52 lines
2.3 KiB
C
52 lines
2.3 KiB
C
/*----------------------------------------------------------------------------
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* Tencent is pleased to support the open source community by making TencentOS
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* available.
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*
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* Copyright (C) 2019 THL A29 Limited, a Tencent company. All rights reserved.
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* If you have downloaded a copy of the TencentOS binary from Tencent, please
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* note that the TencentOS binary is licensed under the BSD 3-Clause License.
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*
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* If you have downloaded a copy of the TencentOS source code from Tencent,
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* please note that TencentOS source code is licensed under the BSD 3-Clause
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* License, except for the third-party components listed below which are
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* subject to different license terms. Your integration of TencentOS into your
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* own projects may require compliance with the BSD 3-Clause License, as well
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* as the other licenses applicable to the third-party components included
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* within TencentOS.
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*---------------------------------------------------------------------------*/
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#include <tos_k.h>
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#include "riscv_port.h"
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__PORT__ void port_systick_config(uint32_t cycle_per_tick)
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{
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// it cost cpu read two times, first mtime_lo and then mtime_hi
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// if mtime_lo == 0xFFFFFFFF and mtime_hi = 0 at first read
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// then mtime_lo == 0 and mtime_hi = 1 at next read
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// the result will be 0x1FFFFFFFF, not 0x100000000
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uint64_t mtime = 0;
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while (1) {
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uint32_t mtime_hi = *(volatile uint32_t *)(CLINT_CTRL_ADDR + CLINT_MTIME + 4);
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uint32_t mtime_lo = *(volatile uint32_t *)(CLINT_CTRL_ADDR + CLINT_MTIME + 0);
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uint32_t mtime_hn = *(volatile uint32_t *)(CLINT_CTRL_ADDR + CLINT_MTIME + 4);
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if(mtime_hi == mtime_hn) {
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mtime += ((uint64_t)mtime_hi << 32) | mtime_lo;
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break;
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}
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}
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// just set mtime to mtimecmp does not accurately reflect the passage of time
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// cause some time cost on the path to deal with the interrupt
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// so, we need to to fix the value with a multiple of cycle_per_tick
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uint64_t tick = mtime / cycle_per_tick;
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uint64_t mtimecmp = (tick + 1) * cycle_per_tick;
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// write to mtimecmp register
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*(volatile uint32_t *)(CLINT_CTRL_ADDR + CLINT_MTIMECMP + 0) = 0xFFFFFFFF;
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*(volatile uint32_t *)(CLINT_CTRL_ADDR + CLINT_MTIMECMP + 4) = 0xFFFFFFFF & (mtimecmp >> 32);
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*(volatile uint32_t *)(CLINT_CTRL_ADDR + CLINT_MTIMECMP + 0) = 0xFFFFFFFF & (mtimecmp >> 0);
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}
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