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, 98 insertions, 0 deletions

diff --git a/drivers/power/reset/syscon-poweroff.c b/drivers/power/reset/syscon-poweroff.c
new file mode 100644
index 000000000..203936f4c
--- /dev/null
+++ b/drivers/power/reset/syscon-poweroff.c
@@ -0,0 +1,98 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Generic Syscon Poweroff Driver
+ *
+ * Copyright (c) 2015, National Instruments Corp.
+ * Author: Moritz Fischer <moritz.fischer@ettus.com>
+ */
+
+#include <linux/delay.h>
+#include <linux/io.h>
+#include <linux/notifier.h>
+#include <linux/mfd/syscon.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/pm.h>
+#include <linux/reboot.h>
+#include <linux/regmap.h>
+
+struct syscon_poweroff_data {
+	struct regmap *map;
+	u32 offset;
+	u32 value;
+	u32 mask;
+};
+
+static int syscon_poweroff(struct sys_off_data *off_data)
+{
+	struct syscon_poweroff_data *data = off_data->cb_data;
+
+	/* Issue the poweroff */
+	regmap_update_bits(data->map, data->offset, data->mask, data->value);
+
+	mdelay(1000);
+
+	pr_emerg("Unable to poweroff system\n");
+
+	return NOTIFY_DONE;
+}
+
+static int syscon_poweroff_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct syscon_poweroff_data *data;
+	int mask_err, value_err;
+
+	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	data->map = syscon_regmap_lookup_by_phandle(dev->of_node, "regmap");
+	if (IS_ERR(data->map)) {
+		data->map = syscon_node_to_regmap(dev->parent->of_node);
+		if (IS_ERR(data->map)) {
+			dev_err(dev, "unable to get syscon");
+			return PTR_ERR(data->map);
+		}
+	}
+
+	if (of_property_read_u32(dev->of_node, "offset", &data->offset)) {
+		dev_err(dev, "unable to read 'offset'");
+		return -EINVAL;
+	}
+
+	value_err = of_property_read_u32(dev->of_node, "value", &data->value);
+	mask_err = of_property_read_u32(dev->of_node, "mask", &data->mask);
+	if (value_err && mask_err) {
+		dev_err(dev, "unable to read 'value' and 'mask'");
+		return -EINVAL;
+	}
+
+	if (value_err) {
+		/* support old binding */
+		data->value = data->mask;
+		data->mask = 0xFFFFFFFF;
+	} else if (mask_err) {
+		/* support value without mask*/
+		data->mask = 0xFFFFFFFF;
+	}
+
+	return devm_register_sys_off_handler(&pdev->dev,
+					     SYS_OFF_MODE_POWER_OFF,
+					     SYS_OFF_PRIO_DEFAULT,
+					     syscon_poweroff, data);
+}
+
+static const struct of_device_id syscon_poweroff_of_match[] = {
+	{ .compatible = "syscon-poweroff" },
+	{}
+};
+
+static struct platform_driver syscon_poweroff_driver = {
+	.probe = syscon_poweroff_probe,
+	.driver = {
+		.name = "syscon-poweroff",
+		.of_match_table = syscon_poweroff_of_match,
+	},
+};
+builtin_platform_driver(syscon_poweroff_driver);