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timer & hw_arndale: don't use any float ops

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The timer driver previously used floating point operations to translate us to
tics and vice versa. This isn't necessary as the rounding error isn't critical
for the given values but expensive which should be avoided in a code path that
must be executed pretty frequent with high priority.

Ref #1628
This commit is contained in:
Martin Stein 2015-07-08 12:17:59 +02:00 committed by Norman Feske
parent dddb536e25
commit 3c49113e64
1 changed files with 8 additions and 22 deletions
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30
repos/os/src/drivers/timer/hw/exynos5/platform_timer_base.h
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@ -27,7 +27,10 @@ namespace Genode
*/
class Pwm : public Mmio
{
enum { PRESCALER = 2 };
enum {
PRESCALER = 2,
TICS_PER_US = Board_base::PWM_CLOCK / PRESCALER / 1000 / 1000,
};
/**
* Timer configuration 0
@ -110,17 +113,6 @@ namespace Genode
}
};
/**
* Timer tics per microsecond
*/
static float tics_per_us() {
return (float)Board_base::PWM_CLOCK / PRESCALER / 1000 / 1000; }
/**
* Microseconds per timer tic
*/
static float us_per_tic() { return (float)1 / tics_per_us(); }
public:
/**
@ -159,20 +151,14 @@ namespace Genode
/**
* Translate timer tics to microseconds
*/
unsigned long tics_to_us(unsigned long const tics) const
{
float const us = tics * us_per_tic();
return (unsigned long)us;
}
unsigned long tics_to_us(unsigned long const tics) const {
return tics / TICS_PER_US; }
/**
* Translate microseconds to timer tics
*/
unsigned long us_to_tics(unsigned long const us)
{
float const tics = us * tics_per_us();
return (unsigned long)tics;
}
unsigned long us_to_tics(unsigned long const us) const {
return us * TICS_PER_US; }
/**
* Sample the timer counter and according wrapped status