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/*
* Copyright (c) 2018 Richard Braun.
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
* DEALINGS IN THE SOFTWARE.
*/
#include <stdint.h>
#include "panic.h"
#include "systick.h"
#include "thread.h"
#define SYSTICK_BASE_ADDR 0xe000e010
#define SYSTICK_CSR_ENABLE 0x1
#define SYSTICK_CSR_TICKINT 0x2
#define SYSTICK_CALIB_NOREF 0x80000000
#define SYSTICK_CALIB_SKEW 0x40000000
#define SYSTICK_CALIB_TENMS_MASK 0x00ffffff
struct systick_regs {
uint32_t csr;
uint32_t rvr;
uint32_t cvr;
uint32_t calib;
};
static volatile struct systick_regs *systick_regs = (void *)SYSTICK_BASE_ADDR;
static void
systick_check_calib(void)
{
uint32_t calib;
calib = systick_regs->calib;
if ((calib & SYSTICK_CALIB_NOREF)
|| (calib & SYSTICK_CALIB_SKEW)
|| (calib & SYSTICK_CALIB_TENMS_MASK) == 0) {
panic("systick: unusable");
}
}
void
systick_setup(void)
{
uint32_t tenms, counter;
systick_check_calib();
tenms = systick_regs->calib & SYSTICK_CALIB_TENMS_MASK;
counter = (tenms * 100) / THREAD_SCHED_FREQ;
systick_regs->rvr = counter;
systick_regs->cvr = 0;
systick_regs->csr = (SYSTICK_CSR_TICKINT | SYSTICK_CSR_ENABLE);
}
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