linux-kernel - Power consumption on 802.11 / ASPM / device measurements

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Date:	Fri, 16 Apr 2010 12:53:52 -0700
From:	"Luis R. Rodriguez" <mcgrof@...il.com>
To:	linux-wireless <linux-wireless@...r.kernel.org>
Cc:	linux-kernel@...r.kernel.org, yanmin.zhang@...el.com,
	shaohua.li@...el.com, Sameer Nanda <snanda@...gle.com>,
	Jonathan May <Jonathan.May@...eros.com>,
	David Quan <David.Quan@...eros.com>
Subject: Power consumption on 802.11 / ASPM / device measurements

We've been accumulating a few power consumption related documents on
the wireless wiki for a while now. One which I saw was missing was for
actual power consumption and review of new PCI-E features which should
be taken into consideration when debugging power consumption or
reviewing it. ASPM is something that I can say I found little to no
documentation for when looking into it so I've done a brain dump of
what I recall from it, the code review of it, and some e-mail
exchanges I've had with Jonathan May @ Atheros.

I've stashed together all the power consumption docs at:

http://wireless.kernel.org/en/users/Documentation/Power-consumption

You'll see there some ASPM docs now and some ath9k specific power
consumption metrics/ASPM details. Please review and enhance as you see
fit.

Yanmin, Shaohua, I see CONFIG_PCIEASPM still marked as experimental,
I'm curious if this is still really that experimental and if there are
plans for it go out of experimental. Also I am little puzzled with
some of the aspm.c code, I see we fill the pci device struct with
capability stuff via pcie_aspm_cap_init() but I also see ASPM
capability stuff exposed on kernels without CONFIG_PCIEASPM (albeit I
see it always disabled on my system at home), so are we filling the
capability elsewhere? I think there are some boxes without this kernel
config enabled and where ASPM capability info is exposed and does show
up as enabled, could be wrong.

Also curious -- how often are BIOSes buggy enough for ASPM to get
disabled by mistake on the modern devices? And for systems that have
no Bios (*cough* ChromeOS) how is this handled?

 Luis
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