[U-Boot] [PATCH 2/9] Exynos: Add timer_get_us function

[Akshay Saraswat]

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=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
---
 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

Re: [U-Boot] [PATCH 2/9] Exynos: Add timer_get_us function

[Simon Glass]

On Wed, Feb 27, 2013 at 2:02 AM, Akshay Saraswat aksha...@samsung.com wrote:
 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=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

 ---
  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