From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeff Garzik Subject: Re: [PATCH RFC] ahci: implement handoff quirk Date: Tue, 14 Apr 2009 05:41:01 -0400 Message-ID: <49E45A2D.8090107@garzik.org> References: <485882FE.1060409@kernel.org> <49E0CB5B.3070807@garzik.org> <49E0D8B7.8010206@kernel.org> <49E0DB1E.8070701@garzik.org> <49E45460.8010809@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from srv5.dvmed.net ([207.36.208.214]:40232 "EHLO mail.dvmed.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755206AbZDNJlF (ORCPT ); Tue, 14 Apr 2009 05:41:05 -0400 In-Reply-To: <49E45460.8010809@kernel.org> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: "Zhao, Richard" , shane.huang@amd.com Cc: IDE/ATA development list Tejun Heo wrote: > Jeff Garzik wrote: >> Tejun Heo wrote: >>> Jeff Garzik wrote: >>>> We probably need to do this... >>>> >>>> it's not a controller requirement but a BIOS one, so in theory even an >>>> existing, deployed AHCI 1.2 platform could suddenly require BIOS/OS >>>> handoff, if a BIOS update suddenly starts doing new and weird stuff >>>> in SMI. >>>> >>>> Note that we need to do BIOS/OS handoff upon resume as well as at boot >>>> time. >>> Yeah, probably. Do you know of any system which makes use of this >>> feature? I'm a bit uneasy about committing it without any testing. >> I don't. >> >> But the purpose of the feature is to tell BIOS to cleanup and stop using >> the hardware. It's a dumb feature, because of compatibility realities, >> but hey, other network and SCSI drivers have been doing this sort of >> synchronization with their on-board firmwares for years. >> >> IMO the more dangerous route is to continue loading ahci, without first >> telling the BIOS to clean up and get out of our way. > > Hmmm.... yeah, I'm just worried a bit about adding a chunk of > completely untested code. How about adding a big fat warning message > which gets triggered if the handoff thing seems to be active? Yeah, printing out something makes a lot of sense, but I would just add it to the flags output in ahci_print_info() or similar. If we don't see any further action from ahci (or the system as a whole), we know something exploded very early in the AHCI driver load. Or maybe AMD (I see they're CC'd) could test this for us? AMD, what say you? Jeff