1 files changed, 122 insertions, 0 deletions
diff --git a/drivers/iommu/generic_pt/pt_log2.h b/drivers/iommu/generic_pt/pt_log2.h
new file mode 100644
index 000000000000..6dbbed119238
--- /dev/null
+++ b/drivers/iommu/generic_pt/pt_log2.h
@@ -0,0 +1,122 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (c) 2024-2025, NVIDIA CORPORATION & AFFILIATES
+ *
+ * Helper macros for working with log2 values
+ *
+ */
+#ifndef __GENERIC_PT_LOG2_H
+#define __GENERIC_PT_LOG2_H
+#include <linux/bitops.h>
+#include <linux/limits.h>
+
+/* Compute a */
+#define log2_to_int_t(type, a_lg2) ((type)(((type)1) << (a_lg2)))
+static_assert(log2_to_int_t(unsigned int, 0) == 1);
+
+/* Compute a - 1 (aka all low bits set) */
+#define log2_to_max_int_t(type, a_lg2) ((type)(log2_to_int_t(type, a_lg2) - 1))
+
+/* Compute a / b */
+#define log2_div_t(type, a, b_lg2) ((type)(((type)a) >> (b_lg2)))
+static_assert(log2_div_t(unsigned int, 4, 2) == 1);
+
+/*
+ * Compute:
+ *   a / c == b / c
+ * aka the high bits are equal
+ */
+#define log2_div_eq_t(type, a, b, c_lg2) \
+	(log2_div_t(type, (a) ^ (b), c_lg2) == 0)
+static_assert(log2_div_eq_t(unsigned int, 1, 1, 2));
+
+/* Compute a % b */
+#define log2_mod_t(type, a, b_lg2) \
+	((type)(((type)a) & log2_to_max_int_t(type, b_lg2)))
+static_assert(log2_mod_t(unsigned int, 1, 2) == 1);
+
+/*
+ * Compute:
+ *   a % b == b - 1
+ * aka the low bits are all 1s
+ */
+#define log2_mod_eq_max_t(type, a, b_lg2) \
+	(log2_mod_t(type, a, b_lg2) == log2_to_max_int_t(type, b_lg2))
+static_assert(log2_mod_eq_max_t(unsigned int, 3, 2));
+
+/*
+ * Return a value such that:
+ *    a / b == ret / b
+ *    ret % b == val
+ * aka set the low bits to val. val must be < b
+ */
+#define log2_set_mod_t(type, a, val, b_lg2) \
+	((((type)(a)) & (~log2_to_max_int_t(type, b_lg2))) | ((type)(val)))
+static_assert(log2_set_mod_t(unsigned int, 3, 1, 2) == 1);
+
+/* Return a value such that:
+ *    a / b == ret / b
+ *    ret % b == b - 1
+ * aka set the low bits to all 1s
+ */
+#define log2_set_mod_max_t(type, a, b_lg2) \
+	(((type)(a)) | log2_to_max_int_t(type, b_lg2))
+static_assert(log2_set_mod_max_t(unsigned int, 2, 2) == 3);
+
+/* Compute a * b */
+#define log2_mul_t(type, a, b_lg2) ((type)(((type)a) << (b_lg2)))
+static_assert(log2_mul_t(unsigned int, 2, 2) == 8);
+
+#define _dispatch_sz(type, fn, a) \
+	(sizeof(type) == 4 ? fn##32((u32)a) : fn##64(a))
+
+/*
+ * Return the highest value such that:
+ *    fls_t(u32, 0) == 0
+ *    fls_t(u3, 1) == 1
+ *    a >= log2_to_int(ret - 1)
+ * aka find last set bit
+ */
+static inline unsigned int fls32(u32 a)
+{
+	return fls(a);
+}
+#define fls_t(type, a) _dispatch_sz(type, fls, a)
+
+/*
+ * Return the highest value such that:
+ *    ffs_t(u32, 0) == UNDEFINED
+ *    ffs_t(u32, 1) == 0
+ *    log_mod(a, ret) == 0
+ * aka find first set bit
+ */
+static inline unsigned int __ffs32(u32 a)
+{
+	return __ffs(a);
+}
+#define ffs_t(type, a) _dispatch_sz(type, __ffs, a)
+
+/*
+ * Return the highest value such that:
+ *    ffz_t(u32, U32_MAX) == UNDEFINED
+ *    ffz_t(u32, 0) == 0
+ *    ffz_t(u32, 1) == 1
+ *    log_mod(a, ret) == log_to_max_int(ret)
+ * aka find first zero bit
+ */
+static inline unsigned int ffz32(u32 a)
+{
+	return ffz(a);
+}
+static inline unsigned int ffz64(u64 a)
+{
+	if (sizeof(u64) == sizeof(unsigned long))
+		return ffz(a);
+
+	if ((u32)a == U32_MAX)
+		return ffz32(a >> 32) + 32;
+	return ffz32(a);
+}
+#define ffz_t(type, a) _dispatch_sz(type, ffz, a)
+
+#endif