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/*
* This file is part of the coreboot project.
*
* Copyright (C) 2013 Alexandru Gagniuc <mr.nuke.me@gmail.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; version 2 of the License or (at your option)
* any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* Timer control and delays for Allwinner CPUs
*
*/
#include <device/mmio.h>
#include <delay.h>
#include "timer.h"
struct a1x_timer_module *const timer_module = (void *)A1X_TIMER_BASE;
struct a1x_timer *const tmr0 =
&((struct a1x_timer_module *)A1X_TIMER_BASE)->timer[0];
static inline u32 read_timer(void)
{
return read32(&tmr0->val);
}
void init_timer(void)
{
u32 reg32;
/* Load the timer rollover value */
write32(&tmr0->interval, 0xffffffff);
/* Configure the timer to run from 24MHz oscillator, no prescaler */
reg32 = TIMER_CTRL_PRESC_DIV_EXP(0);
reg32 |= TIMER_CTRL_CLK_SRC_OSC24M;
reg32 |= TIMER_CTRL_RELOAD;
reg32 |= TIMER_CTRL_TMR_EN;
write32(&tmr0->ctrl, reg32);
}
void udelay(unsigned usec)
{
u32 curr_tick, last_tick;
s32 ticks_left;
last_tick = read_timer();
/* 24 timer ticks per microsecond (24 MHz, divided by 1) */
ticks_left = usec * 24;
/* FIXME: Should we consider timer rollover?
* From when we start the timer, we have almost three minutes before it
* rolls over, so we should be long into having booted our payload.
*/
while (ticks_left > 0) {
curr_tick = read_timer();
/* Timer value decreases with each tick */
ticks_left -= last_tick - curr_tick;
last_tick = curr_tick;
}
}
/*
* This function has nothing to do with timers; however, the chip revision
* register is in the timer module, so keep this function here.
*/
u8 a1x_get_cpu_chip_revision(void)
{
write32(&timer_module->cpu_cfg, 0);
return (read32(&timer_module->cpu_cfg) >> 6) & 0x3;
}
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