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, 105 insertions, 0 deletions

diff --git a/drivers/parisc/hppb.c b/drivers/parisc/hppb.c
new file mode 100644
index 000000000..33709eafe
--- /dev/null
+++ b/drivers/parisc/hppb.c
@@ -0,0 +1,105 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+** hppb.c:
+**      HP-PB bus driver for the NOVA and K-Class systems.
+**
+**      (c) Copyright 2002 Ryan Bradetich
+**      (c) Copyright 2002 Hewlett-Packard Company
+**
+**
+*/
+
+#include <linux/types.h>
+#include <linux/init.h>
+#include <linux/mm.h>
+#include <linux/slab.h>
+#include <linux/dma-mapping.h>
+#include <linux/ioport.h>
+
+#include <asm/io.h>
+#include <asm/hardware.h>
+#include <asm/parisc-device.h>
+
+#include "iommu.h"
+
+struct hppb_card {
+	unsigned long hpa;
+	struct resource mmio_region;
+	struct hppb_card *next;
+};
+
+static struct hppb_card hppb_card_head = {
+	.hpa = 0,
+	.next = NULL,
+};
+
+#define IO_IO_LOW  offsetof(struct bc_module, io_io_low)
+#define IO_IO_HIGH offsetof(struct bc_module, io_io_high)
+
+/**
+ * hppb_probe - Determine if the hppb driver should claim this device.
+ * @dev: The device which has been found
+ *
+ * Determine if hppb driver should claim this chip (return 0) or not 
+ * (return 1). If so, initialize the chip and tell other partners in crime 
+ * they have work to do.
+ */
+static int __init hppb_probe(struct parisc_device *dev)
+{
+	int status;
+	struct hppb_card *card = &hppb_card_head;
+
+	while(card->next) {
+		card = card->next;
+	}
+
+	if(card->hpa) {
+		card->next = kzalloc_obj(struct hppb_card);
+		if(!card->next) {
+			printk(KERN_ERR "HP-PB: Unable to allocate memory.\n");
+			return 1;
+		}
+		card = card->next;
+	}
+
+	card->hpa = dev->hpa.start;
+	card->mmio_region.name = "HP-PB Bus";
+	card->mmio_region.flags = IORESOURCE_MEM;
+
+	card->mmio_region.start = gsc_readl(dev->hpa.start + IO_IO_LOW);
+	card->mmio_region.end = gsc_readl(dev->hpa.start + IO_IO_HIGH) - 1;
+
+	status = ccio_request_resource(dev, &card->mmio_region);
+
+	pr_info("Found GeckoBoa at %pap, bus space %pR,%s claimed.\n",
+			&dev->hpa.start,
+			&card->mmio_region,
+			(status < 0) ? " not":"" );
+
+        return 0;
+}
+
+static const struct parisc_device_id hppb_tbl[] __initconst = {
+        { HPHW_BCPORT, HVERSION_REV_ANY_ID, 0x500, 0xc }, /* E25 and K */
+        { HPHW_BCPORT, 0x0, 0x501, 0xc }, /* E35 */
+        { HPHW_BCPORT, 0x0, 0x502, 0xc }, /* E45 */
+        { HPHW_BCPORT, 0x0, 0x503, 0xc }, /* E55 */
+        { 0, }
+};
+
+static struct parisc_driver hppb_driver __refdata = {
+        .name =         "gecko_boa",
+        .id_table =     hppb_tbl,
+	.probe =        hppb_probe,
+};
+
+/**
+ * hppb_init - HP-PB bus initialization procedure.
+ *
+ * Register this driver.
+ */
+static int __init hppb_init(void)
+{
+        return register_parisc_driver(&hppb_driver);
+}
+arch_initcall(hppb_init);