On Wed, Feb 27, 2013 at 2:02 AM, Akshay Saraswat akshay.s@samsung.com wrote:
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=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
arch/arm/cpu/armv7/s5p-common/pwm.c | 6 ++ arch/arm/cpu/armv7/s5p-common/timer.c | 100 +++++++++++++--------------------- 2 files changed, 44 insertions(+), 62 deletions(-)
diff --git a/arch/arm/cpu/armv7/s5p-common/pwm.c b/arch/arm/cpu/armv7/s5p-common/pwm.c index 44d7bc3..3147f59 100644 --- a/arch/arm/cpu/armv7/s5p-common/pwm.c +++ b/arch/arm/cpu/armv7/s5p-common/pwm.c @@ -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));diff --git a/arch/arm/cpu/armv7/s5p-common/timer.c b/arch/arm/cpu/armv7/s5p-common/timer.c index e78c716..c48a297 100644 --- a/arch/arm/cpu/armv7/s5p-common/timer.c +++ b/arch/arm/cpu/armv7/s5p-common/timer.c @@ -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;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();elsetmo += tmp;/* loop till event */while (get_current_tick() < tmo); /* nop */
unsigned long count_value;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;elsegd->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.
-- 1.8.0