Dear Akshay,
On 28/02/13 19:59, Akshay Saraswat 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 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 <s...@chromium.org>
> Signed-off-by: Akshay Saraswat <aksha...@samsung.com>
> Acked-by: Simon Glass <s...@chromium.org>
> ---
> Changes since v1:
> - Added "Acked-by: Simon Glass".
>
> 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;
is it workaround?
> 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);
There are special reason to change the div value?
Please let me know.
> 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();
> - else
> - tmo += 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)
why convert to int?
> + ;
> }
>
> 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.
>
Thanks,
Minkyu Kang.
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