cxl/port: Quiet warning messages from the cxl_test environment

The cxl_test platform device CXL port hierarchy is useful for testing,
but throws warning messages of the form:

    cxl_mem mem2: at cxl_root_port.1 no parent for dport: platform
    cxl_mem mem3: at cxl_root_port.2 no parent for dport: platform
    cxl_mem mem4: at cxl_root_port.3 no parent for dport: platform
    cxl_mem mem5: at cxl_root_port.0 no parent for dport: platform
    cxl_mem mem6: at cxl_root_port.1 no parent for dport: platform
    cxl_mem mem7: at cxl_root_port.2 no parent for dport: platform
    cxl_mem mem8: at cxl_root_port.3 no parent for dport: platform
    cxl_mem mem9: at cxl_root_port.4 no parent for dport: platform
    cxl_mem mem10: at cxl_root_port.4 no parent for dport: platform

...and this message when running testing in QEMU:

    cxl_region region4: Bypassing cpu_cache_invalidate_memregion() for testing!

Noisy cxl_test warnings have caused other regressions to be missed. In
the interest of using cxl_test for early detection of dev_err() and
dev_warn() messages, silence platform device topology and
cache-invalidation messages.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Author: djbw

drivers/cxl/core/port.c

@@ -1,5 +1,6 @@
 // SPDX-License-Identifier: GPL-2.0-only
 /* Copyright(c) 2020 Intel Corporation. All rights reserved. */
+#include <linux/platform_device.h>
 #include <linux/memregion.h>
 #include <linux/workqueue.h>
 #include <linux/debugfs.h>
@@ -1463,7 +1464,11 @@ int devm_cxl_enumerate_ports(struct cxl_memdev *cxlmd)
 		struct cxl_dport *dport;
 		struct cxl_port *port;
 
-		if (!dport_dev)
+		/*
+		 * The terminal "grandparent" in PCI is NULL and @platform_bus
+		 * for platform devices
+		 */
+		if (!dport_dev || dport_dev == &platform_bus)
 			return 0;
 
 		uport_dev = dport_dev->parent;

drivers/cxl/core/region.c

@@ -129,7 +129,7 @@ static int cxl_region_invalidate_memregion(struct cxl_region *cxlr)
 {
 	if (!cpu_cache_has_invalidate_memregion()) {
 		if (IS_ENABLED(CONFIG_CXL_REGION_INVALIDATION_TEST)) {
-			dev_warn_once(
+			dev_info_once(
 				&cxlr->dev,
 				"Bypassing cpu_cache_invalidate_memregion() for testing!\n");
 			return 0;