From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: [ANNOUNCE] libata EH/NCQ/hotplug/PM git tree Date: Sat, 13 May 2006 12:59:02 +0900 Message-ID: <44655986.3060007@gmail.com> References: <44614592.7080301@gmail.com> <446536C5.80503@pobox.com> <44653807.3030101@gmail.com> <44655496.9030402@pobox.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from nz-out-0102.google.com ([64.233.162.207]:59920 "EHLO nz-out-0102.google.com") by vger.kernel.org with ESMTP id S932318AbWEMD7J (ORCPT ); Fri, 12 May 2006 23:59:09 -0400 Received: by nz-out-0102.google.com with SMTP id 13so607921nzn for ; Fri, 12 May 2006 20:59:08 -0700 (PDT) In-Reply-To: <44655496.9030402@pobox.com> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Jeff Garzik Cc: Alan Cox , Albert Lee , Jens Axboe , Edward Falk , Carlos Pardo , Raymond Liu , "linux-ide@vger.kernel.org" Jeff Garzik wrote: > Tejun Heo wrote: >> Jeff Garzik wrote: >>> Tejun Heo wrote: >>>> tested. I implemented AHCI PM support half-way but then realized = I=20 >>>> don't have any AHCI controller which supports PM (I have ICH7R). = Is=20 >>>> there any AHCI controller which reports PM support? >>> >>> You can always use SCR-based PM support... >>> >> >> Can you elaborate a bit? >=20 > Sections A.1 and 6.1 of the PM spec. You set the PMP field of the=20 > SControl register. This has obvious parallelism limitations, which i= s=20 > why "hardware context switching support" aka native PM support is=20 > greatly preferred. >=20 That cmd-switching PM support is what AHCI SPM bit indicates. As of=20 v1.1, AHCI doesn't define FIS-switching PM support yet. Supports Port Multiplier (SPM): Indicates whether the HBA can support a= =20 Port Multiplier. When set, a Port Multiplier using command-based=20 switching is supported. When cleared to =910=92, a Port Multiplier is n= ot=20 supported, and a Port Multiplier may not be attached to this HBA. And. the SControl section says... 19:16 RO 0h Port Multiplier Port (PMP): This field is not used by AHCI= =2E Which is understandable considering AHCI doesn't construct FISes itself= =2E=20 I don't think PM requires more hardware support than being capable fo= r=20 setting PMP in the FISes, which AHCI certainly can (standing down on=20 collision for SDB notify aside). I can give it a shot but it clearly=20 violates the spec, and even if it works, we would need to print big fat= =20 warning message while attaching PM. --=20 tejun