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, 88 insertions, 0 deletions

diff --git a/drivers/mfd/sky81452.c b/drivers/mfd/sky81452.c
new file mode 100644
index 000000000..771b62a5c
--- /dev/null
+++ b/drivers/mfd/sky81452.c
@@ -0,0 +1,88 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * sky81452.c	SKY81452 MFD driver
+ *
+ * Copyright 2014 Skyworks Solutions Inc.
+ * Author : Gyungoh Yoo <jack.yoo@skyworksinc.com>
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/err.h>
+#include <linux/slab.h>
+#include <linux/i2c.h>
+#include <linux/regmap.h>
+#include <linux/mfd/core.h>
+#include <linux/mfd/sky81452.h>
+
+static const struct regmap_config sky81452_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+};
+
+static int sky81452_probe(struct i2c_client *client)
+{
+	struct device *dev = &client->dev;
+	const struct sky81452_platform_data *pdata = dev_get_platdata(dev);
+	struct mfd_cell cells[2];
+	struct regmap *regmap;
+	int ret;
+
+	if (!pdata) {
+		pdata = devm_kzalloc(dev, sizeof(*pdata), GFP_KERNEL);
+		if (!pdata)
+			return -ENOMEM;
+	}
+
+	regmap = devm_regmap_init_i2c(client, &sky81452_config);
+	if (IS_ERR(regmap)) {
+		dev_err(dev, "failed to initialize.err=%ld\n", PTR_ERR(regmap));
+		return PTR_ERR(regmap);
+	}
+
+	i2c_set_clientdata(client, regmap);
+
+	memset(cells, 0, sizeof(cells));
+	cells[0].name = "sky81452-backlight";
+	cells[0].of_compatible = "skyworks,sky81452-backlight";
+	cells[1].name = "sky81452-regulator";
+	cells[1].platform_data = pdata->regulator_init_data;
+	cells[1].pdata_size = sizeof(*pdata->regulator_init_data);
+
+	ret = devm_mfd_add_devices(dev, -1, cells, ARRAY_SIZE(cells),
+				   NULL, 0, NULL);
+	if (ret)
+		dev_err(dev, "failed to add child devices. err=%d\n", ret);
+
+	return ret;
+}
+
+static const struct i2c_device_id sky81452_ids[] = {
+	{ "sky81452" },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, sky81452_ids);
+
+#ifdef CONFIG_OF
+static const struct of_device_id sky81452_of_match[] = {
+	{ .compatible = "skyworks,sky81452", },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, sky81452_of_match);
+#endif
+
+static struct i2c_driver sky81452_driver = {
+	.driver = {
+		.name = "sky81452",
+		.of_match_table = of_match_ptr(sky81452_of_match),
+	},
+	.probe = sky81452_probe,
+	.id_table = sky81452_ids,
+};
+
+module_i2c_driver(sky81452_driver);
+
+MODULE_DESCRIPTION("Skyworks SKY81452 MFD driver");
+MODULE_AUTHOR("Gyungoh Yoo <jack.yoo@skyworksinc.com>");
+MODULE_LICENSE("GPL v2");