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, 141 insertions, 0 deletions

diff --git a/drivers/gpib/include/nec7210.h b/drivers/gpib/include/nec7210.h
new file mode 100644
index 000000000..9835aa5ef
--- /dev/null
+++ b/drivers/gpib/include/nec7210.h
@@ -0,0 +1,141 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+/***************************************************************************
+ *    copyright            : (C) 2002 by Frank Mori Hess
+ ***************************************************************************/
+
+#ifndef _NEC7210_H
+#define _NEC7210_H
+
+#include "gpib_state_machines.h"
+#include <linux/types.h>
+#include <linux/spinlock.h>
+#include <linux/string.h>
+#include <linux/interrupt.h>
+
+#include "gpib_types.h"
+#include "nec7210_registers.h"
+
+/* struct used to provide variables local to a nec7210 chip */
+struct nec7210_priv {
+#ifdef CONFIG_HAS_IOPORT
+	u32 iobase;
+#endif
+	void __iomem *mmiobase;
+	unsigned int offset;		// offset between successive nec7210 io addresses
+	unsigned int dma_channel;
+	u8 *dma_buffer;
+	unsigned int dma_buffer_length;	// length of dma buffer
+	dma_addr_t dma_buffer_addr;	// bus address of board->buffer for use with dma
+	// software copy of bits written to registers
+	u8 reg_bits[8];
+	u8 auxa_bits;			// bits written to auxiliary register A
+	u8 auxb_bits;			// bits written to auxiliary register B
+	// used to keep track of board's state, bit definitions given below
+	unsigned long state;
+	// lock for chips that extend the nec7210 registers by paging in alternate regs
+	spinlock_t register_page_lock;
+	// wrappers for outb, inb, readb, or writeb
+	u8 (*read_byte)(struct nec7210_priv *priv, unsigned int register_number);
+	void (*write_byte)(struct nec7210_priv *priv, u8 byte, unsigned int register_number);
+	enum nec7210_chipset type;
+	enum talker_function_state talker_state;
+	enum listener_function_state listener_state;
+	void *private;
+	unsigned srq_pending : 1;
+};
+
+static inline void init_nec7210_private(struct nec7210_priv *priv)
+{
+	memset(priv, 0, sizeof(struct nec7210_priv));
+	spin_lock_init(&priv->register_page_lock);
+}
+
+// slightly shorter way to access read_byte and write_byte
+static inline u8 read_byte(struct nec7210_priv *priv, unsigned int register_number)
+{
+	return priv->read_byte(priv, register_number);
+}
+
+static inline void write_byte(struct nec7210_priv *priv, u8 byte, unsigned int register_number)
+{
+	priv->write_byte(priv, byte, register_number);
+}
+
+// struct nec7210_priv.state bit numbers
+enum {
+	PIO_IN_PROGRESS_BN,		// pio transfer in progress
+	DMA_READ_IN_PROGRESS_BN,	// dma read transfer in progress
+	DMA_WRITE_IN_PROGRESS_BN,	// dma write transfer in progress
+	READ_READY_BN,			// board has data byte available to read
+	WRITE_READY_BN,			// board is ready to send a data byte
+	COMMAND_READY_BN,		// board is ready to send a command byte
+	RECEIVED_END_BN,		// received END
+	BUS_ERROR_BN,			// output error has occurred
+	RFD_HOLDOFF_BN,			// rfd holdoff in effect
+	DEV_CLEAR_BN,			// device clear received
+	ADR_CHANGE_BN,			// address state change occurred
+};
+
+// interface functions
+int nec7210_read(struct gpib_board *board, struct nec7210_priv *priv, u8 *buffer,
+		 size_t length, int *end, size_t *bytes_read);
+int nec7210_write(struct gpib_board *board, struct nec7210_priv *priv, u8 *buffer,
+		  size_t length, int send_eoi, size_t *bytes_written);
+int nec7210_command(struct gpib_board *board, struct nec7210_priv *priv, u8 *buffer,
+		    size_t length, size_t *bytes_written);
