--- /dev/null
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2022, Linaro Limited
+ */
+
+#define LOG_CATEGORY UCLASS_RNG
+
+#include <common.h>
+#include <dm.h>
+#include <linker_lists.h>
+#include <log.h>
+#include <rng.h>
+#include <dm/device_compat.h>
+#include <linux/arm-smccc.h>
+#include <linux/bitops.h>
+#include <linux/kernel.h>
+#include <linux/psci.h>
+
+#define DRIVER_NAME "smccc-trng"
+
+/**
+ * Arm SMCCC TRNG firmware interface specification:
+ * https://developer.arm.com/documentation/den0098/latest/
+ */
+#define ARM_SMCCC_TRNG_VERSION 0x84000050
+#define ARM_SMCCC_TRNG_FEATURES 0x84000051
+#define ARM_SMCCC_TRNG_GET_UUID 0x84000052
+#define ARM_SMCCC_TRNG_RND_32 0x84000053
+#define ARM_SMCCC_TRNG_RND_64 0xC4000053
+
+#define ARM_SMCCC_RET_TRNG_SUCCESS ((ulong)0)
+#define ARM_SMCCC_RET_TRNG_NOT_SUPPORTED ((ulong)-1)
+#define ARM_SMCCC_RET_TRNG_INVALID_PARAMETER ((ulong)-2)
+#define ARM_SMCCC_RET_TRNG_NO_ENTROPY ((ulong)-3)
+
+#define TRNG_MAJOR_MASK GENMASK(30, 16)
+#define TRNG_MAJOR_SHIFT 16
+#define TRNG_MINOR_MASK GENMASK(15, 0)
+#define TRNG_MINOR_SHIFT 0
+
+#define TRNG_MAX_RND_64 (192 / 8)
+#define TRNG_MAX_RND_32 (96 / 8)
+
+/**
+ * struct smccc_trng_priv - Private data for SMCCC TRNG support
+ *
+ * @smc64 - True if TRNG_RND_64 is supported, false if TRNG_RND_32 is supported
+ */
+struct smccc_trng_priv {
+ bool smc64;
+};
+
+/*
+ * Copy random bytes from ulong SMCCC output register to target buffer
+ * Defines 2 function flavors for whether ARM_SMCCC_TRNG_RND_32 or
+ * ARM_SMCCC_TRNG_RND_64 was used to invoke the service.
+ */
+static size_t smc32_copy_sample(u8 **ptr, size_t size, ulong *rnd)
+{
+ size_t len = min(size, sizeof(u32));
+ u32 sample = *rnd;
+
+ memcpy(*ptr, &sample, len);
+ *ptr += len;
+
+ return size - len;
+}
+
+static size_t smc64_copy_sample(u8 **ptr, size_t size, ulong *rnd)
+{
+ size_t len = min(size, sizeof(u64));
+ u64 sample = *rnd;
+
+ memcpy(*ptr, &sample, len);
+ *ptr += len;
+
+ return size - len;
+}
+
+static int smccc_trng_read(struct udevice *dev, void *data, size_t len)
+{
+ struct psci_plat_data *smccc = dev_get_parent_plat(dev);
+ struct smccc_trng_priv *priv = dev_get_priv(dev);
+ struct arm_smccc_res res;
+ u32 func_id;
+ u8 *ptr = data;
+ size_t rem = len;
+ size_t max_sz;
+ size_t (*copy_sample)(u8 **ptr, size_t size, ulong *rnd);
+
+ if (priv->smc64) {
+ copy_sample = smc64_copy_sample;
+ func_id = ARM_SMCCC_TRNG_RND_64;
+ max_sz = TRNG_MAX_RND_64;
+ } else {
+ copy_sample = smc32_copy_sample;
+ func_id = ARM_SMCCC_TRNG_RND_32;
+ max_sz = TRNG_MAX_RND_32;
+ }
+
+ while (rem) {
+ size_t sz = min(rem, max_sz);
+
+ smccc->invoke_fn(func_id, sz * 8, 0, 0, 0, 0, 0, 0, &res);
+
+ switch (res.a0) {
+ case ARM_SMCCC_RET_TRNG_SUCCESS:
+ break;
+ case ARM_SMCCC_RET_TRNG_NO_ENTROPY:
