1 files changed, 82 insertions, 0 deletions
diff --git a/drivers/rng/arm_rndr.c b/drivers/rng/arm_rndr.c
new file mode 100644
index 00000000000..55989743eae
--- /dev/null
+++ b/drivers/rng/arm_rndr.c
@@ -0,0 +1,82 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2023, Arm Ltd.
+ *
+ * Use the (optional) ARMv8.5 RNDR register to provide random numbers to
+ * U-Boot's UCLASS_RNG users.
+ * Detection is done at runtime using the CPU ID registers.
+ */
+
+#define LOG_CATEGORY UCLASS_RNG
+
+#include <common.h>
+#include <dm.h>
+#include <linux/kernel.h>
+#include <rng.h>
+#include <asm/system.h>
+
+#define DRIVER_NAME	"arm-rndr"
+
+static bool cpu_has_rndr(void)
+{
+	uint64_t reg;
+
+	__asm__ volatile("mrs %0, ID_AA64ISAR0_EL1\n" : "=r" (reg));
+	return !!(reg & ID_AA64ISAR0_EL1_RNDR);
+}
+
+/*
+ * The system register name is RNDR, but this isn't widely known among older
+ * toolchains, and also triggers errors because of it being an architecture
+ * extension. Since we check the availability of the register before, it's
+ * fine to use here, though.
+ */
+#define RNDR	"S3_3_C2_C4_0"
+
+static uint64_t read_rndr(void)
+{
+	uint64_t reg;
+
+	__asm__ volatile("mrs %0, " RNDR "\n" : "=r" (reg));
+
+	return reg;
+}
+
+static int arm_rndr_read(struct udevice *dev, void *data, size_t len)
+{
+	uint64_t random;
+
+	while (len) {
+		int tocopy = min(sizeof(uint64_t), len);
+
+		random = read_rndr();
+		memcpy(data, &random, tocopy);
+		len -= tocopy;
+		data += tocopy;
+	}
+
+	return 0;
+}
+
+static const struct dm_rng_ops arm_rndr_ops = {
+	.read = arm_rndr_read,
+};
+
+static int arm_rndr_probe(struct udevice *dev)
+{
+	if (!cpu_has_rndr())
+		return -ENODEV;
+
+	return 0;
+}
+
+U_BOOT_DRIVER(arm_rndr) = {
+	.name = DRIVER_NAME,
+	.id = UCLASS_RNG,
+	.ops = &arm_rndr_ops,
+	.probe = arm_rndr_probe,
+};
+
+U_BOOT_DRVINFO(cpu_arm_rndr) = {
+	.name = DRIVER_NAME,
+};