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, 108 insertions, 0 deletions

diff --git a/drivers/power/reset/qcom-pon.c b/drivers/power/reset/qcom-pon.c
new file mode 100644
index 000000000..7e108982a
--- /dev/null
+++ b/drivers/power/reset/qcom-pon.c
@@ -0,0 +1,108 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2017-18 Linaro Limited
+
+#include <linux/delay.h>
+#include <linux/errno.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_platform.h>
+#include <linux/platform_device.h>
+#include <linux/reboot.h>
+#include <linux/reboot-mode.h>
+#include <linux/regmap.h>
+
+#define PON_SOFT_RB_SPARE		0x8f
+
+#define GEN1_REASON_SHIFT		2
+#define GEN2_REASON_SHIFT		1
+
+#define NO_REASON_SHIFT			0
+
+struct qcom_pon {
+	struct device *dev;
+	struct regmap *regmap;
+	u32 baseaddr;
+	struct reboot_mode_driver reboot_mode;
+	long reason_shift;
+};
+
+static int qcom_pon_reboot_mode_write(struct reboot_mode_driver *reboot,
+				    unsigned int magic)
+{
+	struct qcom_pon *pon = container_of
+			(reboot, struct qcom_pon, reboot_mode);
+	int ret;
+
+	ret = regmap_update_bits(pon->regmap,
+				 pon->baseaddr + PON_SOFT_RB_SPARE,
+				 GENMASK(7, pon->reason_shift),
+				 magic << pon->reason_shift);
+	if (ret < 0)
+		dev_err(pon->dev, "update reboot mode bits failed\n");
+
+	return ret;
+}
+
+static int qcom_pon_probe(struct platform_device *pdev)
+{
+	struct qcom_pon *pon;
+	long reason_shift;
+	int error;
+
+	pon = devm_kzalloc(&pdev->dev, sizeof(*pon), GFP_KERNEL);
+	if (!pon)
+		return -ENOMEM;
+
+	pon->dev = &pdev->dev;
+
+	pon->regmap = dev_get_regmap(pdev->dev.parent, NULL);
+	if (!pon->regmap) {
+		dev_err(&pdev->dev, "failed to locate regmap\n");
+		return -ENODEV;
+	}
+
+	error = of_property_read_u32(pdev->dev.of_node, "reg",
+				     &pon->baseaddr);
+	if (error)
+		return error;
+
+	reason_shift = (long)of_device_get_match_data(&pdev->dev);
+
+	if (reason_shift != NO_REASON_SHIFT) {
+		pon->reboot_mode.dev = &pdev->dev;
+		pon->reason_shift = reason_shift;
+		pon->reboot_mode.write = qcom_pon_reboot_mode_write;
+		error = devm_reboot_mode_register(&pdev->dev, &pon->reboot_mode);
+		if (error) {
+			dev_err(&pdev->dev, "can't register reboot mode\n");
+			return error;
+		}
+	}
+
+	platform_set_drvdata(pdev, pon);
+
+	return devm_of_platform_populate(&pdev->dev);
+}
+
+static const struct of_device_id qcom_pon_id_table[] = {
+	{ .compatible = "qcom,pm8916-pon", .data = (void *)GEN1_REASON_SHIFT },
+	{ .compatible = "qcom,pm8941-pon", .data = (void *)NO_REASON_SHIFT },
+	{ .compatible = "qcom,pms405-pon", .data = (void *)GEN1_REASON_SHIFT },
+	{ .compatible = "qcom,pm8998-pon", .data = (void *)GEN2_REASON_SHIFT },
+	{ .compatible = "qcom,pmk8350-pon", .data = (void *)GEN2_REASON_SHIFT },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, qcom_pon_id_table);
+
+static struct platform_driver qcom_pon_driver = {
+	.probe = qcom_pon_probe,
+	.driver = {
+		.name = "qcom-pon",
+		.of_match_table = qcom_pon_id_table,
+	},
+};
+module_platform_driver(qcom_pon_driver);
+
+MODULE_DESCRIPTION("Qualcomm Power On driver");
+MODULE_LICENSE("GPL v2");