69 lines
1.8 KiB
C
69 lines
1.8 KiB
C
/*
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* Copyright (c) 2016 ARM Limited.
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*
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* SPDX-License-Identifier: Apache-2.0
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* Licensed under the Apache License, Version 2.0 (the License);
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include <drivers/rand32.h>
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#include <drivers/system_timer.h>
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#include <misc/sys_log.h>
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#include "fsl_rnga.h"
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void sys_rand32_init(void)
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{
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uint32_t seed = sys_cycle_get_32();
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RNGA_Init(RNG);
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/* The range of seed values acquired by this method is likely
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* to be relatively small. The RNGA hardware uses two free
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* running oscillators to add entropy to the seed value, we
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* take care below to ensure the read rate is lower than the
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* rate at which the hardware can add entropy.
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*/
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RNGA_Seed(RNG, seed);
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RNGA_SetMode(RNG, kRNGA_ModeSleep);
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}
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uint32_t sys_rand32_get(void)
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{
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uint32_t random;
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uint32_t output = 0;
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int i;
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RNGA_SetMode(RNG, kRNGA_ModeNormal);
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/* The Reference manual states that back to back reads from
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* the RNGA deliver one or two bits of entropy per 32-bit
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* word, therefore we deliberately only use 1 bit per 32 bit
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* word read.
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*/
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for (i = 0; i < 32; i++) {
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status_t status;
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status = RNGA_GetRandomData(RNG, &random, sizeof(random));
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__ASSERT(!status, "RNGA_GetRandomData failed");
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if (status) {
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SYS_LOG_ERR("RNGA_GetRandomData failed with %d",
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status);
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}
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output <<= 1;
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output |= random & 1;
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}
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RNGA_SetMode(RNG, kRNGA_ModeSleep);
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return output;
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}
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