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75 lines
1.7 KiB
75 lines
1.7 KiB
/*
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* Copyright (c) 2018, ARM Limited and Contributors. All rights reserved.
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*
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* SPDX-License-Identifier: BSD-3-Clause
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*/
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#include <assert.h>
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#include <string.h>
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#include <lib/mmio.h>
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#include <rpi_hw.h>
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/* Initial amount of values to discard */
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#define RNG_WARMUP_COUNT U(0x40000)
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static void rpi3_rng_initialize(void)
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{
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uint32_t int_mask, ctrl;
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/* Return if it is already enabled */
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ctrl = mmio_read_32(RPI3_RNG_BASE + RPI3_RNG_CTRL_OFFSET);
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if ((ctrl & RPI3_RNG_CTRL_ENABLE) != 0U) {
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return;
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}
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/* Mask interrupts */
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int_mask = mmio_read_32(RPI3_RNG_BASE + RPI3_RNG_INT_MASK_OFFSET);
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int_mask |= RPI3_RNG_INT_MASK_DISABLE;
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mmio_write_32(RPI3_RNG_BASE + RPI3_RNG_INT_MASK_OFFSET, int_mask);
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/* Discard several values when initializing to give it time to warmup */
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mmio_write_32(RPI3_RNG_BASE + RPI3_RNG_STATUS_OFFSET, RNG_WARMUP_COUNT);
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mmio_write_32(RPI3_RNG_BASE + RPI3_RNG_CTRL_OFFSET,
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RPI3_RNG_CTRL_ENABLE);
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}
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static uint32_t rpi3_rng_get_word(void)
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{
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size_t nwords;
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do {
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/* Get number of available words to read */
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nwords = (mmio_read_32(RPI3_RNG_BASE + RPI3_RNG_STATUS_OFFSET)
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>> RPI3_RNG_STATUS_NUM_WORDS_SHIFT)
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& RPI3_RNG_STATUS_NUM_WORDS_MASK;
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} while (nwords == 0U);
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return mmio_read_32(RPI3_RNG_BASE + RPI3_RNG_DATA_OFFSET);
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}
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void rpi3_rng_read(void *buf, size_t len)
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{
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uint32_t data;
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size_t left = len;
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uint32_t *dst = buf;
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assert(buf != NULL);
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assert(len != 0U);
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assert(check_uptr_overflow((uintptr_t) buf, (uintptr_t) len) == 0);
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rpi3_rng_initialize();
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while (left >= sizeof(uint32_t)) {
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data = rpi3_rng_get_word();
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*dst++ = data;
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left -= sizeof(uint32_t);
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}
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if (left > 0U) {
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data = rpi3_rng_get_word();
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memcpy(dst, &data, left);
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}
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}
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