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// 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),
};
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