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, 137 insertions, 0 deletions

diff --git a/drivers/hwmon/occ/common.h b/drivers/hwmon/occ/common.h
new file mode 100644
index 000000000..82f600093
--- /dev/null
+++ b/drivers/hwmon/occ/common.h
@@ -0,0 +1,137 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/* Copyright IBM Corp 2019 */
+
+#ifndef OCC_COMMON_H
+#define OCC_COMMON_H
+
+#include <linux/hwmon-sysfs.h>
+#include <linux/mutex.h>
+#include <linux/sysfs.h>
+
+struct device;
+
+#define OCC_RESP_DATA_BYTES		4089
+
+/*
+ * Same response format for all OCC versions.
+ * Allocate the largest possible response.
+ */
+struct occ_response {
+	u8 seq_no;
+	u8 cmd_type;
+	u8 return_status;
+	__be16 data_length;
+	u8 data[OCC_RESP_DATA_BYTES];
+	__be16 checksum;
+} __packed;
+
+struct occ_sensor_data_block_header {
+	u8 eye_catcher[4];
+	u8 reserved;
+	u8 sensor_format;
+	u8 sensor_length;
+	u8 num_sensors;
+} __packed;
+
+struct occ_sensor_data_block {
+	struct occ_sensor_data_block_header header;
+	u32 data;
+} __packed;
+
+struct occ_poll_response_header {
+	u8 status;
+	u8 ext_status;
+	u8 occs_present;
+	u8 config_data;
+	u8 occ_state;
+	u8 mode;
+	u8 ips_status;
+	u8 error_log_id;
+	__be32 error_log_start_address;
+	__be16 error_log_length;
+	u16 reserved;
+	u8 occ_code_level[16];
+	u8 eye_catcher[6];
+	u8 num_sensor_data_blocks;
+	u8 sensor_data_block_header_version;
+} __packed;
+
+struct occ_poll_response {
+	struct occ_poll_response_header header;
+	struct occ_sensor_data_block block;
+} __packed;
+
+struct occ_sensor {
+	u8 num_sensors;
+	u8 version;
+	void *data;	/* pointer to sensor data start within response */
+};
+
+/*
+ * OCC only provides one sensor data block of each type, but any number of
+ * sensors within that block.
+ */
+struct occ_sensors {
+	struct occ_sensor temp;
+	struct occ_sensor freq;
+	struct occ_sensor power;
+	struct occ_sensor caps;
+	struct occ_sensor extended;
+};
+
+/*
+ * Use our own attribute struct so we can dynamically allocate space for the
+ * name.
+ */
+struct occ_attribute {
+	char name[32];
+	struct sensor_device_attribute_2 sensor;
+};
+
+struct occ {
+	struct device *bus_dev;
+
+	struct occ_response resp;
+	struct occ_sensors sensors;
+
+	int powr_sample_time_us;	/* average power sample time */
+	u8 poll_cmd_data;		/* to perform OCC poll command */
+	int (*send_cmd)(struct occ *occ, u8 *cmd, size_t len, void *resp,
+			size_t resp_len);
+
+	unsigned long next_update;
+	struct mutex lock;		/* lock OCC access */
+	struct mutex hwmon_lock;		/* serialize hwmon registration/removal */
+
+	struct device *hwmon;
+	struct occ_attribute *attrs;
+	struct attribute_group group;
+	const struct attribute_group *groups[2];
+
+	bool active;
+	int error;                      /* final transfer error after retry */
+	int last_error;			/* latest transfer error */
+	unsigned int error_count;       /* number of xfr errors observed */
+	unsigned long last_safe;        /* time OCC entered "safe" state */
+
+	/*
+	 * Store the previous state data for comparison in order to notify
+	 * sysfs readers of state changes.
+	 */
+	int prev_error;
+	u8 prev_stat;
+	u8 prev_ext_stat;
+	u8 prev_occs_present;
+	u8 prev_ips_status;
+	u8 prev_mode;
+};
+
+int occ_active(struct occ *occ, bool active);
+int occ_setup(struct occ *occ);
+int occ_setup_sysfs(struct occ *occ);
+void occ_shutdown(struct occ *occ);
+void occ_shutdown_sysfs(struct occ *occ);
+void occ_sysfs_poll_done(struct occ *occ);
+int occ_update_response(struct occ *occ);
+
+#endif /* OCC_COMMON_H */