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, 41 insertions, 0 deletions

diff --git a/drivers/mcb/Kconfig b/drivers/mcb/Kconfig
new file mode 100644
index 000000000..0a883486f
--- /dev/null
+++ b/drivers/mcb/Kconfig
@@ -0,0 +1,41 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# MEN Chameleon Bus (MCB) support
+#
+
+menuconfig MCB
+	   tristate "MCB support"
+	   default n
+	   depends on HAS_IOMEM
+	   help
+
+	   The MCB (MEN Chameleon Bus) is a Bus specific to MEN Mikroelektronik
+	   FPGA based devices. It is used to identify MCB based IP-Cores within
+	   an FPGA and provide the necessary framework for instantiating drivers
+	   for these devices.
+
+	   If build as a module, the module is called mcb.ko
+
+if MCB
+config MCB_PCI
+	   tristate "PCI based MCB carrier"
+	   default n
+	   depends on PCI
+	   help
+
+	   This is a MCB carrier on a PCI device. Both PCI attached on-board
+	   FPGAs as well as CompactPCI attached MCB FPGAs are supported with
+	   this driver.
+
+	   If build as a module, the module is called mcb-pci.ko
+
+config MCB_LPC
+	   tristate "LPC (non PCI) based MCB carrier"
+	   default n
+	   help
+
+	   This is a MCB carrier on a LPC or non PCI device.
+
+	   If build as a module, the module is called mcb-lpc.ko
+
+endif # MCB