x86/amd_node: Fix PCI device reference counting in amd_smn_init()grafted

The local "root" pointer is a temporary variable used during the device
search. Therefore, refcount related to the search iterators should be cleaned
up after the search is complete.

Use the __free() cleanup macro to ensure the refcount is decremented when the
temporary pointer goes out of scope.

Additionally, increment the refcount when caching a root pointer. This ensures
the in-use refcount is separate from the temporary search refcounting.

Finally, drop the redundant "root = NULL" before the second search loop. The
pci_get_class() iterator always decrements the refcount of its "from"
argument, so the first loop can only fall through with "root" already NULL.

Fixes: 0a4b61d9c2e4 ("x86/amd_node: Fix AMD root device caching")
Closes: https://sashiko.dev/#/patchset/20260806160159.230453-1-jason.andryuk%40amd.com
Reported-by: Sashiko <sashiko-bot@kernel.org>
Assisted-by: LLM
Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Mario Limonciello (AMD) <superm1@kernel.org>
Cc: <stable@kernel.org>
Link: https://patch.msgid.link/20260903154325.74343-1-yazen.ghannam@amd.com

1 files changed, 72 insertions, 0 deletions

diff --git a/drivers/regulator/dummy.c b/drivers/regulator/dummy.c
new file mode 100644
index 000000000..c3e416fd3
--- /dev/null
+++ b/drivers/regulator/dummy.c
@@ -0,0 +1,72 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * dummy.c
+ *
+ * Copyright 2010 Wolfson Microelectronics PLC.
+ *
+ * Author: Mark Brown <broonie@opensource.wolfsonmicro.com>
+ *
+ * This is useful for systems with mixed controllable and
+ * non-controllable regulators, as well as for allowing testing on
+ * systems with no controllable regulators.
+ */
+
+#include <linux/err.h>
+#include <linux/export.h>
+#include <linux/device/faux.h>
+#include <linux/regulator/driver.h>
+#include <linux/regulator/machine.h>
+
+#include "dummy.h"
+
+struct regulator_dev *dummy_regulator_rdev;
+
+static const struct regulator_init_data dummy_initdata = {
+	.constraints = {
+		.always_on = 1,
+	},
+};
+
+static const struct regulator_ops dummy_ops;
+
+static const struct regulator_desc dummy_desc = {
+	.name = "regulator-dummy",
+	.id = -1,
+	.type = REGULATOR_VOLTAGE,
+	.owner = THIS_MODULE,
+	.ops = &dummy_ops,
+};
+
+static int dummy_regulator_probe(struct faux_device *fdev)
+{
+	struct regulator_config config = { };
+	int ret;
+
+	config.dev = &fdev->dev;
+	config.init_data = &dummy_initdata;
+
+	dummy_regulator_rdev = devm_regulator_register(&fdev->dev, &dummy_desc,
+						       &config);
+	if (IS_ERR(dummy_regulator_rdev)) {
+		ret = PTR_ERR(dummy_regulator_rdev);
+		pr_err("Failed to register regulator: %d\n", ret);
+		return ret;
+	}
+
+	return 0;
+}
+
+static struct faux_device_ops dummy_regulator_driver = {
+	.probe = dummy_regulator_probe,
+};
+
+static struct faux_device *dummy_fdev;
+
+void __init regulator_dummy_init(void)
+{
+	dummy_fdev = faux_device_create("reg-dummy", NULL, &dummy_regulator_driver);
+	if (!dummy_fdev) {
+		pr_err("Failed to allocate dummy regulator device\n");
+		return;
+	}
+}