timer_get_us returns the time in microseconds since a certain reference point of history. However, it does not guarantee to return an accurate time after a long period; instead, it wraps around (that is, the reference point is reset to some other point of history) after some periods. The frequency of wrapping around is about an hour (or 2^32 microseconds).
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: Che-Liang Chiou <clch...@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/timer.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/arch/arm/cpu/armv7/s5p-common/timer.c b/arch/arm/cpu/armv7/s5p-common/timer.c index c48a297..de61405 100644 --- a/arch/arm/cpu/armv7/s5p-common/timer.c +++ b/arch/arm/cpu/armv7/s5p-common/timer.c @@ -90,6 +90,21 @@ unsigned long get_timer(unsigned long base) return gd->arch.timer_reset_value / 1000 - base; } +unsigned long timer_get_us(void) +{ + static unsigned long base_time_us; + + struct s5p_timer *const timer = + (struct s5p_timer *)samsung_get_base_timer(); + unsigned long now_downward_us = readl(&timer->tcnto4); + + if (!base_time_us) + base_time_us = now_downward_us; + + /* Note that this timer counts downward. */ + return base_time_us - now_downward_us; +} + /* delay x useconds */ void __udelay(unsigned long usec) { -- 1.8.0 _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot