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, 75 insertions, 0 deletions

diff --git a/drivers/clocksource/mmio.c b/drivers/clocksource/mmio.c
new file mode 100644
index 000000000..0fee8edb8
--- /dev/null
+++ b/drivers/clocksource/mmio.c
@@ -0,0 +1,75 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Generic MMIO clocksource support
+ */
+#include <linux/clocksource.h>
+#include <linux/errno.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+
+struct clocksource_mmio {
+	void __iomem *reg;
+	struct clocksource clksrc;
+};
+
+static inline struct clocksource_mmio *to_mmio_clksrc(struct clocksource *c)
+{
+	return container_of(c, struct clocksource_mmio, clksrc);
+}
+
+u64 clocksource_mmio_readl_up(struct clocksource *c)
+{
+	return (u64)readl_relaxed(to_mmio_clksrc(c)->reg);
+}
+EXPORT_SYMBOL_GPL(clocksource_mmio_readl_up);
+
+u64 clocksource_mmio_readl_down(struct clocksource *c)
+{
+	return ~(u64)readl_relaxed(to_mmio_clksrc(c)->reg) & c->mask;
+}
+EXPORT_SYMBOL_GPL(clocksource_mmio_readl_down);
+
+u64 clocksource_mmio_readw_up(struct clocksource *c)
+{
+	return (u64)readw_relaxed(to_mmio_clksrc(c)->reg);
+}
+EXPORT_SYMBOL_GPL(clocksource_mmio_readw_up);
+
+u64 clocksource_mmio_readw_down(struct clocksource *c)
+{
+	return ~(u64)readw_relaxed(to_mmio_clksrc(c)->reg) & c->mask;
+}
+EXPORT_SYMBOL_GPL(clocksource_mmio_readw_down);
+
+/**
+ * clocksource_mmio_init - Initialize a simple mmio based clocksource
+ * @base:	Virtual address of the clock readout register
+ * @name:	Name of the clocksource
+ * @hz:		Frequency of the clocksource in Hz
+ * @rating:	Rating of the clocksource
+ * @bits:	Number of valid bits
+ * @read:	One of clocksource_mmio_read*() above
+ */
+int clocksource_mmio_init(void __iomem *base, const char *name,
+			  unsigned long hz, int rating, unsigned bits,
+			  u64 (*read)(struct clocksource *))
+{
+	struct clocksource_mmio *cs;
+
+	if (bits > 64 || bits < 16)
+		return -EINVAL;
+
+	cs = kzalloc_obj(struct clocksource_mmio);
+	if (!cs)
+		return -ENOMEM;
+
+	cs->reg = base;
+	cs->clksrc.name = name;
+	cs->clksrc.rating = rating;
+	cs->clksrc.read = read;
+	cs->clksrc.mask = CLOCKSOURCE_MASK(bits);
+	cs->clksrc.flags = CLOCK_SOURCE_IS_CONTINUOUS;
+
+	return clocksource_register_hz(&cs->clksrc, hz);
+}
+EXPORT_SYMBOL_GPL(clocksource_mmio_init);