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, 29 insertions, 0 deletions

diff --git a/Documentation/power/tricks.rst b/Documentation/power/tricks.rst
new file mode 100644
index 000000000..ca787f142
--- /dev/null
+++ b/Documentation/power/tricks.rst
@@ -0,0 +1,29 @@
+================
+swsusp/S3 tricks
+================
+
+Pavel Machek <pavel@ucw.cz>
+
+If you want to trick swsusp/S3 into working, you might want to try:
+
+* go with minimal config, turn off drivers like USB, AGP you don't
+  really need
+
+* turn off APIC and preempt
+
+* use ext2. At least it has working fsck. [If something seems to go
+  wrong, force fsck when you have a chance]
+
+* turn off modules
+
+* use vga text console, shut down X. [If you really want X, you might
+  want to try vesafb later]
+
+* try running as few processes as possible, preferably go to single
+  user mode.
+
+* due to video issues, swsusp should be easier to get working than
+  S3. Try that first.
+
+When you make it work, try to find out what exactly was it that broke
+suspend, and preferably fix that.