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

3 files changed, 98 insertions, 0 deletions

diff --git a/Documentation/arch/arc/arc.rst b/Documentation/arch/arc/arc.rst
new file mode 100644
index 000000000..5923dee37
--- /dev/null
+++ b/Documentation/arch/arc/arc.rst
@@ -0,0 +1,85 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+Linux kernel for ARC processors
+*******************************
+
+Other sources of information
+############################
+
+Below are some resources where more information can be found on
+ARC processors and relevant open source projects.
+
+- `<https://embarc.org>`_ - Community portal for open source on ARC.
+  Good place to start to find relevant FOSS projects, toolchain releases,
+  news items and more.
+
+- `<https://github.com/foss-for-synopsys-dwc-arc-processors>`_ -
+  Home for all development activities regarding open source projects for
+  ARC processors. Some of the projects are forks of various upstream projects,
+  where "work in progress" is hosted prior to submission to upstream projects.
+  Other projects are developed by Synopsys and made available to community
+  as open source for use on ARC Processors.
+
+- `Official Synopsys ARC Processors website
+  <https://www.synopsys.com/designware-ip/processor-solutions.html>`_ -
+  location, with access to some IP documentation (`Programmer's Reference
+  Manual, AKA PRM for ARC HS processors
+  <https://www.synopsys.com/dw/doc.php/ds/cc/programmers-reference-manual-ARC-HS.pdf>`_)
+  and free versions of some commercial tools (`Free nSIM
+  <https://www.synopsys.com/cgi-bin/dwarcnsim/req1.cgi>`_ and
+  `MetaWare Light Edition <https://www.synopsys.com/cgi-bin/arcmwtk_lite/reg1.cgi>`_).
+  Please note though, registration is required to access both the documentation and
+  the tools.
+
+Important note on ARC processors configurability
+################################################
+
+ARC processors are highly configurable and several configurable options
+are supported in Linux. Some options are transparent to software
+(e.g., cache geometries), some can be detected at runtime and configured
+and used accordingly, while some need to be explicitly selected or configured
+in the kernel's configuration utility (AKA "make menuconfig").
+
+However not all configurable options are supported when an ARC processor
+is to run Linux. SoC design teams should refer to "Appendix E:
+Configuration for ARC Linux" in the ARC HS Databook for configurability
+guidelines.
+
+Following these guidelines and selecting valid configuration options
+up front is critical to help prevent any unwanted issues during
+SoC bringup and software development in general.
+
+Building the Linux kernel for ARC processors
+############################################
+
+The process of kernel building for ARC processors is the same as for any other
+architecture and could be done in 2 ways:
+
+- Cross-compilation: process of compiling for ARC targets on a development
+  host with a different processor architecture (generally x86_64/amd64).
+- Native compilation: process of compiling for ARC on a ARC platform
+  (hardware board or a simulator like QEMU) with complete development environment
+  (GNU toolchain, dtc, make etc) installed on the platform.
+
+In both cases, up-to-date GNU toolchain for ARC for the host is needed.
+Synopsys offers prebuilt toolchain releases which can be used for this purpose,
+available from:
+
+- Synopsys GNU toolchain releases:
+  `<https://github.com/foss-for-synopsys-dwc-arc-processors/toolchain/releases>`_
+
+- Linux kernel compilers collection:
+  `<https://mirrors.edge.kernel.org/pub/tools/crosstool>`_
+
+- Bootlin's toolchain collection: `<https://toolchains.bootlin.com>`_
+
+Once the toolchain is installed in the system, make sure its "bin" folder
+is added in your ``PATH`` environment variable. Then set ``ARCH=arc`` &
+``CROSS_COMPILE=arc-linux`` (or whatever matches installed ARC toolchain prefix)
+and then as usual ``make defconfig && make``.
+
+This will produce "vmlinux" file in the root of the kernel source tree
+usable for loading on the target system via JTAG.
+If you need to get an image usable with U-Boot bootloader,
+type ``make uImage`` and ``uImage`` will be produced in ``arch/arc/boot``
+folder.
diff --git a/Documentation/arch/arc/features.rst b/Documentation/arch/arc/features.rst
new file mode 100644
index 000000000..49ff446ff
--- /dev/null
+++ b/Documentation/arch/arc/features.rst
@@ -0,0 +1,3 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+.. kernel-feat:: features arc
diff --git a/Documentation/arch/arc/index.rst b/Documentation/arch/arc/index.rst
new file mode 100644
index 000000000..10bf8c270
--- /dev/null
+++ b/Documentation/arch/arc/index.rst
@@ -0,0 +1,10 @@
+===================
+ARC architecture
+===================
+
+.. toctree::
+    :maxdepth: 1
+
+    arc
+
+    features