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, 82 insertions, 0 deletions

diff --git a/drivers/leds/leds-expresswire.c b/drivers/leds/leds-expresswire.c
new file mode 100644
index 000000000..25c6b159a
--- /dev/null
+++ b/drivers/leds/leds-expresswire.c
@@ -0,0 +1,82 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Shared library for Kinetic's ExpressWire protocol.
+ * This protocol works by pulsing the ExpressWire IC's control GPIO.
+ * ktd2692 and ktd2801 are known to use this protocol.
+ */
+
+#include <linux/bits.h>
+#include <linux/delay.h>
+#include <linux/export.h>
+#include <linux/gpio/consumer.h>
+#include <linux/irqflags.h>
+#include <linux/types.h>
+
+#include <linux/leds-expresswire.h>
+
+void expresswire_power_off(struct expresswire_common_props *props)
+{
+	gpiod_set_value_cansleep(props->ctrl_gpio, 0);
+	fsleep(props->timing.poweroff_us);
+}
+EXPORT_SYMBOL_NS_GPL(expresswire_power_off, "EXPRESSWIRE");
+
+void expresswire_enable(struct expresswire_common_props *props)
+{
+	unsigned long flags;
+
+	local_irq_save(flags);
+
+	gpiod_set_value(props->ctrl_gpio, 1);
+	udelay(props->timing.detect_delay_us);
+	gpiod_set_value(props->ctrl_gpio, 0);
+	udelay(props->timing.detect_us);
+	gpiod_set_value(props->ctrl_gpio, 1);
+
+	local_irq_restore(flags);
+}
+EXPORT_SYMBOL_NS_GPL(expresswire_enable, "EXPRESSWIRE");
+
+static void expresswire_start(struct expresswire_common_props *props)
+{
+	gpiod_set_value(props->ctrl_gpio, 1);
+	udelay(props->timing.data_start_us);
+}
+
+static void expresswire_end(struct expresswire_common_props *props)
+{
+	gpiod_set_value(props->ctrl_gpio, 0);
+	udelay(props->timing.end_of_data_low_us);
+	gpiod_set_value(props->ctrl_gpio, 1);
+	udelay(props->timing.end_of_data_high_us);
+}
+
+static void expresswire_set_bit(struct expresswire_common_props *props, bool bit)
+{
+	if (bit) {
+		gpiod_set_value(props->ctrl_gpio, 0);
+		udelay(props->timing.short_bitset_us);
+		gpiod_set_value(props->ctrl_gpio, 1);
+		udelay(props->timing.long_bitset_us);
+	} else {
+		gpiod_set_value(props->ctrl_gpio, 0);
+		udelay(props->timing.long_bitset_us);
+		gpiod_set_value(props->ctrl_gpio, 1);
+		udelay(props->timing.short_bitset_us);
+	}
+}
+
+void expresswire_write_u8(struct expresswire_common_props *props, u8 val)
+{
+	unsigned long flags;
+
+	local_irq_save(flags);
+
+	expresswire_start(props);
+	for (int i = 7; i >= 0; i--)
+		expresswire_set_bit(props, val & BIT(i));
+	expresswire_end(props);
+
+	local_irq_restore(flags);
+}
+EXPORT_SYMBOL_NS_GPL(expresswire_write_u8, "EXPRESSWIRE");