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, 62 insertions, 0 deletions

diff --git a/Documentation/gpu/amdgpu/ras.rst b/Documentation/gpu/amdgpu/ras.rst
new file mode 100644
index 000000000..047f76e39
--- /dev/null
+++ b/Documentation/gpu/amdgpu/ras.rst
@@ -0,0 +1,62 @@
+====================
+ AMDGPU RAS Support
+====================
+
+The AMDGPU RAS interfaces are exposed via sysfs (for informational queries) and
+debugfs (for error injection).
+
+RAS debugfs/sysfs Control and Error Injection Interfaces
+========================================================
+
+.. kernel-doc:: drivers/gpu/drm/amd/amdgpu/amdgpu_ras.c
+   :doc: AMDGPU RAS debugfs control interface
+
+RAS Reboot Behavior for Unrecoverable Errors
+============================================
+
+.. kernel-doc:: drivers/gpu/drm/amd/amdgpu/amdgpu_ras.c
+   :doc: AMDGPU RAS Reboot Behavior for Unrecoverable Errors
+
+RAS Error Count sysfs Interface
+===============================
+
+.. kernel-doc:: drivers/gpu/drm/amd/amdgpu/amdgpu_ras.c
+   :doc: AMDGPU RAS sysfs Error Count Interface
+
+RAS EEPROM debugfs Interface
+============================
+
+.. kernel-doc:: drivers/gpu/drm/amd/amdgpu/amdgpu_ras.c
+   :doc: AMDGPU RAS debugfs EEPROM table reset interface
+
+RAS VRAM Bad Pages sysfs Interface
+==================================
+
+.. kernel-doc:: drivers/gpu/drm/amd/amdgpu/amdgpu_ras.c
+   :doc: AMDGPU RAS sysfs gpu_vram_bad_pages Interface
+
+Sample Code
+===========
+Sample code for testing error injection can be found here:
+https://cgit.freedesktop.org/mesa/drm/tree/tests/amdgpu/ras_tests.c
+
+This is part of the libdrm amdgpu unit tests which cover several areas of the GPU.
+There are four sets of tests:
+
+RAS Basic Test
+
+The test verifies the RAS feature enabled status and makes sure the necessary sysfs and debugfs files
+are present.
+
+RAS Query Test
+
+This test checks the RAS availability and enablement status for each supported IP block as well as
+the error counts.
+
+RAS Inject Test
+
+This test injects errors for each IP.
+
+RAS Disable Test
+
+This test tests disabling of RAS features for each IP block.