drm/i915/guc: Don't repeat CTB layout calculations

We can retrieve offsets to cmds buffers and descriptor from
actual pointers that we already keep locally.
Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20210603051630.2635-11-matthew.brost@intel.com

drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c

@@ -244,6 +244,7 @@ int intel_guc_ct_enable(struct intel_guc_ct *ct)
 {
 	struct intel_guc *guc = ct_to_guc(ct);
 	u32 base, cmds;
+	void *blob;
 	int err;
 	int i;
 
@@ -251,15 +252,18 @@ int intel_guc_ct_enable(struct intel_guc_ct *ct)
 
 	/* vma should be already allocated and map'ed */
 	GEM_BUG_ON(!ct->vma);
+	GEM_BUG_ON(!i915_gem_object_has_pinned_pages(ct->vma->obj));
 	base = intel_guc_ggtt_offset(guc, ct->vma);
 
-	/* (re)initialize descriptors
-	 * cmds buffers are in the second half of the blob page
-	 */
+	/* blob should start with send descriptor */
+	blob = __px_vaddr(ct->vma->obj);
+	GEM_BUG_ON(blob != ct->ctbs[CTB_SEND].desc);
+
+	/* (re)initialize descriptors */
 	for (i = 0; i < ARRAY_SIZE(ct->ctbs); i++) {
 		GEM_BUG_ON((i != CTB_SEND) && (i != CTB_RECV));
 
-		cmds = base + PAGE_SIZE / 4 * i + PAGE_SIZE / 2;
+		cmds = base + ptrdiff(ct->ctbs[i].cmds, blob);
 		CT_DEBUG(ct, "%d: cmds addr=%#x\n", i, cmds);
 
 		guc_ct_buffer_reset(&ct->ctbs[i], cmds);
@@ -269,12 +273,12 @@ int intel_guc_ct_enable(struct intel_guc_ct *ct)
 	 * Register both CT buffers starting with RECV buffer.
 	 * Descriptors are in first half of the blob.
 	 */
-	err = ct_register_buffer(ct, base + PAGE_SIZE / 4 * CTB_RECV,
+	err = ct_register_buffer(ct, base + ptrdiff(ct->ctbs[CTB_RECV].desc, blob),
 				 INTEL_GUC_CT_BUFFER_TYPE_RECV);
 	if (unlikely(err))
 		goto err_out;
 
-	err = ct_register_buffer(ct, base + PAGE_SIZE / 4 * CTB_SEND,
+	err = ct_register_buffer(ct, base + ptrdiff(ct->ctbs[CTB_SEND].desc, blob),
 				 INTEL_GUC_CT_BUFFER_TYPE_SEND);
 	if (unlikely(err))
 		goto err_deregister;