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arc: add _tsc_read for 64-bit timestamp

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This implementation of _tsc_read returns a 64-bit value that
is derived from the 64-bit tick count multiplied by hwcycles per tick,
and then it adds the current value from the 32-bit timer.
This produces a 64-bit time. There is a bunch of math here, which
could be avoided if the CPU is built with Real-Time-Clock option.
EM Starter Kit SOCs don't have this. I don't think Arduino 101 does
either.

See ZEP-1559

Change-Id: I9f846d170246556ac40fe2f45809e457c6375d8c
Signed-off-by: Chuck Jordan <cjordan@synopsys.com>
This commit is contained in:
Chuck Jordan 2017-02-14 13:17:53 -08:00 • committed by Anas Nashif
commit ae15a26751
3 changed files with 49 additions and 1 deletions
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2
arch/arc/core/Makefile
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@ -3,7 +3,7 @@ ccflags-y +=-I$(srctree)/arch/$(ARCH)/include
obj-y += thread.o thread_entry_wrapper.o \
cpu_idle.o fast_irq.o fatal.o fault.o \
fault_s.o irq_manage.o cache.o \
fault_s.o irq_manage.o cache.o timestamp.o \
isr_wrapper.o regular_irq.o swap.o \
sys_fatal_error_handler.o

42
arch/arc/core/timestamp.c Normal file
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@ -0,0 +1,42 @@
/*
* Copyright (c) 2017 Synopsys, Inc.
*
* SPDX-License-Identifier: Apache-2.0
*/
/**
* @file
* @brief Time Stamp API for ARCv2
*
* Provide 64-bit time stamp API
*/
#include <kernel.h>
#include <toolchain.h>
#include <kernel_structs.h>
extern int64_t _sys_clock_tick_count;
extern int sys_clock_hw_cycles_per_tick;
/*
* @brief Read 64-bit timestamp value
*
* This function returns a 64-bit bit time stamp value that is clocked
* at the same frequency as the CPU.
*
* @return 64-bit time stamp value
*/
uint64_t _tsc_read(void)
{
unsigned int key;
uint64_t t;
uint32_t count;
key = irq_lock();
t = (uint64_t)_sys_clock_tick_count;
count = _arc_v2_aux_reg_read(_ARC_V2_TMR0_COUNT);
irq_unlock(key);
t *= (uint64_t)sys_clock_hw_cycles_per_tick;
t += (uint64_t)count;
return t;
}

6
include/arch/arc/v2/asm_inline_gcc.h
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@ -21,6 +21,12 @@ extern "C" {
#include <stdint.h>
#include <stddef.h>
/**
* @brief read timestamp register (CPU frequency)
*/
extern uint64_t _tsc_read(void);
/* Implementation of sys_io.h's documented functions */
static ALWAYS_INLINE