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, 79 insertions, 0 deletions

diff --git a/drivers/power/reset/axxia-reset.c b/drivers/power/reset/axxia-reset.c
new file mode 100644
index 000000000..797bf6773
--- /dev/null
+++ b/drivers/power/reset/axxia-reset.c
@@ -0,0 +1,79 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Reset driver for Axxia devices
+ *
+ * Copyright (C) 2014 LSI
+ */
+#include <linux/init.h>
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/mfd/syscon.h>
+#include <linux/module.h>
+#include <linux/notifier.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/reboot.h>
+#include <linux/regmap.h>
+
+#define SC_CRIT_WRITE_KEY	0x1000
+#define SC_LATCH_ON_RESET	0x1004
+#define SC_RESET_CONTROL	0x1008
+#define   RSTCTL_RST_ZERO	(1<<3)
+#define   RSTCTL_RST_FAB	(1<<2)
+#define   RSTCTL_RST_CHIP	(1<<1)
+#define   RSTCTL_RST_SYS	(1<<0)
+#define SC_EFUSE_INT_STATUS	0x180c
+#define   EFUSE_READ_DONE	(1<<31)
+
+static int axxia_restart_handler(struct sys_off_data *data)
+{
+	struct regmap *syscon = data->cb_data;
+
+	/* Access Key (0xab) */
+	regmap_write(syscon, SC_CRIT_WRITE_KEY, 0xab);
+	/* Select internal boot from 0xffff0000 */
+	regmap_write(syscon, SC_LATCH_ON_RESET, 0x00000040);
+	/* Assert ResetReadDone (to avoid hanging in boot ROM) */
+	regmap_write(syscon, SC_EFUSE_INT_STATUS, EFUSE_READ_DONE);
+	/* Assert chip reset */
+	regmap_update_bits(syscon, SC_RESET_CONTROL,
+			   RSTCTL_RST_CHIP, RSTCTL_RST_CHIP);
+
+	return NOTIFY_DONE;
+}
+
+static int axxia_reset_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct regmap *syscon;
+	int err;
+
+	syscon = syscon_regmap_lookup_by_phandle(dev->of_node, "syscon");
+	if (IS_ERR(syscon)) {
+		pr_err("%pOFn: syscon lookup failed\n", dev->of_node);
+		return PTR_ERR(syscon);
+	}
+
+	err = devm_register_sys_off_handler(&pdev->dev, SYS_OFF_MODE_RESTART,
+					    128, axxia_restart_handler, syscon);
+	if (err)
+		dev_err(dev, "cannot register restart handler (err=%d)\n", err);
+
+	return err;
+}
+
+static const struct of_device_id of_axxia_reset_match[] = {
+	{ .compatible = "lsi,axm55xx-reset", },
+	{},
+};
+MODULE_DEVICE_TABLE(of, of_axxia_reset_match);
+
+static struct platform_driver axxia_reset_driver = {
+	.probe = axxia_reset_probe,
+	.driver = {
+		.name = "axxia-reset",
+		.of_match_table = of_match_ptr(of_axxia_reset_match),
+	},
+};
+builtin_platform_driver(axxia_reset_driver);