linux-kernel - Re: acpi_idle: Very idle Core i7 machine never enters C3

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Message-id: <alpine.LFD.2.00.1005251138560.4196@localhost.localdomain>
Date:	Tue, 25 May 2010 11:40:25 -0400 (EDT)
From:	Len Brown <lenb@...nel.org>
To:	Matthew Garrett <mjg59@...f.ucam.org>
Cc:	Philip Langdale <philipl@...rt.org>,
	Jeff Garrett <jeff@...rrett.org>,
	Andi Kleen <andi@...stfloor.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-acpi@...r.kernel.org, luming.yu@...el.com, venki@...gle.com
Subject: Re: acpi_idle: Very idle Core i7 machine never enters C3

> > I'm told by the hardware guys that BM_STS is _not_ always
> > a NOP, and so we're not supposed to simply ignore it on C3 --
> > though it should be extremely rare that we see it set.
> > If it is ever set, it should go on and off depending on 
> > activity on some latency sensitive device, like out on the LPC.
> > It may be possible for the BIOS writer to configure the chipset
> > so that BM_STS is enabled always, presumably to accomodate
> > some latency sensitve device -- or maybe by mistake.
> 
> On some hardware we've seen BM_STS be enabled approximately 50% of the 
> time without any obvious cause.

Assuming it is modern hardware, please get the acpidump and lspci -vv
output from that harware to this bug report:

https://bugzilla.kernel.org/show_bug.cgi?id=15886

thanks,
-Len Brown, Intel Open Source Technology Center

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