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Exynos: Change get_timer() to work correctly

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At present get_timer() does not return sane values. It should count up
smoothly in milliscond intervals.

We can change the PWM to count down at 1MHz, providing a resolution
of 1us and a range of about an hour between required get_timer() calls.

Test with command "sf probe 1:0; time sf read 40008000 0 1000".
Try with different numbers of bytes and see that sane values are obtained

Signed-off-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Akshay Saraswat <akshay.s@samsung.com>
Acked-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>
This commit is contained in:
Simon Glass 2013-03-28 04:32:16 +00:00 committed by Minkyu Kang
parent 4f3bfa97c4
commit 3d00c0cb96
2 changed files with 43 additions and 61 deletions
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6
arch/arm/cpu/armv7/s5p-common/pwm.c
View File

@ -174,6 +174,12 @@ int pwm_init(int pwm_id, int div, int invert)
/* set count value */
offset = pwm_id * 3;
/*
* TODO(sjg): Use this as a countdown timer for now. We count down
* from the maximum value to 0, then reset.
*/
timer_rate_hz = -1;
writel(timer_rate_hz, &pwm->tcntb0 + offset);
val = readl(&pwm->tcon) & ~(0xf << TCON_OFFSET(pwm_id));

98
arch/arm/cpu/armv7/s5p-common/timer.c
View File

@ -39,13 +39,33 @@ static inline struct s5p_timer *s5p_get_base_timer(void)
return (struct s5p_timer *)samsung_get_base_timer();
}
/**
* Read the countdown timer.
*
* This operates at 1MHz and counts downwards. It will wrap about every
* hour (2^32 microseconds).
*
* @return current value of timer
*/
static unsigned long timer_get_us_down(void)
{
struct s5p_timer *const timer = s5p_get_base_timer();
return readl(&timer->tcnto4);
}
int timer_init(void)
{
/* PWM Timer 4 */
pwm_init(4, MUX_DIV_2, 0);
pwm_init(4, MUX_DIV_4, 0);
pwm_config(4, 0, 0);
pwm_enable(4);
/* Use this as the current monotonic time in us */
gd->arch.timer_reset_value = 0;
/* Use this as the last timer value we saw */
gd->arch.lastinc = timer_get_us_down();
reset_timer_masked();
return 0;
@ -56,48 +76,28 @@ int timer_init(void)
*/
unsigned long get_timer(unsigned long base)
{
return get_timer_masked() - base;
ulong now = timer_get_us_down();
/*
* Increment the time by the amount elapsed since the last read.
* The timer may have wrapped around, but it makes no difference to
* our arithmetic here.
*/
gd->arch.timer_reset_value += gd->arch.lastinc - now;
gd->arch.lastinc = now;
/* Divide by 1000 to convert from us to ms */
return gd->arch.timer_reset_value / 1000 - base;
}
/* delay x useconds */
void __udelay(unsigned long usec)
{
struct s5p_timer *const timer = s5p_get_base_timer();
unsigned long tmo, tmp, count_value;
unsigned long count_value;
count_value = readl(&timer->tcntb4);
if (usec >= 1000) {
/*
* if "big" number, spread normalization
* to seconds
* 1. start to normalize for usec to ticks per sec
* 2. find number of "ticks" to wait to achieve target
* 3. finish normalize.
*/
tmo = usec / 1000;
tmo *= (CONFIG_SYS_HZ * count_value);
tmo /= 1000;
} else {
/* else small number, don't kill it prior to HZ multiply */
tmo = usec * CONFIG_SYS_HZ * count_value;
tmo /= (1000 * 1000);
}
/* get current timestamp */
tmp = get_current_tick();
/* if setting this fordward will roll time stamp */
/* reset "advancing" timestamp to 0, set lastinc value */
/* else, set advancing stamp wake up time */
if ((tmo + tmp + 1) < tmp)
reset_timer_masked();
else
tmo += tmp;
/* loop till event */
while (get_current_tick() < tmo)
; /* nop */
count_value = timer_get_us_down();
while ((int)(count_value - timer_get_us_down()) < (int)usec)
;
}
void reset_timer_masked(void)
@ -109,30 +109,6 @@ void reset_timer_masked(void)
gd->arch.tbl = 0;
}
unsigned long get_timer_masked(void)
{
struct s5p_timer *const timer = s5p_get_base_timer();
unsigned long count_value = readl(&timer->tcntb4);
return get_current_tick() / count_value;
}
unsigned long get_current_tick(void)
{
struct s5p_timer *const timer = s5p_get_base_timer();
unsigned long now = readl(&timer->tcnto4);
unsigned long count_value = readl(&timer->tcntb4);
if (gd->arch.lastinc >= now)
gd->arch.tbl += gd->arch.lastinc - now;
else
gd->arch.tbl += gd->arch.lastinc + count_value - now;
gd->arch.lastinc = now;
return gd->arch.tbl;
}
/*
* This function is derived from PowerPC code (read timebase as long long).
* On ARM it just returns the timer value.