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, 77 insertions, 0 deletions

diff --git a/drivers/nvmem/uniphier-efuse.c b/drivers/nvmem/uniphier-efuse.c
new file mode 100644
index 000000000..85f9372fb
--- /dev/null
+++ b/drivers/nvmem/uniphier-efuse.c
@@ -0,0 +1,77 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * UniPhier eFuse driver
+ *
+ * Copyright (C) 2017 Socionext Inc.
+ */
+
+#include <linux/device.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/nvmem-provider.h>
+#include <linux/platform_device.h>
+
+struct uniphier_efuse_priv {
+	void __iomem *base;
+};
+
+static int uniphier_reg_read(void *context,
+			     unsigned int reg, void *_val, size_t bytes)
+{
+	struct uniphier_efuse_priv *priv = context;
+	u8 *val = _val;
+	int offs;
+
+	for (offs = 0; offs < bytes; offs += sizeof(u8))
+		*val++ = readb(priv->base + reg + offs);
+
+	return 0;
+}
+
+static int uniphier_efuse_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct resource *res;
+	struct nvmem_device *nvmem;
+	struct nvmem_config econfig = {};
+	struct uniphier_efuse_priv *priv;
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	priv->base = devm_platform_get_and_ioremap_resource(pdev, 0, &res);
+	if (IS_ERR(priv->base))
+		return PTR_ERR(priv->base);
+
+	econfig.stride = 1;
+	econfig.word_size = 1;
+	econfig.read_only = true;
+	econfig.reg_read = uniphier_reg_read;
+	econfig.size = resource_size(res);
+	econfig.priv = priv;
+	econfig.dev = dev;
+	econfig.add_legacy_fixed_of_cells = true;
+	nvmem = devm_nvmem_register(dev, &econfig);
+
+	return PTR_ERR_OR_ZERO(nvmem);
+}
+
+static const struct of_device_id uniphier_efuse_of_match[] = {
+	{ .compatible = "socionext,uniphier-efuse",},
+	{/* sentinel */},
+};
+MODULE_DEVICE_TABLE(of, uniphier_efuse_of_match);
+
+static struct platform_driver uniphier_efuse_driver = {
+	.probe = uniphier_efuse_probe,
+	.driver = {
+		.name = "uniphier-efuse",
+		.of_match_table = uniphier_efuse_of_match,
+	},
+};
+module_platform_driver(uniphier_efuse_driver);
+
+MODULE_AUTHOR("Keiji Hayashibara <hayashibara.keiji@socionext.com>");
+MODULE_DESCRIPTION("UniPhier eFuse driver");
+MODULE_LICENSE("GPL v2");