drm/i915/display: Clean up zero initializers

Just use a simple {} to zero initialize arrays/structs instead
of the hodgepodge of stuff we are using currently.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231012122442.15718-2-ville.syrjala@linux.intel.com
Reviewed-by: Jani Nikula <jani.nikula@intel.com>

drm/i915/display/intel_wm: Fix a little doc-rot in intel_update_watermarks()

Fixes the following W=1 kernel build warning(s):

drivers/gpu/drm/i915/display/intel_wm.c:46: warning: Function parameter or member 'i915' not described in 'intel_update_watermarks'
drivers/gpu/drm/i915/display/intel_wm.c:46: warning: Excess function parameter 'dev_priv' description in 'intel_update_watermarks'

Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Cc: David Airlie <airlied@gmail.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
Cc: intel-gfx@lists.freedesktop.org
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Lee Jones <lee@kernel.org>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230331092607.700644-20-lee@kernel.org

drm/i915/wm: move watermark debugfs to intel_wm.c

Follow the new convention of placing debugfs with the code.

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230215141910.433043-3-jani.nikula@intel.com

drm/i915/wm: add .get_hw_state to watermark funcs

Get rid of the if ladder in intel_modeset_setup_hw_state() and hide a
number of functions by adding a .get_hw_state() hook to watermark
functions. At least for now, combine the platform specific sanitization
to the hw state readouts on the relevant platforms instead of adding a
separate hook for that.

There's a functional change on PCH split platforms: If i9xx_wm_init()
fails to read plane latency and chooses the nop functions,
ilk_wm_get_hw_state() won't get called for readout. Add the
ilk_init_lp_watermarks() call on that path which now won't be called in
.get_hw_state(), as it looks like the only thing that could make a
difference.

v2:
- Add missing static (kernel test robot)

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/6da32831e40606cc8b90491b83196917f2ce36ab.1676317696.git.jani.nikula@intel.com

drm/i915/wm: move functions to call watermark hooks to intel_wm.[ch]

Move the wrappers to call watermark hooks into intel_wm.[ch]. This
declutters intel_display.c nicely.

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/2c8243c5c81b8cd8e34d51f55f3533373c305d0e.1676317696.git.jani.nikula@intel.com

drm/i915/wm: move remaining watermark code out of intel_pm.c

Add new files intel_wm.[ch] and i9xx_wm.[ch] under display/ to hold
generic and pre-SKL watermark code, respectively. SKL+ watermark code
has already been split out to skl_watermark.[ch].

Use the _wm.[ch] naming for brevity; we may want to rename
skl_watermark.[ch] later accordingly.

Add new intel_wm_init() to call either skl_wm_init() or
i9xx_wm_init(i915) depending on the platform, the latter comprising of
the remains of intel_init_pm().

Sprinkle in some minor checkpatch fixes while moving the code.

v2:
- Rebase
- Fix copyright year

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/ddf04a07a37f0368b3fef85d4ebb924082fec6cd.1676317696.git.jani.nikula@intel.com