drm/i915: Prepare for GuC-based command submission

This adds the first of the data structures used to communicate with the
GuC (the pool of guc_context structures).

We create a GuC-specific wrapper round the GEM object allocator as all
GEM objects shared with the GuC must be pinned into GGTT space at an
address that is NOT in the range [0..WOPCM_TOP), as that range of GGTT
addresses is not accessible to the GuC (from the GuC's point of view,
it's permanently reserved for other objects such as the BootROM & SRAM).

Later, we will need to allocate additional GuC-sharable objects for the
submission client(s) and the GuC's debug log.

v2:
    Remove redundant initialisation [Chris Wilson]
    Defer adding struct members until needed [Chris Wilson]
    Local functions should pass dev_priv rather than dev [Chris Wilson]

v5:
    Invalidate GuC TLB after allocating and pinning a new object

v6:
    Rebased

Issue: VIZ-4884
Signed-off-by: Alex Dai <yu.dai@intel.com>
Signed-off-by: Dave Gordon <david.s.gordon@intel.com>
Reviewed-by: Tom O'Rourke <Tom.O'Rourke@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_guc.h

@@ -56,6 +56,9 @@ struct intel_guc {
 	struct intel_guc_fw guc_fw;
 
 	uint32_t log_flags;
+
+	struct drm_i915_gem_object *ctx_pool_obj;
+	struct ida ctx_ids;
 };
 
 /* intel_guc_loader.c */
@@ -64,4 +67,8 @@ extern int intel_guc_ucode_load(struct drm_device *dev);
 extern void intel_guc_ucode_fini(struct drm_device *dev);
 extern const char *intel_guc_fw_status_repr(enum intel_guc_fw_status status);
 
+/* i915_guc_submission.c */
+int i915_guc_submission_init(struct drm_device *dev);
+void i915_guc_submission_fini(struct drm_device *dev);
+
 #endif