From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jesse Barnes Subject: Re: [PATCH] pci: Rework ASPM disable code Date: Fri, 11 Nov 2011 09:28:11 -0800 Message-ID: <20111111092811.54a03027@jbarnes-desktop> References: <1320961113-5050-1-git-send-email-mjg@redhat.com> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=PGP-SHA1; boundary="Sig_/.MBNHS/g+64/X46UHts1VUw"; protocol="application/pgp-signature" Return-path: Received: from oproxy5-pub.bluehost.com ([67.222.38.55]:36068 "HELO oproxy5-pub.bluehost.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1753570Ab1KKR2G (ORCPT ); Fri, 11 Nov 2011 12:28:06 -0500 In-Reply-To: Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: =?UTF-8?B?UmFmYcWCIE1pxYJlY2tp?= Cc: Matthew Garrett , linux-pci@vger.kernel.org, linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org --Sig_/.MBNHS/g+64/X46UHts1VUw Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On Fri, 11 Nov 2011 10:49:02 +0100 Rafa=C5=82 Mi=C5=82ecki wrote: > 2011/11/10 Matthew Garrett : > > Right now we forcibly clear ASPM state on all devices if the BIOS indic= ates > > that the feature isn't supported. Based on the Microsoft presentation > > "PCI Express In Depth for Windows Vista and Beyond", I'm starting to th= ink > > that this may be an error. The implication is that unless the platform > > grants full control via _OSC, Windows will not touch any PCIe features - > > including ASPM. In that case clearing ASPM state would be an error unle= ss > > the platform has granted us that control. > > > > This patch reworks the ASPM disabling code such that the actual clearing > > of state is triggered by a successful handoff of PCIe control to the OS. > > The general ASPM code undergoes some changes in order to ensure that the > > ability to clear the bits isn't overridden by ASPM having already been > > disabled. Further, this theoretically now allows for situations where > > only a subset of PCIe roots hand over control, leaving the others in the > > BIOS state. > > > > It's difficult to know for sure that this is the right thing to do - > > there's zero public documentation on the interaction between all of the= se > > components. But enough vendors enable ASPM on platforms and then set th= is > > bit that it seems likely that they're expecting the OS to leave them al= one. > > > > Measured to save around 5W on an idle Thinkpad X220. > > > > Signed-off-by: Matthew Garrett >=20 > Does it make sense to CC stable? To get it into 2.6.38+? It's a pretty serious change that affects a lot of platforms, so I'd be nervous about sticking it in stable right away. Maybe after some soak time upstream and/or broad testing in distros. --=20 Jesse Barnes, Intel Open Source Technology Center --Sig_/.MBNHS/g+64/X46UHts1VUw Content-Type: application/pgp-signature; name=signature.asc Content-Disposition: attachment; filename=signature.asc -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (GNU/Linux) iQIcBAEBAgAGBQJOvVsrAAoJEIEoDkX4Qk9hABcP/1eENSG0J1UOQx6hdVL6BHOt aKFD88odJqb12rQ3G0pvvf5pygBFHTgFMYMbrixyxLOCiiFDZ64oyV+przAlkpn9 zW9vcb6q0VonwhdhpapiPcwQfZfTSQVQqQ8sdoqYg6+JiTizgtaBqFhEKyelcIIl OrybBKUr+5d480OJQ2Z9wLm3ggDuMlfDqGQfiHpvkTHdbYqPCtU2vwfL+wJ/z63L wcGIGm27x0Ttv7V7MqvP0iF/saa7mmDGldxlaxkPqrU7HtRWQ26t8d8hsWrv2cww qtuQXloeeioxXYKdfNATB2Gr+6YumMKl3WG7z4xwLlH3p7EdCNiBchHEOuZ1uM7C uKeCDN3ttd0P2LpMKkd3laDzJlv9NZ4is4iZ/sirbuPrkOQy1o3hC1uhnSUeXjLf sdWrvw1TG/vV7srm6FyvusdXD8w97CG6o0Nt7Ja1wOMJUYMwo+KGh8vzAK96gUTl 4QyHoCTE5JImbTaE5GwbBMOK9j9eGxFZ107bQshTp5H41oOV2XD2hnIlds2omzRA b/9ZCOz0xCpxODgbNuNikyWYDYGQsiA0m3rix9g5ikX1mF3gPT4F4skkE2ArBPgp eSXO6ewyFLmd2MVKDuPOg2X+Z/NXoAjjkQ5l5Grx289vfD2XABe9DjOKg3OwyjKU 6Xh7XjQjzjAprnIEcx4M =VUiW -----END PGP SIGNATURE----- --Sig_/.MBNHS/g+64/X46UHts1VUw--