+int nec7210_take_control(struct gpib_board *board, struct nec7210_priv *priv, int syncronous);
+int nec7210_go_to_standby(struct gpib_board *board, struct nec7210_priv *priv);
+int nec7210_request_system_control(struct gpib_board *board,
+				   struct nec7210_priv *priv, int request_control);
+void nec7210_interface_clear(struct gpib_board *board, struct nec7210_priv *priv, int assert);
+void nec7210_remote_enable(struct gpib_board *board, struct nec7210_priv *priv, int enable);
+int nec7210_enable_eos(struct gpib_board *board, struct nec7210_priv *priv, u8 eos_bytes,
+		       int compare_8_bits);
+void nec7210_disable_eos(struct gpib_board *board, struct nec7210_priv *priv);
+unsigned int nec7210_update_status(struct gpib_board *board, struct nec7210_priv *priv,
+				   unsigned int clear_mask);
+unsigned int nec7210_update_status_nolock(struct gpib_board *board, struct nec7210_priv *priv);
+int nec7210_primary_address(const struct gpib_board *board,
+			    struct nec7210_priv *priv, unsigned int address);
+int nec7210_secondary_address(const struct gpib_board *board, struct nec7210_priv *priv,
+			      unsigned int address, int enable);
+int nec7210_parallel_poll(struct gpib_board *board, struct nec7210_priv *priv, u8 *result);
+void nec7210_serial_poll_response(struct gpib_board *board,
+				  struct nec7210_priv *priv, u8 status);
+void nec7210_parallel_poll_configure(struct gpib_board *board,
+				     struct nec7210_priv *priv, unsigned int configuration);
+void nec7210_parallel_poll_response(struct gpib_board *board,
+				    struct nec7210_priv *priv, int ist);
+u8 nec7210_serial_poll_status(struct gpib_board *board, struct nec7210_priv *priv);
+int nec7210_t1_delay(struct gpib_board *board,
+		     struct nec7210_priv *priv, unsigned int nano_sec);
+void nec7210_return_to_local(const struct gpib_board *board, struct nec7210_priv *priv);
+
+// utility functions
+void nec7210_board_reset(struct nec7210_priv *priv, const struct gpib_board *board);
+void nec7210_board_online(struct nec7210_priv *priv, const struct gpib_board *board);
+unsigned int nec7210_set_reg_bits(struct nec7210_priv *priv, unsigned int reg,
+				  unsigned int mask, unsigned int bits);
+void nec7210_set_handshake_mode(struct gpib_board *board, struct nec7210_priv *priv, int mode);
+void nec7210_release_rfd_holdoff(struct gpib_board *board, struct nec7210_priv *priv);
+u8 nec7210_read_data_in(struct gpib_board *board, struct nec7210_priv *priv, int *end);
+
+// wrappers for io functions
+u8 nec7210_ioport_read_byte(struct nec7210_priv *priv, unsigned int register_num);
+void nec7210_ioport_write_byte(struct nec7210_priv *priv, u8 data, unsigned int register_num);
+u8 nec7210_iomem_read_byte(struct nec7210_priv *priv, unsigned int register_num);
+void nec7210_iomem_write_byte(struct nec7210_priv *priv, u8 data, unsigned int register_num);
+u8 nec7210_locking_ioport_read_byte(struct nec7210_priv *priv, unsigned int register_num);
+void nec7210_locking_ioport_write_byte(struct nec7210_priv *priv, u8 data,
+				       unsigned int register_num);
+u8 nec7210_locking_iomem_read_byte(struct nec7210_priv *priv, unsigned int register_num);
+void nec7210_locking_iomem_write_byte(struct nec7210_priv *priv, u8 data,
+				      unsigned int register_num);
+
+// interrupt service routine
+irqreturn_t nec7210_interrupt(struct gpib_board *board, struct nec7210_priv *priv);
+irqreturn_t nec7210_interrupt_have_status(struct gpib_board *board,
+					  struct nec7210_priv *priv, int status1, int status2);
+
+#endif	//_NEC7210_H