From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: PMP device port link speed issues Date: Tue, 30 Oct 2007 08:20:56 +0900 Message-ID: <47266AD8.4060505@gmail.com> References: <2A6F278C5B66C4459AF4013E77A40CD301003529@zin33exm20.fsl.freescale.net> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from nz-out-0506.google.com ([64.233.162.232]:2523 "EHLO nz-out-0506.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752933AbXJ2XVK (ORCPT ); Mon, 29 Oct 2007 19:21:10 -0400 Received: by nz-out-0506.google.com with SMTP id s18so1296324nze for ; Mon, 29 Oct 2007 16:21:09 -0700 (PDT) In-Reply-To: <2A6F278C5B66C4459AF4013E77A40CD301003529@zin33exm20.fsl.freescale.net> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Kalra Ashish-B00888 Cc: Jeff Garzik , IDE/ATA development list Kalra Ashish-B00888 wrote: > Hello Tejun, > > This patch will surely fix my problem, but won't it be better to set > each PMP device port link speed directly to > the host<->PMP link speed, during SATA PMP device configuration in > sata_pmp_attach(), instead of calling > sata_link_init_spd() for each link. > > The PMP chip should be responsible for matching link speed difference, > but probably there could be issues with > certain PMP chips, as it looks like in our case, where NCQ hangs are > probably caused due to link speed difference. > It should be simpler to handle it in S/W, by limiting PMP device port > link speeds to host<->PMP link speed. Yeah, I agree. There's nearly nothing to be gained by driving downstream PHYs faster than the upstream PHY. I'll submit a patch to limit downstream port speed by upstream speed. Thanks. -- tejun