linux-kernel - Re: [PATCH 1/9] acpi: Use ACPI C-state type instead of enumeration value to export cpuidle state name

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Date:	Wed, 12 Jan 2011 01:36:17 -0500 (EST)
From:	Len Brown <lenb@...nel.org>
To:	Thomas Renninger <trenn@...e.de>
Cc:	linux-perf-users@...r.kernel.org, mingo@...e.hu,
	arjan@...ux.intel.com, j-pihet@...com, linux-acpi@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/9] acpi: Use ACPI C-state type instead of enumeration
 value to export cpuidle state name

> > But some systems may have more than one state of each type...

> Exported through ACPI tables?

Yes.

It is quite common, for example in the Pentium M
generations, for a BIOS to export C3 and C4 -
both of which are ACPI  C3-type.

> > also, the state->name is somewhat arbitrary.
> > 
> > You'll notice that intel_idle uses the hardware C-state names
> > such as NHM-C1, NHM-C3, NHM-C6 - to match the (arbitrary)
> > names in the hardware documentation.  We could call those
> > states Moe/Larry/Curley just as well.

> That works out with HW specific intel_idle.c driver, but not
> with the generic acpi/processor one.

Actually, C0..Cn work out fine for the acpi/processor driver.
the names are unique, and they also correspond to max_cstate
if somebody wants to use that.


> I restore the ACPI type info as exported by ACPI tables
> with this patch, should be the same as done with
> /proc/acpi/processor/*/power
> Do I miss something?

/proc/acpi/processor/*/power had a type field.
Per the example above, the type field didn't always
match the C-state number.

> Do you want to export additional ACPI table C-state
> info?

I have a 1 line patch someplace to print out the type
for debug info when needed, that should be sufficient
for debugging, which is the only time we care about type.

> Something else, but related:
> You recently said that it might be a good idea to get
> C-/P- state ACPI tables which are often in a separate
> SSDT loaded at runtime via "load" ACPI command, dumped
> with the acpidump  tool. This would be a cool feature.
> Does dynamically loaded SSDT dumping
> via acpidump work already or is/has someone looked at this?

Yakui fixed this a while back.
acpidump in the latest pmtools in
http://userweb.kernel.org/~lenb/acpi/utils/
picks up the dynamic tables from /sys/firmware/acpi/tables.

cheers,
Len Brown, Intel Open Source Technology Center

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