When I debug the hpet with linux v3.10. I found it can not work with
linux-2.6/Documentation/timers/hpet_example.c. But on bare metal,
hpet_example can work!
After tracing, I found the trouble is caused by
drivers/char/hpet.c hpet_timer_set_irq()
gsi = acpi_register_gsi(NULL, irq, ACPI_LEVEL_SENSITIVE,
ACPI_ACTIVE_LOW); --->
According to ICH spec, #PIRQ16~23 will be low-active. And there is an
internal inversion in ICH before the input of ioapic. But in qemu, we
lack the emulation of this inversion.
To fix the hpet problem, I have some solutions.
--Emulation the inversion only in hpet. This will keep current PCI
INTx# logic unchanged.
--Emulation the inversion in ioapic (both qemu and kernel), so PCI
INTx# logic will change.
Any suggestion?
Thx,
Pingfan
