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libpayload: Add a timer_us() function.

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This function returns the number of microseconds scaled from the number of raw
timer ticks. It accepts a base parameter which is subtracted from the current
time, which makes it easy to keep track of relative times.

BUG=None
TEST=With a corresponding change in depthcharge, built and booted on link.
BRANCH=None

Change-Id: I55f2f9e90c0e12cda430bbe88b044f12b0b563c8
Signed-off-by: Gabe Black <gabeblack@google.com>
Reviewed-on: https://chromium-review.googlesource.com/179600
Reviewed-by: Ronald Minnich <rminnich@chromium.org>
Commit-Queue: Gabe Black <gabeblack@chromium.org>
Tested-by: Gabe Black <gabeblack@chromium.org>
This commit is contained in:
Gabe Black 2013-12-06 23:30:10 -08:00 • committed by chrome-internal-fetch
commit 4dd549e18d
2 changed files with 18 additions and 0 deletions
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1
payloads/libpayload/include/libpayload.h
View file

@ -416,6 +416,7 @@ int lib_get_sysinfo(void);
unsigned int get_cpu_speed(void);
uint64_t timer_hz(void);
uint64_t timer_raw_value(void);
uint64_t timer_us(uint64_t base);
/* Generic. */
void ndelay(unsigned int n);
void udelay(unsigned int n);

17
payloads/libpayload/libc/time.c
View file

@ -189,3 +189,20 @@ void delay(unsigned int s)
{
_delay((uint64_t)s * timer_hz());
}
u64 timer_us(u64 base)
{
static u64 hz;
// Only check timer_hz once. Assume it doesn't change.
if (hz == 0) {
hz = timer_hz();
if (hz < 1000000) {
printf("Timer frequency %lld is too low, "
"must be at least 1MHz.\n", hz);
halt();
}
}
return timer_raw_value() / (hz / 1000000) - base;
}