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 09:33:07 -0800 Message-ID: <20111111093307.3072ce80@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_/r0St16k.wJdPI9cNAnTP/eh"; protocol="application/pgp-signature" Return-path: In-Reply-To: <1320961113-5050-1-git-send-email-mjg@redhat.com> Sender: linux-pci-owner@vger.kernel.org To: Matthew Garrett Cc: linux-pci@vger.kernel.org, linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org List-Id: linux-acpi@vger.kernel.org --Sig_/r0St16k.wJdPI9cNAnTP/eh Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable On Thu, 10 Nov 2011 16:38:33 -0500 Matthew Garrett wrote: > Right now we forcibly clear ASPM state on all devices if the BIOS indicat= es > that the feature isn't supported. Based on the Microsoft presentation > "PCI Express In Depth for Windows Vista and Beyond", I'm starting to think > 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 unless > the platform has granted us that control. >=20 > 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. >=20 > 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 these > components. But enough vendors enable ASPM on platforms and then set this > bit that it seems likely that they're expecting the OS to leave them alon= e. >=20 > Measured to save around 5W on an idle Thinkpad X220. >=20 Applied to linux-next, thanks. --=20 Jesse Barnes, Intel Open Source Technology Center --Sig_/r0St16k.wJdPI9cNAnTP/eh Content-Type: application/pgp-signature; name=signature.asc Content-Disposition: attachment; filename=signature.asc -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (GNU/Linux) iQIcBAEBAgAGBQJOvVxTAAoJEIEoDkX4Qk9hiKIQALTMeSwgIeQ2G9z7J+0/f7Rw dpnIiyR5BMEQpaaoLnXgv8GCuSfF5hhc0m/WGZlgN79eLhrYIHieqNLAkKDuwdGM K6i3/i7igm11bu+92t5045aTyHQk2VAZc4eSUEj7lZdBgIcLYBlXKgECfgS+2rGO CuhobcM0iSzvwjz9y4Z5+2dcGg6NPVn0fKRyVW8iLzrCbyZoCviGjwTGYlXSsyad Eo67JFjylQkGRKRn1uWPqqlFr+DjRLjrvXI2Fq4A4ak4ZRtHimLwYLUOkUetMYEC aq2SxEkORA3MJLtHgeUMVNoe1VwN3tOAflQ/CbYheXCcFTPi7yEzS4fnhNq/87rx G2+r12DGAsjxP9PbU5Uk/UPB6Bcd4Avgu4WrEUsKbT/ZrMerXs7/224lyXtKROqs KcxOedUgocNwljWVHDr1z+MMz6iqK3Dp+YAGmYl4Xjx4jjhWuUrTswIj2AWEU7M5 rpwWiWfyg5v6YCe194sokFpqSmL0MWhSyp8cJVMUqrY1VgX3QPC2G5ZIL/u0R46c csk2zhvIxCioVNki2QPig24T3ZxDEuivZsXbis1cWKRqPu5cKbIBYWM1gcy+t1Hp yxU7OYUR1LA0FytHOTY8G8Nx7GVdQffHqGnvMduVb3X4sr5a0QWw+zarqVZBJZB3 foi94HROk/Q0UYada//y =2nAz -----END PGP SIGNATURE----- --Sig_/r0St16k.wJdPI9cNAnTP/eh--