| View previous topic :: View next topic |
| Author |
Message |
Anon5710
Apprentice
Joined: 23 Jul 2004
Posts: 232
Location: Belgium
|
 Posted: Fri Oct 12, 2012 10:09 am Post subject: HPET hardware support ? |
 |
|
Alright, long time ago i posted a message here 
I'm running the ubuntu live-cd on a small board ESM-945ETX (this is an embedded board) http://www.avalue.com.tw/products/ESM-945ETX.cfm
So about HPET, i can't figure out if it is supported or not.
| Code: | ubuntu@ubuntu:~$ dmesg | grep hpet
[ 0.184674] hpet clockevent registered
[ 0.184760] hpet0: at MMIO 0xfed00000, IRQs 2, 8, 0
[ 0.184993] hpet0: 3 comparators, 64-bit 14.318180 MHz counter
[ 0.188067] Switching to clocksource hpet
[ 3.798968] rtc0: alarms up to one day, 114 bytes nvram, hpet irqs
ubuntu@ubuntu:~$ |
However running acpidump to dump my ACPI tables and iasl to decompile them, i do not find any reference to hpet.
So i find it strange that this live cd can find it, acording the hpet specs. The base adress should be reported by the bios aml tabels (ACPI DSDT table), but this adress isn't availabel in the decompiled asl file !
So does this embedded board have hpet support or not ?
Any sure fire way i can find out ?[/u] |
|
| Back to top |
|
 |
Ant P.
Watchman
Joined: 18 Apr 2009
Posts: 6920
|
| Posted: Fri Oct 12, 2012 1:09 pm Post subject: |
|
|
| If the kernel doesn't crash instantly when it switches to hpet, then it has one. |
|
| Back to top |
|
|
Anon5710
Apprentice
Joined: 23 Jul 2004
Posts: 232
Location: Belgium
|
| Posted: Fri Oct 12, 2012 2:10 pm Post subject: |
|
|
So, how does Linux finds the HPET device ?
It can't use the acpi tabels, because the device isn4t listed there.
Is it possibel that Linux reports HPET but actualy uses an other clocksource ?
(Windows XP did this.)
Regards, |
|
| Back to top |
|
|
Ant P.
Watchman
Joined: 18 Apr 2009
Posts: 6920
|
| Posted: Fri Oct 12, 2012 2:27 pm Post subject: |
|
|
| The kernel has code to force-enable a HPET at a hardcoded address in arch/x86/kernel/quirks.c, it matches the address in your dmesg output so that's a possibility. |
|
| Back to top |
|
|
roarinelk
Guru
Joined: 04 Mar 2004
Posts: 520
|
| Posted: Fri Oct 12, 2012 2:46 pm Post subject: |
|
|
ACPI has a "HPET" table; on systems without it sometimes the kernel knows where
the HPET is and force-enables it. The HPET is overrated anyway. |
|
| Back to top |
|
|
Anon5710
Apprentice
Joined: 23 Jul 2004
Posts: 232
Location: Belgium
|
| Posted: Sun Oct 14, 2012 9:36 am Post subject: |
|
|
| Thanks that was helpfull information ! |
|
| Back to top |
|
|
_______0
Guru
Joined: 15 Oct 2012
Posts: 521
|
| Posted: Tue Oct 16, 2012 5:36 pm Post subject: hpet not all that... |
|
|
| Code: | | cat /sys/devices/system/clocksource/clocksource0/available_clocksource |
and to check which one is being used:
| Code: | | cat /sys/devices/system/clocksource/clocksource0/current_clocksource |
apparently acpi_pm si better than hpet nowadays. I read this reading about realtime kernel for audio. |
|
| Back to top |
|
|
|
Kernel & Hardware
