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, 153 insertions, 0 deletions

diff --git a/drivers/gnss/ubx.c b/drivers/gnss/ubx.c
new file mode 100644
index 000000000..23894ff75
--- /dev/null
+++ b/drivers/gnss/ubx.c
@@ -0,0 +1,153 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * u-blox GNSS receiver driver
+ *
+ * Copyright (C) 2018 Johan Hovold <johan@kernel.org>
+ */
+
+#include <linux/errno.h>
+#include <linux/gnss.h>
+#include <linux/gpio/consumer.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/regulator/consumer.h>
+#include <linux/serdev.h>
+
+#include "serial.h"
+
+struct ubx_data {
+	struct regulator *vcc;
+};
+
+static int ubx_set_active(struct gnss_serial *gserial)
+{
+	struct ubx_data *data = gnss_serial_get_drvdata(gserial);
+	int ret;
+
+	ret = regulator_enable(data->vcc);
+	if (ret)
+		return ret;
+
+	return 0;
+}
+
+static int ubx_set_standby(struct gnss_serial *gserial)
+{
+	struct ubx_data *data = gnss_serial_get_drvdata(gserial);
+	int ret;
+
+	ret = regulator_disable(data->vcc);
+	if (ret)
+		return ret;
+
+	return 0;
+}
+
+static int ubx_set_power(struct gnss_serial *gserial,
+				enum gnss_serial_pm_state state)
+{
+	switch (state) {
+	case GNSS_SERIAL_ACTIVE:
+		return ubx_set_active(gserial);
+	case GNSS_SERIAL_OFF:
+	case GNSS_SERIAL_STANDBY:
+		return ubx_set_standby(gserial);
+	}
+
+	return -EINVAL;
+}
+
+static const struct gnss_serial_ops ubx_gserial_ops = {
+	.set_power = ubx_set_power,
+};
+
+static int ubx_probe(struct serdev_device *serdev)
+{
+	struct gnss_serial *gserial;
+	struct gpio_desc *safeboot;
+	struct gpio_desc *reset;
+	struct ubx_data *data;
+	int ret;
+
+	gserial = gnss_serial_allocate(serdev, sizeof(*data));
+	if (IS_ERR(gserial)) {
+		ret = PTR_ERR(gserial);
+		return ret;
+	}
+
+	gserial->ops = &ubx_gserial_ops;
+
+	gserial->gdev->type = GNSS_TYPE_UBX;
+
+	data = gnss_serial_get_drvdata(gserial);
+
+	data->vcc = devm_regulator_get(&serdev->dev, "vcc");
+	if (IS_ERR(data->vcc)) {
+		ret = PTR_ERR(data->vcc);
+		goto err_free_gserial;
+	}
+
+	ret = devm_regulator_get_enable_optional(&serdev->dev, "v-bckp");
+	if (ret < 0 && ret != -ENODEV)
+		goto err_free_gserial;
+
+	/* Deassert safeboot */
+	safeboot = devm_gpiod_get_optional(&serdev->dev, "safeboot", GPIOD_OUT_LOW);
+	if (IS_ERR(safeboot)) {
+		ret = PTR_ERR(safeboot);
+		goto err_free_gserial;
+	}
+
+	/* Deassert reset */
+	reset = devm_gpiod_get_optional(&serdev->dev, "reset", GPIOD_OUT_LOW);
+	if (IS_ERR(reset)) {
+		ret = PTR_ERR(reset);
+		goto err_free_gserial;
+	}
+
+	ret = gnss_serial_register(gserial);
+	if (ret)
+		goto err_free_gserial;
+
+	return 0;
+
+err_free_gserial:
+	gnss_serial_free(gserial);
+
+	return ret;
+}
+
+static void ubx_remove(struct serdev_device *serdev)
+{
+	struct gnss_serial *gserial = serdev_device_get_drvdata(serdev);
+
+	gnss_serial_deregister(gserial);
+	gnss_serial_free(gserial);
+}
+
+#ifdef CONFIG_OF
+static const struct of_device_id ubx_of_match[] = {
+	{ .compatible = "u-blox,neo-6m" },
+	{ .compatible = "u-blox,neo-8" },
+	{ .compatible = "u-blox,neo-m8" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, ubx_of_match);
+#endif
+
+static struct serdev_device_driver ubx_driver = {
+	.driver	= {
+		.name		= "gnss-ubx",
+		.of_match_table	= of_match_ptr(ubx_of_match),
+		.pm		= &gnss_serial_pm_ops,
+	},
+	.probe	= ubx_probe,
+	.remove	= ubx_remove,
+};
+module_serdev_device_driver(ubx_driver);
+
+MODULE_AUTHOR("Johan Hovold <johan@kernel.org>");
+MODULE_DESCRIPTION("u-blox GNSS receiver driver");
+MODULE_LICENSE("GPL v2");