drm/i915/skl: Add DDB allocation management structures

We now need to allocate space in the DDB for planes being scanned out
ourselves. The data structure to represent an allocation mirrors what
we'll need to write in the registers later on: (start, end).

We add that allocation datat to the skl_wm_values structure as part of
the values to program the hardware with.

v2: Split planes and cursor for consistency.

v3: Make the skl_ddb_entry_size() parameter const
Reviewed-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: NDamien Lespiau <damien.lespiau@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_drv.h

@@ -1387,8 +1387,27 @@ struct ilk_wm_values {
 	enum intel_ddb_partitioning partitioning;
 };
 
+struct skl_ddb_entry {
+	uint16_t start, end;	/* in number of blocks */
+};
+
+static inline uint16_t skl_ddb_entry_size(const struct skl_ddb_entry *entry)
+{
+	/* end not set, clearly no allocation here. start can be 0 though */
+	if (entry->end == 0)
+		return 0;
+
+	return entry->end - entry->start + 1;
+}
+
+struct skl_ddb_allocation {
+	struct skl_ddb_entry plane[I915_MAX_PIPES][I915_MAX_PLANES];
+	struct skl_ddb_entry cursor[I915_MAX_PIPES];
+};
+
 struct skl_wm_values {
 	bool dirty[I915_MAX_PIPES];
+	struct skl_ddb_allocation ddb;
 	uint32_t wm_linetime[I915_MAX_PIPES];
 	uint32_t plane[I915_MAX_PIPES][I915_MAX_PLANES][8];
 	uint32_t cursor[I915_MAX_PIPES][8];