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, 231 insertions, 0 deletions

diff --git a/drivers/base/regmap/regmap-fsi.c b/drivers/base/regmap/regmap-fsi.c
new file mode 100644
index 000000000..3d2f3cb31
--- /dev/null
+++ b/drivers/base/regmap/regmap-fsi.c
@@ -0,0 +1,231 @@
+// SPDX-License-Identifier: GPL-2.0
+//
+// Register map access API - FSI support
+//
+// Copyright 2022 IBM Corp
+//
+// Author: Eddie James <eajames@linux.ibm.com>
+
+#include <linux/fsi.h>
+#include <linux/module.h>
+#include <linux/regmap.h>
+
+#include "internal.h"
+
+static int regmap_fsi32_reg_read(void *context, unsigned int reg, unsigned int *val)
+{
+	u32 v;
+	int ret;
+
+	ret = fsi_slave_read(context, reg, &v, sizeof(v));
+	if (ret)
+		return ret;
+
+	*val = v;
+	return 0;
+}
+
+static int regmap_fsi32_reg_write(void *context, unsigned int reg, unsigned int val)
+{
+	u32 v = val;
+
+	return fsi_slave_write(context, reg, &v, sizeof(v));
+}
+
+static const struct regmap_bus regmap_fsi32 = {
+	.reg_write = regmap_fsi32_reg_write,
+	.reg_read = regmap_fsi32_reg_read,
+};
+
+static int regmap_fsi32le_reg_read(void *context, unsigned int reg, unsigned int *val)
+{
+	__be32 v;
+	int ret;
+
+	ret = fsi_slave_read(context, reg, &v, sizeof(v));
+	if (ret)
+		return ret;
+
+	*val = be32_to_cpu(v);
+	return 0;
+}
+
+static int regmap_fsi32le_reg_write(void *context, unsigned int reg, unsigned int val)
+{
+	__be32 v = cpu_to_be32(val);
+
+	return fsi_slave_write(context, reg, &v, sizeof(v));
+}
+
+static const struct regmap_bus regmap_fsi32le = {
+	.reg_write = regmap_fsi32le_reg_write,
+	.reg_read = regmap_fsi32le_reg_read,
+};
+
+static int regmap_fsi16_reg_read(void *context, unsigned int reg, unsigned int *val)
+{
+	u16 v;
+	int ret;
+
+	ret = fsi_slave_read(context, reg, &v, sizeof(v));
+	if (ret)
+		return ret;
+
+	*val = v;
+	return 0;
+}
+
+static int regmap_fsi16_reg_write(void *context, unsigned int reg, unsigned int val)
+{
+	u16 v;
+
+	if (val > 0xffff)
+		return -EINVAL;
+
+	v = val;
+	return fsi_slave_write(context, reg, &v, sizeof(v));
+}
+
+static const struct regmap_bus regmap_fsi16 = {
+	.reg_write = regmap_fsi16_reg_write,
+	.reg_read = regmap_fsi16_reg_read,
+};
+
+static int regmap_fsi16le_reg_read(void *context, unsigned int reg, unsigned int *val)
+{
+	__be16 v;
+	int ret;
+
+	ret = fsi_slave_read(context, reg, &v, sizeof(v));
+	if (ret)
+		return ret;
+
+	*val = be16_to_cpu(v);
+	return 0;
+}
+
+static int regmap_fsi16le_reg_write(void *context, unsigned int reg, unsigned int val)
+{
+	__be16 v;
+
+	if (val > 0xffff)
+		return -EINVAL;
+
+	v = cpu_to_be16(val);
+	return fsi_slave_write(context, reg, &v, sizeof(v));
+}
+
+static const struct regmap_bus regmap_fsi16le = {
+	.reg_write = regmap_fsi16le_reg_write,
+	.reg_read = regmap_fsi16le_reg_read,
+};
+
+static int regmap_fsi8_reg_read(void *context, unsigned int reg, unsigned int *val)
+{
+	u8 v;
+	int ret;
+
+	ret = fsi_slave_read(context, reg, &v, sizeof(v));
+	if (ret)
+		return ret;
+
+	*val = v;
+	return 0;
+}
+
+static int regmap_fsi8_reg_write(void *context, unsigned int reg, unsigned int val)
+{
+	u8 v;
+
+	if (val > 0xff)
+		return -EINVAL;
+
+	v = val;
+	return fsi_slave_write(context, reg, &v, sizeof(v));
+}
+
+static const struct regmap_bus regmap_fsi8 = {
+	.reg_write = regmap_fsi8_reg_write,
+	.reg_read = regmap_fsi8_reg_read,
+};
+
+static const struct regmap_bus *regmap_get_fsi_bus(struct fsi_device *fsi_dev,
+						   const struct regmap_config *config)
+{
+	const struct regmap_bus *bus = NULL;
+
+	if (config->reg_bits == 8 || config->reg_bits == 16 || config->reg_bits == 32) {
+		switch (config->val_bits) {
+		case 8:
+			bus = &regmap_fsi8;
+			break;
+		case 16:
+			switch (regmap_get_val_endian(&fsi_dev->dev, NULL, config)) {
+			case REGMAP_ENDIAN_LITTLE:
+#ifdef __LITTLE_ENDIAN
+			case REGMAP_ENDIAN_NATIVE:
+#endif
+				bus = &regmap_fsi16le;
+				break;
+			case REGMAP_ENDIAN_DEFAULT:
+			case REGMAP_ENDIAN_BIG:
+#ifdef __BIG_ENDIAN
+			case REGMAP_ENDIAN_NATIVE:
+#endif
+				bus = &regmap_fsi16;
+				break;
+			default:
+				break;
+			}
+			break;
+		case 32:
+			switch (regmap_get_val_endian(&fsi_dev->dev, NULL, config)) {
+			case REGMAP_ENDIAN_LITTLE:
+#ifdef __LITTLE_ENDIAN
+			case REGMAP_ENDIAN_NATIVE:
+#endif
+				bus = &regmap_fsi32le;
+				break;
+			case REGMAP_ENDIAN_DEFAULT:
+			case REGMAP_ENDIAN_BIG:
+#ifdef __BIG_ENDIAN
+			case REGMAP_ENDIAN_NATIVE:
+#endif
+				bus = &regmap_fsi32;
+				break;
+			default:
+				break;
+			}
+			break;
+		}
+	}
+
+	return bus ?: ERR_PTR(-EOPNOTSUPP);
+}
+
+struct regmap *__regmap_init_fsi(struct fsi_device *fsi_dev, const struct regmap_config *config,
+				 struct lock_class_key *lock_key, const char *lock_name)
+{
+	const struct regmap_bus *bus = regmap_get_fsi_bus(fsi_dev, config);
+
+	if (IS_ERR(bus))
+		return ERR_CAST(bus);
+
+	return __regmap_init(&fsi_dev->dev, bus, fsi_dev->slave, config, lock_key, lock_name);
+}
+EXPORT_SYMBOL_GPL(__regmap_init_fsi);
+
+struct regmap *__devm_regmap_init_fsi(struct fsi_device *fsi_dev,
+				      const struct regmap_config *config,
+				      struct lock_class_key *lock_key, const char *lock_name)
+{
+	const struct regmap_bus *bus = regmap_get_fsi_bus(fsi_dev, config);
+
+	if (IS_ERR(bus))
+		return ERR_CAST(bus);
+
+	return __devm_regmap_init(&fsi_dev->dev, bus, fsi_dev->slave, config, lock_key, lock_name);
+}
+EXPORT_SYMBOL_GPL(__devm_regmap_init_fsi);
+
+MODULE_LICENSE("GPL");