1 files changed, 119 insertions, 0 deletions
diff --git a/drivers/gpu/drm/xe/xe_guard.h b/drivers/gpu/drm/xe/xe_guard.h
new file mode 100644
index 000000000000..333f8e13b5a1
--- /dev/null
+++ b/drivers/gpu/drm/xe/xe_guard.h
@@ -0,0 +1,119 @@
+/* SPDX-License-Identifier: MIT */
+/*
+ * Copyright © 2025 Intel Corporation
+ */
+
+#ifndef _XE_GUARD_H_
+#define _XE_GUARD_H_
+
+#include <linux/spinlock.h>
+
+/**
+ * struct xe_guard - Simple logic to protect a feature.
+ *
+ * Implements simple semaphore-like logic that can be used to lockdown the
+ * feature unless it is already in use.  Allows enabling of the otherwise
+ * incompatible features, where we can't follow the strict owner semantics
+ * required by the &rw_semaphore.
+ *
+ * NOTE! It shouldn't be used to protect a data, use &rw_semaphore instead.
+ */
+struct xe_guard {
+	/**
+	 * @counter: implements simple exclusive/lockdown logic:
+	 *           if == 0 then guard/feature is idle/not in use,
+	 *           if < 0 then feature is active and can't be locked-down,
+	 *           if > 0 then feature is lockded-down and can't be activated.
+	 */
+	int counter;
+
+	/** @name: the name of the guard (useful for debug) */
+	const char *name;
+
+	/** @owner: the info about the last owner of the guard (for debug) */
+	void *owner;
+
+	/** @lock: protects guard's data */
+	spinlock_t lock;
+};
+
+/**
+ * xe_guard_init() - Initialize the guard.
+ * @guard: the &xe_guard to init
+ * @name: name of the guard
+ */
+static inline void xe_guard_init(struct xe_guard *guard, const char *name)
+{
+	spin_lock_init(&guard->lock);
+	guard->counter = 0;
+	guard->name = name;
+}
+
+/**
+ * xe_guard_arm() - Arm the guard for the exclusive/lockdown mode.
+ * @guard: the &xe_guard to arm
+ * @lockdown: arm for lockdown(true) or exclusive(false) mode
+ * @who: optional owner info (for debug only)
+ *
+ * Multiple lockdown requests are allowed.
+ * Only single exclusive access can be granted.
+ * Will fail if the guard is already in exclusive mode.
+ * On success, must call the xe_guard_disarm() to release.
+ *
+ * Return: 0 on success or a negative error code on failure.
+ */
+static inline int xe_guard_arm(struct xe_guard *guard, bool lockdown, void *who)
+{
+	guard(spinlock)(&guard->lock);
+
+	if (lockdown) {
+		if (guard->counter < 0)
+			return -EBUSY;
+		guard->counter++;
+	} else {
+		if (guard->counter > 0)
+			return -EPERM;
+		if (guard->counter < 0)
+			return -EUSERS;
+		guard->counter--;
+	}
+
+	guard->owner = who;
+	return 0;
+}
+
+/**
+ * xe_guard_disarm() - Disarm the guard from exclusive/lockdown mode.
+ * @guard: the &xe_guard to disarm
+ * @lockdown: disarm from lockdown(true) or exclusive(false) mode
+ *
+ * Return: true if successfully disarmed or false in case of mismatch.
+ */
+static inline bool xe_guard_disarm(struct xe_guard *guard, bool lockdown)
+{
+	guard(spinlock)(&guard->lock);
+
+	if (lockdown) {
+		if (guard->counter <= 0)
+			return false;
+		guard->counter--;
+	} else {
+		if (guard->counter != -1)
+			return false;
+		guard->counter++;
+	}
+	return true;
+}
+
+/**
+ * xe_guard_mode_str() - Convert guard mode into a string.
+ * @lockdown: flag used to select lockdown or exclusive mode
+ *
+ * Return: "lockdown" or "exclusive" string.
+ */
+static inline const char *xe_guard_mode_str(bool lockdown)
+{
+	return lockdown ? "lockdown" : "exclusive";
+}
+
+#endif