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, 133 insertions, 0 deletions

diff --git a/drivers/reset/reset-zynq.c b/drivers/reset/reset-zynq.c
new file mode 100644
index 000000000..688b51288
--- /dev/null
+++ b/drivers/reset/reset-zynq.c
@@ -0,0 +1,133 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2015, National Instruments Corp.
+ *
+ * Xilinx Zynq Reset controller driver
+ *
+ * Author: Moritz Fischer <moritz.fischer@ettus.com>
+ */
+
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/init.h>
+#include <linux/mfd/syscon.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/reset-controller.h>
+#include <linux/regmap.h>
+#include <linux/types.h>
+
+struct zynq_reset_data {
+	struct regmap *slcr;
+	struct reset_controller_dev rcdev;
+	u32 offset;
+};
+
+#define to_zynq_reset_data(p)		\
+	container_of((p), struct zynq_reset_data, rcdev)
+
+static int zynq_reset_assert(struct reset_controller_dev *rcdev,
+			     unsigned long id)
+{
+	struct zynq_reset_data *priv = to_zynq_reset_data(rcdev);
+
+	int bank = id / BITS_PER_LONG;
+	int offset = id % BITS_PER_LONG;
+
+	pr_debug("%s: %s reset bank %u offset %u\n", KBUILD_MODNAME, __func__,
+		 bank, offset);
+
+	return regmap_update_bits(priv->slcr,
+				  priv->offset + (bank * 4),
+				  BIT(offset),
+				  BIT(offset));
+}
+
+static int zynq_reset_deassert(struct reset_controller_dev *rcdev,
+			       unsigned long id)
+{
+	struct zynq_reset_data *priv = to_zynq_reset_data(rcdev);
+
+	int bank = id / BITS_PER_LONG;
+	int offset = id % BITS_PER_LONG;
+
+	pr_debug("%s: %s reset bank %u offset %u\n", KBUILD_MODNAME, __func__,
+		 bank, offset);
+
+	return regmap_update_bits(priv->slcr,
+				  priv->offset + (bank * 4),
+				  BIT(offset),
+				  ~BIT(offset));
+}
+
+static int zynq_reset_status(struct reset_controller_dev *rcdev,
+			     unsigned long id)
+{
+	struct zynq_reset_data *priv = to_zynq_reset_data(rcdev);
+
+	int bank = id / BITS_PER_LONG;
+	int offset = id % BITS_PER_LONG;
+	int ret;
+	u32 reg;
+
+	pr_debug("%s: %s reset bank %u offset %u\n", KBUILD_MODNAME, __func__,
+		 bank, offset);
+
+	ret = regmap_read(priv->slcr, priv->offset + (bank * 4), &reg);
+	if (ret)
+		return ret;
+
+	return !!(reg & BIT(offset));
+}
+
+static const struct reset_control_ops zynq_reset_ops = {
+	.assert		= zynq_reset_assert,
+	.deassert	= zynq_reset_deassert,
+	.status		= zynq_reset_status,
+};
+
+static int zynq_reset_probe(struct platform_device *pdev)
+{
+	struct resource *res;
+	struct zynq_reset_data *priv;
+
+	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	priv->slcr = syscon_regmap_lookup_by_phandle(pdev->dev.of_node,
+						     "syscon");
+	if (IS_ERR(priv->slcr)) {
+		dev_err(&pdev->dev, "unable to get zynq-slcr regmap");
+		return PTR_ERR(priv->slcr);
+	}
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!res) {
+		dev_err(&pdev->dev, "missing IO resource\n");
+		return -ENODEV;
+	}
+
+	priv->offset = res->start;
+
+	priv->rcdev.owner = THIS_MODULE;
+	priv->rcdev.nr_resets = resource_size(res) / 4 * BITS_PER_LONG;
+	priv->rcdev.ops = &zynq_reset_ops;
+	priv->rcdev.of_node = pdev->dev.of_node;
+
+	return devm_reset_controller_register(&pdev->dev, &priv->rcdev);
+}
+
+static const struct of_device_id zynq_reset_dt_ids[] = {
+	{ .compatible = "xlnx,zynq-reset", },
+	{ /* sentinel */ },
+};
+
+static struct platform_driver zynq_reset_driver = {
+	.probe	= zynq_reset_probe,
+	.driver = {
+		.name		= KBUILD_MODNAME,
+		.of_match_table	= zynq_reset_dt_ids,
+	},
+};
+builtin_platform_driver(zynq_reset_driver);