaling, and different limits per scaler, split the checks in two
phases.  We first do a simple check during plane creation and use the
best-case scenario (because we don't know the scaler that may be used
at a later point) and then do a more specific check when the scalers
are actually being set up.
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Reviewed-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
Signed-off-by: Radhakrishna Sripada <radhakrishna.sripada@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221223130509.43245-2-luciano.coelho@intel.com

We now accept timeslots param exactly how the variable
sounds: amount of timeslots, but not ratio timeslots/64.
So for SST case(when we have all timeslots for use), it
should be 64, but not 1.
This caused some issues in the tests.

v2: Fixed comments

References: https://gitlab.freedesktop.org/drm/intel/-/issues/6860
Fixes: 52f14682 ("drm/i915: Bpp/timeslot calculation fixes for DP MST DSC")
Reviewed-by: Manasi Navare <manasi.d.navare@intel.com>
Signed-off-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230109140210.25822-1-stanislav.lisovskiy@intel.com

Fix docs for __intel_wakeref_put() and intel_wakeref_get() to
reflect current behaviour.
Signed-off-by: Nirmoy Das <nirmoy.das@intel.com>
Reviewed-by: Ashutosh Dixit <ashutosh.dixit@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230105203843.30663-1-nirmoy.das@intel.com

There are new cases where we want to block i915 probe, such
as when experimenting or developing the new Xe driver.

But also, with the new hybrid cards, users or developers might
want to use i915 only on integrated and fully block the probe
of the i915 for the discrete. Or vice versa.

There are even older development and validation reasons,
like when you use some distro where the modprobe.blacklist is
not present.

But in any case, let's introduce a more granular control, but without
introducing yet another parameter, but using the existent force_probe
one.

Just by adding a ! in the begin of the id in the force_probe, like
in this case where we would block the probe for Alder Lake:

$ insmod i915.ko force_probe='!46a6'

v2: Take care of '*' and  '!*' cases as pointed out by
    Gustavo and Jani.

Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Gustavo Sousa <gustavo.sousa@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Acked-by: Gustavo Sousa <gustavo.sousa@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230103194701.1492984-1-rodrigo.vivi@intel.com

The busy timeout logic checks for the AUX BUSY, then waits for the
timeout period and then after timeout reads the register for BUSY or
Success.
Instead replace interrupt with polling so as to read the AUX CTL
register often before the timeout period. Looks like there might be some
issue with interrupt-on-read. Hence changing the logic to polling read.

v2: replace interrupt with polling read
v3: use usleep_rang instead of msleep, updated commit msg
v4: use intel_wait_for_regiter internal function
v5: use __intel_de_wait_for_register with 500us slow and 10ms fast timeout
v6: check return value of __intel_de_wait_for_register
v7: using default 2us for intel_de_wait_for_register
Signed-off-by: Arun R Murthy <arun.r.murthy@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221221033209.1284435-1-arun.r.murthy@intel.com

Currently, i915 interacts with the Hardware and not with any DMC
ABI/API, so the API is fixed within the platform, hence no need to get
this so-tied version requirement.

v2:
  - Use link to firmware guide from kernel documentation for
    "References:" instead of mailing list thread. (Rodrigo)
  - Provide a more elaborate justification in the commit message.
    (Rodrigo)

References: https://www.kernel.org/doc/html/v6.1/driver-api/firmware/firmware-usage-guidelines.htmlSigned-off-by: Gustavo Sousa <gustavo.sousa@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221230182422.29680-2-gustavo.sousa@intel.com

Add .has_4tile tag to XE_HP_FEATURES set.
Remove duplicate entry from DG2_FEATURES.
Signed-off-by: Jonathan Cavitt <jonathan.cavitt@intel.com>
Cc: Bommu Krishnaiah <krishnaiah.bommu@intel.com>
Cc: Roper Matthew D <matthew.d.roper@intel.com>
Cc: Kempczynski Zbigniew <Zbigniew.Kempczynski@intel.com>
Cc: Telukuntla Sreedhar <sreedhar.telukuntla@intel.com>
Acked-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Juha-Pekka Heikkila <juhapekka.heikkila@gmail.com>
Signed-off-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221221153514.3874262-1-jonathan.cavitt@intel.com

Sync up with v6.2-rc1.
Signed-off-by: Jani Nikula <jani.nikula@intel.com>

Due to several bugs caused by timers being re-armed after they are
shutdown and just before they are freed, a new state of timers was added
called "shutdown".  After a timer is set to this state, then it can no
longer be re-armed.

