Carsten Schiers
2011-Jun-16 06:47 UTC
AW: RE: RE: RE: [Xen-devel] No C-States any longer...
Maybe a dump question, but in the beginning of our discussion, we had:>> In drivers/scpi/processor_idle.c:...>> On a working Intel machine, it will go through it like this: >> >> - acpi_processor_get_power_info_cst, which returns 0 >> - acpi_processor_get_power_info_default >> - later acpi_processor_power_verify will find some c-states > >this is expected sequence > >> >> On my non-working AMD machine, it will go through like this: >> - acpi_processor_get_power_info_cst, which returns -ENODEV >> - acpi_processor_get_power_info_fadt, which also return -ENODEV >> - this result is returnedThere is a comment in acpi_processor_get_power_info_default it is said that all processors need to support C1 at least. So (hypothesis), if my BIOS is not implemented as specified (neither _CST nor PBLK), shouldn''t acpi_processor_get_power_info_default also bee called on my machine? Is the code exiting too early? Carsten. _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
> From: Carsten Schiers [mailto:carsten@schiers.de] > Sent: Thursday, June 16, 2011 2:48 PM > > Maybe a dump question, but in the beginning of our discussion, we had: > > >> In drivers/scpi/processor_idle.c: > ... > >> On a working Intel machine, it will go through it like this: > >> > >> - acpi_processor_get_power_info_cst, which returns 0 > >> - acpi_processor_get_power_info_default > >> - later acpi_processor_power_verify will find some c-states > > > >this is expected sequence > > > >> > >> On my non-working AMD machine, it will go through like this: > >> - acpi_processor_get_power_info_cst, which returns -ENODEV > >> - acpi_processor_get_power_info_fadt, which also return -ENODEV > >> - this result is returned > > There is a comment in acpi_processor_get_power_info_default it is > said that all processors need to support C1 at least. So (hypothesis), > if my BIOS is not implemented as specified (neither _CST nor PBLK), > shouldn''t acpi_processor_get_power_info_default also bee called on my > machine? Is the code exiting too early? >You can argue that point. It exits at current point because typical BIOS provide either CST or valid FADT/PBLK info. Of course even when ACPI table is broken we can still make a valid C1 entry. But also note that even when such ACPI Cstate information is not gathered, the kernel always invokes hlt when system is idle which achieves the effect. :-) Thanks Kevin _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel