On Wednesday, February 11, 2015 12:33:18 AM Matthew Garrett wrote:

On Wed, Feb 11, 2015 at 01:53:26AM +0100, Rafael J. Wysocki wrote:

quoted

On Wednesday, February 11, 2015 12:26:02 AM Matthew Garrett wrote:

quoted

Hm. It's not clear to me what the bug is describing. If we're not waking 
up more frequently, why aren't we entering PC6?

Good question. :-)

The bug is saying, pretty much, that after a positive _OSI response to "Darwin"
we cannot enter PC6 any more on that machine all other things being equal.

We're using intel_idle, so we should be making idle state determination 
regardless of what ACPI tells us. So is Darwin mode influencing the 
state of some MSR that controls whether PC6 can be entered?

I need to confirm that with Len, but I don't recall there being an MSR
controlling the PC6 availability on Haswell.  There is one for PC7, but
not for PC6 IIRC.

Is the GPU blocking it because of some configuration difference?

That is possible.

I don't know enough about how the chip decides to enter PC6 to be able to
tell.

Well, so honestly how do you expect me to respond here?


-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.