The following script was run to find all the trivial locations where
del_timer() or del_timer_sync() is called in the same function that the
object holding the timer is freed.  It also ignores any locations where
the timer->function is modified between the del_timer*() and the free(),
as that is not considered a "trivial" case.

This was created by using a coccinelle script and the following
commands:

    $ cat timer.cocci
    @@
    expression ptr, slab;
    identifier timer, rfield;
    @@
    (
    -       del_timer(&ptr->timer);
    +       timer_shutdown(&ptr->timer);
    |
    -       del_timer_sync(&ptr->timer);
    +       timer_shutdown_sync(&ptr->timer);
    )
      ... when strict
          when != ptr->timer
    (
            kfree_rcu(ptr, rfield);
    |
            kmem_cache_free(slab, ptr);
    |
            kfree(ptr);
    )

    $ spatch timer.cocci . > /tmp/t.patch
    $ patch -p1 < /tmp/t.patch

Link: https://lore.kernel.org/lkml/20221123201306.823305113@linutronix.de/Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Acked-by: Pavel Machek <pavel@ucw.cz> [ LED ]
Acked-by: Kalle Valo <kvalo@kernel.org> [ wireless ]
Acked-by: Paolo Abeni <pabeni@redhat.com> [ networking ]
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Pull spi fix from Mark Brown:
 "One driver specific change here which handles the case where a SPI
  device for some reason tries to change the bus speed during a message
  on fsl_spi hardware, this should be very unusual"

* tag 'spi-fix-v6.2-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi:
  spi: fsl_spi: Don't change speed while chipselect is active

Merge tag 'regulator-fix-v6.2-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/broonie/regulator

Pull regulator fixes from Mark Brown:
 "Two core fixes here, one for a long standing race which some Qualcomm
  systems have started triggering with their UFS driver and another
  fixing a problem with supply lookup introduced by the fixes for devm
  related use after free issues that were introduced in this merge
  window"

* tag 'regulator-fix-v6.2-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/broonie/regulator:
  regulator: core: fix deadlock on regulator enable
  regulator: core: Fix resolve supply lookup issue

Pull coccicheck update from Julia Lawall:
 "Modernize use of grep in coccicheck:

  Use 'grep -E' instead of 'egrep'"

* tag 'coccinelle-6.2' of git://git.kernel.org/pub/scm/linux/kernel/git/jlawall/linux:
  scripts: coccicheck: use "grep -E" instead of "egrep"

Pull kernel hardening fixes from Kees Cook:

 - Fix CFI failure with KASAN (Sami Tolvanen)

 - Fix LKDTM + CFI under GCC 7 and 8 (Kristina Martsenko)

 - Limit CONFIG_ZERO_CALL_USED_REGS to Clang > 15.0.6 (Nathan
   Chancellor)

 - Ignore "contents" argument in LoadPin's LSM hook handling

 - Fix paste-o in /sys/kernel/warn_count API docs

 - Use READ_ONCE() consistently for oops/warn limit reading

* tag 'hardening-v6.2-rc1-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux:
  cfi: Fix CFI failure with KASAN
  exit: Use READ_ONCE() for all oops/warn limit reads
  security: Restrict CONFIG_ZERO_CALL_USED_REGS to gcc or clang > 15.0.6
  lkdtm: cfi: Make PAC test work with GCC 7 and 8
  docs: Fix path paste-o for /sys/kernel/warn_count
  LoadPin: Ignore the "contents" argument of the LSM hooks

Pull pstore fixes from Kees Cook:

 - Switch pmsg_lock to an rt_mutex to avoid priority inversion (John
   Stultz)

 - Correctly assign mem_type property (Luca Stefani)

* tag 'pstore-v6.2-rc1-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux:
  pstore: Properly assign mem_type property
  pstore: Make sure CONFIG_PSTORE_PMSG selects CONFIG_RT_MUTEXES
  pstore: Switch pmsg_lock to an rt_mutex to avoid priority inversion