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, 104 insertions, 0 deletions

diff --git a/Documentation/driver-api/zorro.rst b/Documentation/driver-api/zorro.rst
new file mode 100644
index 000000000..664072b01
--- /dev/null
+++ b/Documentation/driver-api/zorro.rst
@@ -0,0 +1,104 @@
+========================================
+Writing Device Drivers for Zorro Devices
+========================================
+
+:Author: Written by Geert Uytterhoeven <geert@linux-m68k.org>
+:Last revised: September 5, 2003
+
+
+Introduction
+------------
+
+The Zorro bus is the bus used in the Amiga family of computers. Thanks to
+AutoConfig(tm), it's 100% Plug-and-Play.
+
+There are two types of Zorro buses, Zorro II and Zorro III:
+
+  - The Zorro II address space is 24-bit and lies within the first 16 MB of the
+    Amiga's address map.
+
+  - Zorro III is a 32-bit extension of Zorro II, which is backwards compatible
+    with Zorro II. The Zorro III address space lies outside the first 16 MB.
+
+
+Probing for Zorro Devices
+-------------------------
+
+Zorro devices are found by calling ``zorro_find_device()``, which returns a
+pointer to the ``next`` Zorro device with the specified Zorro ID. A probe loop
+for the board with Zorro ID ``ZORRO_PROD_xxx`` looks like::
+
+    struct zorro_dev *z = NULL;
+
+    while ((z = zorro_find_device(ZORRO_PROD_xxx, z))) {
+	if (!zorro_request_region(z->resource.start+MY_START, MY_SIZE,
+				  "My explanation"))
+	...
+    }
+
+``ZORRO_WILDCARD`` acts as a wildcard and finds any Zorro device. If your driver
+supports different types of boards, you can use a construct like::
+
+    struct zorro_dev *z = NULL;
+
+    while ((z = zorro_find_device(ZORRO_WILDCARD, z))) {
+	if (z->id != ZORRO_PROD_xxx1 && z->id != ZORRO_PROD_xxx2 && ...)
+	    continue;
+	if (!zorro_request_region(z->resource.start+MY_START, MY_SIZE,
+				  "My explanation"))
+	...
+    }
+
+
+Zorro Resources
+---------------
+
+Before you can access a Zorro device's registers, you have to make sure it's
+not yet in use. This is done using the I/O memory space resource management
+functions::
+
+    request_mem_region()
+    release_mem_region()
+
+Shortcuts to claim the whole device's address space are provided as well::
+
+    zorro_request_device
+    zorro_release_device
+
+
+Accessing the Zorro Address Space
+---------------------------------
+
+The address regions in the Zorro device resources are Zorro bus address
+regions. Due to the identity bus-physical address mapping on the Zorro bus,
+they are CPU physical addresses as well.
+
+The treatment of these regions depends on the type of Zorro space:
+
+  - Zorro II address space is always mapped and does not have to be mapped
+    explicitly using z_ioremap().
+    
+    Conversion from bus/physical Zorro II addresses to kernel virtual addresses
+    and vice versa is done using::
+
+	virt_addr = ZTWO_VADDR(bus_addr);
+	bus_addr = ZTWO_PADDR(virt_addr);
+
+  - Zorro III address space must be mapped explicitly using z_ioremap() first
+    before it can be accessed::
+ 
+	virt_addr = z_ioremap(bus_addr, size);
+	...
+	z_iounmap(virt_addr);
+
+
+References
+----------
+
+#. linux/include/linux/zorro.h
+#. linux/include/uapi/linux/zorro.h
+#. linux/include/uapi/linux/zorro_ids.h
+#. linux/arch/m68k/include/asm/zorro.h
+#. linux/drivers/zorro
+#. /proc/bus/zorro
+