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, 71 insertions, 0 deletions

diff --git a/Documentation/fb/efifb.rst b/Documentation/fb/efifb.rst
new file mode 100644
index 000000000..3d4aab406
--- /dev/null
+++ b/Documentation/fb/efifb.rst
@@ -0,0 +1,71 @@
+===================================
+efifb - Generic EFI platform driver
+===================================
+
+This is a generic EFI platform driver for systems with UEFI firmware. The
+system must be booted via the EFI stub for this to be usable. efifb supports
+both firmware with Graphics Output Protocol (GOP) displays as well as older
+systems with only Universal Graphics Adapter (UGA) displays.
+
+Supported Hardware
+==================
+
+- iMac 17"/20"
+- Macbook
+- Macbook Pro 15"/17"
+- MacMini
+- ARM/ARM64/X86 systems with UEFI firmware
+
+How to use it?
+==============
+
+For UGA displays, efifb does not have any kind of autodetection of your
+machine.
+
+You have to add the following kernel parameters in your elilo.conf::
+
+	Macbook :
+		video=efifb:macbook
+	MacMini :
+		video=efifb:mini
+	Macbook Pro 15", iMac 17" :
+		video=efifb:i17
+	Macbook Pro 17", iMac 20" :
+		video=efifb:i20
+
+For GOP displays, efifb can autodetect the display's resolution and framebuffer
+address, so these should work out of the box without any special parameters.
+
+Accepted options:
+
+======= ===========================================================
+nowc	Don't map the framebuffer write combined. This can be used
+	to workaround side-effects and slowdowns on other CPU cores
+	when large amounts of console data are written.
+======= ===========================================================
+
+Options for GOP displays:
+
+mode=n
+        The EFI stub will set the mode of the display to mode number n if
+        possible.
+
+<xres>x<yres>[-(rgb|bgr|<bpp>)]
+        The EFI stub will search for a display mode that matches the specified
+        horizontal and vertical resolution, and optionally bit depth, and set
+        the mode of the display to it if one is found. The bit depth can either
+        "rgb" or "bgr" to match specifically those pixel formats, or a number
+        for a mode with matching bits per pixel.
+
+auto
+        The EFI stub will choose the mode with the highest resolution (product
+        of horizontal and vertical resolution). If there are multiple modes
+        with the highest resolution, it will choose one with the highest color
+        depth.
+
+list
+        The EFI stub will list out all the display modes that are available. A
+        specific mode can then be chosen using one of the above options for the
+        next boot.
+
+Edgar Hucek <gimli@dark-green.com>