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, 144 insertions, 0 deletions

diff --git a/drivers/soc/versatile/soc-realview.c b/drivers/soc/versatile/soc-realview.c
new file mode 100644
index 000000000..cf91abe07
--- /dev/null
+++ b/drivers/soc/versatile/soc-realview.c
@@ -0,0 +1,144 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2014 Linaro Ltd.
+ *
+ * Author: Linus Walleij <linus.walleij@linaro.org>
+ */
+#include <linux/device.h>
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/slab.h>
+#include <linux/sys_soc.h>
+#include <linux/platform_device.h>
+#include <linux/mfd/syscon.h>
+#include <linux/regmap.h>
+#include <linux/of.h>
+
+/* System ID in syscon */
+#define REALVIEW_SYS_ID_OFFSET 0x00
+
+static const struct of_device_id realview_soc_of_match[] = {
+	{ .compatible = "arm,realview-eb-soc",	},
+	{ .compatible = "arm,realview-pb1176-soc", },
+	{ .compatible = "arm,realview-pb11mp-soc", },
+	{ .compatible = "arm,realview-pba8-soc", },
+	{ .compatible = "arm,realview-pbx-soc", },
+	{ }
+};
+
+static u32 realview_coreid;
+
+static const char *realview_arch_str(u32 id)
+{
+	switch ((id >> 8) & 0xf) {
+	case 0x04:
+		return "AHB";
+	case 0x05:
+		return "Multi-layer AXI";
+	default:
+		return "Unknown";
+	}
+}
+
+static ssize_t
+manufacturer_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	return sprintf(buf, "%02x\n", realview_coreid >> 24);
+}
+
+static DEVICE_ATTR_RO(manufacturer);
+
+static ssize_t
+board_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	return sprintf(buf, "HBI-%03x\n", ((realview_coreid >> 16) & 0xfff));
+}
+
+static DEVICE_ATTR_RO(board);
+
+static ssize_t
+fpga_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	return sprintf(buf, "%s\n", realview_arch_str(realview_coreid));
+}
+
+static DEVICE_ATTR_RO(fpga);
+
+static ssize_t
+build_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	return sprintf(buf, "%02x\n", (realview_coreid & 0xFF));
+}
+
+static DEVICE_ATTR_RO(build);
+
+static struct attribute *realview_attrs[] = {
+	&dev_attr_manufacturer.attr,
+	&dev_attr_board.attr,
+	&dev_attr_fpga.attr,
+	&dev_attr_build.attr,
+	NULL
+};
+
+ATTRIBUTE_GROUPS(realview);
+
+static void realview_soc_socdev_release(void *data)
+{
+	struct soc_device *soc_dev = data;
+
+	soc_device_unregister(soc_dev);
+}
+
+static int realview_soc_probe(struct platform_device *pdev)
+{
+	struct regmap *syscon_regmap;
+	struct soc_device *soc_dev;
+	struct soc_device_attribute *soc_dev_attr;
+	struct device_node *np = pdev->dev.of_node;
+	int ret;
+
+	syscon_regmap = syscon_regmap_lookup_by_phandle(np, "regmap");
+	if (IS_ERR(syscon_regmap))
+		return PTR_ERR(syscon_regmap);
+
+	soc_dev_attr = devm_kzalloc(&pdev->dev, sizeof(*soc_dev_attr), GFP_KERNEL);
+	if (!soc_dev_attr)
+		return -ENOMEM;
+
+	ret = of_property_read_string(np, "compatible",
+				      &soc_dev_attr->soc_id);
+	if (ret)
+		return -EINVAL;
+
+	soc_dev_attr->machine = "RealView";
+	soc_dev_attr->family = "Versatile";
+	soc_dev_attr->custom_attr_group = realview_groups[0];
+	soc_dev = soc_device_register(soc_dev_attr);
+	if (IS_ERR(soc_dev))
+		return -ENODEV;
+
+	ret = devm_add_action_or_reset(&pdev->dev, realview_soc_socdev_release,
+				       soc_dev);
+	if (ret)
+		return ret;
+
+	ret = regmap_read(syscon_regmap, REALVIEW_SYS_ID_OFFSET,
+			  &realview_coreid);
+	if (ret)
+		return -ENODEV;
+
+	dev_info(&pdev->dev, "RealView Syscon Core ID: 0x%08x, HBI-%03x\n",
+		 realview_coreid,
+		 ((realview_coreid >> 16) & 0xfff));
+	/* FIXME: add attributes for SoC to sysfs */
+	return 0;
+}
+
+static struct platform_driver realview_soc_driver = {
+	.probe = realview_soc_probe,
+	.driver = {
+		.name = "realview-soc",
+		.of_match_table = realview_soc_of_match,
+	},
+};
+builtin_platform_driver(realview_soc_driver);