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/* Copyright 2015 The Chromium OS Authors. All rights reserved.
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#include "common.h"
#include "flash_log.h"
#include "init_chip.h"
#include "registers.h"
#include "trng.h"
void init_trng(void)
{
#if (!(defined(CONFIG_CUSTOMIZED_RO) && defined(SECTION_IS_RO)))
/*
* Most of the trng initialization requires high permissions. If RO has
* dropped the permission level, dont try to read or write these high
* permission registers because it will cause rolling reboots. RO
* should do the TRNG initialization before dropping the level.
*/
if (!runlevel_is_high())
return;
#endif
GWRITE(TRNG, POST_PROCESSING_CTRL,
GC_TRNG_POST_PROCESSING_CTRL_SHUFFLE_BITS_MASK |
GC_TRNG_POST_PROCESSING_CTRL_CHURN_MODE_MASK);
GWRITE(TRNG, SLICE_MAX_UPPER_LIMIT, 1);
GWRITE(TRNG, SLICE_MIN_LOWER_LIMIT, 0);
GWRITE(TRNG, TIMEOUT_COUNTER, 0x7ff);
GWRITE(TRNG, TIMEOUT_MAX_TRY_NUM, 4);
GWRITE(TRNG, POWER_DOWN_B, 1);
GWRITE(TRNG, GO_EVENT, 1);
}
uint32_t rand(void)
{
while (GREAD(TRNG, EMPTY)) {
if (GREAD_FIELD(TRNG, FSM_STATE, FSM_IDLE)) {
/* TRNG timed out, restart */
GWRITE(TRNG, STOP_WORK, 1);
#if !defined(SECTION_IS_RO) && defined(CONFIG_FLASH_LOG)
flash_log_add_event(FE_LOG_TRNG_STALL, 0, NULL);
#endif
GWRITE(TRNG, GO_EVENT, 1);
}
}
return GREAD(TRNG, READ_DATA);
}
void rand_bytes(void *buffer, size_t len)
{
int random_togo = 0;
int buffer_index = 0;
uint32_t random_value;
uint8_t *buf = (uint8_t *) buffer;
/*
* Retrieve random numbers in 4 byte quantities and pack as many bytes
* as needed into 'buffer'. If len is not divisible by 4, the
* remaining random bytes get dropped.
*/
while (buffer_index < len) {
if (!random_togo) {
random_value = rand();
random_togo = sizeof(random_value);
}
buf[buffer_index++] = random_value >>
((random_togo-- - 1) * 8);
}
}
#if !defined(SECTION_IS_RO) && defined(TEST_TRNG)
#include "console.h"
#include "watchdog.h"
static uint32_t histogram[256];
static int command_rand(int argc, char **argv)
{
int count = 1000; /* Default number of cycles. */
struct pair {
uint32_t value;
uint32_t count;
};
struct pair min;
struct pair max;
if (argc == 2)
count = strtoi(argv[1], NULL, 10);
memset(histogram, 0, sizeof(histogram));
ccprintf("Retrieving %d random words.\n", count);
while (count-- > 0) {
uint32_t rvalue;
int size;
rvalue = rand();
for (size = 0; size < sizeof(rvalue); size++)
histogram[((uint8_t *)&rvalue)[size]]++;
if (!(count % 10000))
watchdog_reload();
}
min.count = ~0;
max.count = 0;
for (count = 0; count < ARRAY_SIZE(histogram); count++) {
if (histogram[count] > max.count) {
max.count = histogram[count];
max.value = count;
continue;
}
if (histogram[count] >= min.count)
continue;
min.count = histogram[count];
min.value = count;
}
ccprintf("min %d(%d), max %d(%d)", min.count, min.value,
max.count, max.value);
for (count = 0; count < ARRAY_SIZE(histogram); count++) {
if (!(count % 8)) {
ccprintf("\n");
cflush();
}
ccprintf(" %6d", histogram[count]);
}
ccprintf("\n");
return EC_SUCCESS;
}
DECLARE_CONSOLE_COMMAND(rand, command_rand, NULL, NULL);
#endif /* !defined(SECTION_IS_RO) && defined(TEST_TRNG) */
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