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, 140 insertions, 0 deletions

diff --git a/drivers/parisc/wax.c b/drivers/parisc/wax.c
new file mode 100644
index 000000000..a82a5e88e
--- /dev/null
+++ b/drivers/parisc/wax.c
@@ -0,0 +1,140 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *	WAX Device Driver
+ *
+ *	(c) Copyright 2000 The Puffin Group Inc.
+ *
+ *	(c) 2000-2023 by Helge Deller <deller@gmx.de>
+ */
+
+#include <linux/errno.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/ioport.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <linux/types.h>
+
+#include <asm/io.h>
+#include <asm/hardware.h>
+
+#include "gsc.h"
+
+#define WAX_GSC_IRQ	7	/* Hardcoded Interrupt for GSC */
+
+static void wax_choose_irq(struct parisc_device *dev, void *ctrl)
+{
+	int irq;
+
+	switch (dev->id.sversion) {
+		case 0x73:	irq =  1; break; /* i8042 General */
+		case 0x8c:	irq =  6; break; /* Serial */
+		case 0x90:	irq = 10; break; /* EISA */
+		default:	return;		 /* Unknown */
+	}
+
+	gsc_asic_assign_irq(ctrl, irq, &dev->irq);
+
+	switch (dev->id.sversion) {
+		case 0x73:	irq =  2; break; /* i8042 High-priority */
+		case 0x90:	irq =  0; break; /* EISA NMI */
+		default:	return;		 /* No secondary IRQ */
+	}
+
+	gsc_asic_assign_irq(ctrl, irq, &dev->aux_irq);
+}
+
+static void __init
+wax_init_irq(struct gsc_asic *wax)
+{
+	unsigned long base = wax->hpa;
+
+	/* Wax-off */
+	gsc_writel(0x00000000, base+OFFSET_IMR);
+
+	/* clear pending interrupts */
+	gsc_readl(base+OFFSET_IRR);
+
+	/* We're not really convinced we want to reset the onboard
+         * devices. Firmware does it for us...
+	 */
+
+	/* Resets */
+//	gsc_writel(0xFFFFFFFF, base+0x1000); /* HIL */
+//	gsc_writel(0xFFFFFFFF, base+0x2000); /* RS232-B on Wax */
+}
+
+static int __init wax_init_chip(struct parisc_device *dev)
+{
+	struct gsc_asic *wax;
+	struct parisc_device *parent;
+	int ret;
+
+	wax = kzalloc_obj(*wax);
+	if (!wax)
+		return -ENOMEM;
+
+	wax->name = "wax";
+	wax->hpa = dev->hpa.start;
+
+	wax->version = 0;   /* gsc_readb(wax->hpa+WAX_VER); */
+	printk(KERN_INFO "%s at 0x%lx found.\n", wax->name, wax->hpa);
+
+	/* Stop wax hissing for a bit */
+	wax_init_irq(wax);
+
+	/* the IRQ wax should use */
+	dev->irq = gsc_claim_irq(&wax->gsc_irq, WAX_GSC_IRQ);
+	if (dev->irq < 0) {
+		printk(KERN_ERR "%s(): cannot get GSC irq\n",
+				__func__);
+		kfree(wax);
+		return -EBUSY;
+	}
+
+	wax->eim = ((u32) wax->gsc_irq.txn_addr) | wax->gsc_irq.txn_data;
+
+	ret = request_irq(wax->gsc_irq.irq, gsc_asic_intr, 0, "wax", wax);
+	if (ret < 0) {
+		kfree(wax);
+		return ret;
+	}
+
+	/* enable IRQ's for devices below WAX */
+	gsc_writel(wax->eim, wax->hpa + OFFSET_IAR);
+
+	/* Done init'ing, register this driver */
+	ret = gsc_common_setup(dev, wax);
+	if (ret) {
+		kfree(wax);
+		return ret;
+	}
+
+	gsc_fixup_irqs(dev, wax, wax_choose_irq);
+	/* On 715-class machines, Wax EISA is a sibling of Wax, not a child. */
+	parent = parisc_parent(dev);
+	if (parent->id.hw_type != HPHW_IOA) {
+		gsc_fixup_irqs(parent, wax, wax_choose_irq);
+	}
+
+	return ret;
+}
+
+static const struct parisc_device_id wax_tbl[] __initconst = {
+	{ HPHW_BA, HVERSION_REV_ANY_ID, HVERSION_ANY_ID, 0x0008e },
+	{ 0, }
+};
+
+MODULE_DEVICE_TABLE(parisc, wax_tbl);
+
+static struct parisc_driver wax_driver __refdata = {
+	.name =		"wax",
+	.id_table =	wax_tbl,
+	.probe =	wax_init_chip,
+};
+
+static int __init wax_init(void)
+{
+	return register_parisc_driver(&wax_driver);
+}
+arch_initcall(wax_init);