68 lines
1.8 KiB
C
68 lines
1.8 KiB
C
/*
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* Copyright (c) 2017 Intel Corporation
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*
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* SPDX-License-Identifier: Apache-2.0
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*/
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#include <kernel.h>
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#include <arch/cpu.h>
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#include <device.h>
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#include <system_timer.h>
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#include <altera_common.h>
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#include "altera_avalon_timer_regs.h"
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#include "altera_avalon_timer.h"
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static u32_t accumulated_cycle_count;
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static void timer_irq_handler(void *unused)
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{
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ARG_UNUSED(unused);
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accumulated_cycle_count += sys_clock_hw_cycles_per_tick;
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/* Clear the interrupt */
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alt_handle_irq((void *)TIMER_0_BASE, TIMER_0_IRQ);
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_sys_clock_tick_announce();
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}
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int _sys_clock_driver_init(struct device *device)
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{
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ARG_UNUSED(device);
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IOWR_ALTERA_AVALON_TIMER_PERIODL(TIMER_0_BASE,
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sys_clock_hw_cycles_per_tick & 0xFFFF);
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IOWR_ALTERA_AVALON_TIMER_PERIODH(TIMER_0_BASE,
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(sys_clock_hw_cycles_per_tick >> 16) & 0xFFFF);
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IRQ_CONNECT(TIMER_0_IRQ, 0, timer_irq_handler, NULL, 0);
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irq_enable(TIMER_0_IRQ);
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alt_avalon_timer_sc_init((void *)TIMER_0_BASE, 0,
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TIMER_0_IRQ, sys_clock_hw_cycles_per_tick);
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return 0;
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}
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u32_t _timer_cycle_get_32(void)
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{
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/* RTOS-2676: Per the Altera Embedded IP Peripherals guide, you cannot
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* use a timer instance for both the system clock and timestamps
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* at the same time.
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*
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* Having this function return accumulated_cycle_count + get_snapshot()
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* does not work reliably. It's possible for the current countdown
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* to reset to the next interval before the timer interrupt is
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* delivered (and accumulated cycle count gets updated). The result
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* is an unlucky call to this function will appear to jump backward
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* in time.
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*
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* To properly obtain timestamps, the CPU must be configured with
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* a second timer peripheral instance that is configured to
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* count down from some large initial 64-bit value. This
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* is currently unimplemented.
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*/
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return accumulated_cycle_count;
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}
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