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/*
* ARM Cortex M3/M4/M7 SysTick timer driver
* (C) Copyright 2017 Renesas Electronics Europe Ltd
*
* Based on arch/arm/mach-stm32/stm32f1/timer.c
* (C) Copyright 2015
* Kamil Lulko, <kamil.lulko@gmail.com>
*
* Copyright 2015 ATS Advanced Telematics Systems GmbH
* Copyright 2015 Konsulko Group, Matt Porter <mporter@konsulko.com>
*
* SPDX-License-Identifier: GPL-2.0+
*
* The SysTick timer is a 24-bit count down timer. The clock can be either the
* CPU clock or a reference clock. Since the timer will wrap around very quickly
* when using the CPU clock, and we do not handle the timer interrupts, it is
* expected that this driver is only ever used with a slow reference clock.
*
* The number of reference clock ticks that correspond to 10ms is normally
* defined in the SysTick Calibration register's TENMS field. However, on some
* devices this is wrong, so this driver allows the clock rate to be defined
* using CONFIG_SYS_HZ_CLOCK.
*/
#include <common.h>
#include <asm/io.h>
DECLARE_GLOBAL_DATA_PTR;
/* SysTick Base Address - fixed for all Cortex M3, M4 and M7 devices */
#define SYSTICK_BASE 0xE000E010
struct cm3_systick {
uint32_t ctrl;
uint32_t reload_val;
uint32_t current_val;
uint32_t calibration;
};
#define TIMER_MAX_VAL 0x00FFFFFF
#define SYSTICK_CTRL_EN BIT(0)
/* Clock source: 0 = Ref clock, 1 = CPU clock */
#define SYSTICK_CTRL_CPU_CLK BIT(2)
#define SYSTICK_CAL_NOREF BIT(31)
#define SYSTICK_CAL_SKEW BIT(30)
#define SYSTICK_CAL_TENMS_MASK 0x00FFFFFF
/* read the 24-bit timer */
static ulong read_timer(void)
{
struct cm3_systick *systick = (struct cm3_systick *)SYSTICK_BASE;
/* The timer counts down, therefore convert to an incrementing timer */
return TIMER_MAX_VAL - readl(&systick->current_val);
}
int timer_init(void)
{
struct cm3_systick *systick = (struct cm3_systick *)SYSTICK_BASE;
u32 cal;
writel(TIMER_MAX_VAL, &systick->reload_val);
/* Any write to current_val reg clears it to 0 */
writel(0, &systick->current_val);
cal = readl(&systick->calibration);
if (cal & SYSTICK_CAL_NOREF)
/* Use CPU clock, no interrupts */
writel(SYSTICK_CTRL_EN | SYSTICK_CTRL_CPU_CLK, &systick->ctrl);
else
/* Use external clock, no interrupts */
writel(SYSTICK_CTRL_EN, &systick->ctrl);
/*
* If the TENMS field is inexact or wrong, specify the clock rate using
* CONFIG_SYS_HZ_CLOCK.
*/
#if defined(CONFIG_SYS_HZ_CLOCK)
gd->arch.timer_rate_hz = CONFIG_SYS_HZ_CLOCK;
#else
gd->arch.timer_rate_hz = (cal & SYSTICK_CAL_TENMS_MASK) * 100;
#endif
gd->arch.tbl = 0;
gd->arch.tbu = 0;
gd->arch.lastinc = read_timer();
return 0;
}
/* return milli-seconds timer value */
ulong get_timer(ulong base)
{
unsigned long long t = get_ticks() * 1000;
return (ulong)((t / gd->arch.timer_rate_hz)) - base;
}
unsigned long long get_ticks(void)
{
u32 now = read_timer();
if (now >= gd->arch.lastinc)
gd->arch.tbl += (now - gd->arch.lastinc);
else
gd->arch.tbl += (TIMER_MAX_VAL - gd->arch.lastinc) + now;
gd->arch.lastinc = now;
return gd->arch.tbl;
}
ulong get_tbclk(void)
{
return gd->arch.timer_rate_hz;
}
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