Exynos: Change get_timer() to work correctly
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>
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 @@
/* 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 @@
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 @@
*/
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 @@
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.