+ continue;
+ default:
+ return -EIO;
+ }
+
+ rem -= sz;
+
+ sz = copy_sample(&ptr, sz, &res.a3);
+ if (sz)
+ sz = copy_sample(&ptr, sz, &res.a2);
+ if (sz)
+ sz = copy_sample(&ptr, sz, &res.a1);
+ }
+
+ return 0;
+}
+
+static const struct dm_rng_ops smccc_trng_ops = {
+ .read = smccc_trng_read,
+};
+
+static bool smccc_trng_is_supported(void (*invoke_fn)(unsigned long a0, unsigned long a1,
+ unsigned long a2, unsigned long a3,
+ unsigned long a4, unsigned long a5,
+ unsigned long a6, unsigned long a7,
+ struct arm_smccc_res *res))
+{
+ struct arm_smccc_res res;
+
+ (*invoke_fn)(ARM_SMCCC_ARCH_FEATURES, ARM_SMCCC_TRNG_VERSION, 0, 0, 0, 0, 0, 0, &res);
+ if (res.a0 == ARM_SMCCC_RET_NOT_SUPPORTED)
+ return false;
+
+ (*invoke_fn)(ARM_SMCCC_TRNG_VERSION, 0, 0, 0, 0, 0, 0, 0, &res);
+ if (res.a0 & BIT(31))
+ return false;
+
+ /* Test 64bit interface and fallback to 32bit interface */
+ invoke_fn(ARM_SMCCC_TRNG_FEATURES, ARM_SMCCC_TRNG_RND_64,
+ 0, 0, 0, 0, 0, 0, &res);
+
+ if (res.a0 == ARM_SMCCC_RET_TRNG_NOT_SUPPORTED)
+ invoke_fn(ARM_SMCCC_TRNG_FEATURES, ARM_SMCCC_TRNG_RND_32,
+ 0, 0, 0, 0, 0, 0, &res);
+
+ return res.a0 == ARM_SMCCC_RET_TRNG_SUCCESS;
+}
+
+ARM_SMCCC_FEATURE_DRIVER(smccc_trng) = {
+ .driver_name = DRIVER_NAME,
+ .is_supported = smccc_trng_is_supported,
+};
+
+static int smccc_trng_probe(struct udevice *dev)
+{
+ struct psci_plat_data *smccc = dev_get_parent_plat(dev);
+ struct smccc_trng_priv *priv = dev_get_priv(dev);
+ struct arm_smccc_res res;
+
+ if (!(smccc_trng_is_supported(smccc->invoke_fn)))
+ return -ENODEV;
+
+ /* At least one of 64bit and 32bit interfaces is available */
+ smccc->invoke_fn(ARM_SMCCC_TRNG_FEATURES, ARM_SMCCC_TRNG_RND_64,
+ 0, 0, 0, 0, 0, 0, &res);
+ priv->smc64 = (res.a0 == ARM_SMCCC_RET_TRNG_SUCCESS);
+
+#ifdef DEBUG
+ smccc->invoke_fn(ARM_SMCCC_TRNG_GET_UUID, 0, 0, 0, 0, 0, 0, 0, &res);
+ if (res.a0 != ARM_SMCCC_RET_TRNG_NOT_SUPPORTED) {
+ unsigned long uuid_a0 = res.a0;
+ unsigned long uuid_a1 = res.a1;
+ unsigned long uuid_a2 = res.a2;
+ unsigned long uuid_a3 = res.a3;
+ unsigned long major, minor;
+
+ smccc->invoke_fn(ARM_SMCCC_TRNG_VERSION, 0, 0, 0, 0, 0, 0, 0, &res);
+ major = (res.a0 & TRNG_MAJOR_MASK) >> TRNG_MAJOR_SHIFT;
+ minor = (res.a0 & TRNG_MINOR_MASK) >> TRNG_MINOR_SHIFT;
+
+ dev_dbg(dev, "Version %lu.%lu, UUID %08lx-%04lx-%04lx-%04lx-%04lx%08lx\n",
+ major, minor, uuid_a0, uuid_a1 >> 16, uuid_a1 & GENMASK(16, 0),
+ uuid_a2 >> 16, uuid_a2 & GENMASK(16, 0), uuid_a3);
+ } else {
+ dev_warn(dev, "Can't get TRNG UUID\n");
+ }
+#endif
+
+ return 0;
+}
+
+U_BOOT_DRIVER(smccc_trng) = {
+ .name = DRIVER_NAME,
+ .id = UCLASS_RNG,
+ .ops = &smccc_trng_ops,
+ .probe = smccc_trng_probe,
+ .priv_auto = sizeof(struct smccc_trng_priv),
+};
projects / platform / kernel / u-boot.git / commitdiff