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/*
* Timer control and delays for Allwinner CPUs
*
* Copyright (C) 2013 Alexandru Gagniuc <mr.nuke.me@gmail.com>
* Subject to the GNU GPL v2, or (at your option) any later version.
*/
#include "timer.h"
#include <arch/io.h>
#include <delay.h>
#include <timer.h>
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(0xffffffff, &tmr0->interval);
/* 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(reg32, &tmr0->ctrl);
}
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;
}
}
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