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* Add a limit to how often we retry the calibration. It's there as an upper

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bound to prevent spinning forever if we have a very unstable TSC that we
  simply can't calibrate. Shouldn't really happen though.
* Set the gate low for channel 2 on exit if we used it as the counter.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@41678 a95241bf-73f2-0310-859d-f6bbb57e9c96
This commit is contained in:
Michael Lotz 2011-05-23 12:36:43 +00:00
parent 34d3f13c64
commit 2d62c17d26
1 changed files with 30 additions and 2 deletions
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32
src/system/boot/platform/bios_ia32/cpu.cpp
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@ -68,6 +68,13 @@ uint32 gTimeConversionFactor;
#define PIT_CHANNEL_2_SPEAKER_OFF_MASK ~0x02
// Maximum values
#define MAX_QUICK_SAMPLES 20
#define MAX_SLOW_SAMPLES 20
// TODO: These are arbitrary. They are here to avoid spinning indefinitely
// if the TSC just isn't stable and we can't get our desired error range.
#define CPUID_EFLAGS (1UL << 21)
#define RDTSC_FEATURE (1UL << 4)
@ -238,6 +245,9 @@ calculate_cpu_conversion_factor()
double conversionFactorQuick, conversionFactorSlower, conversionFactorSlow;
uint16 expired;
uint32 quickSampleCount = 1;
uint32 slowSampleCount = 1;
quick_sample:
calibration_loop(224, channel, tscDeltaQuick, conversionFactorQuick,
expired);
@ -249,7 +259,8 @@ slower_sample:
double deviation = conversionFactorQuick / conversionFactorSlower;
if (deviation < 0.99 || deviation > 1.01) {
// We might have been hit by a SMI or were otherwise stalled
goto quick_sample;
if (quickSampleCount++ < MAX_QUICK_SAMPLES)
goto quick_sample;
}
// Slow sample
@ -259,7 +270,8 @@ slower_sample:
deviation = conversionFactorSlower / conversionFactorSlow;
if (deviation < 0.99 || deviation > 1.01) {
// We might have been hit by a SMI or were otherwise stalled
goto slower_sample;
if (slowSampleCount++ < MAX_SLOW_SAMPLES)
goto slower_sample;
}
// Scale the TSC delta to timer units
@ -282,6 +294,22 @@ slower_sample:
gKernelArgs.arch_args.system_time_cv_factor = gTimeConversionFactor;
gKernelArgs.arch_args.cpu_clock_speed = clockSpeed;
//dprintf("factors: %lu %llu\n", gTimeConversionFactor, clockSpeed);
if (quickSampleCount > 1) {
dprintf("needed %lu quick samples for TSC calibration\n",
quickSampleCount);
}
if (slowSampleCount > 1) {
dprintf("needed %lu slow samples for TSC calibration\n",
slowSampleCount);
}
if (channel == 2) {
// Set the gate low again
out8(in8(PIT_CHANNEL_2_CONTROL) & ~PIT_CHANNEL_2_GATE_HIGH,
PIT_CHANNEL_2_CONTROL);
}
}