Return-path: Received: from mail-pz0-f46.google.com ([209.85.210.46]:44188 "EHLO mail-pz0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755066Ab0GZWUn (ORCPT ); Mon, 26 Jul 2010 18:20:43 -0400 MIME-Version: 1.0 In-Reply-To: <20100726211424.GA5197@srcf.ucam.org> References: <1276859156.19554.2.camel@maxim-laptop> <1276870309.23783.3.camel@maxim-laptop> <1276933774.16697.11.camel@maxim-laptop> <20100619123841.GA31838@hash.localnet> <1276952554.3332.3.camel@maxim-laptop> <1276961564.5173.12.camel@maxim-laptop> <20100726201322.GI14855@tux> <1280177362.3721.7.camel@maxim-laptop> <20100726210651.GJ14855@tux> <20100726211424.GA5197@srcf.ucam.org> From: "Luis R. Rodriguez" Date: Mon, 26 Jul 2010 15:20:23 -0700 Message-ID: Subject: Re: [ath5k-devel] [PATCH v3] ath5k: disable ASPM To: Matthew Garrett Cc: Maxim Levitsky , Luis Rodriguez , Bob Copeland , "Luis R. Rodriguez" , Jussi Kivilinna , "ath5k-devel@lists.ath5k.org" , "linux-wireless@vger.kernel.org" , linux-kernel , "kernel-team@lists.ubuntu.com" , "tim.gardner@canonical.com" , David Quan Content-Type: text/plain; charset=UTF-8 Sender: linux-wireless-owner@vger.kernel.org List-ID: On Mon, Jul 26, 2010 at 2:14 PM, Matthew Garrett wrote: > On Mon, Jul 26, 2010 at 02:06:51PM -0700, Luis R. Rodriguez wrote: > >> No, ASPM must be enabled by the Systems Integrator through the BIOS, there are >> other settings that have to be taken care of like modifying some PCI entrance and >> exit latency timers, the number of FTS packets we send to exit L0s, amongst >> other things. If a user selectively enables L1 but the BIOS had it disabled on >> the device it may not work correctly. > > That's really the job of the driver. The problem is that sometimes tweaks need to be done on the PCI controller/root complex, not the PCIE device/endpoint. Today these sort of changes *are* handled by the respective systems integrator/BIOS team and varies depending on the root complex used. Atheros does not handle these at all in the driver. > If the ASPM policy is set to > powersave, the fadt doesn't indicate that ASPM should be disabled and > the bus's _OSC method grants full control then the kernel will enable > whatever combination of L states meet the latency constraints. If the > hardware has additional constraints then the hardware-specific driver > needs to handle them. This makes sense but Is there an API for this? > We don't rely on the BIOS to set up ASPM states. Nor does Windows. Understood, but today some tweaks seem to be done on the BIOS depending on the endpoint / root complex. Luis