drm/xe/guc: Don't allocate temporary policies object

Since we are already using reusable buffer objects from the GuC
buffer cache, we can directly write into their CPU pointers and
spare unnecessary temporary allocation.

While around, also make sure to clear obtained buffer, to avoid
sending some stale data.

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Link: https://lore.kernel.org/r/20250702142504.1656-1-michal.wajdeczko@intel.com

Author: mwajdecz

drivers/gpu/drm/xe/xe_guc_ads.c

@@ -995,16 +995,6 @@ static int guc_ads_action_update_policies(struct xe_guc_ads *ads, u32 policy_off
 	return xe_guc_ct_send(ct, action, ARRAY_SIZE(action), 0, 0);
 }
 
-static int guc_ads_update_policies(struct xe_guc_ads *ads, const struct guc_policies *policies)
-{
-	CLASS(xe_guc_buf_from_data, buf)(&ads_to_guc(ads)->buf, policies, sizeof(*policies));
-
-	if (!xe_guc_buf_is_valid(buf))
-		return -ENOBUFS;
-
-	return guc_ads_action_update_policies(ads, xe_guc_buf_flush(buf));
-}
-
 /**
  * xe_guc_ads_scheduler_policy_toggle_reset - Toggle reset policy
  * @ads: Additional data structures object
@@ -1015,13 +1005,16 @@ static int guc_ads_update_policies(struct xe_guc_ads *ads, const struct guc_poli
  */
 int xe_guc_ads_scheduler_policy_toggle_reset(struct xe_guc_ads *ads)
 {
-	struct xe_device *xe = ads_to_xe(ads);
 	struct guc_policies *policies;
-	int ret;
+	struct xe_guc *guc = ads_to_guc(ads);
+	struct xe_device *xe = ads_to_xe(ads);
+	CLASS(xe_guc_buf, buf)(&guc->buf, sizeof(*policies));
 
-	policies = kmalloc(sizeof(*policies), GFP_KERNEL);
-	if (!policies)
-		return -ENOMEM;
+	if (!xe_guc_buf_is_valid(buf))
+		return -ENOBUFS;
+
+	policies = xe_guc_buf_cpu_ptr(buf);
+	memset(policies, 0, sizeof(*policies));
 
 	policies->dpc_promote_time = ads_blob_read(ads, policies.dpc_promote_time);
 	policies->max_num_work_items = ads_blob_read(ads, policies.max_num_work_items);
@@ -1031,7 +1024,5 @@ int xe_guc_ads_scheduler_policy_toggle_reset(struct xe_guc_ads *ads)
 	else
 		policies->global_flags &= ~GLOBAL_POLICY_DISABLE_ENGINE_RESET;
 
-	ret = guc_ads_update_policies(ads, policies);
-	kfree(policies);
-	return ret;
+	return guc_ads_action_update_policies(ads, xe_guc_buf_flush(buf));
 }